In the industrial world a seal is a mechanical device that is used to contain liquid, hydraulic and gaseous pressure. Some types of seals are fitted on shafts and in housings to prevent fluids from moving from a high pressure area to a low pressure area. There are various types of seals such as bung, O-ring, labyrinth seal, compression seal, gasket, wiper seal, coating, plug, diaphragm, hydrostatic seal, hydrodynamic seal, radial shaft seal, and Bridgman seal, etc. Seals can also be made out of various materials.
These devices are commonly used in things such as hydraulic pumps, in automobiles, airplanes, chemical process equipment, food and beverage, and pumps, etc. Seals are used in just about every type of industry imaginable, especially those that deal in water and other liquids such as plumbing, shipping, and water treatment plants, etc.
Some types of seals have a rubber gasket with a circular spring inside of them. The rubber gasket fits around a shaft in a groove and the spring holds it securely in place. The mounting diameter of the seal needs to be very precisely machined, as a loose fitting seal will be of no use to you. Also, the edges of the seal should be burr free and should have a smooth, chatter free guiding chamber or else the rubber seal will be torn. To make sure that the seal is smooth you may have to use a deburring tool.
A bung seal is one that is pushed into the lid of an enclosure to make sure it is sealed properly and nothing can escape it. An O-ring is a loop of flexible material, usually rubber, which is placed between two items during their assembly and is then compressed between them to make sure of a good seal with no leakage. A labyrinth seal is a threaded object that fits around a rotating shaft and is made to help prevent any fluid leakage. A gasket is very similar to an O-ring however it is made from a variety of materials in an assortment of shapes.
After the assembly of a seal it is recommended that the area be checked with hydraulic pressure to make sure that the device is working properly and nothing can leak through it.