Quick Detail

PMSS Ball Valve: Primary Metal Seated and Secondary Soft Seated

The PMSS is designed to engage the metal seat at all times, with the soft seat as a back-up to provide bubble-tight shut off for both gas and liquid service.

In the PMSS system, a resilient material is inserted into the metal seat holder to provide a soft seating action in addition to the metal to metal seating between the ball and the seat rings. The flexible soft sealing in the seating rings is first effective at low pressure ranges.

The testing have proven the primary metal seat alone, without the soft seat installed, will provide effective shut off for both gas and liquid.  With leak rates for gas service in the range of ISO 5208 Rate D.

The ball and seats are commonly coated with either tungsten carbide, or most often an electroless nickel as it is important to maintain a differential hardness between the ball and seat to prevent galling of the substrate.  When provided with ENP, the ball is heat treated following ENP for maximum hardness and the seat ring is not...thereby achieving the differential hardness.