This seal is used primarily for dry air, nitrogen and dry vacuum services, but may be used for any dry gas which is non-hazardous and where a small leakage can be tolerated. The seal bushing is stationary and has machined grooves and ridges ("teeth"). Sealing is achieved by the repeated throttling and expansion of air or gas across the teeth.

When liquid is entrained or injected into the air or gas being compressed, it must be kept out of the bearing areas and lube oil. This seal incorporates a rotating grooved stainless-steel sleeve with a babbitt-lined stationary bushing, plus a water slinger which prevents moisture from leaking along the shaft. This is the standard seal for wet vacuum service.

When a leak of the gas being compressed cannot be tolerated, labyrinth seals may be used to inject air or another purge gas at a pressure slightly higher than compressor discharge. In addition, by injecting an inert purge gas, these seals may be used to prevent air in-leakage from mixing with the gas being compressed.

Where the gas compressed is hazardous or expensive and where purging may not be practical, face-type mechanical seals can be supplied. These employ rotating seal rings which make vertical contact against stationary surfaces. A separate oil system is used to pressurize and cool the seals.

Oil seal face contact seals assemble with unit components for ease of handling and installation. In comparison to clearance seals, contact seals on the process side offer substantially reduced leakage rates, normally less than five GPD per seal.

Circumferential barrier seals use a compact, self-contained, cartridge design with contact carbon seal rings segmented with overlapping positive joints that seal against a hard-faced sleeve. These seals provide minimum leakage rates-typically less than 1 SCFM per seal during normal operation at pressure differentials less than 25 PSI.

Dry gas face seal assemblies can be either a face contact seal or a lift geometry seal combined with a secondary circumferential barrier seal. A bi-directional, cartridge arrangement allows for installation at all shaft locations. Face seals provide the primary sealing while barrier seals isolate bearing oil from the face seals. Barrier seals also prevent seal leakage from escaping through the bearings during normal operation or in the event of primary seal failure.