In the process industry there is a requirement to protect pumps against the damaging effects of reverse flow and pump overheating owing to minimum flow (insufficient flow) through the pump not being maintained.
Protection Against Reverse Flow
Two types of automatic protection valves exist to protect pumps from reverse flow:
The difference between the two solutions is that for a tilting disc check valve the non-return function is achieved automatically via a counter-weight attached to the valve lever that ensures valve is normally closed. The counterweight is sized so that flow (upstream pressure) is required to open the valve which overcomes the effect of the counter-weight. The disadvantage of this type of valve is that the valve is never fully open such the the full valve flow coefficient is attained. As a result there are pressure losses in the system which lead to potentially costly pumping inefficiencies.
An improvement on the “tilting disc check valve” is the “combined shut off and non return valve”. This design valves FULLY OPENS when flow upstream is detected, and FULLY CLOSES when there is no flow or reverse flow detected. This is achieved by providing an actuator and a control system to control the position of the valve.
Protection Against Minimum Flow Through Pump
Automatic Recirculation Valves are designed as a safety device to prevent pump instability, overheating, and cavitation by ensuring that there is always a minimum flow through the pump in response to varying process conditions. This type of valve is self-acting (i.e. mechanical device not requiring any actuators) that is a simple but effective alternative to using a more complicated control valve system.
For more information or to discuss your requirements please contact us by Email: