When to use:
1) If the piping system has a significant elevation change, then back-flow through the pump on system shut down can spin the pump backwards damaging the pump or the pump driver. This can also happen if the pump breaks suction when running on snore.
2)
If a pump is operating in parallel with other pumps and there is no check valve present, a reverse flow could be induced when a single pump is shut down or fails. The reverse flow may spin this pump backwards and damage it or the pump driver. In addition, flow diverted backward through the idle pump would further reduce the production within the overall system.
3) If the system incorporates a long pipeline, the significant friction component within the system head will be absent on an empty pipe start up. This will cause the pump to operate at run-out conditions as the pipeline is filled. A check valve can limit this problem to the initial charging of the line and thereby reduce possible damage due to cavitation.
Other Considerations:
1) Pumps operating against a high static closing pressure on the check valve may not be able to move enough liquid through the impeller to open the check valve and establish flow. This could require a relief valve between the pump and the check valve and for the relief valve to be temporarily opened every time the pump is started. This may not be required if the pump is fully submerged and not air-bound at startup.
2) In locations that are subject to freezing weather conditions, dump valves must be installed to drain the line after a shut down when check valves are present.
3) Solids settling in the line and the possibility of a plug forming can add further complications. If check valves are employed, procedures for line flushing must be in place. In addition, dump valves are strongly recommended so lines can be drained of solids should an unscheduled shut down suddenly occur.