BY PRESSURE CLASS
Low-Pressure Valves
Service envelope language used in Chinese and ASME/GB catalogues. Class is not a substitute for the nameplate and the standard.
Choosing Low-Pressure Valves
Low pressure is a service description, not a universal rating band. Selection can be governed by the small pressure available to overcome a valve restriction or operate a pilot. Give the actual pressures and flow conditions instead of relying on the category label.
What to include in the RFQ
- State normal, minimum and maximum pressures with units and gauge/absolute basis.
- Specify allowable pressure loss and required flow capacity.
- For automatic or pilot-operated designs, request the minimum operating differential.
Selection scenario
On a gravity-fed tank outlet, compare capacity at the available head and verify that any solenoid pilot can operate during start-up.
Common selection mismatch
A large nominal port does not guarantee useful flow at a small differential. An assisted valve may also need a minimum driving pressure.