Concentric, double offset and triple offset butterfly valves in wafer, lug and double-flanged bodies, for water, seawater, utilities and hydrocarbon lines. Made in Britain by Young & Cunningham, selected, supplied and supported in the GCC by Petromarsh.
Tap a part to see what it does. Left: the valve seen along the pipe. Right: a section from above, with the disc part open and its closed position dashed. The red marks show the three offsets.
Gearbox and handwheel. A worm gearbox turns the shaft through 90 degrees with a few turns of the handwheel and holds the disc at any angle. Small valves use a lever; actuated valves bolt to the same ISO 5211 top flange.
Shaft. Carries the disc and turns it. In the plan section it is the dark dot. Where it sits relative to the seat and the pipe centre is what the offsets describe.
Body. A short ring between two pipe flanges. Its face-to-face length is much shorter than a gate or globe valve, so butterfly valves save weight and space, especially in large sizes.
Disc. Sits in the flow even when open, so it causes some pressure drop. Turned 90 degrees it closes against the seat. Part open, it can throttle, within the limits the maker gives.
Seat. A rubber or PTFE liner in a concentric valve, a PTFE or metal ring in a double offset valve, and a laminated or solid metal ring in a triple offset valve.
The three offsets. 1: the shaft sits behind the seat, so the seal is unbroken. 2: the shaft sits off the pipe centreline, so the disc swings clear of the seat as it opens. 3: the seat is a slanted cone, so the metal disc only touches the seat in the last moment of closing, with no rubbing.
A butterfly valve closes with a disc that turns on a shaft across the pipe. Turned in line with the flow, the valve is open. Turned across the pipe, the disc seals against a ring seat. It is the lightest and shortest valve for a given pipe size.
The shaft runs through the centre of the disc and the disc squeezes into a rubber liner. Simple and low cost for water and utilities, but the rubber limits pressure and temperature.
Moving the shaft behind the seat and off the pipe centre lets the disc lift away from the seat as it opens. Less rubbing means longer seat life and higher pressure ratings.
A cone-shaped seat added to the two offsets means the disc only touches the seat as it closes. This allows metal seats, fire-safe, high-temperature duty and tight shut-off.
Butterfly valves are defined by the offsets, which decide the seat and the duty, and by the body style, which decides how the valve fits between the flanges. Tap a type to see where it fits.
The disc and shaft sit on the pipe centre and seal into a rubber liner such as EPDM or NBR, which also keeps the fluid off the body. Low cost and bubble-tight, but limited in pressure and temperature.
Common on cooling water, firewater and desalination plant lines across the GCC.
The shaft is behind the seat and off the pipe centre, so the disc cams away from the seat as it opens. Seat wear is low and ratings are higher, typically ASME Class 150 to 600.
Used on process, utility steam and hydrocarbon lines where a rubber liner is not suitable.
A third offset gives a conical seat, so the disc seals metal to metal with no rubbing. Torque-seated and bi-directional designs can reach zero leakage on test, and they suit high temperature and fire-safe duty.
Often chosen in place of large gate valves on GCC refinery, gas and power plant lines.
A thin body held between the pipe flanges by long through-bolts. The lightest and lowest cost body. The line must be drained to remove the valve, and it cannot be used for dead-end service.
Common on water and HVAC lines where the system can be drained for maintenance.
Threaded lugs around the body take the flange bolts from each side separately. One side of the pipe can be removed while the valve still holds pressure, so it can serve at the end of a line within the maker's rating.
Used where equipment downstream is removed for maintenance.
The body has its own flanges and bolts to the pipe like a spool. The strongest body style, standard for large sizes and for triple offset valves in high-class lines.
Typical for large seawater intake, cooling water and triple offset hydrocarbon valves.
In a butterfly valve the disc sits in the flow all the time, so its material matters as much as the body. In the Gulf seawater is the main enemy, followed by sour gas and high temperature.
| Part | Iron and carbon steel | Stainless and duplex | Bronze and special alloys |
|---|---|---|---|
| Body | Ductile iron for water, carbon steel for processEN-GJS-400 · A536 · A216 WCB | 316 stainless, duplex and super duplexA351 CF8M · A995 4A / 5A | Aluminium bronze for seawaterB148 C95800 |
| Disc | Ductile iron, coated or nylon-coatedEN-GJS-400 + coating | 316, duplex or super duplexCF8M · 4A · 5A | Aluminium bronze or PTFE-coated discsC95800 |
| Seat | EPDM for water, NBR for oil, PTFE for chemicals in concentric valves; PTFE or metal for double offset; laminated graphite and stainless or solid metal for triple offsetAPI 609 · EN 593 | ||
API 609 covers oil and gas service. EN 593 is the general European standard. Your datasheet names which applies, with face-to-face and test codes.
Lined and lug, wafer and double-flanged butterfly valves. Category A is concentric, Category B is offset.
Industrial metallic butterfly valves, widely used for water and utility service.
Face-to-face lengths for flanged valves, so a replacement fits the existing gap.
Pressure and temperature ratings and wall thickness for steel valves.
Shell and seat leak tests for API valves.
Pressure testing and leakage rates for valves built to EN standards.
Fire type testing for soft-seated and metal-seated quarter-turn valves.
Top flange and drive dimensions for gearboxes and actuators.
Material and hardness limits for hydrogen sulphide service.
Your engineers red-line our drawings, you approve the design twice before production starts, and you can witness the tests. Tap a step to see what happens and which documents you receive.
Young & Cunningham has made valves in Britain since the 1920s, with a long history of supplying the UK Ministry of Defence. Their butterfly valves come in wafer, lug, double-flanged and mono-flanged bodies, with lever, gear or actuated operation, and discs in aluminium bronze, stainless steel and ductile iron with EPDM, NBR or PTFE liners. Petromarsh is their exclusive representative in the GCC.
If you have valve datasheets or a line list, send them. If you do not, the items on the right are enough for us to select the valve and reply with a proposal.
