Soft Seated

We can supply floating or trunnion mounted soft seated ball valves that are built in accordance with the design requirements of API 6D and, upon request, B16.34; both in two and three piece bolted construction.

Independent floating spring loaded seat rings are always in contact with the ball to provide an effective tight seal at low differential pressures. At higher differential pressures, the upstream seat ring becomes pressure energised against the ball to ensure the seal, whilst the downstream seat remains spring loaded. The single sealing feature, standard on trunnion mounted ball valves, is ideal for block and bleed service to API 6D. The valve body cavity can be vented to atmosphere through a bleed valve and completely drained by removing the drain plug with the ball in closed position, even when the line is pressurised. This feature also allows easy replacement of upper stem seal and the checking of the sealing of the seats, while the valve is installed in the pipeline.

The whole range may be supplied with two basic seating design criteria:
- SELF RELIEVING SEATS (standard) providing the self-relieving of the body cavity overpressure
- DOUBLE PISTON EFFECT (upon request) providing a double barrier against the fluid. In this case when the upstream seat fails, the downstream seat ensures the seat tightness (the valve body is equipped with an automatic safety valve to release the body overpressures in case of expanding fluids).

All valves meet the antistatic requirements of BS 5351. Positive anti blow-out stem design retained by the valve body on complete product range prevents the stem removal when valve is installed. The body and top flange joints incorporate double sealing components (secondary seal is made of expanded graphite) to ensure safe body sealing even in the event of a fire.

All valves are tested to resist fire exposure, both outside and on-line, with very low losses, in compliance with BS 6755 part. 2 and API 607 IV Ed. Valves size 6” and above may be equipped with seat injection fittings to perform the emergency sealing by the injection of sealant through an orifice and special grooves of the seat ring into seating area.

Typical factory seat Inserts include PTFE, PTFE+15%GF, PTFE+25%GF, PTFE+50%SS, PTFE+20%Carbon+5%Grafite, NYLON, PEEK, KEL-F and VITON.