Check valve selection and water hammer
What a check valve must do
A check valve allows flow in one direction and closes when flow stops or reverses — with no operator. Two properties dominate selection: the cracking pressure (the forward differential that opens the valve) and the closing behaviour (how fast and how far the closure member travels when forward flow decays). Closing behaviour is where water hammer comes from.
Water hammer in one paragraph
When a pump stops or a valve slams, the flowing column reverses; if the check valve closes only after reverse flow has built up, the sudden stop turns the column’s kinetic energy into a pressure spike — the slam and surge known as water hammer. The remedy is a valve whose closure member travels a short distance and begins closing as forward flow decays, before significant reverse flow develops: spring-assisted discs, dual plates with torsion springs, and axial-flow designs exist for exactly this reason. A non-slam execution is worth its premium wherever column separation can occur — long risers, multiple pumps, fast-closing automated lines.
The published check-valve executions
The catalogue publishes these check-valve executions as identifier pages, each with its own provenance-backed spec table. Counts are published model pages per subtype.
| Subtype | Published model pages |
|---|---|
| swing check valve | 8 |
| dual plate check valve | 4 |
| tilting disc check valve | 2 |
| lift check valve | 2 |
| pressure seal swing check valve | 1 |
| foot valve | 1 |
| axial flow check valve | 1 |
| triple duty valve | 1 |
| silent check valve | 1 |
Selection factors beyond type
Orientation matters: some executions close by gravity or spring and some by disc swing, so horizontal vs vertical (flow up) installation changes which executions work. Media with solids push toward full-bore swing or rubber-lined executions; low-pressure systems need a cracking pressure the available differential can actually open. For compressed-air service the same physics appear in compressor discharge valves with different construction — match the execution to the medium, not just the DN.
Each published check-valve page states its own size span, pressure class, materials and standards. Where a cell shows "confirm at RFQ", the value has not been established by the collected evidence for that exact execution — state the requirement in the inquiry instead of assuming.