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There are many applications for mechanical joints, which are often used in liquid and vapor systems that operate under temperature and pressure. Generally, these joints are not absolutely tight and there is a limit to how well one will seal. A gasket is often used for joints that must seal tightly to prevent leaking and maintain operating performance. Gasket sealant is a material that is used, alone or in combination with a gasket, to prevent the escape of a liquid or a gas.
Gasket sealant usually comes in a tube and has a paste-like consistency when applied. Sealant materials are available in foam, rubber, silicone, plastic, and metallic-based forms. Gasket sealant is used with many different types of materials including various metals, wood, plastic, rubber, ceramics, glass, and even concrete. The type of sealant selected for a specific application depends on the material to be sealed, environmental conditions, temperature, and operating pressures in the system.
One type of gasket sealant material remains flexible over time. This type is referred to as non-hardening. Mechanical connections between objects can expand and contract with changes in operating conditions, such as temperature fluctuations or exposure to vibration. A flexible sealant is able to accommodate expansion and contraction while maintaining its sealing properties.
Some gasket sealants will harden shortly after application. These are referred to as hard setting. This type of sealant is typically recommended for use with rigid and permanent assemblies that are exposed to little or no vibration. Gasket sealants are also made with different drying rates, quick setting capabilities, a combination of sealing and gluing properties, and chemical resistance.
Gasket sealant is frequently used for automotive repair. A head gasket is used to seal the engine block and cylinder head in an automobile engine. The head gasket is a flat, semi-rigid, graphite material cut to the shape of the two mating surfaces. A sealant is often applied to both sides of the head gasket to ensure that the small surface irregularities in each mating surface are filled, and that the two surfaces seal properly when joined together.
Flanged connections are used in many plumbing and utility piping applications. A flange is typically a raised lip or rim around the flat end of a pipe. Two flanges are usually placed in surface contact with each other to form a joint. These connections are often made using bolts as well as gaskets and sealants to ensure a leak-tight seal. Threaded piping connections also frequently use gasket sealants to prevent leakage through the very small clearance areas between the threads.