Pressure surges in oil and gas applications cause problems that can include back-flows leading to contamination of service fluids and potential damage to pipelines, process units and vessels.
There is therefore an obvious need to protect systems against this kind of contamination.
Check Valves, often referred to as non-return valves, provide this function for surface and subsea installations. Their duties can include injection, control, isolation and system protection.
A check valve simply permits gases and liquids to flow only in one direction which prevents the process flow from reversing.
The fluid flow in the desired direction opens the valve and the backflow forces the valve closed.
Swing Check valves are designed with the closing element attached to the top of the cap. This element is pushed aside by the flow, but swings back into the close position upon flow reversal – hence the name ‘swing check’.
These valves tend not to be good choices in services with frequent flow reversal, as the disc is often pounded into the seat and wears quickly.
These valves may be installed vertically or horizontally, although when mounted vertically a lever and counter-balance or torsion spring should be applied to reduce the valves tendency to stay open in situations where flow velocity changes slowly.
Piston Check valves have a disc that is guided and are available as a spring loaded type. The style that lacks the spring must be mounted in such a way as to allow gravity to close disc.
Ball-check valves use a free-floating or spring loaded ball resting in a seat ring as the closure element. Upon reverse flow, the ball is forced back into its seat preventing backflow. These valves are good for most services. They can even handle fluids that produce gummy deposits. Since the disc is free to rotate wear is distributed evenly and this all helps to keep the valve seats clean.
BEL Valves manufactures Check valves in bore sizes from 1/2 to 24 inches up to 15,000psi. They are available in flanged, butt weld, socket weld of hub connectors.
