| A | |
| Abrasion | The wearing away of a material surface by friction. Particles become detached by a combined cutting, shearing and tearing action. Furnace carbon blacks are the best ingredients found for increasing the resistance of rubber compounds to abrasion. |
| Abrasion Resistance | The resistance of a material to loss of surface particles due to friction. |
| Abrasion resistance index | A measure of the abrasion resistance of a rubber relative to that of a standard rubber under the same specified conditions, expressed as a percentage. |
| Accelerated Aging | Procedures for subjecting pressure - sensitive label stock to special environmental conditions in order to predict the course of natural aging. |
| Accelerated life test: | The testing of a material by subjecting it to conditions in excess of its normal service parameters in an effort to approximate, in a short time, the deteriorating effect of normal longterm service conditions. |
| Accelerated Service Test | Any set of test conditions designed to reproduce in a short time the deteriorating effect obtained under normal service conditions. |
| Accelerator | A chemical which speeds up the vulcanisation reaction. This allows the rubber to cure in a shorter timeframe, at a lower temperature or both. |
| Acetate | A plastic synthesized from cellulose dissolved in acetic acid which exhibits rigidity, dimension stability, and ink receptivity. |
| Acid acceptors | Mostly used in fluoroelastomers to absorb the acid produced by the chemical reactions that take place during curing and to some degree during service. Acid acceptors are usually metal oxides. |
| Acid resistance | The ability of a material to resist attack as a result of exposure to acids. The degree of attack is both temperature and concentration dependant. |
| Acid Resistant | Withstands the action of acids. |
| ACM | Abbreviation for acrylic rubbers. |
| ACN | Abbreviation for acrylonitrile. |
| Acrylic Adhesive | Adhesive made from acrylic monomers that have been polymerized. They have good resistance to UV radiation, plasticizer and extreme temperatures. |
| Acrylate Rubber | General term used to describe a class of elastomers based on acrylate esters. (Examples, Hycar 4021, 4051, 4054.) See ACM above. |
| Acrylic Rubber | See Acrylate Rubber above, which is the preferred usage. |
| Acrylonitrile | A chemical CH2CHCN, also known as vinyl cyanide, manufactured from propylene and copolymerized with butadiene to produce butadiene/acrylonitrile elastomers. (Examples, Hycar 1041,1032.) |
| Activator | A substance, which by chemical interaction promotes a chemical action of a second substance. Most commonly used in elastomers to activate accelerators. |
| Active Inhibitor | A type of galvanic corrosion inhibitor added to packing. It acts as a sacrificial anode, corroding in preference to the surrounding metal. Zinc dust is added to the surface of some packing materials as an active inhibitor. See also “Galvanic Corrosion”. Compare with “Passive Inhibitor”. |
| Actuate | To cause movement of a valve stem either by raising, lowering, or turning it. |
| Actuator | A device, attached to a valve, which moves the stem, usually by means of a motor or pneumatics. A valve fitted with an actuator is usually referred to as a control valve. |
| Adapters | A “V” shaped ring either male or female to fit together with “V” shaped rings to form a set of adjustable hydraulic packing. |
| Adhesion (a) | The state in which two surfaces are held together by interfacial forces which may consist of molecular forces or interlocking action, or both. |
| Adhesion (b) | The clinging or sticking of two (2) material surfaces to one another. In rubber parlance, the strength of bond or union between two (2) rubber surfaces or plies cured or uncured. The bond between a cured rubber surface and a non-rubber surface, e.g., glass, metal, wood, fabric. |
| Adhesion Failure | The separation of two materials at the surface interface rather than within one of the materials itself. |
| Adhesive - Contact | An adhesive that is apparently dry to the touch but which will adhere to itself upon contact. |
| Adhesive - Heat Activated | A dry adhesive film that is rendered tacky or fluid by application of heat or heat and pressure. |
| Adhesive - Solvent Activated | A dry adhesive film that is rendered tacky just prior to use by application of a solvent. |
| Aftercure | The amount of cure received after the termination of the cure proper. The term is also applied to the continuation of the curing effect that results from exposure of the article to heat in use, or from accelerated ageing. See Post cure. |
| Age resistance | The ability of a given material to resist deterioration of its properties caused by ageing. |
| Agglomerate | A cluster of particles of one or more compounding materials loosely held together. One of the primary roles of the mixing process is to break down agglomerates and promote good dispersion. |
| Aging (a) | (1) The irreversible change of material properties after environ- mental exposure for an interval of time; (2) Exposing materials to an environment for an interval of time. |
| Aging (b) | Changes in physical and mechanical properties that occur when low carbon steel is stored for some time. Aging is also accelerated by exposure of steel to elevated temperatures. |
| Aging (c) | A progressive change in the chemical and physical properties or rubber, especially vulcanized rubber, usually marked by deterioration. Aging may be retarded by the use or antioxidants. |
| Aging, Air Oven | Exposing materials to the action of circulating air in an oven at elevated temperature for a specified period of time. A more severe test than air test tube aging. |
| Aging, Air Test Tube | Exposing materials to the action of static air within a closed test tube inserted in an oven. Less severe than air oven aging, but more reproducible, as it prevents transfer of volatiles from one set of samples to another. |
| Air Checks | The surface markings of depressions due to trapping air between the product being cured and the mold or press surface. |
| Air-Curing | Curing or vulcanization in air at room or elevated temperatures. Normally at atmospheric pressure. |
| Air traps | "A rubber moulding defect that can occur either at the surface of the moulding due to air being trapped between the mould and the material, or within the moulding. The use of vacuum technology both at the extrusion and press stage can greatly reduce the risk of air traps." |
| Artificial Aging | Speeding up the natural aging cycle by heating the metal for a short time. Air Curing – The vulcanization of a rubber product in air, as distinguished from vulcanizing in a press or steam vulcanizer. |
| Aluminum | A pliable, lightweight metal that has good electrical and thermal conductivity, high reflectivity, and resistance to oxidation. |
| Aluminum Seal Rings | Sealing rings for pistons made from high grade aluminum alloy |
| Ambient Temperature | The temperature of the surrounding environment. |
| Amorphous | Having no definite shape; non-crystalline. |
| Anchor | Terminal point or fixed point from which directional movement occurs. |
| Angles | L-Shaped steel member used either as a duct flange or as the fastening connection of an expansion joint. Angles are also used for bolting the joint to the mating flange surfaces of the duct work or adjacent equipment. |
| Angular Movement | Movement which occurs when one flange of the expansion joint is moved to an out of parallel position with the other flange. Angular movement is measured in degrees. |
| Aniline point | The lowest temperature at which equal parts of aniline and a test liquid (usually oil) will mix or blend. In general, the lower the aniline point of an oil, the more a given rubber compound will swell, therefore the test indicates if an oil is likely to damage an elastomer with which it has come into contact. |
| Annealing | A process involving high-temperature heating and cooling of the as-rolled cold rolled steel substrate to make it softer and more formable |
| Anodize | The controlled oxidation of aluminum using an electro-chemical process to create a porous surface that is receptive to color dying. |
| ANSI | Abbreviation for “American National Standard Institute”. |
| Antidegradants | These are materials added to a rubber compound to reduce the effect of deterioration caused by oxidation, ozone, light and/or combinations of these. |
| Anti-Extrusion Rings | Also, called back-up rings or anti-extrusion rings, used to fit behind rubber o-ring seals to prevent extrusion into the gap between the metal pieces |
| Antiflex cracking agent | A material added to a rubber compound to reduce cracking caused by cyclic deformations. |
| Antioxidant | Usually organic and nitrogenous. A substance which inhibits, or retards, oxidation and certain other kinds of aging. Some antioxidants cause staining or discoloration of the rubber compound on exposure to light and are used only in black or dark- colored goods. Others (phenolic), described as non-staining, are used in white or light-colored goods. |
| Anti-ozonant: | A material added to a rubber compound to reduce damage resulting from the effects of ozone. |
| Antistatic Agents | Chemicals which when added to a rubber compound will help dissipate the buildup of electron charges, thereby eliminating a spark or shock risk |
| Anti-tack | Substance applied to the surface of an elastomer to stop it adhering either to itself or other elastomers. |
| Anti-vibration Mounts | Rubber molded pieces used as padding between a motor and the frame to prevent vibration transfer to the machine to which it is mounted. |
| AOV | Abbreviation for “Air Operated Valve”, a pneumatically actuated valve |
| API | Abbreviation for American Petroleum Institute |
| Apportionment | Referred to here as a part of Reliability Engineering. Synonymous with the term Reliability Apportionment, which is the assignment of reliability goals from system to subsystem in such a way that the whole system will have the required reliability? |
| Aqueous Solutions | Any fluid solution containing water. See further discussion under “pH.” |
| Aramid | A family of polymers used in a fibrous form as packing materials. Kevlar® is a DuPont trade name for an aramid fiber known for its excellent abrasion resistance, high tensile strength, and its characteristic deep yellow color. Nomex® is the DuPont trade name for another type of aramid fiber. |
| Arrhenius principle | An empirical relationship stating that the rate of a chemical reaction increases exponentially with temperature. |
| Ash | The residue of mineral matter left when a material is subjected to high heat and all organic material is burned away. |
| ASME | Abbreviation for American Society of Mechanical Engineers. |
| Assembled Splice | A splice that is constructed of multi layers of materials and connected by use of elastomeric cements, adhesives, etc. |
| Assembled Spring Inside Diameter | The inner diameter of the garter spring, with the ends securely joined. |
| Assortment Kits | A convenient package containing several sizes of the same seal, o-ring or retainer ring. |
| ASTM | Abbreviation for American Society for Testing and Materials. |
| Atmospheric cracking | Cracks on the surface of a material as a result of exposure to atmospheric conditions. This is usually as a result of sunlight and/or ozone. |
| AU | Abbreviation for polyester type polyurethane rubbers. |
| Autoclave | In the rubber sheet manufacturing industry, the device used to vulcanize (cure) elastomers. Typically the autoclave is drum-shaped, open on one end, and is steam-heated. |
| Automatic U-joints | Also called u-cups, u-cups or u cups. A “U” shaped sealing ring made from a strong pliable plastic or rubber. |
| Axial | In the direction of a shaft or stem axis. |
| Axial Clearance | The gap between the toe face to the head section and the inside surface of the inner case. |
| Axial Compression | The dimensional shortening of an expansion joint parallel to its logitudinal axis. Such movement being measured in inches or millimeters and usually caused by thermal expansion of the piping/ducting system. |
| Axial Extension | The dimensional lengthening of an expansion joint parallel to its logitudinal axis. Such movement being measured in inches or millimeters. |
| Axial squeeze | Compression applied to the top and bottom of a seal’s surface. |
| Axial Surface Roughness | Surface roughness of a shaft measured in a direction parallel with the centerline axis. |
| B | |
| Backer Coat | Usually refers to the coating on the reverse side of a prepainted sheet. The backer coating is generally not as narrowly specified with reference to its color, thickness and composition as is the topcoat. |
| Backrinding | Defect in which the rubber adjacent to the mold parting line shrinks below the level of the molded product, often leaving the parting line ragged and torn. |
| Backringing | Distortion at the mold parting line usually in the form of wrinkles, folds, tears or indention’s. In severe cases may cause over-all dimensional changes. |
| Back-Up Bars | Metals bars used for the purpose of clamping a rectangular/square expansion joint to mating ductwork. |
| Baffle/ Flow Liner | A metal shield that is designed to protect the expansion joint from the abrasive particles in the gas stream and to reduce flutter caused by air turbulence in the gas stream. Baffles/Flow Liners may be welded or bolted into position. |
| Baffle Rings | A ring used to slow the flow of fluids along a shaft. |
| Ball Valve Seats | A PTFE ring shaped to fit against the ball in a flow control valve. |
| Banbury Mixer | A specific type of internal mixer used to mix rubber or plastic compounds with fillers and other ingredients. |
| Bank | This term can relate to the amount of rubber adjacent to the nip of the rolls on both mills and calenders. |
| Barrel | That part of an extruder in which the screw rotates or the ram moves. |
| Batch | The product of the one mixing operation in an intermittent process. |
| Bead | The annular structure of wire, fabric and rubber compound as part of a tire that holds the tire to the rim of the wheel. |
| Bearings | A machined or molded plastic ring used as a guide ring or wear ring in a hydraulic cylinder. |
| Bearing Seals | A seal ring made to snap-fit into a ball, roller or spherical bearing to exclude dust, dirt or trash. |
| Beater Add (Beater Saturated) | A manufacturing process for making non-metallic sheet that employs a paper-making process using Fourdrinier or cylinder-type paper machines. |
| Belleville Washer | A disc spring washer used to live-load a packing gland. |
| Bellows | A corrugated rubber or plastic piece which can stretch with a shaft to keep the shaft clean. |
| Belts | A v-belt, flat belt or drive belt made from plastic or rubber. |
| Belt Type Expansion Joint | An expansion joint in which the flexible bellows portion of the joint is made flat and bolted or clamped to metal adapter flanges or frames. |
| Bench Mark | Marks of known distance apart applied to a test specimen and used to measure elongation. |
| Bench Test | A modified service test in which the service conditions are approximated using laboratory equipment not necessarily identical with the equipment in which the product will be employed. |
| Bevel Cut | An angled cut at the seam (or joint) of a packing ring. |
| Bezel | A grooved rim, which holds another covering or item. Similar to a frame. |
| Bias | The angle at which the textile material is cut with respect to the running edge of the fabric. |
| Bias Angle | (1) Acute angle between the direction of the cut and the diameter of the wrap in the production of wrapping for hose; (2) Acute angle between the direction of the cut and the direction of the cords in the production of fabric plies. |
| Billet | A large rod of PTFE; the initial stage of manufacture for skive PTFE. |
| Bill of Material | Total list of all components/materials required to manufacture the product. |
| Blank | A measured weight or dimension of a rubber compound suitable to fill the cavity of a compression or transfer mould. Usually the blank weight/volume is slightly higher than the finished component to allow for full compression in the cavity. |
| Bleeding | The flow of a compounding material, often oils or lubricants, from the surface of vulcanised or unvulcanised rubber. Can also be referred to as leaching. |
| Blemish | A mark, deformity, or injury which impairs the appearance. |
| Blister | A cavity or sac that deforms the surface of a material. |
| Blocking Agent | A coating applied to braided packing to fill the area between the fibers, blocking the passage of media through the body of the braid, and improving its sealing characteristics. This may be a grease, an oil, or a PTFE dispersion. |
| Bloom | A solid or liquid material that has migrated to the surface of a rubber material normally leaving a waxy or milky deposit. |
| Blow | The volume expansion that occurs in the production of cellular or sponge rubber resulting from the action of a blowing agent incorporated into the compound. |
| Blowing agent | A compounding ingredient introduced into an elastomer which produces a gas by chemical or physical action during the processing stage. Used in the manufacture of sponge rubbers. |
| Bolt Hole Pattern Or Drill Pattern | The systematic location of bolt holes in the mating flanges and expansion joint flanges where joint is to be bolted. |
| Bolt In Baffle/Flow Liners | A baffle that is designed to be bolted to the breach flange. NOTE: Bolt in baffles/flow liners require the use of a seal gasket. |
| Bolt Torque | The amount of twisting or turning effort (expressed as Ft- Lb or N-m) required to turn the nuts on a gland follower. The load that the gland follower exerts on a valve packing set can be expressed in terms of a specific bolt torque. |
| Bond | The union of materials by use of adhesives, usually used in related parts vulcanized after attaching. |
| Bonded Seals | A flat steel washer with a rubber sealing ring molded into the center to fit over a bolt to provide a seal. |
| Bonding Agents | Substances or mixtures of substances that are used for attaching rubber to metal, fabrics or other substrates. Generally the rubber compound is vulcanized by heat in the process. Cyclized rubber or rubber isomers, halogenated rubber, rubber hydrochloride, reaction product of natural rubber and acrylonitrile, polymers containing diisocyanates, are all used. |
| Boot Or Belt | The flexible element of an expansion joint usually consisting of rubber and rubbercoated fabric. |
| Bore Diameter | The outside dimension of the annular space that packing is inserted into. Also called the stuffing box bore. |
| BR | Abbreviation for rubber based on butadiene. |
| Braid | Yarns or filaments woven together to form a hollow or solid structure. A braid may have a round (Braid over Braid), square (Simple Crossing Pattern), or LATTICE (Interlocking) weave pattern. Braids may have round, square, or rectangular cross-sectional shape. |
| Braid Over Braid | A type of braiding construction in which a series of round braided layers are braided on top of one another. |
| Braid Over Core | A type of braiding construction in which yarns are round braided over a core. Cores may be composed of an elastomer extrusion, a plastic compound extrusion, another braid, or other materials. |
| Braider | A mechanical device which interweaves yarns to produce a braid. |
| Breach Flange Or Duct Flange | The portion of the duct system, usually an angle or a channel that interfaces with the flange of the expansion joint. |
| Breach Opening | The distance between the mating duct flanges in which the joint is to be installed. |
| Breakdown | The plasticising of raw rubber prior to the incorporation of compounding ingredients. This is normally the first stage of the mixing process. |
| Break-In Lubricant | A lubricant added to the surface of braided packing. Break-in lubricants are used to protect the packing from charring during the initial start-up of rotating equipment, such as pumps and mixers. |
| Breakout friction | The force required to initiate sliding between a rubber seal and the surface in which it is in contact. |
| Brittleness | Tendency to crack when subjected to deformation. |
| Brittle point | The highest temperature at which a rubber specimen will break under a measured sudden impact. This is one indication of low temperature flexibility. |
| BS | Abbreviation for British Standard. |
| BSI | Abbreviation for British Standards Institution. |
| Bubble Sealing | A sealing level that does not exceed 1.0 x 10-4 atm cc/sec of Helium. |
| Bulk Density | The density of loose material (powder, cubes, etc.) expressed as a ration of weight to volume (lbs./ft cubed or grams/cm cubed). |
| Bulk Dipping | An economical method for applying coating to a packing material simply by dipping a container of braid into a tank containing the coating material. |
| Bull Ring | See “Anti-Extrusion Ring”. |
| Bumpers | A rubber or plastic part used to prevent metal-to-metal contact. |
| Bumping | The operation of opening and closing the press rapidly in the first stages of the cure. This action is designed to drive out any trapped air in the mould cavity. Also referred to as breathing. |
| Buna N | A general term for the copolymers of butadiene and acrylonitrile. Typical commercial polymers are Hycar and Paracril. |
| Buna S | A general term for the copolymers of butadiene and styrene. |
| Burst | A rupture caused by internal pressure. |
| Bushing | A rubber or plastic spacer to provide a wear surface around a shaft. |
| Butadiene | CH2=CH-CH=CH2. A gaseous hydrocarbon of the diolefin series, boiling at 5~C. Also known as erythrene, divinyl, pyrollylene, polymerizable to a synthetic rubber, polybutadiene. Butadiene is the chief raw material for making the synthetic rubbers today. Co polymerized with styrene it yields SBR or GR-S; with acrylonitrile the various Buna N or nitrile synthetic rubbers are obtained. |
| Butt Cut | A straight cut at the seam (or joint) of a packing ring. |
| Butt Joint | Joining two ends of material whereby the junction is perpendicular to the ID of an O-ring. |
| Butt Splice | A joint made before or after vulcanization in a rubber part by placing the two pieces to be joined edge to edge. |
| Butyl | A synthetic rubber of the polybutene type exhibiting very low permeability to gases. |
