Packing Constructions

TWIST	Twist is made from multiple yarns, roving, or metallic ribbons by turning the individual strands around each other at a constant number of turns per meter. Usually it is round in cross section but in the case of metallic ribbons, it is normally formed into a square cross section but in the case of metallic ribbons. This means that one size may be stocked to seal several stuffing box cross sections. Twisted metallic packings are frequently used as shaft bearing support in gear pumps in addition to performing their packing function.
BRAID OVER BRAID BRAID OVER CORE	Braid-over-braid is made on may-pole type braiding machines usually having between 8 and 32 yarn carriers on the braider deck. These machines generate a braided tube which may be used as a gasket tape. If center stands of a plastic core are used, braid-over-braid and braid-over-core are generated. The finished packings are usually calendared into a square or rectangular cross section. Braid-over-braid and braid-over-core packings are quite dense and, when wire reinforced are normally used in slow speed (below 2.8 m/sec) high pressure applications like valve stems, blade type gate valves, expansion joints, older design plunger pumps, and in gear pumps. Braid-over-braid, when not reinforced with wire, is quite conformable and this is useful in medium speed (7.6 m/sec) low pressure situation when equipment is worn.
PLAIT BRAID	Plait braid, commonly known as square braid, is manufactured on 8 to 24 carrier braiders having two tracks. This classic braid form, generated in a square cross section, is quite soft and normally contains a high percentage of lubricant. It is useful in high speed – low pressure applications (rotary and reciprocating pumps and valves). Since it is ‘softer” than interlocking braid, it is also useful where equipment is worn.
INTERLOCKING BRAID	Interlocking braid is generated on 3 and 4 track braiding machines usually with 12, 18, 20, 32 or 36 yarn carriers which weave the yarns from the surface diagonally though the body of the packing. Because each strand is locked into position by other strands, an integral structure is formed that cannot easily work apart or unravel in use. In normally constructed interlocking braid, there is an even density throughout the braid when straight. It is relatively dense yet is flexible and conformable. These characteristics make it the most universal braid for use in rotating and reciprocating pumps, valves and other equipment even at the highest speeds and pressure.