PURPOSE: To provide a seal satisfying regulation standard of toxic fluid emission matter and of low price and easy constitution, in an environment in which regulation is more and more strengthened toward zero emission.
CONSTITUTION: A double, back to back oriented mechanical end face seal for use in sealing toxic or corrosive fluids having an intermediate buffer fluid chamber into which a relatively inert gas, such as nitrogen is provided for use as a buffer fluid. The nitrogen gas is maintained at a pressure which exceeds the process fluid pressure by at least 10 p.s.i. In a preferred embodyment, spiral pumping grooves 44 of the mating rings of the respective seals are shaped and dimensioned to pump the nitrogen buffer gas through the first seal 22 from the intermediate chamber into the process fluid chamber and through the second seal 24 from the intermediate chamber into the environment external to the housing 12 and sealing area, thereby avoiding the escape of the process fluid into the intermediate buffer chamber and to the atmosphere. Contamination of the process fluid by the buffer gas may be tolerated.
DAGURASU JIEI BOORUDEN
JIEEMUZU PII NETSUTSUERU
