Trouble-Shooting Compression Packing Failures

March 3rd at 5:59am

Packing may fail for a variety of reasons. Beside improper installation, packing failures are often due to worn or faulty equipment, shaft misalignment, uneven take-up on the gland bolts, and other causes. If you are having trouble, carefully remove and examine the old packing set. DO NOT THROW THE SET AWAY, because it often gives clues as to the condition of the equipment, and may be the means of solving the problem. The following clues and possible causes were found by examining sets of packing which failed in service.

CLUE-1  Excessive reduction in cross-section of packing directly beneath the rod, shaft or plunger. 

POSSIBLE CAUSE  Rod or plunger out of alignment, and in the case of the rod or shaft, the bearings may be badly worn, causing whipping of shaft.

CLUE-2  Excessive reduction in the thickness of the packing directly over, or in either side of the rod or shaft. 

POSSIBLE CAUSE  Rod or plunger out of alignment, and in the case of the rod or shaft, the bearings may be badly worn, causing whipping of shaft. 

CLUE-3 A whole ring, or part of a ring is missing from set. 

POSSIBLE CAUSE  Bottom of stuffing box badly worn, with packing being extruded into the system. 

CLUE-4  Wear on the outside of one or more rings. 

POSSIBLE CAUSE  Rings rotating with shaft, or loose in the box. Packing too small. 

CLUE-5  Axial bulge in one or more rings. 

POSSIBLE CAUSE  Adjacent rings cut too short or too long, depending on the style of material used, causing packing under pressure to be deformed. 

CLUE-6  Packing shows tendency to extrude between rod or shaft, and the gland follower. 

POSSIBLE CAUSE  Excessive gland bolt pressure and/or too much clearance between the rod or shaft and the gland follower.

CLUE-7  Rings next to gland follower badly damaged, with bottom rings in fair condition. 

POSSIBLE CAUSE  Improper installation of packing and excessive gland bolt pressure used. 

CLUE-8  Wearing surface of rings dried and charred with rest of packing in good condition. 

POSSIBLE CAUSE  High temperature and lack of adequate lubrication. 

CLUE-9  Innermost ring deteriorated. 

POSSIBLE CAUSE  Packing incompatible with fluid handled. 

Grateful acknowledgement to the Fluid Sealing Association in their role in the compilation of About Compression Packing.

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