| Butyl Rubber | A copolymer of isobutylene and isoprene, polymerized almost instantaneously in methyl chloride with aluminum chloride at about ñ140F. Butyl is resistant to ozone and the action of many other corrosive chemicals. Butyl rubber is resistant to permeation by gases. |
| C | |
| CAD | Abbreviation for computer-aided design. |
| Calender | A step in the production of braided packing where a braided material is fed through rollers to squeeze it to its finished size. 2) A machine which is used to calender a braid. |
| Caliper | The thickness of a sheet material. The thickness is usually expressed in one thousands of an inch and in millimeters (i.e. 0.050 is expressed as 50 mils). |
| CAM | Abbreviation for computer-aided manufacture. |
| Camber | The deviation of a side edge from a straight line, the measurement being taken on the concave side with a straight edge. |
| Carbon Black (a) | Elemental carbon in finely divided form used to reinforce elastomeric compounds. |
| Carbon Black (b) | Finely divided carbon formed by the incomplete combustion of natural gas or petroleum in large, closed furnaces. |
| Carbonization | The reduction of a material to carbon. |
| Carbon Black Masterbatch | A mixture of an elastomer with a high content of carbon black. It may be produced by mill or Banbury mixing the black into the rubber or adding the black to a synthetic rubber latex such as SBR followed by coagulation, washing and drying of the mixture. |
| Carbon Steel | Steel which owes its properties chiefly to carbon without substantial amounts of other alloying elements; also known as straight carbon steel or plain carbon steel. |
| Case Od Sealer | A coating applied to the case OD to prevent leakage between the seal case and the housing bore. |
| Cast | To form a part by filling a mold cavity with a liquid resin or rubber and then curing to a solid at room temperature or with heat, but generally without pressure. |
| Catalyst | A chemical in small quantities which accelerates a chemical reaction without itself necessarily becoming part of the final product. |
| Cavitation | An undesirable phenomenon that sometimes occurs in pumps, in which small vapor bubbles are created in the area of the impeller. As these vapor bubbles move along the vanes of the impeller to an area of higher pressure, they rapidly collapse. This collapse or “implosion” is so rapid that it may be heard as a rumbling noise or felt as vibration. The forces generated as a result of cavitation may damage the impeller or even the packing set. |
| Cavity | The area on a die where blades are formed to cut. A die with 1 or more cutouts that are the same size for each label cut. |
| Cell | A single, small open space surrounded partially or completely by walls (as in sponge). |
| Cellular Material | A generic term for materials containing many cells, either open or closed, dispersed throughout the mass. |
| Cellular Rubber | Rubber products which contain cells or small hollow receptacles. The cells may either be open or interconnecting or closed and not interconnecting. |
| Celsius | A temperature scale in which 0°C is the freezing point and 100°C is the boiling point of water (formerly called centigrade). |
| Cement (Rubber) | An adhesive that is either a liquid dispersion or a solution of raw or compounded rubber, or both, usually dissolved in solvent, and used to bond rubbers to other rubber or non-rubber products. |
| Centering Ring (Or Guide Ring) | A solid piece of metal used on the OD of a gasket winding in order to center the gasket properly on the sealing surface by locating the ring against the studs in the connection. The ring also acts as a compression limiter to prevent overcompression of the winding. |
| Centrifugal Pump | A type of pump which relies on the rotation of an impeller to generate pressure and cause flow. |
| Chalking | The formation of a residue on the surface of a rubber which is commonly as a result of UV damaging the surface of the material. |
| Characteristics Matrix | An analytical technique for displaying the relationship between process parameters and manufacturing stations. |
| Checking | The short, shallow cracks on the surface of a rubber product, resulting from damaging action by environmental conditions. |
| Checking. Sunlight | The development of minute surface fissures as a result of exposing rubber articles to sunlight, generally accelerated by bending or stretching. |
| Chemical Resistance | The resistance offered by elastomer products to physical or chemical reactions as a result of contact with or immersion in various solvents, acids, alkalis, salts, etc.. |
| Chemical Treatment | An aqueous solution of corrosion-inhibiting chemicals, typically chromates or chromate/phosphate. |
| Chevron Packings | Also called V-Packing, Vee packing, Chevron Packing, Parachute packing or v-set packing. A complete vee packing set contains multiple “V” shaped sealing rings stacked and nested together with a male adapter on one end and a female adapter on the other end. |
| Chloroprene | 2-Chloro-l, 3-butadiene, a volatile, colorless liquid which boils at 59c., synthesized from acetylene. It is used in the manufacture of neoprene, which is obtained by polymerizing chloroprene under suitable conditions. |
| Chlorosulfonated Polyethylene | An elastomeric material sold as Hypalon*. |
| C.I. | The abbreviation for cloth- inserted, indicating a sheet of rubber containing one or more plies of fabric covered with rubber. |
| Circumferential Surface Roughness | Surface roughness of a shaft measured in a direction (plane) normal to the centerline axis. |
| Clamp Bars | Same as back-up bars. |
| Closed Cell | A cell totally enclosed by its walls and hence not interconnecting with other cells. |
| Cloth Both Sides (Cbs) | Rubber sheet consisting of a ply of fabric or cloth on each surface. CDS: Cloth on just one side. |
| Cloth Inserted (Ci) | Rubber sheet containing one or more plies of fabric or cloth, in which the fabric is completely covered with rubber. |
| CM | ASTM designation for Chlorinated Polyethylene. |
| CO | Epichlorohydrin homopolymer |
| Coagent | An ingredient added to a rubber compound, usually in small amounts to increase the cross-linking efficiency of non-sulphur vulcanising systems, such as organic peroxides. |
| Coated fabric | A product constructed by coating a fabric with a rubber, resulting in a flexible material which can be moulded into products or used in conjunction with rubbers to provide higher rigidity and improved extrusion resistance. |
| Cocked Assembly | An installation in which the plane of the outside seal face is not perpendicular to the shaft axis. |
| Coefficient Of Friction | Between rubber and dry surfaces, is the ratio of the force required to move one surface over the other to the force pressing the two surfaces together. |
| Coefficient of thermal expansion | The average expansion per degree over a stated temperature range, expressed as a fraction of the initial dimension. |
| Coil | One turn of the coiled wire garter spring. |
| Coil Breaks | Creases or ridges in sheet that appear as parallel lines across the direction of rolling, and that generally extends the full width of the sheet or strip. |
| Coker Gasket | Gasket for the coke unit in petroleum refineries. |
| Cold Bend | A test in which a sample of wire or cable is wound around a mandrel of a specified size within a cold chamber, at a specified temperature for a given number of turns at a given rate of speed. The sample is removed and examined for defects or deterioration in the materials of construction. |
| Cold flexibility | Flexibility of the elastomer following exposure to a specified low temperature for a specified period of time. |
| Cold flow | Continued deformation under stress. |
| Cold resistant | The ability of an elastomer to function at low temperatures. |
| Cold Rolled Products | Flat rolled products for which the required final thickness has been obtained by rolling at room temperature. |
| Cold Working | Applying a mechanical force (such as deep drawing) to metal at room temperature at such a rate that strain-hardening occurs. |
| Color Standard | A painted sheet panel with a prescribed color of paint representing the precise color it is intended to produce in the prepainted sheet. The color standard will preferably also be expressed in terms of physical attributes of hue, lightness and saturation called tristimulus values or derivatives of these values. A complete color standard definition will usually include painted panels representative of the limits of acceptable deviation from the precise standard color as well. |
| Coefficient of Expansion | The coefficient of linear expansion is the ratio of the change in length per degree to the length at 0 Celsius. The coefficient of surface expansion is two (2) times the linear coefficient. The coefficient of volume expansion (for solids) is three (3) times the linear coefficient. The coefficient of volume expansion for liquids is the ratio of the change in volume per degree to the volume at 0 Celsius. |
| Commercial Steel (CS) | Sheet of this quality is for simple bending or moderate forming. Commercial Steel sheet can be bent flat upon itself in any direction at room temperature. |
| Compact Seals | Multi-piece seal sets, generally used as piston seals in a hydraulic cylinder. Made to fit in a limit space, compact piston seals contain a primary sealing component, guide rings and back-up rings in one convenient set. |
| Compatibility | The ability of different materials to blend and form a homogeneous system. |
| Composite | A homogeneous material created by the synthetic assembly of two or more materials (a selected filler or reinforcing elements and compatible matrix binder) to obtain specific characteristics and properties. |
| Compound (a) | A term applied to either vulcanized or unvulcanized mixtures of elastomers and other ingredients necessary to make a useful rubber-like material. |
| Compound (b) | In chemistry, it is the material resulting from the chemical union of two or more elements in definite proportions and in which the properties of the individual elements have disappeared. – 2). In rubber manufacture, it is the composition or formula of stock, the ingredients of which, however, may not all be chemically combined and is therefore more of a physical mixture. |
| Compounding Material | A substance used as part of a rubber mix |
| Compressed Height | The height of a packing ring or packing set after it has been compressed in the stuffing box. |
| Compressed Sheet | A gasketing material primarily containing fibers, rubber and fillers, manufactured on a special calender (known as a “sheeter”) in such a manner that the compound is caused to build up under high load as an oriented sheet on one roll of the sheeter. |
| Compressibility | The quality or state of being compressible. In the case of gasketing, it is the percent loss of thickness when subject to a given load. |
| Compression Deflection Characteristics | The tests for compression-deflection characteristics constitute methods of compression stiffness measurement. One compression test involves the determination of a load required to case a specified deflection, and another is a compression test in which a specified weight or compressive force is placed on the specimen and the resulting deflection is measured and recorded. |
| Compression Limiter | Ring used in conjunction with a seal to control or limit compression of the seal. |
| Compression moulding | A moulding process in which an uncured rubber blank is placed directly in the mould cavity and compressed to its final shape by closing the mould. This process normally results in excess material in the form of flash. |
| Compression Packing | A deformable material used to prevent or control the passage of a pressurized fluid between surfaces that move in relation to each other. |
| Compression set | The residual decrease in thickness of a test specimen measured 30 minutes after removal from a suitable loading device in which the specimen has been subjected for a definite time to compressive deformation under specified conditions of load application and temperature. Method a measures compression set of vulcanized rubber under constant load. Method B employs constant deflection. |
| Compressive Stress | Force per unit area compressing (squeezing) the seal. |
| Conductive | To conduct or transmit heat or electricity. |
| Conductive Adhesive | An adhesive that incorporates conductive fibers. These fibers have the ability to conduct electricity through the thickness of the adhesive and/or in the plane of the adhesive. Ideal for EMI/RFI shield and EMI/RFI gasket attachment. |
| Conductive rubber | A rubber which has been produced such that it is capable of conducting electricity. |
| Conflat Flange | A common vacuum industry flange. |
| Conformability | The ability of an adhesive tape to mold itself to the shape of an object without wrinkling or creasing. Converting – The process of taking a material or adhesive and altering it from one form to another. |
| Contact Approach Angle | Synonym: Angle, Outside Lip. |
| Contact Line | The line of intersection between the outside and inside lip surfaces of a radial lip seal. In a cross-sectional view, this intersection is illustrated as a point. |
| Contact Line Height | The axial distance from the outside seal face to the lip contact line. |
| Contact stain | Discoloration of a product by another material or by a rubber article in the area directly touching it. |
| Contact Width | The width of the lip contact area of a radial lip seal, measure in the axial direction. |
| Continuous Operating Temperature (Cot) | Actual operating temperature of service. |
| Continuous Vulcanization | A process where the vulcanization of a rubber compound takes place in a continuous manner such as by drawing a hose or coated wire through a jacketed tube which may be 200 ft. long and under internal steam pressure of 1.4 MPa (200 psi). Or also by pass- ing through a liquid salt or bead bath at 204°C (400°F) at atmospheric pressure. |
| Copolymer (a) | A polymer consisting of two different monomers chemically combined. |
| Copolymer (b) | A copolymer is a high polymer consisting of molecules containing large numbers of units of two or more chemically different types in irregular sequence. Butadiene (78) and styrene (22) forms a copolymer known as GR-S. |
| Copper Seal Rings | Rings made from thin copper formed over fibrous filler to seal in high temperature. |
| Corners | Molded, formed, or radius belt corners of rectangular/square expansion joint. |
| Corrosion | Gradual chemical or electrochemical attack on a metal by atmospheric moisture or other agents. |
| Corrosion Inhibitor | An ingredient added to packing, which decreases or eliminates the possibility of galvanic corrosion in the stuffing box. Corrosion inhibitors may be classified as either passive or active. See “Active Inhibitor”, “Passive Inhibitor”, and “Galvanic Corrosion”. |
| Corrugated | Formed into alternating peaks and valleys; typically limited to sheet metal 0.024″ and thinner. |
| Cover | The outermost ply of material of an elastomeric expansion joint. |
| CR | Abbreviation for chloroprene rubbers |
| Crack | A sharp break or fissure in the sealing element. |
| Cracking | A sharp break or fissure in the surface, generally due to excessive strain. |
| Crazing | A surface effect on rubber articles characterized by many minute cracks. |
| Creep | The deformation, in either cured or uncured rubber under stress, which occurs with lapse of time after the immediate deformation. |
| Creep Relaxation | In a flange gasket, loss of stress accompanied by constantly decreasing compressed thickness. This type of relaxation is encountered in bolted flange joints. |
| Critical Surface | Intended for material applied to critical exposed/painted applications where cosmetic surface imperfections are objectionable. The prime side surface will be free of repetitive type imperfections, gouges, scratches, scale and slivers. This surface can only be furnished as a pickled product. |
| Crosshead Extruder | An extruder so constructed that the axis of the emerging product is a right angle to the axis of the extruder screw, commonly used for applying the cover to braided or spiraled hose or covering wire conductors. |
| Cross linked | The establishment of a chemical bond between the molecular chains of a given polymer, thereby enhancing physical properties. |
| Cross-linking | (see also vulcanising): The formation of chemical bonds between polymer chains to give a threedimensional network structure. |
| Cross-link density | A measure for the relative number of cross-links in a given volume of elastomer. |
| Cross-Section | 1) The view of a part as if it were cut to show its internal structure. 2) The distance between the shaft or stem surface and the bore of a stuffing box. See also “Packing Space”. 3) The shape of a packing ring at a cut. A packing ring could have a square, rectangu- lar, or round crosssection. |
| Crude Rubber | Refers to raw natural rubber. |
| Crumb rubber | Vulcanised waste or scrap rubber which has been ground down to a known mesh size and can then be added to new compound as a filler. |
| Crush Test | A specification test employed for o-ring hydraulic packings in which the ring, in twisted condition, is subjected to a severe compressive load. |
| Crush Washers | A washer made to be crushed to form a seal. |
| Crown | A contour on a sheet where the thickness increases from some edge measurement to the center. |
| Cryogenic | Of or relating to a very low temperature. |
| Crystallinity | The orientation of the disordered long-chain molecules of a polymer into repeating ordered patterns. Many rubber materials have a degree of crystallinity, and some will tend to crystallise under certain conditions. The degree of crystallinity effects stiffness, hardness, low temperature flexibility and heat resistance. |
| CSM | ASTM designation for Chloro Sulfonyl Polyethylene (Hypalon*) |
| Cup And Cone | The shape of certain types of die-formed ring sets. In a “cup and cone” set the rings have conical surfaces that nest into one another. |
| Cup Packing | Sealing devices made in the shape of a cup with outer lips curved upward usually made from rubber, fabric reinforced rubber or polyurethane. |
| Curatives | The collective term for the chemicals involved in curing the rubber material. These include, for example, accelerators, vulcanising chemicals such as sulphur, and activators. |
| Cure | The act of vulcanization. See Vulcanization. |
| Cure time | The required amount of time needed to complete the curing process to a pre-determined level. The time taken to cure is depen- dent on the temperature, material type and section of the rubber profile. |
| Curing Agent | A chemical which will cause cross linking to occur. |
| Curing temperature | The temperature at which vulcanisation takes place. |
| Cushioning Seals | Sealing rings mounted into a cylinder to cushion the stroke or prevent metal to metal contact. |
| Custom Molded Products | Special shaped parts molded from rubber or plastic made to fit the machine or device it is used in. |
| Cut | The distance between cuts or parallel faces of articles produced by repetitive slicing or cutting of long preshaped rods or tubes such as lathe cut washers. Cut Edge – Removal of the as-rolled hot mill edge. Coil ends are cropped back to gauge when cut edge is ordered. Cut Outs – The spaces or holes designated in the label. This material is punched and removed during the manufacturing process. |
| Cut-Ring Set | A braided material cut into individual rings for a specific stem/stuffing box size and packaged as a set. |
| Cycle | One complete operation of a molding press from closing time to closing time. |
| Cycle And Adjust Procedure | A procedure used to consolidate a packing set after it has been installed in a stuffing box. This procedure helps to reduce the amount of gland load relaxation that occurs after the valve has been put into service. |
| Cycletight® | VSP Technologies’ family of “spring loaded,” corrugated insert ePTFE gaskets. Enhances the handleability and performance capa- bilities of conventional expanded PTFE gaskets. |
| Cycletight® Type 7 Manway Gasket | Semi-metallic expanded PTFE gasket designed for use in general purpose tank car manway dome lids. VSP Technologies’ patented construction allows the CycleTight® gasket to fit securely into the manway cover to provide low assembly torque and multiple reuses across a broad range of chemical services. |
| Cystalinity | Stretched natural rubber forms a high oriented state and shows X-ray diffraction patterns and other properties common to truly crystalline materials. The amorphous and crystalline regions are not mechanically separable phases, but the same molecule may at the same time have part of its length in a crystalline, and the remainder in an amorphous region. |
| Cylinder | A device which converts fluid power into linear mechanical force and motion. It usually consists of a moveable element such as a piston and piston rod, plunger rod, plunger, or ram, operating within a cylindrical bore. |
| Cylinder Bore | The internal diameter of the cylinder. |
| Cylinder Double Rod | A cylinder with a piston rod extending from each end. |
| Cylinder, Ram-Type | A cylinder in which the piston and piston rod are one and the same. These cylinders are single-acting and are mounted vertically: the weight of the load retracts the cylinder. |
| Cylinder Single Rod | A cylinder with a piston rod extending from one end. |
| D | |
| Damper | The use of a variety of materials to deaden or damp a vibration. |
| Damping | The property of a material or system that causes it to convert mechanical energy to heat when subjected to deflection. In rubber, the property is caused by hysteresis. |
| Deep Drawing | The process of working metal blanks in dies on a press into shapes which are usually more or less cup-like in character. |
| Deep Drawing Steel (DDS) | Sheet of this designation should be used when Drawing Steel will not provide a sufficient degree of ductility for fabrication of parts having stringent drawing requirements, or applications that require the sheet be free from aging. This quality is made by special steelmaking and finishing practices. |
| Deflashing | The process of removing excess material from the flash-line resulting from the moulding process.Various methods exist, including buffing and cryogenic trimming. |
