What are the characteristics of cryopump mechanical seal

Mechanical seals under low temperature conditions have different setting requirements from mechanical seals under other conditions, which is very common in the petrochemical industry.

Some media have very low critical temperatures and lower operating temperatures. For example, the working temperature of the methane pump is around -95~-100°C. At such low temperatures, the properties of the material change and become generally brittle, making common plastics and rubber unusable and limiting the use of other materials. Another feature of the cryopump is the high working pressure. The inlet pressure of the methane pump is about 3MPa. The deformation of the parts should be considered when designing the sealing rings and other parts of the mechanical seals. In addition, the low-temperature medium has a small specific gravity, poor lubricity, and is easy to vaporize. Once it leaks out, frost will emerge, which will aggravate the wear of the sealing end faces of the mechanical seals. In view of these characteristics, most of the mechanical seals of cryopumps adopt double seals, and an isolation chamber is set between the medium and the atmosphere, and a sealing liquid is passed through it to alleviate the influence of low temperature and achieve sealing.

In the next article, we will take the methane pump as an example to discuss how to configure the mechanical seal systems for the cryopumps.