Concept reference

Valves in a Pump Station

C.1Plain-language definition

A valve exists to create a particular state: isolate equipment, stop reverse flow, regulate flow or pressure, or manage air. Its symbol is less important than the failure it prevents and the states it must survive. Every valve also adds resistance and needs access, indication and a credible maintenance path.

C.2Governing relation or decision logic

For a valve at a stated opening, hv = K V²/(2g). Control-valve sizing may instead use a manufacturer flow coefficient, whose numerical form depends on unit convention and fluid properties. Check-valve closure belongs to transient analysis; its deceleration and closure dynamics cannot be reduced to steady K alone.

C.3The failure to name

A check valve selected only for low head loss may close too slowly and slam, while one oversized for the pipe may chatter because its disc never reaches stable travel. An isolation valve with no upstream/downstream means to drain or relieve pressure is not safely maintainable.

C.4Field review checklist

• Name each valve’s duty, normal state, failure state and required indication/actuation.
• Check steady loss at actual velocity and opening.
• Review check-valve stability and closure against system deceleration and surge.
• Provide access, lifting, drainage, pressure relief and isolation needed for replacement.

C.5Where it fits in the course

§4.4 treats valve loss; §8.4 places check and isolation valves.