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Comparison Of Dry Gas Seals And Mechanical Seal Performance
Jun 16, 2017

First, dry gas seals working principle

Compared with the ordinary mechanical seal, dry gas seals in the structure is basically the same. The important difference is that one of the sealing rings of the dry gas seals is machined with a well-distributed shallow groove. The gas entering the shallow tank during operation is compressed and a local high pressure zone is formed between the seal rings to open the sealing surface so as to be able to operate in a non-contact state to achieve sealing.

1. Dry gas seals overview

As early as the late 1960s, laid on the basis of gas dynamic pressure bearing applications, dry gas seals developed and become a new non-contact seal. The seal uses the principle of hydrodynamics to achieve non-contact operation of the sealing end face by opening a dynamic pressure groove on the sealing end face. Initially, the use of dry gas seals form, mainly in order to improve the high-speed centrifugal compressor shaft seal problem. As the seal to take non-contact mode of operation, so the sealing of the friction material is basically not affected by the PV value of any impact, especially in high-voltage equipment, high-speed equipment applications, has good prospects.

2. Comparison of dry gas seals and mechanical seal performance

Mechanical seal is a traditional seal type, which is characterized by a simple sealing structure, technology is mature, processing accuracy requirements are not too high. The drawback is the high leakage rate, frequent failures.

Dry gas seals is the most advanced non-contact seal type, compared with the traditional mechanical seal form, the use of Dry Gas Seals technology, mainly with the following advantages:

(1) the use of Dry Gas Seals technology, which can effectively improve the quality of sealing and use of time to ensure safe, reliable and stable operation.

(2) the use of Dry Gas Seals technology, energy consumption is small.

(3) Dry Gas Seals technology applied to the auxiliary system is more reliable, simple operation, in the course of the use of any maintenance means.

(4) the use of Dry Gas Seals technology, less leakage, the application effect is good.

3. Dry gas seals working principle

In general, the typical Dry Gas Seals technology, including the static ring, moving ring (rotating ring), sub-sealed O-ring, static seal, spring and spring seat and so on. The static ring is located in the spring seat and is sealed with a sub seal O-ring. The spring in the sealed no load state to the static ring and fixed on the axis of the ring (rotating ring) with the seal and the mechanical seal is that it is a kind of film lubrication of the fluid dynamic, static pressure combined with non- Contact mechanical seal. Dynamic ring and static ring with the surface has a high degree of flatness and finish, usually in the dynamic ring surface processing has a series of special slot. With the rotation, the gas is pumped inward to the root of the tank, and the groove-free area outside the root is called a dam. The dam is resistant to gas flow and increases the gas membrane pressure. With the pressure generated between the surface, so that the static ring surface and moving ring from the left to maintain a small gap. When the closing pressure generated by the gas pressure and the spring force is equal to the opening pressure of the gas film, a stable equilibrium gap is established.

Dry gas seals structure according to the different sealing medium, the medium pressure and the different working speed can be divided into single-ended dry gas seals, double-sided dry gas seals and series dry gas seals.

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