ABSTRACT
Compression packings are still made in numerous plaited, braided, rolled, folded, and pressed shapes. For many years, packings based on asbestos fiber appeared to be ideal because they have excellent chemical resistance and thermal stability. However in recent decades asbestos was found to be carcinogenic, so its use was discontinued, although none of the alternatives could be regarded as a direct replacement over the whole range of operating conditions that asbestos packings could handle. The alternatives include aramid, glass, polytetrafluorethylene (PTFE) and graphite fibers, and expanded graphite. Advantages of compression packing for sealing the rotating shaft of a centrifugal pump include economy of manufacture of the hardware and the low cost of the sealing material. In practice, to achieve low leak rates with compression packings it is vital to ensure concentricity of shaft to bore, and minimize shaft run-out.
