Dry Gas Seals

Dry gas seals, also known as Dry running gas seals, are widely used in mechanical sealing technology in rotating equipment such as centrifugal compressors and pumps. Originating in the 1960s, dry gas seals are a new type of non-contact mechanical seal inspired by the design of gas dynamic pressure bearings. They primarily add hydrodynamic grooves to the end face of the mechanical seal rotating ring and incorporate corresponding auxiliary systems to achieve non-contact operation of the seal end face. This gives them characteristics of gas sealing, non-contact, gas film lubrication, simple operation and maintenance, and long service life. The function is to prevent leakage of the working medium while reducing friction and wear, and thereby improving the reliability and service life of the equipment.

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Sealing structure
  • Dry gas seals usually consist of two main components: a rotating ring and a stationary ring (sealing O-ring, spring, spring seat
  • The rotating ring is mounted on the rotating shaft, while the stationary ring is fixed on the sealing housing.
Gas film formation
  • The key to dry gas sealing is to achieve sealing through a gas film. It is formed between the rotating ring and the stationary ring, which plays a role in sealing and lubrication.
  • The formation of the gas film relies on high-pressure gas (such as nitrogen, air, etc.) to be injected into the sealing cavity, so that a thin layer of 3 microns of gas is always maintained between the rotating ring and the stationary ring.
Sealing principle
  • When the equipment is running, a thin gap will be formed between the hydrodynamic pressure groove on the end face of the rotating ring and the stationary ring. In this gap, the high-pressure gas will form a gas film to prevent the working medium from leaking from the high-pressure side to the low-pressure side.
  • Due to the existence of the gas film, there is basically no direct contact between the rotating ring and the stationary ring, thereby reducing friction and wear.
  • Micro grooves or structures on the sealing surface help stabilize the gas film. These grooves will form a dynamic pressure effect between the sealing surfaces, making the gas film more stable.
  • The thickness and stability of the gas film are maintained by adjusting the pressure and flow of the gas, thereby ensuring the sealing effect.
Working process
  • When the equipment is started, high-pressure gas first enters the sealing chamber to form an air film.
  • As the speed of the equipment increases, the thickness and stability of the air film will gradually reach the optimal state, achieving effective sealing.
  • During the operation of the equipment, the air film is continuously maintained to prevent the leakage of the working medium and reduce the wear of the rotating parts.
Auxiliary system
  • The dry gas sealing system is usually equipped with an auxiliary gas supply system to ensure the continuous supply of high-pressure gas.
  • The monitoring system is used to monitor the state of the seal in real time to ensure the reliability of the sealing performance.
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