Service conditions
A butterfly valve changes the available flow area as its disc rotates about the stem. Its compact rotary arrangement is widely used for pipeline isolation. Flow-control duty also requires assessment of disc position, differential pressure, flow response and actuator control capability.
Construction and description
Position signals communicate operating status to monitoring systems. Define switching position, contacts or output, power and wiring. Review indication or alarm functions separately from actual isolation capability.
Match the operator to the valve load and site operating method. Manual operation needs accessible clearance. Frequent cycling or remote control also calls for assessment of output capability, duty and position feedback.
Define fluid composition and continuous and start-stop operating conditions, then assess body, internals and seals as a combination. Particles, deposits and cleaning affect sealing surfaces and mechanisms; plan maintenance for the actual service.