BY FUNCTION
Check / Non-Return Valves
What the valve is asked to do in the line — isolation, non-return, regulation, protection or diversion.
Choosing Check / Non-Return Valves
A check valve responds to the line fluid to permit forward flow and resist reverse flow. Lift, swing and spring-assisted arrangements have different opening and closing behavior. The selection must account for the actual flow range and mounting orientation, not only pipe diameter.
What to include in the RFQ
- Provide minimum and maximum flow, fluid density and the pressure available to open the valve.
- Request permitted orientation, opening characteristics and full-open pressure loss.
- Describe pump shutdown behavior, reverse-flow risk and required seat leakage.
Selection scenario
At a pump discharge, compare the expected low-flow condition as well as normal operation. Ask the designer to consider the transient event when the pump stops, rather than assuming any check valve prevents surge.
Common selection mismatch
For live-steam maintenance, a check valve must not substitute for an isolation valve. Reverse-flow prevention and a safe isolation boundary are different requirements.