| Deformation | A stress induced change of form or shape. |
| Degassing | The passing of a gas out of a rubber, normally generated by the volatile ingredients in the rubber mix which are activated at elevated temperatures. |
| Delamination | The separation of layers of rubber (normally in a plied format) or the rubber separating from a surface to which it is bonded. |
| Demattia Flex Test | This laboratory test to determine the flexible life of a material. It measures the rate of formation of cracks in a standard molded test bar. |
| Demoulding | The operation of removing a vulcanised rubber product from the mould in which it has been cured. This can be done carefully by hand, but in some cases pins or brushes can be incorporated into the mould or press to perform this function automatically. |
| Density | The weight per unit volume of a material – usually expressed in PCF (pounds per cubic foot). |
| Dent Resistant | BH Series- Sheet of this designation is produced from partially stabilized steel and offers a unique combination of as-received formability and final properties after fabrication. Sheet of this designation combines strength and high formability. Although this steel is non-aging at room temperature, it gains strength from work-hardening during fabrication and from carbon-aging during paint-baking. (Sometimesreferred to as “bake hardenable.”) |
| Desiccant | A rubber compounding ingredient used to absorb moisture irreversibly, particularly for the purpose of minimising the risk of porosity and/or blisters during vulcanisation. |
| Design Failure Mode and Effects Analysis (DFMEA) | An analytical technique used by a design responsible engineer/team as a means to assure, to the extent possible, that potential failure modes and their associated causes/mechanisms have been considered and addressed. |
| Design for Manufacturability and Assembly | A simultaneous engineering process designed to optimize the relationship between design function, manufacturability; and ease of assembly. |
| Design Information Checklist | A mistake proofing checklist designed to assure that all important items are considered in establishing design requirements. |
| Design Pressure/Vacuum | The pressure or vacuum condition that exists during system start-up and/or shut-down operations. During this cyclic phase in the system, both pressure and vacuum conditions may occur. |
| Design Reviews | A proactive process to prevent problems and misunderstandings. |
| Design Temperature | The maximum or most severe temperature expected during normal operation caused by equipment failure. (See Excursion Temp.) |
| Design Validation | Testing to ensure that product conforms to defined user needs and/or requirements. Design validation follows successful design verification and is normally performed on the final product under defined operating conditions. Multiple validations may be performed if there are different intended uses. |
| Design Verification | Testing to ensure that all design outputs meet design input requirements. Design verification may include activities such as: |
| Design Review | Performing Alternate Calculations – Understanding Tests and Demonstrations – Review of Design Stage Documents Before Release |
| Diametral clearance gap | The difference in diameters between two mating surfaces. |
| Diaphragm Sheet | PTFE or sheet rubber (generally fabric-reinforced) from which flat diaphragms are cut. |
| Die | The shaped plate fitted in the head of an extruder designed to create a profile suitable for the moulding process. |
| Dielectric strength | The measure of a product’s ability to resist passage of a disruptive discharge produced by an electric stress; the voltage that an insulating material can withstand before breakdown occurs. |
| Die Cut | Shaped articles cut with a die from a sheet of material |
| Die Cutting | When parts are cut into individual pieces using a steel rule die. Sharp steel rule dies are formed to desired shape in a wooden carrier for cutting labels. A die may be one or more “up” (one cavity or more). Common knife refers to a multiple-up die with a kiss cut or a single knife cut to the release liner between labels, known at LustreCal as a strip die. The other basic format is a multiple die with space between cavities, known at LustreCal as an individual units die. The space between cavities allows for cutting down to individual units. A single cavity die is an individual unit’s die. |
| Die Forming | A manufacturing process in which braid or graphite foil is compressed in a mold to form a ring. |
| Die Guide | A guide around a label that assists with positioning of die and /or keeping art to edge tolerances. Die Impression – A piece of material that has been cut with a die, but not cut all the way through. |
| Die swell | The change in dimensions of an extruded rubber section as it exits the die. This swell is mainly due to the elastic recovery of the material. |
| Differential pressure | The difference in pressure between the high-pressure and low-pressure side of a sealing system. |
| Dimensional stability | The ability of the elastomer to retain its original shape and size having been exposed to a combination of stresses and temperatures. |
| DIN | Abbreviation for Deutsches Institut für Normung. English translation is German Industry Standard – it is the European equivalent to ASTM. |
| Dipping | A method of manufacturing rubber articles by dipping a former of the shape required into a rubber solution. |
| Discharge Pressure | The fluid pressure measured on the discharge (or outlet) side of the pump where the fluid exits the volute. |
| Dished Diaphragm | A molded diaphragm in which the entire center is depressed below the plane of the rim. |
| Discs | Flat, round saucer shaped pieces made from rubber or plastic. |
| Disperse | To cause particles or molecules of matter to separate and become uniformly scattered throughout a medium. In a rubber compound, the particles of compounding ingredients are dispersed in the rubber. In latex, rubber globules are dispersed in an aqueous medium. |
| Dispersion | The distribution of particles throughout a medium. For rubbers this often refers to the distribution of compounding ingredients in rubber mix. |
| Distributor Seals | Sealing rings used to seal in oil and seal out dust, dirt or trash on an automobile engine electric spark distributor. |
| Double Acting Seals | Seal rings which seal in two directions, on the push and the pull stroke of a hydraulic or pneumatic cylinder. |
| Double-Coated | Tape with adhesive on both sides. |
| Dough | Rubber compounded and swollen in solvent and worked on a ‘wet’ mill until it reaches the consistency of dough. It is then applied behind the doctor blade of a spreading machine through which the fabric to be coated is passing. Self-curing doughs are used in the repair of rubber products (tyre tread cut-filling) and the splicing of belting. |
| Drawing Steel (DS) | Sheet of this quality has a greater degree of ductility and is more consistent in performance than Commercial Steel because of higher standards in production, selection and melting of the steel. |
| Drill Pattern | The systematic location of bolt holes on the mating and expansion joint flange through which the expansion joint will be attached. |
| Drum Cure | A method of vulcanizing rubber in which the product is wrapped around a drum and cured in hot air or steam, usually with a separator or wrapping jacket. |
| Dumbbell | A standard, flat strip specimen shaped like a dumbbell that is used in many physical tests. |
| Durometer Hardness | An arbitrary numbering scale that indicates the resistance to indentation of the indentor point of the Durometer. High values indicate harder materials. The value may be taken immediately, (highest point) or after a very short specified time. |
| Dynamic Properties | Mechanical properties exhibited under repeated cyclic deformations. |
| Dynamic properties | The response in an elastomer to forces applied to them. |
| Dynamic seal | A seal used in an environment that is subjected to any type of movement relative to its position and that of the contact / sealing surface. |
| Duck | A compact, firm, heavy, plain weave fabric made from cotton or synthetic fibers, or a combination of both. Duck is also known as canvas, army duck, belt duck harvester duck, hose duck and shoe duck. |
| Duct Id | The inside dimension of the ductwork measured from the duct walls prior to any form of coating. |
| Ductility | The ability to permit change of shape without fracture. In flat rolled steel, ductility is usually measured by hardness or mechanical properties in a tensile test. |
| Dumb-Bell (Test-Piece) | In the physical testing of rubber, a strip test-piece is used that is shaped like a dumb-bell, i.e., constricted in the middle and flaring out at the ends, as distinguished from circular or ring test-piece. The dumb-bell is the most commonly used form or test-piece. Dimensions are set by ASTM standards. |
| Duocone Seals | A special cone-shaped sealing ring. |
| Durability | The probability that an item will continue to function at customer expectation levels, at the useful life without requiring overhaul or rebuild due to wearout. |
| Durometer | The most common Durometer. Type A or A-2 is an instrument for determining the hardness or rubber by measuring its resistance to the penetration (without puncturing) of a blunt indentor point impressed on the rubber surface against the action of a spring; a hand and special scale indicate the resistance to penetration 01. “Hardness”. The scale reads from zero (0) to 100, zero (0) being very soft and 100 being very hard. The Type D durometer has a sharp indentor point and is used to measure varying degrees of hard rubber up to ebonite. |
| Durometer Hardness | An arbitrary numerical value measuring the resistance to indentation (without puncturing) of the indentor into the surface or rubber. |
| Dust Seals | Seals used to exclude dust from a machine or device. |
| Dynamic Runout | Twice the distance the center of the shaft is displaced from the center of rotation and expressed in TIR. That runout to which the seal lip is subjected due to the outside diameter of the shaft not rotating in a true circle. Synonym: Shaft Runout. |
| Dynamic Seal | A seal required to prevent leakage past parts which are in relative motion. The opposite of static seal. |
| E | |
| Ebonite | ‘Hard rubbers’ which are formed when they are cured with high levels of vulcanising agents. |
| Eccentricity | The distance that the central axis of a shaft is offset from the center of the stuffing box through which it passes. |
| ECO | Epichlorohydrin copolymer with ethylene oxide. |
| E-Coating | A coating process where an electric charge is used to bond the paint to the metal outer ring for Garlock spiral wound gaskets. The result is a smooth, drip-free finish with superior chip resistance. The process is also environmentally friendly, as no ozone-depleting propellants are used in the process. |
| Efficient vulcanisation | A term applied to vulcanisation systems in which sulphur or a sulphur donor is used very efficiently for cross-linking the rubber. |
| Elasticity | The property of an article which tends to return to its original shape after deformation. |
| Elastic Limit | The limiting extent to which a body may be deformed and yet return to its initial shape after removal of the deforming force. |
| Elastic Modulus | The value of the load (in pounds per square inch of original cross-section) required to give an intermediate elongation, is usually called the modulus at that elongation. The expression used is “modulus at 300 percent elongation.” Tensile-stress observations of this sort arc exceedingly useful in characterizing a particular compound, since by indicating the position and shape of the stress- curve. They show the relative toughness of the vulcanization. |
| Elastomer | A macromolecular material which, in the vulcanized state, at room temperature can be stretched repeatedly to at least twice its original length and which, upon release of the stress, will immediately return to approximately its original length. |
| Elongation | In the physical testing of rubber, the increase in length of a test-piece when stretched, usually expressed as a percentage of the original length; for example a 1″ piece stretched (0 6″ has an elongation of 500%. Elongation at break — the elongation of a test-piece at the moment of rupture, usually expressed as percentage of the original length. |
| Elongation at break | The elongation measured at the point of rupture. A high value is important if substantial stretching is required during fitting of the product. |
| Elongation, per cent | The extension of a specimen as a result of an applied tensile stress, expressed as a percentage of the original length. |
| Elongation, Ultimate | The elongation at time of rupture. |
| Emboss | A process of forming a portion of the substrate to rise above the normal level of the substrate. An example is a button or a raised logo. |
| Embossed sheet | An embossed sheet is one having a prominent, impressed texture or pattern on its surface(s). If the defined texture is applied to essentially on surface only, it is most properly termed a coined surface. If the texture or pattern carries through the entire body of the sheet and appears on both surfaces it is a true embossed surface. |
| Embossing | The production of a design in relief on a rubber surface by molds or by engraved rolls. |
| Embrittlement | A rubber compound becoming brittle during low or high temperature exposure or in the process or aging. |
| Emissions | Gaseous or liquid leakage given off by a piece of equipment. This usually refers to volatile organic hydrocarbons monitored by government agencies. It is typically expressed in parts per million volumetric (ppmv, or simply ppm). |
| Endothermic | A chemical reaction that absorbs heat energy. |
| End Play | A measure of axial movement encountered or allowed, usually in reference to the shaft on which the seal lip contacts. |
| End Ring | A ring used at the top or bottom of a packing set, usually functioning as a wiper ring and/or an anti-extrusion ring. See also “Anti- extrusion Ring”, “Junk Ring”, and “Wiper Ring”. |
| Encapsulated O-rings | A rubber o-ring with a thin jacket of PTFE or PTFE surrounding the softer core material, which allows it to be used in chemical applications. |
| Epa | Abbreviation for “Environmental Protection Agency”, the US government agency responsible for enforcing the regulations imposed by the Clean Air Act Amendment. |
| Epa Method 21 | A method established by the EPA for performing emissions measurements on equipment such as valves, pumps, and flanges. |
| EPDM | ASTM abbreviation for a terpolymer of ethylene, propylene, and a diene with the residual unsaturated portion of the diene in the side chain. |
| EPM | Abbreviation for ethylene-propylene rubber. |
| EPR | Abbreviation for ethylene-propylene rubber. |
| EU | Abbreviation for polyether urethane |
| EU | Abbreviation for polyether urethane |
| Excluders | Also called wipers or scrapers – used in a hydraulic or pneumatic cylinder to exclude and scrape the rod clean. |
| Exclusion Device | A device capable of excluding contaminating particles and fluids that would otherwise be dragged back into the primary sealing area of the equipment. |
| Excurision Temperture | The temperature the system could reach TEMPERTURE: during an equipment failure such as an air heater failure. Excursion temperature should be defined by maximum temperatures and time duration of excursion. |
| Exothermic | A chemical reaction in which heat energy is liberated. |
| Expanded Rubber | Cellular rubber having closed cells made from a solid rubber compound. |
| Expansion | The increase in any linear dimension or volume. |
| Explosive decompression | See Rapid gas decompression |
| Extender | A material added to a rubber compound which is designed to reduce the cost of the compound without imparting any enhanced physical properties. |
| Extensometer | A device used to determine the elongation of a specimen as it is strained under testing conditions. Often these machines can also record the tensile strength and modulus values of a given material. |
| External Arch Corner | An expansion joint corner with the arch formed outwardly that is designed primarily for pressure service, generally used in conjunction with a rectangular or square expansion joint. |
| External Pressure | Pressure (Lbs./Sq. Inch) exerted on the OD of a seal. |
| Extraction | The process of removing one or more components of a homogeneous mixture by treating the mixture with a liquid (solvent) in which the components to be removed are soluble but not the mixture as a whole. |
| Extraction Test | A test involving the separation of certain components from a solid by dissolving them in a liquid solvent under suitable conditions. |
| Extra Deep Drawing Steel | Sheet of this designation has superior formability and excellent uniformity. It is produced from steel having a very low carbon content with stabilizing elements added to make it interstitial free. It is a non-aging steel sheet with high resistance to thinning during drawing and is suitable for critical forming applications. |
| Extra Smooth Galvanized | An Extra-Smooth finish is imparted to hot-dip metallic-coated steel sheet by temper rolling after coating to decrease the surface relief that occurs when the molten coating solidifies. The spangle pattern (grain pattern) is made distinctly less visible by the matte finish imparted by the rolling operation. Most Extra-Smooth sheet is intended for either prepainted or post painted applications. |
| Extrudate | (also referred to as extrusion): The profiled material which results from the extrusion process. |
| Extruder | A machine designed to create a profiled rubber shape by forcing the rubber through a die which has a shape similar to that of the required profile. The two most common types are screw and ram. |
| Extrusion | 1) Distortion, under pressure, of portion of seal into clearance between mating metal parts. 2) Material, under pressure, which is forced through the opening of a die in order to obtain a desired cross sectional shape. |
| Extrusion (seal) | The distortion, under pressure, of some of the sealing element into the clearance between mating parts. |
| Exudation | Delayed phase separation of incompatible material, also called bleeding, blooming, spewing, or sweating. |
| F | |
| Fabric Impression | A pattern in the rubber surface formed by contact with fabric during vulcanization (usually during Drum Curing). |
| Face Seals | Rubber rings used like a gasket between two flat pieces of metal. |
| Fade-O-Meter | An apparatus for accelerated light aging and light fastness testing of sample of vulcanized rubber and plastic specimens under the action of artificial light from an electric arc between two carbons. |
| Failure Modes Analysis (FMA) | A formal, structured procedure used to analyze failure mode data from both current and prior processes to prevent occurrence of those failure modes in the future. |
| Fastener Seals | See Bonded Seals. |
| Fatigue | The weakening or deterioration of a material occuring when a repetition or continuous application of stress causes strain. |
| Fatigue life | The number of deformations required to produce a specified state of fatigue in a test specimen. |
| FDA | Food and Drug Administration (USA). |
| FEA | Abbreviation for finite element analysis. |
| Feasibility | A determination that a process, design, procedure, or plan can be successfully accomplished in the required time frame. |
| FEPM | Abbreviation for tetrafluoroethylene/propylene dipolymers. |
| FFKM | Abbreviation for perfluoroelastomers. |
| Fiber Seal Rings | A gasket or other die cut, waterjet cut or formed ring used to seal between two surfaces. |
| Field Assembly | A joint that is assembled at the jobsite due to its size ( too large to ship ) or the location of the breach opening makes it more practical to install in sections. |
| Filler | Any compounding material, usually in powder form, added to rubber in a substantial volume to improve quality or lower cost. The most important reinforcing filler is carbon black. The most important inert filler, diluent or extender is whiting. |
| Filler, Inert | A filler added for cost or processing reasons that have little affect on physical properties. |
| Finish, Mold | The quality or appearance of the machined surface of a mold. |
| Finish, Product | The quality or appearance of the surface of a rubber product. |
| Finish (See Rms) | Surface condition of materials for metals, measured in terms of RMS. |
| Finite Element Analysis | A technique for modeling a complex structure. When the mathematical model is subjected to known loads, the displacement of the structure may be determined. |
| Fire retardant | An additive used in rubber compounding to reduce the fire hazard |
| FKM | Abbreviation for fluorocarbon rubber. |
| Flame resistance | The resistance to burning of a rubber material. |
| Flange | Rim or edge projecting at right angles to provide strength, or a means of attachment to another part |
| Flange Joint | A joint formed by two abutting flanges. |
| Flange Packing | A pipe flange gasket. |
| Flanges | That part of an expansion joint used for fastening the joint into the system. Can be either metal or same materials as the bellows. |
| Flange Seals | A seal used on the bolt-up flange on a hydraulic system – usually on the hose fitting or pipe flanges. |
| Flash | Excess rubber on a molded product resulting from cavity overflow at the parting lines where the mold sections are separated. |
| Flatness | Flatness is a measure of a cut length sheet’s ability to conform to a flat horizontal surface. Maximum deviation from that surface is the degree to which the sheet is out of flat. Flatness is often expressed quantitatively in either Steepness or I-Units. |
| Flex cracking | A cracking condition of the surface of rubber articles such as tires and footwear, resulting from constantly repeated bending or flexing in service. |
| Flex Life | The relative ability of a rubber article to withstand cyclical bending stresses. |
| Flexural strength | Ability of an elastomer to flex without permanent distortion or damage. |
| Flow Direction | Direction of media (fluid, gas, air, etc.) movement through the system. |
