Envelope Gasket

Polytetrafluoroethylene (PTFE) envelope gaskets are composite gaskets, consisting of a core material such as CNAF wrapped with a sleeve of PTFE. This hybrid gasket possesses the chemical resistance of PTFE as well as the strength and properties of the core insert material. Superior chemical resistance means that process contamination is prevented, and the highest level of hygiene is maintained. PTFE envelope gaskets are also non-corrosive, non-wetting, non-contaminating and odourless.

There are three basic designs of envelopes:

Slit Type:

Sliced from cylinders and split from the outside diameter to within approximately 1/16” of the inside diameter. The bearing surface is determined by the filler dimensions. Clearance is required between the I.D. of the filler and the envelope I.D. The gasket O.D. normally rests within the bolt hole circle and the I.D. is approximately equal to the nominal I.D. of pipe. Available in sizes to a maximum O.D. of 24”.

Milled Type:

machined from cylinder stock. The jacket is machined from the O.D. to within approximately 1/32” of the I.D. The jacket I.D. fits flush with pipe bore and the O.D. nests within the bolts. Available in sizes up to a maximum O.D. of 24”. Milled envelopes are more expensive than slit type since considerably more material is lost in machining.

Formed Tape Type:

large diameter (over 12” NPS) and irregularly shaped envelops are formed from tape and heat sealed to produce a continuous jacket construction.