Rotary barrier face seal

A rotary barrier face seal for sealing a toxic process fluid at a space between a housing and a rotatable shaft, comprising:

• a stationary ring unit coaxially surrounding said rotatable shaft within said housing and arranged for movement axially of said rotatable shaft under a resilient pressure;
• a rotary ring unit coaxially surrounding said rotatable shaft within said housing and prevented from axial movement relative to said rotatable shaft when in operation position;
• each of said ring units having an end face for mutual engagement under said resilient pressure to form a sealing interface;
• one of said ring units being mounted for rotation with said rotatable shaft;
• one of said end faces comprising a plurality of helical grooves, said plurality of helical grooves extending inward, the innermost extent of said plurality of helical grooves defining an inner groove diameter, said inner groove diameter being larger then the diameter of the innermost extent of either of said end faces;
• one of said end faces comprises a plurality of crescent-shaped pockets each containing a buffer gas supply opening adjacent each terminus of each pocket and each said opening being positioned at a fluid supply diameter concentric with said rotatable shaft and communicating with said sealing interface each supply opening being positioned above a buffer gas supply bore, the diameter of the supply opening being larger than the diameter of the supply bore;
• and
• buffer fluid supply means communicating with said at least one supply bore to supply a buffer fluid to the sealing interface.