| Flow Liner (Baffle) | A metal shield that is designed to protect the abrasive media in the stream and to reduce flutter caused by the air turbulence in the gas stream. Flow Liner/Baffles may be welded or bolted into position. |
| Flow Marks | Surface imperfections due to improper flow and failure of stock to knit or blend with itself during the molding operation. |
| Flow Meter | A device used to measure the flow rate of a fluid through a pipe. In packing applications a flow meter may be used to measure the amount of flushing fluid that is entering and/or leaving the stuffing box. |
| Fluid Side | The side of the seal which in normal use faces toward the fluid being sealed. |
| Flushing Fluid | A clean liquid (usually water) which is injected through a flush port to exclude solid particles from the stuffing box area and minimize abrasive wear. A flushing fluid might also be used to cool the packing in a high temperature application, or to keep air from being drawn into a pump in a suction application. |
| Flush Port | A hole in the side of a stuffing box through which a cleansing or lubricating fluid is injected. |
| Flutter | The action that occurs on the joint body caused by turbulence of the system media or vibration set-up in ducting system. |
| FMQ | Abbreviation for fluoro methyl silicone. |
| Foam Rubber | Cellular rubber formed by whipping latex to a froth and then vulcanizing. |
| Foil | Another name for thin gauge aluminum (see Aluminum). |
| Follower | See “Gland Follower”. |
| Force Pounds | The total load required to deflect an expansion joint a distance equal to the maximum rated movement of the product. |
| Foreign Material | |
| Formula | A list of the ingredients and their amounts used in the preparation of a compound. |
| Formulation | Kinds and proportions of ingredients for a mix, together with the method of incorporation. Also called recipe. |
| FPM | Abbreviation for “Feet per Minute”, a measure of the surface speed of a rotating shaft. |
| Frame | The complete angle iron or plate frame to which belt of bellows portion of the expansion joint is attached. |
| Free Sulfur | That portion of the sulfur originally present in the compound which did not react during vulcanization. |
| Friction | Resistance to motion due to the contact of surfaces. |
| Friction Coating | A rubber covering applied to the weave of a fabric simultaneously with impregnation. |
| Friction Factor | An empirically determined factor used to estimate the frictional force generated by the packing on a valve stem. It is important to note that this is not the same as “Coefficient of Friction”. |
| Frictioning | Process of impregnating woven fabric with rubber using a calender whose rolls rotate at different surface speeds. |
| FSA | Fluid Sealing Association, an American-based trade association for the mechanical packing industry. |
| Fsa (Fluid Sealing Assoc.) | The name of the American-based trade association for the Mechanical Packing Industry. |
| Fugitive Emissions | An unintentional gaseous or liquid leakage given off by a piece of equipment. See also “Emissions”. |
| Full-Face Gasket | A gasket covering the entire flange surface and including bolt holes. |
| Functional Lip Diameter | The apparent inner diameter of the seal when the seal case is concentric with the outer diameter of the sizing mandrel in an air gage, light box, or similar inspection equipment. |
| FVMQ | Abbreviation for fluoro vinyl methyl silicone. |
| G | |
| Gage | Refers to a dimension, generally thickness of a product, as measured by a gage of some type |
| Galvanic Corrosion | An electrochemical reaction that may occur between a metal and a more chemically noble material such as another metal, carbon, or graphite. When both materials are immersed in an electrically conductive media called an electrolyte, a galvanic cell is formed and current flows between the two materials. The least noble material (called the anode) will corrode, while the more noble material (the cathode) will not. |
| Gap Seals | A seal ring used to seal between the gaps of metal or plastic. |
| Garter Spring | A helically coiled wire with its ends connected to form a ring. It is used in tension for maintaining a radial sealing force between element of a radial lip seal and a shaft. |
| Garvey Die Extrusion Test | A procedure for rating the extrusion characteristics of a rubber compound by extruding under prescribed conditions through a die of prescribed contour and dimensions. Named after its inventor, Benjamin Garvey. |
| Gasket | A flat, non-moving, compressible rubber-like device squeezed between two flat surfaces forming a static seal. Gaskets can be made from homogeneous rubber, fabric reinforced rubber, fibrous materials with rubber binders, flexible graphite, PTFE and many other materials. Some gaskets are made from a combination of metal and fibrous materials and some are all metal. An o-ring, while not flat is also referred to as a gasket at times. |
| Gasketing | Material in bulk form from which gaskets may be cut. |
| Gasket Spacer | A gasket material cut to fit in a stuffing box between braided packing rings. Gasket spacers may be used to provide protection against abrasive particles, to increase the pressure resistance of some packing sets, or to reduce the flow of fluid through the body of the braid. |
| Gate | (rubber injection or transfer mold) – The orifice used to control the flow of rubber, and through which a shaped cavity in a mold is filled with rubber. |
| Gate mark | A witness mark left on the moulding as a result of injecting rubber through the gate. This can be either a raised or sunken mark on the surface of the moulding. |
| Gauge | The thickness of a material. |
| Gehman Freeze Test | An apparatus for measuring the relative stiffening of rubber specimens at low temperatures by measuring the resistance to twisting at specified temperatures. |
| Gland Bearing Rings | Also called guide rings or wear rings used as a bearing surface for the rod of a hydraulic ram or cylinder. |
| Gland Follower | A part which protrudes into a stuffing box to compress a packing set or packing ring. |
| Gland Load | The amount of load applied to a packing set. This may be expressed in terms of force (Lbs., N) or in terms of pressure (psi, kPa). |
| Gland Pressure | The amount of pressure applied to a compression packing set by the gland follower, usually expressed in psi or kPa. |
| Gland Seals | Seals or packings used as the main sealing device in a ram or cylinder. |
| Glandsele | The brand name of a type of rod seal. |
| Gland Stud | A threaded rod or eye bolt, extending from a valve or pump body, that is used to compress a packing set. |
| Glass Temperature (Tg) | The temperature at which a rubber becomes glass-like. A more recent name for Second Order Transition point. |
| Glass Transition Point | Temperature at which a material loses its glass-like properties and becomes a semi-liquid. |
| Glass Transition Temperature (Tg) | The point at which the material loses its flexibility at low temperature. This point is affected by system pressure and varies for different polymers. |
| Globe Valve Discs | PTFE rings used to seal in a globe valve. |
| Gloss | The property of a surface related to its ability to reflect light. The most common type of gloss of interest to appearance attributes is specular gloss. The parameters which must be specified for the determination of this property are the angles of incidence of the light source, the angle of viewing of the gloss and the angular dispersions of the measuring beams. |
| Glyd Ring | Also known as wear rings or guide rings – made from plastic, PTFE or soft metal to act as a bearing surface for a cylinder rod. |
| Gough-Joule effect | When rubber is stretched adiabatically (without heat entering or leaving the system) heat is generated by the material. The effect was originally discovered by Gough in 1805 and re-discovered by Joule in 1859. |
| Grain | The unidirectional orientation of rubber or filler particles occurring during processing (extrusion, milling, calendering) resulting in anisotropy of a rubber vulcanizate. |
| Grain Direction | The arrangement of a pattern on the material. |
| Grease Seals | Also called oil seals, rotary seals or shaft seals. Made of rubber to seal grease in a housing with a rotating shaft. |
| Green Stock | Raw, unvulcanized compound |
| Green Strength | (1) The resistance to deformation of a rubber stock in the uncured state. (2) Uncured adhesion between plied or spliced surfaces. |
| Grommets | A rubber ring used to fit into a hole in sheet metal allow wires, shafts or rod to exit the housing without touching the metal. |
| Groove | The area in which a hydraulic seal is contained for the purpose of sealing against a rod, or cylinder wall or an annular seal cavity. |
| Gr-S | Obsolete description of styrene-butadiene rubber. Current ASTM designation is SBR. |
| Guayule Rubber | A form of natural rubber obtained from the guayule shrub. It is soft and highly resinous. There is currently little commercial use. |
| Guiding Elements | Wear rings, guide rings, guiding rings, bearing rings for hydraulic cylinder rods. |
| Guide Rings | See also wear rings, guide rings or bearing rings. Usually made from a form of PTFE or PTFE. |
| Gum Stock Or Compound | A rubber compound containing only those ingredients necessary for vulcanization and small amounts or other ingredients such as process aids, colors and antioxidants. It contains no filler, reinforcing agents or plasticizers. |
| Gutta-Percha | A form of rubber obtained from trees in a manner similar to Hevea (natural) rubber. It differs in that it is highly transpolyisoprene like balata as compared to natural (Hevea) rubber which is cis-polyisoprene. Its commercial usage is generally limited to underwa- ter cable. |
| H | |
| Halogen | Class of elements containing Chlorine, Bromine, Iodine and Fluorine. |
| Halogenation | The reaction of a halogen element with an organic compound by direct addition or by substitution for a hydrogen atom. |
| Hand Wheel | A wheel located at the top of a manually operated valve that is used to actuate the valve stem. |
| Hat (Flange) Packing: | An old form of sealing rods, which seals on the ID only. |
| Hardness (a) | The relative resistance of rubber to the penetration (without puncturing) of a blunt point impressed on its surface. |
| Hardness (b) | Resistance of metal to penetration of the surface. |
| Hard Rubber | See Ebonite. In ground form as “dust,” it is used as a filler in other hard rubber articles as a process aid and to reduce the possibility of thermal generated in the vulcanization of hard rubber (high sulfur) parts. |
| Hat Packings | Usually made from leather, it is used as a rod seal or ram seal in a hydraulic cylinder. |
| Head | The pressure at any point in a fluid can be thought of as being caused by a vertical column of the liquid that, due to its weight, exerts pressure at the point in question. The height of this column is called the “static head” (or sometimes simply “head”) and is expressed in terms of feet or meters of liquid. |
| Heat ageing | A test for the reduction in physical properties of an elastomer as a result of exposure to temperature. |
| Heat Build Up | The generation of heat due to hysteresis when rubber is rapidly or continually deformed |
| Heat Embrittlement | The hardening of a vulcanized rubber compound when aged at elevated temperatures in air, accompanied by increased modulus and decreased tensile and elongation. Characteristics of diene containing polymers. |
| Heat Exchanger | A piece of equipment designed to transfer thermal energy from one media to another. The unit is typically a long cylindrical body with multiple tubes passing within the body. Media of one temperature flows within the body but external to the tubes, while media of another temperature flows within the tubes, thus allowing thermal energy to exchange without cross-contamination of the products. |
| Heat history | The accumulated amount of heat a rubber stock has been subjected to during processing operations, usually after incorporation of the vulcanizing agents. Incipient cure or scorch can take place if heat history has been excessive. |
| Heat resistance | A rubber’s ability to undergo exposure to some specified level of elevated temperature and retain a high level of its original properties. |
| Heavy Gauge Foil | Aluminum foil greater than .008” thick (8 mils). |
| Heel Section | The portion of a lip seal which is attached to the seal case and bounded by the flex section and the outside face. |
| Helical Motion | The circular, screw-like, up and/or down motion of a rod or valve stem. |
| Helicoflex® Seal | Metal seal composed of a helical, wound spring with a single or double jacket wrapped around the spring. Cross-section of the seal is circular and various shapes and sizes can be created using different jacket wrappings. |
| Helium Seal | A sealing level that does not exceed 1.0 x 10-9 atm cc/sec of Helium. |
| Helix Contact Width | The axial width of that portion of the contact surface of a helix seal which is formed by the helical ribs. It is equal to the total axial width of the contact surface minus the width of the static lip. |
| Helix Seal Rib Seal | The angle formed by the leading edge of the rib and a line perpendicular to a plane tangent to the outside lip surface at the centerline of rib base. |
| Helix Seal Rib Width | The maximum width of a helical rib measured perpendicular to the ribOs longitudinal axis. |
| Hertz, Hz | Unit of frequency equal to one cycle per second |
| Heteropolymer | A polymer composed of differing monomers. |
| HiClean | A brand name for rod wipers. |
| High Pressure Seals | Seals to be used in high pressure hydraulic applications made from PTFE, urethane or fabric reinforced material. |
| HNBR | Abbreviation for hydrogenated nitrile rubber. |
| Homogeneous | Of uniform composition throughout. |
| Homopolymer | A polymer formed from a single monomer. |
| Hooke’s law | Within the limits of elasticity of a material, tension is proportional to elongation, or strain is proportional to the stress producing it. |
| Hot Melt Adhesive | A thermoplastic adhesive compound, usually solid at room temperature which becomes fluid on heating for use. |
| Hot Rolled Sheet | Steel sheet that is processed to its final thickness by rolling at high temperatures on a specially designed hot-rolling facility. Also commonly known as hot rolled unprocessed. |
| Hot Rolled Sheet Non-Temper Rolled | A U. S. Steel definition for product supplied as a coil directly off the Hot Strip Mill with no additional processing. |
| Hot Rolled Sheet Pickled | A U. S. Steel definition for a mill edge coil that is pickled, oiled and temper rolled with coil ends cropped back to meet gauge tolerances. |
| Hot Rolled Sheet Pickled Non-Temper Rolled | A U. S. Steel definition for a mill edge coil that is pickled and oiled with coil ends cropped back to meet gauge tolerances. |
| Housing Bore | A cylindrical surface which mates with the outside diameter of the outer seal case. |
| H-ring | Also called H-Wiper. An “H” shaped rod wiper ring made from NBR or polyurethane for a hydraulic or pneumatic cylinder. |
| Hydraulic Cylinder Kits | A selection of seals used to completely repair a cylinder or ram. |
| Hydraulic Packings | Packing rings used in a hydraulic ram or cylinder. |
| Hydrocarbon | An organic chemical compound containing only the elements carbon and hydrogen. Aliphatic hydrocarbons are straight chain compounds and aromatic hydrocarbons are based on the cyclic or benzene ring. They may be gaseous, (methane, ethylene, butadiene) liquid (hexane, benzene) or solid (natural rubber, naphthalene, cis-polybutadiene). |
| Hydrodynamic Seal | A dynamic sealing device which utilizes the viscous shear and inertia forces of the fluid; imparted by a helically grooved or ribbed seal lip, to generate a pressure differential that opposes fluid flow. |
| Hydrolysis | Chemical decomposition of a substance involving the addition of water. |
| Hysteresis (a) | The heat generated by rapid deformation of a vulcanized rubber part. It is the difference between the energy of the deforming stress and the energy of the recovery cycle. |
| Hysteresis (b) | Hysteresis or energy loss is the difference between the work input and the work output as measured under the curves or extension and retraction (stress and elongation curves). The difference becomes heat build-up. |
| Hysteresis loss | The loss of mechanical energy due to hysteresis. |
| I | |
| ID | Abbreviation for “Inside Diameter”. Used when denoting the inside dimension of a packing set, usually equal to the stem or shaft diameter. |
| Iir | ASTM designation for isobutene-isoprene rubber, or “butyl” rubber |
| Immediate set | The deformation found by measuring immediately after removal of the force causing deformation. |
| Impact Test | A test which is intended to evaluate the brittleness, toughness, adhesion and hardness of paint films applied to metals by subjecting them to an indent impact force. |
| Impact resistance | The resistance to fracture under a quickly applied load. |
| Impact strength | A measure of the toughness of the material to rapidly applied loads. It is often represented as the energy required to break a specimen with a single swinging blow. |
| Impeller | The part of a centrifugal pump that, when rotated, will generate pressure and cause flow. |
| Impregnate | To force material into all the openings of a fabric. |
| Impression | During vulcanization, the design formed in the surface of any rubber article by a method of transfer. See “Fabric Finish.” |
| Inclusions | Particles of foreign material (such as oxides, sulfides or silicates) in steel as cast. |
| Incompatibility | Inability of material to form a homogeneous system |
| Inert | A material that has little tendency to reinforce or have any other effect upon the properties of vulcanizates |
| Inhibitor | A compounding ingredient which is added to a mix to suppress a chemical reaction such as the curing of a rubber material. |
| Injection Molding | A method of forming articles (such as plastic) by heating the molding material until it can flow and injecting it into a mold. |
| Injection moulding | Moulding process where preheated rubber is injected under pressure through a series of runners and into a closed mould cavity. |
| Inner Case | A rigid, cup-shaped component of a seal assembly, which is placed inside the outer seal case. It has one or more of the following functions: reinforcing member, shield, spring retainer, lip-clamping device. |
| Inner Ply | The inside ply of a multiple-layered joint. |
| Inner Ring | A solid ring used on the ID of a spiral wound gasket in higher pressure applications. This ring also acts as a compression limiter and provides protection from the media stream. |
| Inorganic Chemicals | Chemicals whose composition is based on atoms other than carbon (salt, clay, silica, caustic, hydrochloric acid, etc.). |
| Inpherno® Gaskets | Fire-safe PTFE spiral wound gaskets that successfully passed API 607 fourth edition fire test, providing low stress to seal (torque), high tightness, and PTFE inertness and chemical compatibility. A GORE® patented product licensed to VSP Technologies. |
| Insert | A part, usually metal, which is placed in a mold and appears as an integral part of the molded product. |
| Inside Face | That surface of the inner case which faces, and is usually in contact with, the fluid being sealed. |
| Inside Lip Angle | The angle between the inside lip surface and the axis of the seal case. |
| Installed Face-To-Face Distance | The distance between the expansion joint flanges after installation when the system is in the cold (off) position. |
| Integrally Flanged Type Expansion Joint | An expansion joint in which the joint flanges are made of the same material as the body of the joint, as in ÒUÓ type joints. |
| Internal Arch Corner | An expansion joint corner with the arch formed inwardly that is designed primarily for vacuum service. Generally used in conjunction with a rectangular or square expansion joint. |
| Internal Mixer | An enclosed mixing machine of high power for rubber or other suitable material, inside of which are two counter-rotating heavy mixing rotors with small clearance between themselves and the enclosing walls. The mixing chamber is jacketed and may be heated or cooled, as may be the rotor |
| Internally lubricated rubber | A rubber containing lubricating additives designed to reduce the material’s coefficient of friction. |
| Internal Mixer | An enclosed mixing machine for rubber or other suitable material, inside or which are two (2) heavy mixing rotors which revolve in opposite directions with a small clearance between themselves and tine enclosing walls. The mixing chamber is jacketed or otherwise arranged for water-cooling, and is provided with a feeding hopper which can be closed by means of a pneumatically operated, vertical ram. Leading examples are the Banbury, the Boiling and the Shaw mixers. |
| Internal Pressure | Pressure (Lbs/Sq. Inch) exerted on the ID of a seal. |
| Intra-Lock™ | Unique segmented-gasket technology providing tighter, more mechanically secure fits between gasket segments. |
| IRHD (International Rubber Hardness) | For complete definition see ASTM D 1415-68 Standard Method of Test for International Hardness of Vulcanized Natural And Synthetic Rubbers. |
| ISO | Abbreviation for International Standards Organization. |
| Isolators | A term used to describe a bearing seal – which replaces an oil seal providing more reliable sealing. |
| Isoprene | (CH2CICH3)-CH=CH2, a liquid hydrocarbon, the fundamental repeating unit in natural rubber and the monomer from which IR, (or polyisoprene) is produced |
| Izod Impact Test | A test procedure to determine the impact toughness of a rigid material. It consists of a notched specimen supported as a cantilever which is struck by a pendulum blow. |
| J | |
| Jacketed Gasket | Type of gasket with a metallic cover either partially or completely surrounding a filler material to improve temperature, pressure, chemical and crush resistance. |
| Joint | An interstice (crevice) between rigid members of a fluid container. |
| Junk Ring | A ring added to the bottom of a packing set as either an anti-extrusion ring or as a bushing. See also “Anti-extrusion Ring”, and “Wiper Ring”. |
| K | |
| Kantseal | A brand name of a special seal. Kiss-Cut – Die-cutting material so that it stays in roll form. The finished pieces are easily peeled from the release liner. |
