Seals are divided into dynamic seals and static seals. Static seals are divided into three categories: gasket seals, rubber seals, and contact seals. Dynamic seals can also be divided into two categories: rotary seals and reciprocating seals The sealing forms are specifically divided into two categories: static sealing between relatively static joint surfaces and dynamic sealing between relatively moving joint surfaces.
1. Static seal: according to the working pressure, static seal can be divided into medium and low pressure static seal and high pressure static seal. Medium and low pressure static seals are usually made of soft gaskets with wide gaskets, while high pressure static seals are made of metal gaskets with hard materials and narrow contact width.
2. Dynamic seal: it can be divided into contact seal and non-contact seal according to whether the seal is in contact with its relative moving zero parts.
Generally speaking, the contact seal has good sealing performance, but is limited by friction and wear, and is suitable for occasions with low sealing surface line. According to the contact position of the sealing element, the contact seal can be divided into circumferential (radial) seal and end face seal. Face seal is also called mechanical seal. The non-contact dynamic seal includes labyrinth seal and power seal.
The former uses the throttling effect of fluid between clearances to limit leakage, with large leakage, and is usually used for sealing properties such as interstage sealing; An occasion with low requirements. The power seal includes centrifugal seal, floating ring seal, spiral seal, etc. The power component generates a pressure head to offset the pressure difference on both sides of the seal to overcome leakage. It has high sealing performance, but it consumes large energy and is difficult to obtain a high-pressure head. The non-contact seal has small starting power and long service life because the sealing surface does not contact directly.
If the design is reasonable, the leakage will not be too large. However, this kind of seal works by using the balance state of fluid mechanics. If the operating conditions change, it will cause a large fluctuation of leakage. Moreover, such seals cannot be purchased in the market, and they are basically designed by users.