More about Seals

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Mechanical seals are used to keep contamination from entering an enclosure. They can also be used to containing pressure or in equipment that necessitates rotation, such as compressors and pumps. The mechanical seal can be categorized into two types, pusher types and nonpusher or bellows types. Pusher seals are inexpensive and easily available in a wide range of configurations and sizes. They operate by using a secondary seal which moves to maintain contact at the seal faces. On the other hand, a bellow seal uses a metal or rubber bellows configuration to create pressure on the primary seal. A third kind of seal is the “cartridge” seal, which has use in more complicated applications. Mechanical seals can be made from many kinds of substances, including Polyurethane, Neoprene, Ethylene Propylene and Fluorosilicone.

Because almost all seals are designed to leak to some extent, when dangerous chemicals or petroleums are used in manufacturing modification of the sealing system must be made. In these situations, a second seal is often placed after the primary seal. The space in between the seals is then filled with a neutral liquid. This arrangement is called a double seal.

O-rings are one of the most popular kinds of mechanical seals because they are cheap and easy to use. They are sometimes used as a secondary seal and can withstand thousands of psi. O-rings are designed to create a seal at the interface of two or more parts during assembly.

The diaphragm seal is a flexible membrane that permits the effects of pressure differences to cross the barrier but keeps the material being sealed isolated in the enclosure. The diaphragm seal is used to protect pressure sensors from the fluid that is being measured for pressure. Other kinds of seals include the labyrinth, radial shaft, Bridgman, compression, wiper, hydrostatic, and hydrodynamic.