| Knit mark | Where raw stock did not unite into a homogeneous mass during the vulcanization. This is also called poor knitting. See Flow marks |
| Knit line | (also known as weld line): A line present in a moulding as a result of opposing flow fronts during the forming of the rubber material in a mould not knitting together. A knit line is an area weakness in the moulding. |
| Knots | Lumps which appear in a stretched rubber part, generally due to poor dispersion of a curative, such as sulfur. |
| K-Type Fluid Seals | A “K” shaped sealing ring used in a hydraulic or pneumatic cylinder. |
| L | |
| Labyrinth Seals | A non-contacting, rotary seal with a series of internal grooves to divert the flow and lubricating fluids in the direct of its source used on a shaft. |
| Laminate | Product made by bonding together two or more layers of like, or unlike materials. |
| Lantern Rings | A spacer ring with grooves and port holes used in the stuffing box of a pump or other rotating equipment utilizing braided packings, to allow an outside source of lubrication. |
| Lateral Deflection Or Lateral Movement | The relating displacement of the two ends of the expansion joint perpendicular to its longitudinal axis. Lateral movement is usually caused by the thermal expansion of the ducting system and measured in inches or millimeters. |
| Lateral Offset | The offset distance between two adjacent flanges or faces. Can be due to misalignment, equipment settling, or by design to compensate for excessive displacement in the opposite direction during cycle. |
| Latex | A stable dispersion of a polymeric substance in an aqueous medium. |
| Latex Cement | An adhesive cement made from latex by compounding with suitably prepared curing agents, fillers and tackifiers. |
| Lathe Cut Seals | A seal or gasket ring cut square on a lathe. |
| Lattice Braid® | A Garlock trade name for a type of braided construction. In this method, the yarn is braided in an interlocking weave, making it very difficult to unravel. This construction yields a dense, tightly woven packing material having a square cross-section. Other packing manufacturers have different names for this braiding method. |
| Leaching | See Bleeding |
| Lead Press Cure | A process for curing hose where the uncured hose is covered with lead in an extruding machine, cured in steam and the lead stripped off. The lead covering acts as a mold during vulcanization. |
| Leakage | An escape of gases or liquids from a piece of equipment. |
| Leakage Rate | The quantity of fluid passing through (or around) a seal in a given period of time. |
| Life test | A test of the amount and duration of a product’s resistance to destructive forces. |
| Light Aging | Deterioration of compounds when exposed to light (direct or indirect, natural or man-made). |
| Lim | Liquid injection molding. A molding process in which one or more liquid materials are injected into a mold held at room or elevated temperatures catalysed to cure in a very short period of time. RIM, reaction injection molding, is a special case referring to catalyzed liquid urethanes reacting in the mold at room temperature. also called LRM, or liquid reaction molding. |
| Liner Side | The adhesive side covered by the release liner. |
| Lip Diameter | The inner diameter of the seal lip, measured with the spring installed. |
| Lip Force | The radial force exerted by an extension spring and/or lip of a seal on the mating shaft. Lip force is expressed as force per unit of shaft circumference. |
| Lip Height | The axial distance from the outside seal face to the toe face. |
| Lip Id To Id Eccentricity | See: Radial Wall Variance. |
| Lip Interference: | The tendency for a seal’s actual dimension at the lip area to be smaller than the ID or larger than the OD sealing surfaces. |
| Lip Opening Pressure | The pressure necessary for flowing air at 10000 cm3/m between the contact surface of a radial lip seal and shaft-size mandrel under the following conditions: the seal case outer diameter clamped to be concentric with the mandrel and the pressurized air applied to the outside lip surface. |
| Lip Packing & Rings | Could be the description of a u-cup or of an oil seals. A seal with a lip design to provide sealing. |
| Lip Seals | Seal rings having lips to provide a flexible, dynamic sealing against a shaft. |
| Liquid silicone rubber | High purity platinum cured silicone with low compression set, great stability and ability to resist extreme temperatures of heat and cold. |
| Litharge | Lead monoxide, PbO, formerly used as an inorganic accelerator but now mainly used as a vulcanising agent in some polychloroprene rubbers. |
| Live Loading | The use of Belleville spring washers on packing gland bolts to reduce load loss over time. |
| Loaded Lip Seals | A hydraulic u-cup which has an o-ring or quad ring fitted into the u-shaped groove to assure good low pressure sealing on a reciprocating shaft. |
| Loaded U-Cups | Same as loaded lip seals. |
| Loading | The kind and quantity of fillers mixed with rubber. |
| Loadlock™ Gaskets | Machined profile gaskets designed and fabricated by VSP Technologies. |
| Lot | 1) A mass of material or collection of articles of similar composition and characteristics. 2) An amount of material produced at one time and of uniform composition. |
| Low Film | A thin film of oil on the shaft of a hydraulic cylinder. |
| Low temperature flexibility | The ability of a rubber product to be flexed, bent, or bowed at specified low temperature without loss of serviceability. |
| Low Temperature Retraction | Behavior of a compound when tested in T-50 test. It is designed to evaluate the crystallizing tendency of cured compounds at low temperatures. The specimen is elongated, frozen to an inelastic state, and released while allowing the temperature to rise at a uniform rate. The length of the specimen is measured at regular temperature intervals while it is retracting. |
| Lubricant Starvation | Lack of proper lubrication at the seal interface which may cause premature wear and early failure. |
| Lubricants | Internal (mixed into the compound) to reduce tendency to stick to processing equipment or to lower heat build up on flexing. External (sprayed on) to reduce tendency to stick to a mold |
| Lubrication | The use of a liquid or fluid to reduce the friction, heat or wear between two surfaces where movement is taking place. |
| M | |
| “M” Factor | The factor that provides additional preload capability in the flange fasteners to maintain sealing pressure on a gasket after the internal pressure is applied to the joint. For M+Y Values see “Enginnering Tools” under “Services” |
| Magnesia | (a) Heavy calcined: Magnesium oxide by calcination of magnetite (natural magnesium carbonate), and then ground for use as a compounding ingredient for molded goods and hard rubber. (b)Light calcined: Magnesium oxide by calcinations of purified magnesium carbonate and/or magnesium hydroxide. It has a fine particle size and a bulk factor of 10 to 30 pds. Per cubic ft. Used chiefly in neoprene stocks. (c)Extra light calcined: Prepared similarly by calcinations of magnesium carbonate, but with a bulk factor of 4 to 6 pds. Per cubic ft. Used chiefly in neoprene stocks. |
| Maintainability | The probability that a failed system can be made operable in a specified interval or downtime. |
| Make-up | Uncured elastomer that is cut to a profile, weight and/or length prior to placing in a mould. |
| Mandrel | A bar, serving as a core, around which rubber is extruded, forming a center hole. |
| Manufactured Flange To Flange Dimension | The manufactured width of the joint measured from the joint flange face to flange face. |
| Marching Modulus | A curing characteristic of a compound where the modulus never quite levels off but keeps increasing with cure time. |
| Masterbatch | A preliminary mixture of rubber and one or more compound ingredients for such purposes as more thorough dispersion or better processing, and which will later become part of the final compound in a subsequent mixing operation. |
| Master Batch | A mixture of rubber with one (1) or more ingredients in definite but higher concentrations than those in which they normally occur in a complete rubber mix. Used for efficiency in compounding, and also to avoid the handling of small quantities of accelerators, antioxidants, color, etc… |
| Masticate | To work rubber on a mixing mill or in an internal mixer till it becomes soft and plastic. To break down. MASTICATOR – A machine for plasticizing rubber by mechanical work. |
| Mastication | The breakdown or softening of raw rubber by the combined action of mechanical work (shear). This can be accelerated by the use of a peptiser. |
| Matrix | 1) Mold or form in which anything is cast or shaped. 2) Continuous medium in which discrete particles are dispersed, as chopped fiberglass in polyester resin |
| Matte | A satin or flat finish on the surface of a label. |
| Matte Finish | A more uniform surface finish imparted to the sheet surface by temper rolling with shot-blasted rolls. |
| Mechanical Properties | The properties of a material that reveal its elastic and inelastic behavior when force is applied, thereby indicating its suitability for mechanical applications. |
| Mechanical Rubber Goods | A general term covering rubber goods manufactured for use in engineering and industrial applications, covering belting, hose , gaskets, rolls, milking inflations, etc. |
| Media | The fluid which is being sealed. |
| Memory | Ability of a rubber to return to its original shape after deformation. |
| MerKamm | This is a basic Camprofile with no outer ring. It is used in a confined space or recessed flange such as tongue and groove or male/ female. |
| MerKamm IG | This is designed with an integral outer guide ring for aligning accuracy. This is primarily used in standard ANSI B 16.5 flanges, raised face or flat face. |
| MerKamm LG | This is designed with a loose fitting outer guide ring. It is used for flanges where thermal expansion may be encountered. |
| Metal C-Ring | C-section metal seal with low load characteristics. Plating and coating are added for improved performance. |
| Metal O-rings | An o-ring usually made from hollow stainless steel tubing, with a small vent hole. |
| Metal Seal | Seal composed entirely of metal components, which, when compressed between two stationary faces, prevents the passage of a particular media through a specified space or opening. |
| Method 21 | See “EPA Method 21″. |
| Micrometer | A caliper for making precise measurements that has a spindle moved by a finely threaded screw. |
| Micron | A unit of length equal to .0001 cm or 10,000 angstrom units. Now replaced by micrometer. |
| Micro-Voids | The spaces in a gasket, on a micro level, that allow media permeation. |
| Microwave curing | Vulcanisation of rubbers by heat produced by high frequency radiation. |
| Migration | The movement of materials within a rubber product to the surface, from an area of high concentration to one of low concentration, or into another material to which it is laminated |
| Mill | A machine consisting of two (2) adjacent, heavy, chilled iron rolls set horizontally, and which revolve in opposite directions (i.e., upper surfaces rotate), used for the mechanical working of rubber Mills are of different types. For masticating, and mixing compounds the rolls are smooth and revolve with differential speed. For creeping and washing rubber, mills have scored or fluted rolls and differential speeds and may be equipped to spray the rubber with water. Mills with even-speed rolls are occasionally used for different purposes. Mills are corridor hollow and equipped for internal heating with steam or cooling with water. |
| Mill Shrinkage | The amount of shrinkage, expressed in percent, of a polymer or compound after being subjected to a specified amount of mill breakdown. A square of known dimension is cut from the band on the mill using a metal template and the dimension in mill direction measured after a specified period of time and compared to the original template dimension. |
| Mineral oils | Petroleum and other hydrocarbons oils obtained from mineral sources. In rubber compounds they act as softeners and extenders. |
| Mirror Finish | A bright, polished surface. |
| Misalignment | The out-of-line condition that exists between the adjacent face of the equipment/system flanges. |
| Mixer | A machine with a closed chamber in which specially shaped rotors masticate the rubber and incorporate compounding materials through the action of mechanical work (shear) with the aim of creating a homogenised finished material. |
| Mixing | The process of incorporating the ingredients or a rubber compound into the rubber, usually done on a mixing mill or in an internal mixer. The mixing process consists in (1) breaking down the rubber, (2) gradual incorporation or compounding ingredients, (3) final working of the rubber after all ingredients are in, and (4) removing the mixed compound from the mill in sheets. |
| Modulus | The ratio of stress to strain. In the physical testing of rubber, the load necessary to produce stated percentage of elongation, compression or shear. |
| Modulus of elasticity | The ratio of stress to strain in an elastic material. |
| Molded Type Expansion Joint | An expansion joint in which the entire wall of the joint is molded into a ÒUÓ or convoluted configuration. The joint is manufactured by a molding process. |
| Mold Lubrication | Lubricants, usually insoluble in rubber, sprayed or brushed on the face of a mold to facilitate removal of the article from the mold after cure. Soaps and silicones are most widely used. |
| Mold Register | Means used to align the parts of a mold. |
| Mold Shrinkage | The difference in dimensions, expressed in inches per inch, between a molding and the mold cavity in which it was molded, both the mold and the molding being at room temperature when measured. |
| Molecular weight | The weight of a molecule of a substance. |
| Monomer | A simple chemical compound that enters into the production of a polymer. |
| Mooney scorch | A measure of the incipient curing characteristics of a rubber compound using the Mooney viscometer. |
| Mooney Viscometer | A laboratory testing machine for measuring the plasticity of raw rubber or unvulcanized rubber compounds. A knurled steel rotor disc winch is centrally embedded iii the heated rubber specimen firmly held in a cavity under pressure is caused to rotate at a low speed (2 rpm). The resistance offered by the plastic rubber mass to the rotation of the rotor disc is the measure of the plasticity of the rubber. The machine is also used to determine the scorch characteristics of rubber mixes. |
| Mooney viscosity | A measure of the viscosity of a rubber or rubber com- pound determined in a Mooney shearing disc viscometer. |
| Mould cavity | Profiled shape cut into a mould within which the rubber is cured to produce the product. |
| Mould marks | An imperfection transferred to a moulded product from corresponding marks present on the mould surface. |
| Mould release | A substance applied to the surface of a mould cavity to aid the release of the rubber product after curing. |
| Mould shrinkage | Dimensional loss in a moulded rubber product that occurs during cooling after it has been removed from the mould. |
| Mounts | A rubber molded part used as a motor mount or to mount device against a frame without allowing vibration to pass through the mounting. |
| MOV | Abbreviation for “Motor Operated Valve”, a motor-actuated control valve. |
| Movements | The dimensional changes which the expansion joint is required to absorb, such as those resulting from thermal expansion or contraction. |
| MRO | Abbreviation for “Maintenance and Repair Organization”. |
| MSS | Abbreviation for “Manufacturers Standardization Society of the Valves and Fittings Industry”. |
| MTI | Abbreviation for Material Technology Institute of the Chemical Process Industry. |
| Mylar | A non-metallic material derived from polyester. |
| N | |
| Natural Rubber | Rubber formed in a living plant or tree, usually referring to Hevea Brasiliensis. |
| NBR | Abbreviation for nitrile-butadiene rubber. |
| NBS | National Bureau of Standards |
| Nibbling | Normally observed when pressure cycling occurs. When system pressure is applied the housing lifts or dilates, causing the clearance to increase. A nub of rubber extrudes into this clearance and is subsequently ‘nibbled’ off when the pressure is dropped and the clearance is reduced. |
| Necking | The localized reduction in cross section that may occur in a material under tensile stress. |
| Nip | The radial distance between the rolls on a mill or calender, measured at the line of centres. |
| Nebar | A special type of gasket material used in electrical transformers. |
| Neoprene | Synthetic rubber made by polymerizing 2-chlor-1, 3-butadiene. Neoprene compounds are rioted for their resistance to oil, sunlight and ozone. There are various types, most of which are vulcanizable without the use or sulfur. |
| Nerve | The elastic resistance of unvulcanized rubber or rubber compounds to permanent deformation during processing. |
| Nilos Rings | A special seal ring. |
| Nitrile Rubber | A generic term comprising the various copolymers of butadiene and acrylonitrile. The copolymers vary essentially in butadiene- acrylonitrile ratios, Mooney values and staining properties. They are resistant to solvents, oils, and greases and to bent and abrasion. Some trade names are Chemigum, Krynac, Nipol, Hycar, and Paracril. The Germans first produced the nitrile rubbers and called them Buna N and Perbunan. |
| NMR | Nuclear magnetic resonance. A type of radio frequency or microwave spectrosopy, based on the magnetic field generated by the spinning of the electrically charged nucleus of certain atoms. This is used for qualitative and quantitative analysis and the following of chemical rates of reaction. |
| Non-Blooming | The absence of a bloom. |
| Non-fill | A defect in a rubber product caused by the rubber failing to completely fill the mould. |
| Non-Metallic | Any material that lacks the characteristics of a metal. |
| Non-Metallic Expansion Joint | Expansion joint which utilizes flexible non-metallic material to accommodate joint movements. |
| Non-Staining | An accelerator, antioxidant or similar substance that will not discolor other goods placed next to the rubber in which it is used. Sometimes used as well to describe non-discoloring in white or colored goods. |
| Non-sulphur vulcanisation | The process of vulcanisation without the use of sulphur. |
| Novathan | A name for a type of polyurethane sealing material. |
| NR | Abbreviation for natural rubber. |
| O | |
| O.D. | Outside diameter measured at tangency between bottom radius (R1) and side. |
| Odorant | An aromatic substance for masking the odor of vulcanized compounds |
| OEM | Abbreviation for “Original Equipment Manufacturer”. |
| Offset | The radial distance between the axis of the seal bore and axis of shaft rotation. |
| Oil Black Masterbatch | A rubber (generally SBR) masterbatch containing petroleum oil and carbon black, both added to the SBR latex prior to coagulation. |
| Oil Masterbatch | Similar to oil black masterbatch but without the carbon black. The addition of the oil as a process aid allows the use of much higher molecular weight, tougher, SBR than could be normally processed, providing improved physical properties, such as abrasion resistance, at lower cost. |
| Oil Resistance | Ability to withstand swelling by a specified oily liquid for specified time and temperature, expressed as percentage swelling or volume increase of specimen. |
| Oil Resistance | as applied to vulcanized elastomer compositions: resistance to change in size and shape and resistance to loss in physical (mechanical) properties due to contacts with or immersion in an oil. |
| Oil Resistant | Ability of a vulcanized rubber to resist the swelling and deteriorating effects of various types of oils. |
| Oil Seals | Also called grease seals, rotary seals or shaft seals. Made of rubber to seal grease in housing with a rotating shaft. |
| Oil Swell | The change in volume of a gasketing product resulting from contact with oil. |
| Olefin | A family of unsaturated aliphatic hydrocarbons having the general formula CnH2n. They contain one or more double bonds and hence, are chemically reactive. They are named after the corresponding paraffins by adding “-ene” or “ylene” to the stem. (Example: butadiene, from butane, having two (-di-) sets of double bonds.) |
| Omni-Directional Strength | Strength in all directions. |
| Open Cell | A cell not totally enclosed by its walls and hence interconnecting with other cells. |
| Open Steam Cure | A vulcanization process that takes place under direct steam pressure in an autoclave. It is used where direct pressure molding is not possible. In -the case of vulcanization of sheeting, or coated fabrics, rolls of product are wound onto steel drums (with suitable interleaf) which are placed in the autoclave for cure. Some tubing arid shaped products are placed on pans for extra curing. |
| Operating Pressure/Vacuum | The temperature at which the system generally will operate during normal conditions. |
| Opra Gasket Designs | Reduced area gaskets for fragile or low bolt load flanges. VSP Technologies’ patented gasket design creates a modified full-face gasket with minimal gasket contact area to match available flange bolt load. |
| Optimum Cure (a) | State of vulcanization at which maximum desired property is attained. |
| Optimum Cure (b) | The physical properties of a rubber compound vulcanized at a given temperature for increasing periods of time undergo continuous change. For example, tensile strength may rise to a maximum, continue on a plateau, and then decline; whereas breaking elongation may continuously decrease. Therefore it is impossible to choose any one time of cure at which every property will be at its optimum, hence optimum cure is a compromise and may be considered as that time required obtaining the combination of properties most desirable for the article under consideration. |
| Opti-Seal | A special seal ring to provide optimum sealing. |
| Orange peel | Pitted or uneven surface on a moulded part, resembling the surface of an orange. |
| Organic | Refers to chemical structure based on the carbon atom, natural and synthetic |
