Carbon ring seal and dry gas seal

1. Seal: It is a component or measure that prevents fluid or solid particles from leaking from between adjacent joint surfaces and prevents external impurities such as dust and moisture from intruding into the interior of machinery and equipment. 　　Seals can be divided into two categories: static seals and dynamic seals. There are three main categories of static seals: gasket seals, sealant seals and direct contact seals. According to the working pressure, static seals can be divided into medium and low pressure static seals and high pressure static seals. Medium and low pressure static seals commonly use gasket seals made of softer material and wider width, while high-pressure static seals use metal gaskets made of harder material and narrow width. Dynamic seals can be divided into two basic types: rotating seals and reciprocating seals. According to whether the seal is in contact with the parts that move relative to it, it can be divided into contact seals and non-contact seals. ； According to the seal and contact position, it can be divided into circumferential seal and end face seal. End face seal is also called mechanical seal. The centrifugal seal and spiral seal in dynamic seals are sealed by applying power to the medium when the machine is running, so they are sometimes called dynamic seals. 2. Dry gas sealing principle: When the moving ring with a fluid dynamic pressure groove (2.5~10µm) on the outside of the end face rotates, the hydrodynamic pressure groove pumps the high-pressure isolation gas on the outer diameter side (called the upstream side) into the space between the sealing end faces, and the air film pressure gradually increases from the outer diameter to the groove diameter, and automatically The air film pressure gradually decreases from the groove diameter to the inner diameter. Due to the increase in end face film pressure, the opening force formed is greater than the closing force acting on the sealing ring. A very thin layer of air film (1~3µm) is formed between the friction pairs, so that the seal works in a non-contact state. The formed air film completely blocks the relatively low-pressure sealing medium leakage channel, achieving zero leakage or zero escape of the sealing medium.

Judging from the two seals you compared, you used them on gas-sealing equipment. The two sealing principles are different. The carbon ring seal relies on gap throttling and step-by-step pressure reduction to reduce leakage, rather than complete sealing. Therefore, harmless barrier gas needs to be injected between the stages of the carbon ring seal to cause the barrier gas to leak in both directions inside and outside the equipment. This amount of leakage is controlled by the gap between the carbon ring and the shaft. Dry gas sealing you can go http://bbs.hcbbs.com/thread-218658-1-1.html learn. I won’t go into details here.