Gas seal, non-contacting. Used to seal turbo compressors. In its basic design and operation, the gas seal is like a conventional mechanical seal but does not require an additional oil system. It consists of a rotating counter ring with a structured sliding face and spring-backed stationary seat. The seal can be employed in single, double and tandem configurations. Its operating limits extend to differential pressures of around 120 bar and circumferential speeds of up to some 150 m/s. Mode of operation: The gas is conveyed by the rotation of the counter ring into the spirally appointed V grooves. Compression of the gas in the two exit directions of the annular groove results from the drag. The resultant increase of pressure causes the seal face to lift and the seal to run without contact (see figure). Seal balancing is selected so that the opening force in the gap equals the closing force on the seal face. The gas seal's key operating variable is the sealing gap height. It is decisive for the leakage rate and for the quantity of gas required forthe cooling.

Gas seal in tandem arrangement. Buffer gas between the two seals (e.g. nitrogen) prevents toxic or explosive gases escaping into the atmosphere. The seal on the atmosphere side serves simultaneously as a safety seal if ever the product-side seal should fail.

Principle of operation of the gas seal

Counter ring of a gas seal with the spiral V grooves