| Organosol | A suspension of a finely divided polymer (PVC) in a plasticizer together with a volatile organic liquid. |
| O-Ring | An elastomeric seal of homogeneous composition molded in one piece to the configuration of a torus (ring) with circular cross- section |
| OS & D Hose | Abbreviation for oil suction and discharge service hose |
| Outer Case | The outer thin-wall rigid structure of the lip-seal assembly which contains the inner case, the primarily-seal ring, the spring parts, and the secondary seal. |
| Outer Cover | The outside ply of material in a multiplelayer joint. |
| Outgassing | The release of vapours or gases from a rubber compound. |
| Outside Lip Angle | The angle between the outside lip and the axis of the seal case. |
| OVA | Abbreviation for “Organic Vapor Analyzer”, a device used to measure the concentration of volatile organic compounds (VOC’s) in the vicinity of a stuffing box, flange, or any seal. An OVA is sometimes referred to as a “sniffer”. |
| Oven-Aging Test | See Aging, Air Oven |
| Overcure | A state of excessive vulcanization resulting from overstepping the optimum cure, i.e., vulcanizing longer than necessary to attain full development of physical strength. Manifested by softness or brittleness, and impaired age resisting quality of the vulcanization. |
| Overflow | See Flash |
| Oxidation | Active oxygen organic materials. This is called oxidation. Rate of degradation will increase with rising temperatures. |
| Oxidizer | See “Strong Oxidizer”. |
| Oxygen Bomb | A pressure resisting apparatus used in an aging test in which rubber is deteriorated in hot compressed oxygen. |
| Ozone | An allotropic from oxygen, (03), produced by (he action of electrical discharges in air. It is a gas with a characteristic odor, and Is a powerful oxidizing agent. Rubber compounds in a stretched condition are susceptible to the deteriorating action of ozone in the atmosphere, which results in a cracked condition. |
| Ozone cracking | The surface cracks, checks, or crazing caused by exposure to an atmosphere containing ozone. |
| Ozone resistance | The ability to withstand the deteriorating effect of ozone. |
| P | |
| Packaging | A unit that provides protection and containment of items plus ease of handling by manual or mechanical means. |
| Packing | An adjustable sealing device on a ram, valve stem or pump shaft - old technology and leakage is required for lubrication. If packing leaks, it is simply tightened slightly to ‘control’ the leakage. For pumps and valves, packings can be rope-like, braided into continuous lengths and then cut to size to fit a shaft. For hydraulic applications, v-shaped fabric reinforced rubber rings are used. Early hydraulic packings were made from leather. For a rubber o-ring, that particular item can be found called a seal, a gasket and a packing ring - even in U.S. government technical specifications dating back 50 years |
| Packing Gland | The space into which a compression packing is inserted. Also known as a Stuffing Box. |
| Packing Groove | A groove machined into a flange or joint to accommodate a packing ring. |
| Packing Hook | A tool, similar to a corkscrew, for removing packing from a stuffing box. |
| Packing, Mechanical | A deformable material used to prevent or control the passage of matter between surfaces which move in relation to each other. (Example: the packing around the hydraulic ram of a press.) |
| Packing Space | The distance between the shaft or stem surface and the bore of a stuffing box. Packing space (x) can be calculated by the following equation: x = (OD-ID)/2. |
| Pads | A rubber part used as an anti-vibration device. |
| Pale Crepe | The highest grade of unsmoked plantation rubber |
| Pan-Based Carbon | A carbon fiber derived from the carbonization process of a poly acrylonitrile fiber in an inert gas. |
| Paper Finish | Finish resulting from vulcanizing in contact with paper. |
| Parachute Packings | Also called V-Packing, Vee packing, Chevron Packing, Parachute packing or v-set packing. A complete vee packing set contains multiple “V” shaped sealing rings stacked and nested together with a male adapter on one end and a female adapter on the other end. |
| Paraffins | A class of aliphatic hydrocarbons characterized by saturated carbon chains. They vary from gases (Methane) to waxy solids. |
| Parbacks | A back-up ring with a concave shape on one side, used as an anti-extrusion ring for an o-ring. |
| Parting line | The line on the surface of a moulded part where the separate mould parts meet and create a small clearance gap. |
| Paste | 1) An adhesive composition having a characteristic plastic-type consistency. 2) Description of a PVC resin dispersion in plasticizer, a plastisol. |
| Passive Inhibitor | A type of galvanic corrosion inhibitor added to packing which acts as a protective coating to block the transfer of electrons and keep a galvanic reaction from occurring. Graphite foil can be produced with phosphorus added as a passive corrosion inhibitor. See also “Galvanic Corrosion”. Compare with “Active Inhibitor”. |
| PB | Abbreviation for polybutadiene |
| PCP | Abbreviation for polychloroprene |
| Peptiser | A compounding material used to accelerate, by chemical action, the softening of rubber under the influence of mechanical action or heat (or both). |
| Peptizer | A chemical used in small proportions added to a rubber compound to accelerate by chemical action the breakdown and softening of rubber under the influence of mechanical action or heat, or both |
| Perforated | To make a line of holes for purposes of easing the separating of two or more items. |
| Performance Test | See Service Test |
| Permanent Set | The amount by which an elastic material fails to return to its original form after a deformation. In the case of elongation, the difference between the length after retraction and the original length, expressed as a percentage of the original length, is called the permanent set. Permanent set is dependent on quality and type of rubber, degree and type of filler loading, state of vulcanization, and amount of deformation. |
| Permeability | To permit passage of gas through the molecular structure of a given material. |
| Peroxide | One of the ingredients which can be used for vulcanising rubbers. |
| Ph | The measure of the strength of an acid or base. On the pH scale, a neutral solution (neither acidic or basic) has a pH of 7. Solutions with a pH below 7 are acidic; the smaller the pH value, the more acidic the solution. Solutions with a pH above 7 are basic. |
| Phase | A physically homogeneous, mechanically separable portion of a material system |
| Phenolic | A synthetic resin produced by the condensation of an aromatic phenol with an aldehyde, particularly phenol with formaldehyde. |
| PHR | Abbreviation for parts per hundred of rubber, used for indicating the proportions of ingredients in a rubber ompound. |
| Pickling | Removing surface oxides from metals by a chemical reaction. |
| Pig | Roll of rubber cut from a mill. |
| Pigment | A material used to impart colour to a rubber compound. |
| Piston | A cylindrically-shaped part which fits within a cylinder and transmits or receives motion by means of a connecting rod (Cylinder Rod). |
| Piston Bearing Rings | Also called guide rings, wear rings, piston guide rings. |
| Piston Guide Rings | Also called guide rings, wear rings, piston rings usually made from nylon or POM. |
| Piston Rings | Any ring used on the piston of a hydraulic or pneumatic cylinder. |
| Piston Seals & Packings | Any seal or packing ring used on the piston of a hydraulic or pneumatic cylinder. |
| Piston T-Seals | A “T” shaped rubber seal, with back-up rings of a harder material on each side, used as a piston seal. |
| Pita® Gasket | 100% expanded PTFE gasket with fully encapsulated corrugated, stainless steel insert. VSP Technologies’ patented construction transforms conventional ePTFE into a “spring energized” PTFE gasket that maintains high tightness throughout thermal cycling in all chemical services. |
| Pitch-Based Carbon | A carbon fiber derived from the carbon residue found at the bottom of a cat cracker in a refinery. |
| Pitting | Surface cavities that occur on a metal as a result of galvanic corrosion or mechanical erosion. |
| Plaited | Braided. |
| Plantation Rubber | Crude natural rubber obtained from cultivated rubber trees as opposed to wild or uncultivated trees. |
| Plastic Flow, Or Deformation | The deformation of a plastic material beyond the point of recovery, accompanied by continuing deformation with no further increase in stress |
| Plasticiser | A substance, usually a heavy liquid or oil, which is added to an elastomer to decrease stiffness, improve low temperature properties, reduce cost and/or improve processing. |
| Plasticity | (1) A measure of the resistance to shear of an unvulcanized elastomer; (2) A tendency of a material to remain deformed after reduction of the deforming stress to or below its yield stress. |
| Plasticizer | A substance that softens or plasticizes another substance through its solvent action. |
| Plastisol | A suspension of a finely divided polymer (such as PVC) in a plasticizer |
| Plastometer | An instrument for measuring the plasticity of a material |
| Plateau Effect | The maintenance of the properties of a rubber composition over a broad range of vulcanization times. |
| Plate Finish | A commercially smooth surface, resulting from vulcanization between press plates (platens). |
| Platen | The flat steel or cast iron part of a press that applies heat and pressure to a mold. |
| Plunge Ground | The surface texture of shaft or wear sleeve produced by presenting the grinding wheel perpendicular to the rotating shaft without axial motion. |
| Plunger | A cylindrically shaped part that has a uniform diameter and is used to transmit thrust (as in a hydraulic cylinder) or develop pressure and cause flow (as in a reciprocating pump). |
| Plunger Pump Seals | Packing seal rings used to seal the plunger of a reciprocating pump. |
| Plunger Seals | Sealing rings used on a plunger. |
| Plugs | A cone shaped rubber part used to be forced into a tube end or hole to make a complete seal. |
| Ply | One layer in a laminated structure |
| Ply Adhesion | The force required to separate two adjoining plies in a rubber product. |
| Pmq | ASTM designation for silicone rubbers having both methyl and phenyl substituent groups on the polymer chain. All similar designations ending in Q denote silicone rubbers |
| Pneumatic Seals | Any seal or packing ring, usually flexible rubber, used to seal against compressed air instead of hydraulic fluid or other liquid. |
| Pock marks | Uneven blister-like elevations, depressions, or pimpled appearance. |
| Points of Tangency | The points at which the straight portions of the shell walls intersect the beginning of the radius corners. |
| Poisson’s Ratio | The ratio of lateral concentration per unit of diameter to longitudinal extension per unit of length in a bar of material longitudinally stressed. For a body which does not change its volume on deformation, it is 0.5. For metals, the ratio is usually considerably less than 0.5. In the case of vulcanized rubber, pure gum, having practically no volume change on extension, shows a ratio of approximately 0.5 for small deformations; compounded rubber may increase in volume on extension, consequently the ratio drops below 0.5. For rubber the ratio is constant only for small extensions. |
| Polyblend | A term used to describe colloidal blends of compatible polymers such as PVC and nitrile rubber. At one time, a BFGoodrich registered trademark |
| Polybutadiene | Various polymers formed by the chemical combination of monomers having either the same or different chemical composition |
| Polyester | A durable substrate that is resilient to moisture, solvents, oils, and chemicals. It is available as clear or white material and with a moralized finish. |
| Polymer (a) | A material formed by the joining together of many (poly) individual units (mar) of a monomer. |
| Polymer (b) | A polymer is a very long chain of units of monomers prepared by means of an addition and/or a condensation polymerization. The units may be the same or different. There are copolymers, dipolymers, tri- or terpolymers, quadripolymers, high polymers, etc… |
| Polymer Chain | The chain of elements that form the basis of the structure of a polymer. The elements may be all carbon atoms, carbon and oxygen, silicone, nitrogen, etc |
| Polymerization | A chemical reaction in which the molecules of a monomer are linked together to form large molecules whose molecular mass is a multiple of the original substance. When two or more different monomers are involved, the process is called copolymerization. Polymerization may be via emulsion (SBR, nitrile), ionic (butyl), solution (EPDM, cis-polyisoprene), suspension or bulk (PVC) processes. |
| Polyurethane | A synthetic elastomeric material made by chemically reacting a polyol and a diisocyanate in such a manner that a high molecular weight polymer is formed. |
| Porosity | The presence of numerous small holes or voids. |
| Post cure | Heat or radiation treatment, or both, to which a cured or partially cured thermosetting plastic or rubber composition is subjected to enhanced the level of one or more properties. |
| Pound-Volume | A concept used to calculate the volume cost of a rubber compound as compared to its weight cost. The cost per pound times the specific gravity of the material or compound equals the pound-volume cost |
| Pre-Assembled Joint | The combination of the metal framework and a bellows, factory assembled into a single assembly. |
| Pre-Compression | Compression of the expansion joint during installation (shortening the F/F) so that in the cold position the joint has a given amount of compression in addition to the rated amount of compression. The purpose of pre-compression is to allow for unexpected or additional axial extension. |
| Precure | 1) Premature vulcanization taking place during the process prior to vulcanization. Similar to scorch. 2) Vulcanization taking place in the latex state |
| Preliminary Bill of Material | An initial Bill of Material completed prior to design and print release. |
| Preliminary Process Flow Chart | An early depiction of the anticipated manufacturing process for a product. |
| Prepolymers | As used in polyurethane production, a reaction intermediate of a polyol with an isocyanate, in which either component is in considerable excess of the other. It is capable of further reaction after processing. |
| Pre-Set | Dimension that joints are deflected to insure that desired movements will take place. See Lateral Offset and Manufactured F/F. |
| Press Cure | A method of vulcanizing rubber by the use of heated platens, which can be brought together and separated by hydraulic pressure or mechanical action, to cure rubber sheet under pressure. |
| Preform | The preshaped, uncured material placed in a mold for vulcanization. Preshaping is done to facilitate mold flow, control weight accuracy, etc |
| Press-in Wipers | A wiper or scraper ring for a hydraulic cylinder which has a metal outside diameter so that it can be press-fitted into a housing. |
| Press Length | The length of a product that can be vulcanized at one time in a press, limited by the length measurement of the press. |
| Pressure | Force per unit area, usually expressed in pounds per square inch (PSI) or kilograms per square centimeter. |
| Pressure Absolute | The pressure above zero absolute. (i.e the sum of atmospheric and gage pressure) |
| Pressure, Atmospheric | Pressure exerted by the atmosphere at any specific location. Sea level pressure is approximately 14.7 lbs./sq.in. absolute. |
| Pressure Cycling | The variation of pressure in a system. |
| Pressure, Gauge (Psig) | Pressure differential above or below atmospheric pressure, expressed as lbs./sq.in. or psig. |
| Pressure – (No, Low, Poor) | May refer to inadequate pressure in mold/press, oven heater or autoclave during Cure. Symptoms may be porosity, unfills, blister, low adhesions, etc… |
| Pressure Sensitive | Adhesive that can be applied to a substrate by using light pressures. |
| Pressure Vessel Steel (PVS) | Product intended for pressure vessels and similar end use applications. |
| Primer | A coating applied to the surface of a material, prior to the application of an adhesive to improve the performance of the bond |
| Primary Lip | The normally flexible elastomeric component of a lip seal assembly, which rides against the rotating surface and affects the seal. |
| Process Failure Mode and Effects Analysis (PFMEA) | An analytical technique used by a manufacturing responsible engineer/ team as a means to assure that, to the extent possible, potential failure modes and their associated causes/mechanisms have been considered and addressed. |
| Processability | The relative ease with which raw or compounded rubber can be processed. This can relate to all aspects of manufacturing. |
| Processing Aids | Waxes, low molecular weight polyethylene, metal soaps, petroleum oils, and other agents which dissolve or lubricate rubbers, soften them and act as processing aids. |
| Product Assurance Plan | A part of the Product Quality Plan. It is a prevention-oriented management tool that addresses product design, process design, and when applicable software design. |
| Production Trial Run | Product made using all production tools, processes, equipment, environment, facility; and cycle time. |
| Proofed Goods | Fabrics that have been coated with rubber by spreading rubber solution or dough on the surface. |
| Protective Cover | Outer cover material used to protect boot material during shipment and installation. |
| Protectors | A rubber or plastic cap or cup shaped ring used to protect threads or fragile items during shipping or assembly. |
| Proto-Types | A part that is made during the design process to determine the feasibility or suitability of a project. |
| Proto Types | See proto-types |
| PSI | Abbreviation for “Pounds per Square Inch”, a unit of pressure. |
| PTFE | Abbreviation for Polytetrafluoroethylene, a polymer having excellent chemical resistance. PTFE dispersion is used as a coating for many styles of packing. Some packing styles are constructed of PTFE fibers. Teflon® is DuPont’s trade name for their PTFE materials. |
| PU | Abbreviation for polyurethane. |
| Pulp | In the papermaking industry, pulp is the primary raw material from which paper is made. It is a cellulose fiber product produced by the mechanical and/or chemical processing of wood. |
| Pump Shaft | The metal rod connecting the impeller of a pump to the motor. |
| Pure Gum Stock | See gum stock |
| Purge Fluid | A clean liquid (usually water) which is injected through a flush port to flush solid particles from the stuffing box area to minimize abrasive wear. |
| Purge Port | A hole in the side of a stuffing box through which a flushing fluid is injected. |
| Pusher Rings | A ring that fits against another sealing device to push it in order to activate it or energize it in the absence of pressure or in low pressure applications. |
| P X T Value | A numerical value resulting from the multiplication of the internal pressure and the temperature of the fluid involved. In English system, usually psi x °F = PTValue. |
| Q | |
| QPL | Abbreviation for Qualified Products List (associated with U.S. Government specifications). |
| Quarter Turn Valve | A valve that will fully open or close with a 90-degree rotation of the stem. |
| R | |
| Radial | In the direction perpendicular to a shaft axis. |
| Radial Expansion | The ability for a packing material to spread out in the radial direction of a stuffing box when it is compressed. |
| Radial Lip Seal | A type of seal which features a flexible sealing member referred to as a lip. The lip is usually of an elastomeric material. It exerts radial sealing pressure on a mating shaft in order to retain fluids and/or exclude foreign matter. |
| Radial Load | The total force (load) acting on the seal lip which tends to maintain contact of the lip on the shaft. It is the sum of the forces developed from seal interference and the garter spring. |
| Radial seal | Seal having compression applied to its outside and inside diameters. |
| Radial Shaft Seals | Also called grease seals, rotary seals or shaft seals. Made of rubber to seal grease in housing with a rotating shaft. |
| Radial squeeze | Compression on a seal’s outside and inside diameters. |
| Radial Wall Variation | The difference between the minimum and maximum radial wall dimensions when measured around 360I of the seal lip. |
| Radius Corners | Rounded corners. Measurement from the center of a diameter to its circumference. |
| Raff™ Gaskets | The lowest stress to seal, 100% PTFE-based gaskets. Designed by VSP Technologies for chemical service on FRP/plastic and thin, flat-face flanges such as API 607 manways. |
| Rapid gas decompression (RGD) | Also known as explosive decompression (ED). The rapid release of applied system pressure, causing dissolved gases in the rubber to rapidly expand. If the force of the expanding gas is greater than the strength of the material then cracks, blisters and catastrophic material failures can occur. |
| Rate Of Cure | The relative time required to reach a predetermined state of vulcanization under specified conditions. |
| Raw Rubber | Unprocessed, vulcanizable elastomer, normally implying the natural product. |
| Rebound | Rebound is a measure of the resilience, usually as the percent- age of vertical return of a body which has fallen and bounced. |
| Rebound test | Method of deter- mining the resilient properties of vulcanized rubber, by measuring rebound of a steel ball or pendulum falling from a definite height onto a rubber sample. |
| Reciprocating | Motion of a shaft back and forth in the direction of its axis. |
| Reciprocating Motion | An oscillating, back and forth motion as it normally pertains to a piston rod or valve stem. |
| Reciprocating Pump | A type of pump that relies on the reciprocating motion of a plunger, or series of plungers, to generate pressure and cause flow. |
| Reclaim | Reclaimed rubber, resulting from the treatment of scrap vulcanized rubber in various operations. Reclaim is generally used as an extender or processing aid in natural and SBR compounds rather than by itself. It contains all the constituents of the original rubber scrap (elastomer, carbon black, filler, antioxidants, plasticizers, sulfur, etc.) and runs approximately 50% rubber hydrocarbon. |
