What Is a Flange Seal?

B. Turner

A flange seal is a type of gasket used to fill gaps or spaces between a set of flanges. These flanges consist of raised rings around the edges of a pipe that are used to join multiple sections of piping together via compression. Without a proper seal, this joint is susceptible to leaks in the form of liquid or vapor. A flange seal prevents leaks by correcting any minor irregularities or even larger spaces between the faces of each flange. Some seals are built into the flanges themselves, while others consist of rubber rings or similar materials that are cut to fit the flange during installation.

Car and truck engines use many types of gaskets that help prevent leakage of fluids and gases, such as exhaust.
Car and truck engines use many types of gaskets that help prevent leakage of fluids and gases, such as exhaust.

A variety of materials can be used to make flange seals, depending on where and how they will be installed. The most common variety of flanges are made from elastomeric substances, including rubber, polyethylene, and similar synthetic materials. Elastomeric flange seals are an economical option for general purpose applications, but may be subject to corrosion or damage if exposed to sunlight or certain types of chemicals.

Traditional flange seals were made from fibrous materials, particularly asbestos. Now that asbestos has largely been phased out, manufacturers have turned to fiberglass, carbon fiber, and other alternatives. These fibrous flange seals are highly resistant to fire, heat, and corrosion, but may cost more than elastomeric models. Graphite and vermiculite gaskets may also be used for specialty applications.

Each flange seal must be carefully matched to the joint where it will be used. The most effective seals are designed to fit a particular flange style. They cover the entire face of the flange, with pre-cut holes to match those in the flange itself. For more general applications, a flange seal may be designed to simply fit inside the perimeter of the bolts, rather than extending all the way to the edges of the face. Some simple joints are even sealed using rings of rubber that are cut to size in the field from larger sheets of material.

When used to seal plumbing joints, a flange seal can serve a number of purposes. It fills gaps and imperfections between two adjacent flanges, which helps to prevent liquid leaks. These gaskets also keep fumes, vapors, or steam from seeping out between the flanges. By reducing leaks, flange seals help keep facilities clean while maximizing performance and efficiency. This type of gasketing also reduces respiratory ailments and other health issues associated with chemical leaks and spills.

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