The diaphragm, made of elastomer or PTFE backed by rubber, both seals the flow and isolates the operating mechanism from the process, so there is no packing to leak. Weir-type bodies are standard in pharmaceutical and sanitary systems because they drain fully and clean easily; straight-through bodies suit slurries. Temperature and pressure limits are set by the diaphragm material, and the diaphragm is the part you replace.
WFI loop valves are all diaphragm valves, and QA wants the diaphragm change dates on every one.
Also heard as
- weir valve
Related terms
Pinch valve
A valve that shuts off flow by squeezing a flexible rubber sleeve closed, either mechanically or with air pressure.
Packing
Compressible rings packed around a valve stem to stop process fluid leaking out to atmosphere.
Fugitive emissions
Small unintended leaks of process gas or vapor to atmosphere, mostly from valve stem seals and joints.
Seat
The surface inside a valve that the closure member presses against to stop flow.