| Recovery | The degree to which a product returns to its normal dimensions or shape after being distorted. |
| Recovery (Gasketing) | The increase in thickness of a gasket after a load is removed. |
| Reduced Area Full Face (Raff) Gaskets | Developed by VSP Technologies for low pressure, utility steam systems in U.S. Navy ships per Navy Advisory NR.011-04, MIL-G-24696 GASKET MATERIAL R 031917Z JAN 05. |
| Register | The accurate matching of the plates of a mold. |
| Regular Braid | A type of braided construction which yields a soft, flexible packing material having a square cross-section. Also referred to as “Square Braid”. |
| Reinforcement | The act of increasing the mechanical strength of a rubber. |
| Reinforcing Agent | In rubber compounding, a finely-divided substance or filler which, when properly dispersed in rubber, produces improved physical properties in the vulcanized product, i.e., greater energy of resilience, greater resistance to abrasion, higher modules of elasticity and tensile strength Certain grades of furnace blacks are the most important reinforcing agents for black stocks. For light-colored stocks, calcium silicate, precipitated calcium carbonates, silica and clay are the most commonly used? |
| Reinforcing filler | A compounding ingredient added to the rubber to increase the resistance of the material to mechanical forces. |
| Release Liner | Coated paper applied to the adhesive to protect it until ready for use. |
| Reliability | The probability that an item will continue to function at customer expectation levels at a measurement point, under specified environmental and duty cycle conditions. |
| Remote Handling | Handling without direct individual contact, usually done with robotic arms. |
| Removable Adhesive | Adhesive that can be removed from a surface without leaving a residue. |
| Reproducibility | The variation in the average of measurements made by different operators using the same gage when measuring identical characteristics of the same parts. |
| Resilience (a) | The property of a material that enables it to return to its original size and shape after removal of the stress which causes the deformation. |
| Resilience (b) | The energy returned by vulcanized rubber when it is suddenly released from a state of strain or deformation. The returned energy, expressed as a percentage of the original potential energy, is a measure of the resilience. Various rebound testers are used to measure rebound (Bashore, Lupke). |
| Resilient | Able to recover rapidly, i.e. elastic. |
| Retaining Rings | Segmented metal rings installed directly against the back of the expansion joint flange and bolted through to the metal flange of the pipe. |
| Retarder | Any substance whose presence in relatively small proportions retards a chemical reaction. Specifically, a substance which when added in small proportion to a rubber compound retards the rate of vulcanization. An anti-scorching agent; examples, phthalic anhydride, salicylic acid. |
| Reversion (a) | A deterioration of physical properties that may occur upon excessive vulcanization of some elastomers, evidenced by a decrease in hardness and tensile strength, and an increase in elongation; (2) A similar change in proper- ties after air aging at elevated temperatures. Natural rubber, butyl, polysulfide and epichlorobydrin polymers exhibit this effect (extreme reversion may result in tackiness). Most other polymers will harden and suffer loss of elongation on hot air aging. |
| Reversion (b) | The softening of some vulcanized rubbers when they are heated too long. Usually accompanied by an increase in extensibility, a decrease in tensile strength and a lowering of the stress required to produce a given elongation. Extreme reversion may result in tackiness; the rubbers “revert” to an unvulcanized then to a non-polymeric condition. |
| Rex Hardness | The hardness of a rubber compound as determined by the Rex gage. It has the same values as Durometer hardness. |
| Rhc | The Rubber Hydrocarbon Content of a rubber, reclaim or compound. Natural rubber is 92-95% hydrocarbon. |
| Rheology | The science of deformation and flow of matter. Deals with the laws of plasticity, elasticity and viscosity and their connections with paints, plastics, rubber, oils, glass, cement, etc… |
| Rheometer (Monsanto) | An oscillating disk cure meter used for determining vulcanization characteristics of a rubber compound. |
| Rib | A long, narrow projection which is normally triangular in cross-section and which is molded into the outside lip surface of a helix seal. It is oriented at an angle to the shaft axis. One end of the rib forms part of the seal-lip contact surface. |
| Rimseal | A sealing device used on the rim of round plate or rim of a wheel. |
| Rings | Round sealing devices. |
| Rising/Rotating Stem Valve | A valve in which the movement of the stem is both reciprocating and rotating at the same time, usually following a helical path. |
| Rising Stem Valve | A valve in which the movement of the stem is simply reciprocating, with no rotation. |
| RMA | Abbreviation for the Rubber Manufacturers Association. |
| RMS | Root Mean Square – The measure of surface roughness, obtained as the square root of the sum of the squares of micro-inch deviation from true flat. |
| Rms (See Finish) | Root Mean Square, or average deviation from a theoretically perfect surface, is used to define surface finish roughness. |
| Rod | The metal shaft which extends from the piston to outside the cylinder. |
| Rod Seals | Any seal used on the rod of a hydraulic or pneumatic cylinder made from rubber or plastic. |
| Roll | Sheet rubber and gasketing material of a uniform width rolled up on itself from which gaskets and other products of various shapes may be cut. |
| Rollers | A round, flat ring used as a wheel or guide. |
| Rotary | The motion of a body turning on an axis. |
| Rotary Seals | Seals used on rotating shafts – see lips seals, grease seals, oil seals. |
| Rotary Service | A dynamic type of sealing application in which one member remains stationary while the other moves past it in a rotating mode. This type of service generally involves a continuous motion between members and higher surface speeds than those encountered in reciprocating applications. The generally higher degree of frictional heating combined with the fact it is concentrated in one area, sometimes lead to heat-related seal problems. |
| Rotational Molding Or Casting | A procedure used to make hollow articles from liquid polymers or dispersion; may be thermoplstic or thermoset. The material is charged into a hollow mold capable of being rotated in one or more planes. The heated mold fuses the plastic or cures the reactive liquid polymer after the rotation has caused it to cover all surfaces. |
| Rotation (Flange) | The warping, bowing or bending of a flange that can occur from too much bolt load. |
| Roto Glyd | A flat plastic, PTFE or PTFE ring used on a rotating shaft. |
| Roughness | Irregularities in shaft surface texture which result from the production process. (See SAE J448a [June, 1963].) |
| Rough Trim | A trimmed surface with irregularities on the outside and inside lip surfaces in the immediate vicinity of the contact line. |
| Round Braid | A braiding method that yields a hollow tube of yarn. See also “Braid Over Braid” and “Braid Over Core”. |
| RPM | An abbreviation for “Revolutions Per Minute”, a measurement of the rotary speed of a rotating shaft. |
| RTV | Abbreviation for room temperature vulcanisation. |
| Rubber | A material that is capable of recovering from large deformations quickly and forcibly, and can be, or already is, modified to a state in which it is essentially insoluble (but can swell) in boiling solvent, such as benzene, methyl ethyl ketone, and ethanol-toluene azeotrope. A rubber in its modified state, free of diluents, retracts within 1 minute to less than 1.5 times its original length after being stretched at room temperature (18 to 29oC) twice its length and held for 1 minute before release. |
| Rubber Based Adhesive | Made from natural and synthetic rubber compounds. They have excellent initial tack but low temperature and aging resistance. |
| Rubber Latex | Colloidal aqueous emulsion of an elastomer. |
| Run Out | A measurement of how far a shaft moves in the radial direction. |
| S | |
| SAE | Society of Automotive Engineers. |
| SBR | Abbreviation for styrene-butadiene rubber. |
| Scarf Cut | See “Bevel Cut”. |
| Scission | Breaking of chemical bonds |
| Scoop Trim | A trimmed surface which is concave. |
| Scorch | Premature vulcanization of a rubber compound, generally due to excessive heat history. Also see Mooney Scorch; |
| Scorching | A term frequently used to denote premature vulcanization of a rubber compound, occurring on a mill or calendar, or in an extruder. Same as burning or “setting up”. |
| Scoring | Marking the substrate with lines, grooves, or notches for bending or contouring purposes. |
| Scraper Rings | A ring which rides tight against a rod, with a sharp lip to scrape or wipe off excess oil, dirt or dust in a hydraulic or pneumatic cylinder. |
| Scrapers | Also, called a wiper ring – A ring which rides tight against a rod, with a sharp lip to scrape or wipe off excess oil, dirt or dust in a hydraulic or pneumatic cylinder. |
| Scratch | A shallow discontinuity in the seal material whereby no material is removed. |
| Screw | Rotating member with a helical groove to propel rubber through the barrel of an extruder. |
| Seal | An elastomeric ring-shaped component used in a constantly moving, dynamic application – either reciprocating or rotating shaft – providing a near positive no leak mode in a hydraulic cylinder, ram, mixer or gear box – as examples. (Note: no sealing device is absolutely 100% positive). Seal rings can be u-shaped, v-shaped, o-shaped, metal inserted, radial lipped, multiple lipped or a simple flat ring. |
| Sealability | The measure of fluid leakage both through and across both faces of a gasket. Measured either by using ASTM F-37 or DIN 3535 equipment and procedures. |
| Seal Assembly | A group of parts, which includes sealing surfaces, provisions for initial loading, and a secondary sealing mechanism which accommodates the radial movement necessary for installation and operation. |
| Seal Cages | A special device used to assist a seal ring. |
| Seal Case | A rigid member to which the seal lip is attached |
| Seal Gasket | A gasket that is placed between two adjacent metal parts to make a gas tight connection. |
| Seal Kits | Any group of seals, o-rings, wiper rings and back-up rings used to repair a specific hydraulic cylinder. |
| Seal Outer Diameter | The external diameter of a lip-seal assembly, which normally corresponds to the outer diameter of the outer seal case. |
| Seal Solution | Any gasket or seal, which, when properly installed, prevents the escape of matter. |
| Seams | A line, groove, or ridge formed by the joining of edges. A seam can be a weak or vulnerable area, especially for EMI considerations. |
| Seating Load | The load required to properly compress a seal. This will vary depending on the size and shape of the seal. (This does not include operating hydro end forces.) |
| Seats | A stationary ring which is pressed into housing and acts as the matching face of a mechanical seal. |
| Seamless Construction | An exceptional attribute of deep drawn shells. Deep drawn shells have no seam. |
| Secondary accelerator | An accelerator used in smaller concentrations, when compared to the primary accelerator, to achieve a faster rate of vulcanisation. |
| Self-Energizing O-Ring | O-ring with a hole drilled on the pressure side, allowing pressure to equalize inside the O-ring; prevents collapse of the ring. |
| Service Test | A test in which the product is evaluated under actual service conditions |
| Set | Deformation remaining after complete release of the force producing the deformation |
| Set Back (Stand Of Height) | The distance the expansion joint is set back from gas stream to allow for lateral movements and to prevent the joint from protruding into the stream or rubbing on the baffle when operating under negative pressure. Set back also reduces the heat input and prevents abrasion from solids or particles in the stream. |
| Set Up | When a stock is said to be “set up,” it has scorched, and vulcanization has started. It can no longer be processed smoothly. |
| SI | Abbreviation for International System of Units. (See ASTM E380.) |
| Shaft | The metal rod connecting the impeller of a pump to the motor. |
| Shaft Eccentricity | The radial distance which the geometric center of a shaft is displaced from the axis of shaft rotation. |
| Shaft Lead | Spiral grooves on a shaft surface caused by relative axial movement of grinding wheel to shaft. |
| Shaft Repair Kits | A package of seals which includes all seals needed to repair the rod end of a hydraulic or pneumatic cylinder. |
| Shaft Runout | See: Dynamic Runout. |
| Shaft Seal & Packings | Any seal ring used on the rod of a hydraulic ram. |
| Shaft Surface Finish | See: Shaft Surface Texture. |
| Shaft Surface Texture | A term used to describe the quality, appearance, or characteristics of the shaft surface resulting from operations, such as grinding, polishing, burnishing, etc. See SAE J448a (June,1963) for additional information. |
| Shallex | A brand name for vee packings, chevron or parachute packings. |
| Sheeter | The special calender used to make compressed sheet. |
| Sheet Materials | Rubber or fibrous material used to make gaskets. |
| Sheet Molding Compound | “SMC” is a compression molding material consisting of glass fibers in a thickened polyester resin, possibly modified with liquid nitrile polymers for increased fracture resistance |
| Shelf Aging | The natural deterioration of rubber articles kept in storage or “on the shelf” under normal atmospheric conditions. This slow deterioration is due primarily to oxygen and ozone attack. |
| Shelf Life | The length of time a product can be stored, under specific conditions, before the product expires. Each product varies depending on the material, adhesive, and printing process (check with Production for specifics). |
| Shims | Flat, thin metal gasket-like parts used as spacers to position machinery or align equipment. |
| Shipping Straps Or Bars | Braces that are located between the two expansion joint flanges to prevent overcompression or distortion during shipment and joint assembly. |
| Shore A Hardness | An indentation method of rating the hardness of rubber using a Shore Durometer with the A scale from 0 to 100. |
| Shore hardness | The relative hardness of an elastomer measured on a Shore durometer instrument. |
| Shrinkage | Contraction of molded rubber upon cooling. |
| Silicone Adhesive | Adhesives made from silicone polymers that have excellent high temperature resistance. |
| Silicone Rubber | A rubber prepared by the action of moisture on dimethyl dichloro silane and other halosilanes. They are characterized by serviceability at very low and very high temperatures. |
| Simulation | The practice of mimicking some or all of the behavior of one system with a different, dissimilar system. |
| Single Acting Seals | Rings which are designed to seal only in one axial direction. |
| Single-End Coating | The process of applying a coating to the individual yarns (or “ends”) of a packing before they are braided. This process results in a very thorough, uniform coating throughout the braid. |
| Sink Mark | A depression in the surface of a part caused by: 1) the collapse of blister or bubble, or 2) internal shrinkage in injection molded parts, or 3) shrinkage over rubber area in rigid sheet plastics |
| Size, Actual | Actual dimensions of the part, including tolerance limits. |
| Size, Nominal | Approximate size of part in fractional dimensions. |
| Skim Coat | A layer of rubber laid on a fabric but not forced into the weave. Normally laid on frictioned fabric. |
| Skin | A relatively dense layer at the surface of a cellular material. |
| Skive | The process of slicing or veneering off a sheet of PTFE from a billet. |
| Skive Cut | See “Bevel Cut”. |
| Slab | A thick sheet |
| Sleeve | A metal cylinder that is placed over a pump shaft in the sealing area. In pumping applications, certain media and packing materials can cause abrasive wear on the rotating surface. A sleeve is a relatively inexpensive, replaceable component which protects the pump shaft from wear. |
| Slip O-rings | A type of ring which fits over an o-ring to relieve friction. |
| Slip Stick | A friction related phenomena in which the sealing element tends to adhere and rotate with the shaft surface momentarily until the elastic characteristics of the sealing element overcome the adhesive force, causing the seal lip to lose connection with the rotating shaft long enough to allow leakage. This cycle repeats itself continuously and is normally associated with non-lubricated and boundary-lubricated conditions. |
| Slurry | A fluid mixed with solid particles. In packing applications handling slurries, abrasion is a major concern. Steps must be taken to minimize abrasive wear of the packing materials. |
| Smoke sheets | Plantation natural rubber sheets that, after passing through a mill that puts the conventional ribbing design on them, are washed and hung on racks in a smoke house where they undergo a combined smoking and drying process. |
| Snap-in Wipers | A rod wiper which is made from one homogeneous material, either rubber or polyurethane, which is designed to snap-fit into a matching machined groove. |
| Soapstone | A soft powder or stone, basically hydrated magnesium silicate, having a soapy feel, used to dust the surface of unvulcanized rubber compounds it keep them from sticking together. Similar to talc. |
| Solubility | The degree to which one substance will dissolve in another |
| Spacers | A ring with flat sides to provide specific dimensional spacing between two components. |
| Special Characteristics | Product and process characteristics designated by the customer including govern- mental regulatory and safety; and/or selected by the supplier through knowledge of the product and process. |
| Specifications (Specs) | The details of a part: dimensions, material call outs, type style, size information, etc. |
| Specific Contact Pressure | Seating load divided by seal contact area. |
| Specific gravity | The ratio of the mass of a unit volume of a material to that of the same volume of water at a specified temperature. |
| Specific Volume | The reciprocal (1/Sp. Grav.) of specific gravity. Also expressed as the ratio between the volume of one pound of water and the volume of one pound of material |
| Speedy Sleeves | The name of a thin, round tube which slips over a rotating shaft to provide a new, clean sealing surface for rubber lip oil or grease seal. |
| Spiral Trim | A trimmed surface which has a spiral pattern. |
| Splices | Procedure for making endless boot or bellows from open-ended material. Splicing may be accomplished by one or more of the following: cementing, bonding, heat sealing, stitching, vulcanizing, or mechanical fasteners. |
| Sponge Rubber | Cellular structure produced by adding gasifying substance to rubber compound, expanding and curing in heated mold. Cells may be open (interconnecting) or closed. |
| Spool Packing | Packing material that is braided and sold on a spool, as opposed to cut-ring sets or die-formed ring sets. |
| Spreading | Coating, normally a fabric, with rubber. |
| Spring Energized Seals | Any sealing ring that utilizes a metal garter spring or finger spring to assist in energizing the seal when there is not sufficient pressure. |
| Spring Groove | A depression formed in the head section of the seal. It is generally semicircular in form and serves to accommodate and locate the garter spring. |
| Spring Loaded Seals | See spring energized seals above. |
| Spring Outside Coil Diameter | The outer diameter of an individual helical coil of a garter spring. |
| Spring Rate | The force in pounds required to deflect an expansion joint one inch in compression and elongation or in a lateral direction. |
| Spring Retaining Lip | The portion of the primary lip that restricts the axial movement of the extension spring from a predetermined position. |
| Spring Witness Marks | A series of indentations or depressions remaining in the spring groove of a radial lip seal after the spring has been removed or dislocated. |
| Sprue | (1) The primary feed channel that runs from the outer face of an injection or transfer mold to mold gate in a single cavity mold or to runners in a multiple cavity mold; (2) The piece of material formed or partially cured in the primary feed channel. |
| Sprue mark | A mark, usually elevated, left on the surface of an injection or transfer molded part, after removal of the sprue. |
| Square Braid | A type of braiding construction that yields a soft, flexible packing material having a square cross-section. Also referred to as “Regular Braid”. |
| Squeeze | Cross section diametrical compression of O-ring between bottom surface of the groove and surface of other mating metal part in the gland assembly. |
| Squeeze Seal | Also known as “Installation Activated”, a squeeze seal relies on the squeeze or compression it achieves at installation to create a seal. This squeeze or compression is due to its high degree of interference. This type of seal generally seals well at low pressure; however, in dynamic applications, it is characterized by a high wear rate and friction. |
| Stabiliser | A substance added to a rubber to maintain properties at or near their initial values during its production, processing and storage. |
| Stack Height | 1) The combined height of all the rings of a packing set. 2) The combined height of all the components in a stack of Belleville washers used to live-load a packing set. |
| Staining | Change of colour of a rubber when exposed to light or change of colour in a material in contact with, or adjacent to, a rubber. |
| State of cure | The cure condition of vulcanization relative to that at which optimum physical properties are obtained. |
| Static Seal | A seal whose sealing surface sees no motion-the opposite of dynamic seal. |
| Stem | The metal rod that connects the internal components of a valve to a handwheel, handle, or actuator. |
