Trunnion Ball Valve Cavity Release

Oil and gas pipelines often pass over long distances through rough environments. They face exposure to temperature variations and other weather influences.

When the trunnion mounted ball valves are in closed position, some fluid will be trapped in body cavity. The trapped fluid will expand and the pressure will increase when heated because it’s trapped in a fixed space.  Thus, it is essential that the trunnion ball valves are featured with cavity relief, to get teh trapped fluid to the pipline.

To fullfill the trunnion ball valves cavity relief, Relia has single piston effect seats (SPE) for it. This design does an automatic pressure release into the pipeline.

Trunnion ball valves cavity relief

It uses “self-relieving seats” to release this pressure. Trunnion mounted ball valves constrain the ball by bearings. It is only allowed to rotate, but the ball seats can move. The pressure increases in the cavity when heated. It pushes the ball seat of the downstream side away from the ball by rising pressure against the spring load. When this happens, the pressure gets released.