Butterfly Valves
Butterfly valves use a disc that rotates 90° about its own axis to open or close. A short face-to-face length, small size and low weight make them an economical and efficient choice for isolation and throttling in large-diameter lines. By connection they are wafer, lug or double-flanged; by sealing they are resilient-seated (centreline) or triple-offset metal-seated. Resilient-seated butterfly valves press the disc against a rubber or PTFE seat to achieve bubble-tight shutoff and suit ambient-temperature water and gas service. Lug-type valves can be installed at the end of a line and allow the downstream pipe section to be removed easily. The triple-offset metal-seated design uses three offsets so the disc never rubs the seat during travel, giving metal-to-metal zero leakage, high temperature resistance, wear resistance and fire safety, and can be extended to cryogenic duty; it has the widest temperature range of any butterfly design. Pressure ratings cover ASME Class 150–600 (PN 20–PN 100). Body materials include ductile iron, WCB and CF8/CF8M. Sealing surfaces can be hardfaced with Stellite 6 or similar carbides. Design and manufacture follow API 609, EN 593 and ISO 5752.
Triple Offset Metal-Seated Butterfly Valve
The triple offset metal-seated butterfly valve uses a three-fold offset — between the seat axis, the disc rotation axis and the sealing cone — so that the disc fully disengages from the metal seat during opening and closing without friction, and contacts the seat only in the final wedge-in phase of closure. The result is metal-to-metal, friction-free and zero-leakage sealing. Hard metal seating (stainless steel / Stellite weld overlay) provides high-temperature resistance, wear resistance and fire safety, with a wide temperature range that can extend to both cryogenic and high-temperature duties. Sealing is reliable and service life is long; the valve can replace gate and ball valves on large-diameter pipelines in some duties. Design basis: API 609, EN 593.
Flanged Butterfly Valve
The flanged butterfly valve has integral flanges at both ends and is bolted to the pipeline flanges, so no wafer clamping is needed during installation. Sealing is more reliable and the installation requires less coaxiality, which makes the valve suitable for large diameters and important lines. The double-flanged construction has good rigidity and can be fitted with electric or pneumatic actuators for remote control. It is widely used in large-diameter water supply and drainage, circulating water, flue gas and air lines, and is the main valve type for shutoff and regulation in large water systems.
Lug Type Butterfly Valve
The lug type butterfly valve has threaded lugs around the body circumference, and each lug is bolted hole by hole to the pipeline flange, so the downstream pipe can be removed on its own without disturbing the valve mounting. The valve is therefore suitable for pipe ends and makes maintenance on one side of the line easier. The construction is the same as the wafer centreline resilient-seated butterfly valve, with good sealing performance and flexible installation. It is the first choice where a valve must be installed at the end of a line or where the downstream pipe section has to be removed in service, and is widely used for shutoff in water treatment and industrial piping.
Wafer Butterfly Valve
The wafer butterfly valve opens and closes by rotating a disc 90° about its axis. The body is clamped between two pipeline flanges, so it is compact, small and light; it is one of the most widely used valves in water treatment and HVAC systems. The construction is a centreline resilient-seated type: the disc presses tightly on a vulcanised rubber seat to give bubble-tight shutoff. Because a wafer installation has no integral flanges, the valve cannot be used as a pipe end on its own and must be clamped between pipeline flanges. It can be fitted with a lever handle, worm gearbox or pneumatic/electric actuator and suits shutoff and regulation of water and gas at large diameters and low differential pressure.