Mechanical seals are intended for applications in which a rotating shaft and its housing are under a state of stress, including a combination of high pressure, temperature, and speed.
Mechanical seal varieties are used to prevent the unwanted release of pressure, lubricants, hydraulic fluids and other properties of a system that makes use of them. Seals are also used to prevent the contamination of those systems by dirt and other hazards. Equipment like agitators, mixers, gas seals, pumps, valves, actuators and many other kinds of machinery all involve the use of some variety of mechanical seal.
In addition to preventing leaks, mechanical seals also keep contaminants from entering and help to maintain pressure levels. Piston seals, flange gaskets and diaphragm seals are also kinds of mechanical seals, and they are all essential to the functioning of certain kinds of equipment.
Most mechanical seals are specially designed to prevent leaks in particular applications and cannot be interchanged with those seals used in other mechanisms. A piston seal, for example, cannot be used as a flange gasket; they are shaped differently, made out of different materials and feature different mechanical properties. The shape, size, and composition of a given mechanical seal always depends on the conditions in which it will be applied.
Also, depending on the narrowness or broadness of a given understanding of the words “mechanical seal,” certain kinds of seals may or may not qualify. Simple plastic lids qualify by the broadest definitions, while some of the strictest definitions might only include seals applied in industrial process equipment or in heavy machinery.
In either case, mechanical seals perform the same task: to isolate and contain materials in an enclosure. Correctly pairing seals with their applications is essential to the safe and effective use of the equipment in which they are installed. For example, Teflon is often chosen for use in hydraulic cylinders because it is resistant to corrosion induced by exposure to hydraulic fluids.
Natural rubber, on the other hand, may degrade when exposed to such chemicals. The decision to employ a given seal material should always be chosen carefully; this will ensure sustained effective and safe operation of the seal and the equipment it protects.