Butterfly Valve

Overview

A butterfly valve throttles or isolates flow with a disc that rotates on a central shaft inside the pipe bore. A quarter turn swings the Disc / Vane from edge-on, where it offers little resistance, to face-on against the seat, where it seals. Because the disc stays in the flow stream the valve is compact and light relative to its line size, and the modified equal-percentage characteristic of a centred disc makes it usable for modulating control as well as on/off duty. The lug body lets the valve be bolted into the line and serve dead-end without a downstream flange.

How it works

The pressure boundary is the Valve Body, a ductile-iron lug casting with tapped bosses that match the pipe flange bolt circle. The sealing element is a molded Seat Liner elastomer liner that wraps the bore and the flange faces, so the same part seals the disc edge and the pipe joints. The disc is carried on a two-piece Stem Assembly: an upper drive stem and a lower stub stem running in journal bushings, with an anti-blowout collar and graphite gland packing retaining and sealing the shaft.

Rotation comes from a Electric Actuator mounted to the valve neck through the Mounting Flange, machined to the ISO 5211 interface. Inside the actuator a reversible motor drives a worm-and-spur reduction to produce the ninety-degree output, with potentiometric feedback, limit switches and a control board running the positioning loop; a declutchable handwheel allows manual operation on power loss. A Position Indicator beacon on the actuator top reports valve state. Flange and stem seals are supplied as an O-Ring Set and the bolting as a Fastener Set.