Gasket rings

Two types of gaskets are available, gaskets which cover from the face of the flange to the inside edge of the bolts so called raised face and gaskets which cover the whole face of the flange including the bolt holes so called full face.

The thickness of a pipe gasket is governed by several requirements. The condition of the flange face has an important part to play. A thicker gasket may be required for a poor-quality surface, as it will flow into and takes up the deformities on the face ensuring a good seal. With a clean and smooth flange, a thinner gasket can be considered.

Pressure and media are other factors that can decide the thickness of gasket required. Putting too thick a gasket into a flange joint will increase the surface area that the system pressure can work against. For this reason, a general rule: the thinner the gasket the better.

The most common standards are:

• BS10: 2009 British standard specification for flanges and bolting for pipes, valves and fittings.

• DIN: Deutsches Industrie Norm the German Institute for Standardization

• ANSI: The American National Standards Institute

• ASA: The American Standards Association (now ANSI)

• ASME: The American Society of Mechanical Engineers

• JIS: Japanese Industrial Standards