Production, processing and transmission applications need protection from back flow and the resultant fluid contamination so it is important to select the right check valve for the job. Check valves are an important line of defence designed to prevent the backflow of fluids when dealing with pressure surges.
Why check valves, the operational benefits.
Check valves simply allow flow of process fluid in one direction and automatically prevent backflow (reverse flow). Therefore in the event of a downstream pressure surge, reverse flow cannot cause damage or contaminate the service fluids. Unlike most other valves, check valves are self-operating, not requiring manual or actuated assistance to open or close. Internal sealing of a check valve closing element and seat relies on fluid back-pressure, this means that allowable seat leakage rates can be greater for check valves than for on/off valves. For gas applications, at lower pressures which require zero leakage, it is usually recommended that elastomers are used for sealing. Additional factors to consider when selecting the check valve are material compatibility with the process medium, line size, flow conditions and installation orientation.
Benefits of BEL Valves Swing and Piston Check valve design.
The three designs offered by BEL Valves are; swing check which has a disc that ‘swings’ on a hinge to allow the forward flow and shuts under reverse flow conditions; a piston check which also prevents backflow by using a piston that lifts with the flow and falls with reverse flow; and the axial check which has a symmetrical and unrestricted flow path between the valve inner and outer body. The compact axial check valve is a reliable option for use in protecting rotating equipment as its ‘in line’ configuration results in limited pressure drop across the valve. The piston check valve has a piston (or ball) that has a line of action inclined away from the pipe axis, which rises or falls as the flow varies. Under normal operating conditions this piston forms a gas tight seal when closed, and a dampening system is incorporated to avoid slamming in the event of sudden pressure reversals. The swing check valve is ideally suited to manage the severe shock duties sometimes experienced in service with the disc designed and manufactured as a one piece construction. It is the only check valve that can be pigged. Discussing your requirements at an early stage, we will advise you regarding the specific configuration needed. For example, applications which require occasional flow in both directions will require the addition of a manually operated lock open mechanism to hold the disc up and out of the flow.
Standard and Optional Features.
Materials, specification and approvals.
All of our check valve designs are in accordance with the relevant industry codes and standards including ISO 10423, ISO 14313, API 6D, API 6A, API 6FA and API 6AVI.