Compression seal fitting

A compression seal fitting, also known as a sealing gland, is intended to seal some type of element (probe, wire, conductor, pipe, tube, fiber optic cable) when the element must pass through a pressure or environmental boundary. Typical applications include pressure vessels, autoclaves, holding tanks, pipelines, furnaces, or anywhere wires or sensors need to pass from inside to outside a vessel or wall where the pressure differentials or hazardous environments cause concern.

A compression seal fitting, opposed to an epoxy seal, uses an axial force to compress a soft sealant inside a body which then creates a seal. An epoxy seal differs in that it is composed of some type of compound which is poured into a mold in attempt to create a seal. A very basic compression seal fitting is composed of four mechanical parts:

1. The body, which holds the elements being sealed and enables the other components to compress into it.
2. The cap, which secures the sealant and follower into the body. Most importantly, when it is torqued into the body, it pushes the follower into the sealant which creates the axial force and creates the seal.
3. The follower, which is pushed into the sealant from the torque on the cap and compresses the sealant. The sealant then fills all void spaces around the element and between the body.
4. The soft sealant, which surrounds the elements being sealed and when it is compressed by axial force, a hermetic(airtight) seal is created. The continuous tension in the torqued body acts like a spring to maintain compression on the sealant and maintain a positive seal. Some soft sealants include Neoprene, Viton, Teflon, Lava and Grafoil. The appropriate sealant for a gland depends on the environment you are trying to seal against.

This soft sealant technology, in regards to compression seal fittings, was developed in the 1950s by Conax Technologies. The history of compression seal fittings has changed since the 1950s and a compression seal fitting has advanced to include multiple variations for different applications.