COMPRESSION PACKING

Engineering Data/FAQs

Construction

Compression packings are made in a variety of shapes, sizes and constructions, from various materials. The following is a description of basic constructions which are commonly used, and the virtues of each.

Braid-Over-Braid (Figure 1)

Also known as round braid or multiple braid. Round braiding machines braid tubular jackets using yarns, rovings, ribbons and other forms of various materials, either alone or in combination. Size is obtained by braiding jackets one over the other (braid-over-braid). Finished packings can be supplied in round, square or rectangular cross section. Braid-over-braid packings are relatively dense and are recommended for high-pressure, slow-speed applications such as valve stems, expansion joints, groove gasketing, etc.

Braid-Over-Core (Not Shown)

Finished product is produced by round braiding one or more jackets of yarns, rovings, ribbons or other forms of various materials over a core, which may be extruded, twisted, wrapped or knitted. This construction allows for a wide range of densities and different cross sectional shapes.

Square Braid (Figure 2)

Yarns, rovings, ribbons and other various materials, either alone or in combination are processed on equipment where strands pass over and under strands running in the same direction. Resulting packings are usually supplied in square cross section, but rectangular sizes can also be braided by this method. The packing is usually soft and can carry a large percentage of lubricant. Square braided packings are easy on equipment and are generally used for high-speed rotary service at relatively low pressure. The packing's softness makes it usable on old or worn equipment.

LATTICE BRAIDŽ (Figure 3)

Yarns, rovings, ribbons and other forms of various materials, either alone or in combination, are processed on equipment where the strands criss-cross from the surface diagonally through the body of the packing. Each strand is strongly locked by other strands to form a solid integral structure that cannot easily ravel or come apart in service. There are no jackets to wear through, and no plaits to come loose. LATTICE BRAID packing has a more even distribution of yarn density throughout and has the potential for improved lubricant retention. The finished packing is relatively dense, but flexible. LATTICE BRAID packings are suitable for applications on both reciprocating and centrifugal pumps, agitators, valves, expansion joints and in grooves.

Die-Formed

A pre-compressed ring form in which many compression packing materials can be supplied to provide controlled density and size.

Mandrel Cut

Rings formed by wrapping braided stock on a mandrel or shaft equal to the desired I.D., utilizing required cross section.

Graphite Tape

Flexible graphite tape (ribbon) is manufactured by exfoliating (expanding) and then compressing natural graphite flakes to a specific density. Graphite has almost universal chemical inertness and is naturally lubricious, compactable and resilient, as well as nuclear radiation resistant.

Flexible graphite tape can be die molded or compressed to form endless true labyrinth rings. Graphite tape packings have a low coefficient of friction, a pH range of 0-14 and are noted for their excellent thermal properties enabling them to be used in applications to 5500°F (3000°C) in non-oxidizing atmospheres. Due to their temperature resistance and density, they make ideal valve packings in steam, VOC, hydrocarbons or chemical applications when used in combination with braided end rings such as #1303 FEP, #98 or G-700.

Lubricants

Compression packings generally contain lubricants when they are used on rotary equipment where frictional heat is generated. The lubricants provide a resiliency that allows the packing to deform and recover under slight mechanical deficiencies such as shaft deflection. They may also provide interfiber lubricity that reduces frictional heat.

Blocking Agents

Lubricants that act as a fluid barrier by closing the voids that are present in braided materials to prevent leakage through the cross section of the packing.

Single End Coating

A proprietary Garlock process that coats each yarn used in packing prior to the braiding process. This provides a more consistent coating of packing materials for better sealing.