| Steam Cure (Open) | A method of vulcanizing rubber parts by exposing them directly to steam in a vulcanizer |
| Stem Packing | A type of homogeneous or multi-braided packing used on the stem of a valve to stop leakage. |
| Stepseal | A seal ring with a step cut groove to match up against a housing machine to fit. |
| Stock | In the papermaking industry, stock is the wet pulp mixture at any point in the papermaking process. |
| Strain | The unit change, due to force (stress), in the size or shape of a body compared to its original size or shape-it is non-dimensional quantity, but is frequently expressed in inches per inch, centimeters per centimeter, etc. |
| Strain Harden | Tempering through strain. Same as work harden. |
| Strength-to-Weight Ratio | The ratio of tensile strength to the weight of a material. |
| Stress | Force per unit of original cross sectional area required to stretch a specimen to a stated elongation. |
| Stress relaxation | The decrease in stress after a given time of constant strain. |
| Stress-Strain | The relationship of load and deformation in a body under stress. In rubber this is most commonly the relationship of tension (stress) and elongation (strain). |
| Strong Oxidizer | In packing applications, strong oxidizers cause the degradation of organic packing materials such as carbon, graphite and cellulos- ic fibers. PTFE packing materials are usually used in these applications due to their oxidation resistance. |
| Stuffing Box | The space into which compression packing is inserted. Also known as a “Packing Gland”. |
| Substrate | A material upon the surface of which an adhesive promoter is applied for any purpose such as bonding or coating. |
| Subsystem | A major part of a system which itself has the characteristics of a system, usually consisting of several components. |
| Suction Pressure | The fluid pressure measured on the suction (or inlet) side of the pump where the fluid enters the volute. |
| Sulphur | An agent responsible for the vulcanisation of some rubbers |
| Sun Checking | Surface deterioration in the form of cracks, checks, or crazing caused by exposure to direct or indirect sunlight. |
| Surface Finish | A measure of the roughness of a surface, usually expressed in microinches or micrometers. |
| Surface Speed | The linear speed of a point on the surface of a rotating shaft, usually expressed in FPM or m/sec. |
| Surge Pressure | Operating pressure plus the increment above operating pressure that the expansion joint will be subjected to for a very short time period. Surge Pressure is typically due to pump starts, valve closing, etc. |
| Sw | A Garlock Metallic Gasket style consisting of a winding alone, without a centering ring |
| Swelling | The increase in volume or linear dimensions of a specimen immersed in a liquid or exposed to a vapor. |
| Swi | A Garlock Metallic Gasket style consisting of a winding and an inner ring. |
| Switch Seals | Seals used in electrical switching devices to keep moisture out. |
| Symmetrical Seals | A seal that has the same shape on either side of its center line. |
| System | A combination of several components or pieces of equipment integrated to perform a specific function. |
| T | |
| Tack | The ability to adhere to itself; a sticky or adhesive quality. |
| Tackifier | A compounding material that enhances the ability of vulcanised rubber to adhere to itself or another material. |
| Team Feasibility Commitment | A commitment by the Product Quality Planning Team that the design can be manufactured, assembled, tested, packaged, and shipped in sufficient quantity at an acceptable cost, and on schedule. |
| Tear Resistance | Resistance to tearing, measured as the force required to tear completely across a specially-designed nicked rubber test piece or right-angled test piece by elongating it at a specified rate. Express in lbs. per inch of thickness of specimen. |
| Tear Strength | The maximum load required to tear apart a specified specimen, the load acting substantially parallel to the major axis of the test specimen. |
| Telescopic Packing | Packing sets used on telescopic cylinders, each stage having a different diameter. |
| Temperature Range | Lowest temperature at which rubber remains flexible and highest temperature at which it will function. |
| Tensile Strength | The capacity of a materiel to resist a force tending to stretch it. Ordinarily the term is used to denote the force required to stretch a material to rupture, and is known as “breaking load”, “breaking stress “ultimate tensile strength”. lit rubber testing, it is the load in lbs. per square inch or kilos per square centimeter of original cross-sectional area, supported at the moment of rupture by a piece of rubber being elongated at a constant rate. |
| Tensile Stress | The applied force per unit of original cross sectional area of a specimen. |
| Tensile Stress at Given Elongation | The tensile stress required to stretch a uniform section of a specimen to a given elongation. |
| Tension Set | The extension remaining after a specimen has been stretched and allowed to retract. |
| Terpolymer | A polymer formed from three monomer species. |
| Texture | A screen-printing process that applies a coating to the surface of the substrate. The coatings are available in fine or coarse finishes. This process allows for the protection from chemical attack, it can improve the light distribution of a LED, and it can protect the surface of an overlay from scratches. |
| Texturization | The process of embossing a texture on the surface of graphite foil to achieve better adhesion between layers of graphite foil, and prevent delamination of a die-formed graphite ring. |
| TGA | Thermogravimetric Analysis. A test procedure used to determine the thermal stability or composition of a material. Two modes are possible; determining the change of weight of a specimen while changing temperature at a given rate of the change of weight of a specimen with time at a fixed temperature. |
| Thermal Barrier | A layer of insulating material designed to reduce the surface temperature at the gas sealing layer to a level compatible with its heat resistance capability. |
| Thermal Conductivity | A measure of the rate at which thermal energy is transferred through a substance. High thermal conductivity is an advantage in pump packing applications where it is important to transfer frictional heat away from the shaft/ packing interface so that the packing does not burn. |
| Thermal Cycling | The repeated heating and cooling of a tank, vessel or piping system. The duration of the cycle can vary tremendously. |
| Thermal degradation | An irreversible change in the properties of a material due to exposure to heat. |
| Thermal Deterioration | The elongation at the moment of rupture. |
| Thermal Expansion | The increase in volume or length of a material that occurs as a result of a temperature increase. |
| Thermal Movements | Movements created within a system caused by a thermal change. Can be axial, lateral, or torsional. |
| Thermoplastic | Applied to high polymers which soften by the application of heat and which may be resoftened by heating, provided chemical decomposition does not take place. |
| Thermoplastic elastomer (TPE) | A diverse family of rubber-like materials that, unlike conventional vulcanised rubbers, can be processed and recycled like thermoplastic materials. |
| Thermoplastic Rubber | Rubber that does not require chemical vulcanization and will repeatedly soften when heated and stiffen when cooled; and which will exhibit only slight loss of its original characteristics. |
| Thermoset | Materials that undergo chemical cross-linking of their molecules when processed, and cannot be softened and reshaped following further application of heat. |
| Thermosetting | Capable of being changed into a substantially infusible or insoluble product when cured under application of heat or chemical means. |
| Thermosetting Rubber | Chemically vulcanized rubber that cannot be remelted or remolded without destroying its original characteristics. |
| Thorseals | A brand name for a polyurethane hydraulic u-cup seal. |
| Timing Plan | A plan that lists tasks, assignments, events, and timing required to provide a product that meets customer needs and expectations. |
| Tinsel | Fine slit widths of metallic foil. Die-formed rings are made from tinsel and used as junk rings, bushings, and in some cases even as bearings. Garlock manufactures rings made from copper tinsels. |
| Tips | A rubber cup-shaped part used on the end of a rod or shaft to provide shock resistance or cushioning. |
| Tolerance | The specification of allowable deviation from exact original (measurable) specifications. |
| Torsilastic Spring | A cylindrical rubber spring consisting of an inner shaft, an outer shell, and a solid layer of rubber of substantial thickness between, and adhered to the shaft and shell. |
| Torsional Rotation | The twisting of one end of an expansion joint with respect to the other end about its longitudinal axis. Such movement being measured in degrees as is angular rotation. |
| TR-10 | A measure of the low-temperature capability of an elastomer. It is the temperature at which a stretched and frozen specimen has retracted 10% of the stretched amount. TR stands for 'temperature retraction'. |
| Tr Test | A method for evaluating the low temperature characteristics of a vulcanized part by measuring the temperature at which retraction over the range of 10 to 70% of original elongation occurs. The test is generally employed to determine the susceptibility of a rubber crystallize. The specimen is stretched at room temperature, cooled to very low temperature, released and warmed at a uniform rate. |
| Transfer moulding | The process of moulding a material by forcing rubber from a reservoir chamber through a gate into the moulding cavity of a closed mould. |
| Transfer Tape | An unsupported adhesive on a liner. |
| Trapped Air | The air that is enclosed in a product or between a mold surface and a product during vulcanization. |
| Trim | The process Involving removal of mold flash. |
| Trim Cut | Damage to the elastomeric portion of the seal during trimming. |
| Trimmed Lip Diameter | The lip diameter in the free state (no spring) developed by knife trimming the molded portion of the sealing element to form the contact line. |
| Trimming Angle | The angle between the trimmed face of a seal lip and the seal axis. |
| T-Seals | A “T” shaped rubber sealing ring with harder back-up rings on each side for rod or piston sealing. |
| Tube | The inner ply of the expansion joint that is in direct contact with the system media. |
| Tube Springs | A rubber or plastic cushioning device used to assist spring or cover the outer portion of a coil spring. |
| Tumbling | A finishing process for removing flash from a molded part by placing in a rotating barrel with or without the added finishing material such as shells, dry ice, etc. |
| U | |
| U-Cup | a type of seal used in a hydraulic or pneumatic cylinder. It’s cross section is U-shaped to allow oil to energize the seal body to properly block oils and seal correctly. |
| U-cups | A “U” shape cup sealing ring designed to seal in one direction along a shaft or rod in a hydraulic or pneumatic cylinder. |
| Undercure | Degree of cure less titan optimum. May be evidenced by tackiness, loginess (lack of snap or resilience), or inferior physical properties. |
| UL94 | Underwriters Laboratory’s rating for flame spread. |
| Ultra Accelator | A generic term for a class of vulcanization accelerators that are very active and are generally used in very small quantities (less than 1 part). |
| Ultraviolet Light | A form of energy occupying a position in the spectrum of sunlight beyond the violet, and having wavelengths of less than .4mm. which is the limit of visible light. Ultraviolet rays are very active chemically, exhibit bactericidal action, and cause many substances to fluoresce. Their action accelerates deterioration of rubber pats exposed to them and can initiate polymerization. |
| Ultimate Elongation | The maximum elongation prior to rupture. |
| Unbonded Flash | Flash which does not properly adhere to the mating material to which it is intended to be bonded. |
| Uncompressed Height | The height of a packing set or packing ring before being compressed in the stuffing box. |
| Undercure | State of vulcanization less than optimum. It may be evidenced by tackiness or inferior physical properties. |
| Unirotational Seal | A seal, designed for applications having a single direction of shaft rotation. |
| Unitized Seal | A seal assembly in which all components necessary for accomplishing the complete sealing function are retained in a single package. |
| Unsaturation | In organic compounds the linking of some of the atoms of the molecule by more than one valency bond, ie, double or triple bonds. |
| U-Packings | A “U” shape cup sealing ring designed to seal in one direction along a shaft or rod in a hydraulic or pneumatic cylinder. |
| U-Seals | A packing in which the element has a “U”-shaped cross-section. |
| UV absorber | A compounding material that retards the deterioration caused by sunlight and other UV light sources. |
| V | |
| Vacuum | Negative pressure, when a gasket or seal is used to prevent the passage of external media or air into the system. |
| Valve Body | The part of a two-piece valve that houses the internal workings of the valve. The flanges that attach the valve to a pipeline are also part of the body. |
| Valve Bonnet | The part of a two-piece valve that attaches to the valve body. It houses the stuffing box and provides support to guide the valve stem. |
| Valve Discs | A PTFE or PTFE disc used on a valve as a seat to provide positive sealing when shut off. |
| Value Engineering (Value Analysis) | A planned, clean sheet approach to problem solving, focusing on specific product design and process characteristics. Where value analysis is employed to improve value after production has begun, value engineering is employed to maximize value prior to expenditures of facilities and tooling money. |
| Valve Packing | Braided packing used in the stuffing box of a valve stem to make a positive seal. |
| Valve Seats | A PTFE or PTFE disc or ring used on a valve as a seat to provide positive sealing when shut off. |
| Valve Stem | See “Stem”. |
| Valve Stem Packing | Braided packing used in the stuffing box of a valve stem to make a positive seal. |
| Vee Packing | Also called V-Packing, Vee packing, Chevron Packing, Parachute packing or v-set packing. A complete vee packing set contains multiple “V” shaped sealing rings stacked and nested together with a male adapter on one end and a female adapter on the other end. |
| Vibration | The ability of a flexible connector to absorb mechanical oscillations in the system. |
| Vibration Mounts | A rubber piece used to eliminate vibration between to components. |
| Vinyl | Vinyl is cost effective and highly versatile. Vinyl is strong, durable, abrasion and moisture resistant; withstands rust and corrosion; is electrically non-conductive and has excellent fire performance properties. Vinyl can be produced in almost any color, with products ranging from opaque to crystal-clear. |
| Visco-elasticity | A combination of viscous and elastic properties in a material. |
| Viscosity | The resistance of a material to flow under stress. |
| Vhap | Abbreviation for “Volatile Hazardous Air Pollutant”. |
| VMQ | Abbreviation for vinyl methyl silicone. |
| VOC | Abbreviation for “Volatile Organic Compound”. |
| Voice of the Customer | Customer feedback both positive and negative including likes, dislikes, problems and suggestions. |
| Voice of the Process | Statistical data that is feedback to the people in the process to make decisions about the process stability and/or capability as a tool for continual improvement. |
| Voids | The absence of material or an area devoid of materials where not intended. |
| Volume Cost | Costs calculated on the basis of unit volume rather than unit weight. (See Pound Volume.) |
| Volume Swell | Increase in physical size caused by the swelling action of a liquid. |
| Volute | The internal area (housing) of a centrifugal pump where the fluid comes in contact with the impeller. |
| V-Packings | Also called V-Packing, Vee packing, Chevron Packing, Parachute packing or v-set packing. A complete vee packing set contains multiple “V” shaped sealing rings stacked and nested together with a male adapter on one end and a female adapter on the other end. |
| V-Rings | Also called V-Packing, Vee packing, Chevron Packing, Parachute packing or v-set packing. A complete vee packing set contains multiple “V” shaped sealing rings stacked and nested together with a male adapter on one end and a female adapter on the other end. |
| Vsp Anti-Buckling Spiral Wound Gasket Designs | A revolutionary spiral gasket design that eliminates radial buckling at the source. Patented gasket design redirects gasket compression, thus eliminating the need for expensive inner rings and allowing for full gasket compression, even on lightly loaded ASME class 150 flanges. Currently available as Garlock EDGE® gasket. |
| Vulcanisation | Heat induced process whereby the long chains of the rubber molecules become cross-linked by a vulcanising agent to form three dimensional elastic structures. |
| Vulcanising agent | A compounding material that produces cross-linking in rubbers. |
| Vulcanizate | Rubber in its cured or vulcanized state. |
| Vulcanized Splice | A splice that is bonded with heat and pressure. |
| Vulcanizating Agent | Any material which can produce in rubber the change in physical properties known as vulcanization, such as sulfur, polysulfides, organic polynitro derivatives, peroxides arid quinone dioximes. |
| Vulcanization | An irreversible process during which a rubber compound through a change in its chemical structure (for example, cross-linking) becomes less plastic and more resistant to swelling by organic liquids and elastic properties are conferred, improved, or extended over a greater range of temperature. |
| W | |
| Washers | Round, flat rings used as spacers, gaskets or slip devices under the head of a bolt. |
| Water Absorption | The increase in weight and volume after immersion in water. |
| Water resistance | The ability to withstand swelling by water for a specified time and temperature. |
| Wear Rings | Wear rings, guide rings, guiding rings, bearing rings for hydraulic cylinder rods. |
| Wear Sleeves | Wear rings, guide rings, guiding rings, bearing rings for hydraulic cylinder rods. |
| Wear Strips | Strips of abrasion resistant plastic, PTFE or PTFE material – Wear rings, guide rings, uiding rings, bearing rings for hydraulic cylinder rods. |
| Weathering | The surface deterioration of a rubber article during outdoor exposure, such as cracking, crazing, or chalking. |
| Weepage | A minute amount of liquid leakage by a seal. |
| Weld In Baffle | A baffle that is designed to be welded to the duct wall. This design can be either single or double acting type. |
| Welding Blanket | A fire resistant blanket that is placed over the expansion joint to protect it from weld splatter during field welding operation. |
| Weld line | See Knit line |
| Wetting | Completeness of contact between particles dispersed in a medium, such as carbon black rubber. |
| Wheels | Round rollers to provide easy movement of a machine or component. |
| Whip | Deflection of a shaft (usually on a mixer or pump) due to a rotating mechanical load. A long shaft that is not supported by bearings is more susceptible to whip than a short shaft or one that is supported by bearings. |
| Wicking | Leakage through a gasket, not around it. |
| Wiper Rings | Also, called a wiper ring – A ring which rides tight against a rod, with a sharp lip to scrape or wipe off excess oil, dirt or dust in a hydraulic or pneumatic cylinder. |
| Wire-Reinforced | A product containing wire(s) to give added strength, increased dimensional stability or crush resistance. |
| Work Pressure | The maximum operating pressure encountered during normal service. |
| Wrapped Cure | A vulcanizing process using a tensioned wrapper (usually fabric tape) to apply external pressure. |
| X | |
| Rings | Also called quad rings or quatro rings, rubber rings of a special shape used to replace o-rings and eliminate the rolling found when using o-rings. |
| XNBR | Abbreviation for carboxylated nitrile rubber. |
| Y | |
| Yerzley Resilience | Resilience as measured on a Yerzley oscillograph, determined by dividing the vertical height of the rebound of the first cycle of the oscillating system by the preceding vertical height of fall. |
| “Y” Factor | The minimum design seating stress in either psi or megapascals over the contacted area of a particular gasket. The stress required to provide a sealed joint with a 2 psig (virtually 0 psig) internal pressure in the joint. |
| Yarn | Generic term for continuous strands of textile fibers or filaments in a form suitable for weaving or otherwise intertwining to form a textile fabric. |
| Yield | The length of a packing material of a specified weight (Ft/ Lb). The inverse of this value (Lb/Ft) is also sometimes referred to as yield. |
| Yield Point | The load or stress at which a marked increase in the deformation of the sheet occurs without increasing the applied load. Yield point is one of the characteristics of low-carbon steels after they have been annealed. The yield point is usually calculated using a tensile-test specimen, and it is the load that is commensurate with the point beyond the elastic limit at which the specimen lengthens considerably without an additional increase in load. |
| Yield Strength | The stress at which a material exhibits a specified deviation from a linear proportionality between load and elongation. In the tension test, the load associated with an offset of 0.2% from linearity is used for many metals to calculate the yield strength. |
| Young’s modulus | The ratio of normal stress to corresponding stress or compressive stresses below the proportional limit of the material. |
| Z | |
| Zinc Oxide, Activator | Accelerators of vulcanization do not always exert their full influence unless the rubber mixture contains substances known as activators. Zinc oxide is an activator and gives its best activity in the presence of an organic acid like stearic acid with which it forms a rubber-soluble soap. |
| Zurcon | A type of material used to make guide rings, wear rings, bearings or seals. |