|Metallic – Ring Gasket
|Compressed Non-Asbestos Fibre Gasket (CNAF)
|Oval Ring Gasket
|Spiral Wound Gaskets
|Octagonal Ring Gasket
|Metal Jacketed Gasket
These can be made from CNAF (Compresses non-asbestos fibre), PTFE, Rubber, Teflon or Graphite. Non-metallic gaskets can compress easily with low tension bolting. They’re generally used for low pressure applications and low temperatures. One exception is graphite gaskets, which can be used for temperatures as high as 460 degrees centigrade. Rubber and elastomer gaskets are not used for pipelines used to transport hydrocarbons.
Metal is used for ring type joints in high-pressure applications, such as oil and gas supply production. RTJs are also used on valves and pipework, assemblies in refineries and other process industries. They seal by an initial line contact or a wedging action as the compressive forces are applied. Metal ring type gaskets are available with oval and octagonal cross sections. Octagonal include the BX type designed to seal pressure up to 20,000 psi, in accordance with API 6A pressure ratings.
Composite gaskets are a combination of metal and non-metal material based on service requirement. Spiral wound, Metal Jacketed, and Kamprofile gasket are well known in composite gasket category. They’re used in a wide range of pressure and temperature services. Composite gaskets are cost effective as compared to metal gaskets, but careful handling is required. Composite gaskets are used on raised face, male-female, and tongue-and-groove flanges.
Gasket dimensions are covered in the following standards.