stationary seat unit of metal bellow mechanical seal

Background Knowledge：
Common failures of metal bellows mechanical seals are as follows:
1) The bellows loses elasticity under high temperature, and/or the bellows breaks under high pressure.
2) Coking and carbon deposition are usual phenomena at the wave valleys between the wave plates of the bellows of the metal bellow mechanical seals, which make the bellows lose elasticity and cannot be compensated, so metal bellow mechanical seals  cannot be used in pumps with coking, carbon deposition and crystallization.
3) For external mechanical seal, when the pressure in the sealing cavity exceeds 0.2mpa, the sealing surface can be pushed open because the elastic force of bellows is small and cannot withstand high medium pressure. Therefore, external bellows mechanical seal cannot be used when medium pressure is high.
4) Effective diameter and load factor must be calculated when using metal bellow mechanical seals because bellows mechanical seals are of a balanced structure.Otherwise, their working states will be  unstable in propane and propylene pumps with high pressure, and the phenomenon of 'spray leakage' will easily occur.