What Is a Flange Gasket?

When pipes that are intended to carry a fluid or gas are jointed, the connections between the individual pipes need to be sealed to prevent leakage or ingress of external contaminants. The products used to seal these pipe joints are known as gaskets. A flange gasket is the particular style of gasket utilized to create a seal when two flanged pipe ends are bolted together.

The most common use for gaskets is in the services industry, where water pipes need to be sufficiently sealed to prevent water leaks, loss of pressure, or external foreign contaminants entering the pipe. The main types of pipe joints in regular use in this industry are socket and spigot joints, also known as Tyton joints in some locations, and flanged joints. In socket and spigot applications, the gaskets take the form of a thick, rounded section of rubber, which fits into the socket of the receiving pipe. This gasket is then compressed when the spigot end of the adjacent pipe is inserted, creating the seal.

In water pipe applications, flanged joints are commonly specified for above-ground pipelines and for pipes and fittings within chambers. Flanged pipes feature wide, flattened ends that will commonly be supplied with predrilled holes to allow the flanged ends of adjacent pipes to be bolted together. When connecting flanged pipes to spigot pipe ends or sections of cut pipe, a flanged adapter can be utilized to produce a flanged end for the adjacent pipe to be bolted to.

Commonly manufactured from heavy-duty rubber, a flange gasket is a flat ring designed to match the flattened end of the pipes to which it will be fixed. The flange gasket will feature holes to allow the connecting bolts to bypass the gasket and affix to the adjacent pipe end. When the connecting bolts are tightened, the rubber flange gasket is compressed, therefore creating the seal against leaks and contaminant ingress.

Other types of flange gaskets are available in the form of corrugated metal, ring, and spiral-wound gaskets. These kinds of gaskets are made from steel and are used mostly in the oil and gas industries. Ring gaskets are solid steel rings that can also be manufactured in different shapes to match the cross-sectional appearance of the host pipe. Spiral wound gaskets consist of wound rings of stainless steel tape arranged in a V formation, with the open end of the V facing toward the outer face of the flange. Pressure on the base of the V causes the sides to spread out, creating the seal against the flange faces.