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Definition and Uses of Compression Packings

Control of fluid loss is essential to the successful operation of mechanical equipment used in fluid handling. Various methods are utilized to control leakage at shafts, rods, or valve stems and other functional parts of equipment requiring containment of liquids or gases.

The oldest and still most common of these sealing devices is the compression packing, so called because of the manner in which it performs the sealing function. Made from relatively soft, pilant materials, compression or jam packings consist of a number of rings which are inserted into the annular space (stuffing box) between the rotating or reciprocating member and the body of the pump or valve. (See figure 1.) By tightening a follower or packing gland against the top or outboard ring, pressure is transmitted to the packing set, expanding the rings radially against the side of the stuffing box and the reciprocating or rotating member, effecting a seal.

Compression packings find their major use in the process industries such as petrochemical, pharmaceutical, chemical, pulp & paper, steel mills, service industries like utilities, marine water, sewage, food and fossil/nuclear power plants. They seal all types of fluids including water, steam, acids, caustics, solvents, gases, oil, gasoline, and other chemicals over a broad range of temperature and pressure conditions. They are used in rotary, centrifugal and reciprocating pumps, mixers, agitators, dryers, valves, expansion joints, soot blowers, and many other types of mechanical equipment.

Compression packings are relatively easy to install and maintain. With proper attention, a high degree of successful operation can be anticipated.

Successful sealing with compression packings is a function of several important related factors:

1) Careful selection of packing materials to meet the specific application requirements.
2) Complete consideration of surface speeds, pressures, temperatures, and medium being sealed.
3) Proper attention to good installation and break-in procedures.
4) High standards of equipment maintenance.

These factors are discussed in other segments of this publication and are covered in detail in most of the product bulletins of the major packing manufacturers.