Non-contacting gas compressor seal

A method of sealing between a housing containing a process fluid and a relatively rotating shaft utilizing a non-contacting seal assembly comprising a pair of spaced sets of relatively rotating rings defining an intermediate chamber to receive a barrier gas at a pressure exceeding process fluid pressure;

• each said set including a non-rotatable ring and a rotatable ring, one of said rings being moveable axially relative to the other, each ring of each set defining a generally radial annular sealing face in relatively rotating sealing relation to the to the sealing face of the other ring of said set at a sealing interface;
• one of said rings of at least one set having a pumping mechanism thereon and disposed between said interface to pump barrier gas toward the process fluid in the housing, the steps comprising:
• providing a barrier gas in said intermediate chamber at a pressure in excess of the pressure of said process fluid, pumping barrier gas from said intermediate chamber between said interface when the pressure of the barrier gas exceeds the pressure of the process fluid;
• pumping process fluid between said interface of said seal set when the process fluid pressure exceeds the pressure of the barrier gas;
• wherein said pumping mechanism includes a pattern of spiral grooves and lands formed on the radial sealing face of said one ring of said set, said grooves are open to the intermediate chamber at one circumferential periphery of the interface between the relatively rotating sealing faces of said set, and terminate at an ungrooved area defining a sealing dam;
• and wherein the pumping mechanism on the face of said one of said rings of said set disposed to pump barrier gas toward the process fluid in the housing includes a pattern of oppositely directed spiral grooves and lands adapted for communication with the process fluid at the other circumferential periphery of said interface to pump in a direction opposite the pattern of spiral grooves open to said intermediate chamber, the steps further comprising utilizing said grooves to respectively pump said barrier gas and said process fluid;
• wherein said set disposed to pump barrier gas toward said process fluid includes a retainer to support said axially moveable ring for axial translation thereon, said retainer and said ring defining an axially elongated annular pocket therebetween;
• an O-ring seal disposed in said pocket;
• said O-ring being sized such that it has a cross-sectional diameter that is smaller than both the axial and radial extent of the pocket;
• the steps further comprising providing a secondary seal between said axially moveable ring and said retainer utilizing said O-ring;
• wherein said retainer includes an outer cylindrical sealing surface forming part of said pocket and supporting said O-ring thereon and a radial sealing surface forming an axial end of said pocket, said retainer further including a conical ramp extending radially outward between said cylindrical sealing surface and said radial sealing surface, said O-ring being moveable from a position on said cylindrical sealing surface of said retainer to a position on said conical ramp in sealing contact with said radial sealing surface of said retainer;
• the steps further comprising providing said secondary seal with said O-ring on said outer cylindrical surface when said barrier gas pressure exceeds the pressure of said process fluid, and providing said secondary seal with said O-ring on said conical ramp when said process fluid pressure exceeds the pressure in said intermediate chamber.