Butterfly valves: wafer, lug or double-flanged
A butterfly valve is lighter and cheaper than a gate valve of the same DN, but the body style decides how it is installed, maintained and whether it can serve as end-of-line isolation.
TAZ Engineering Team · · 6 min
Wafer
The body is clamped between two pipe flanges with long through-bolts. It is the lightest and most compact option. If one mating flange is removed, the valve loses support, so wafer valves are not used for end-of-line service or for dismantling a section under pressure. Common in water supply, cooling and HVAC.
Lug
The body has threaded lugs, so each flange is bolted to the valve independently. The pipe can be removed on one side while the valve holds pressure on the other. Lug valves are chosen for end-of-line isolation, upstream of equipment that is removed for service, and in pump stations.
Double-flanged
The body has its own flanges. It is the strongest option for large DN, trunk water mains and locations with bending loads from the pipeline. Face-to-face length and weight are higher, but fitters handle it like a gate valve.
Seat and disc
Water service usually uses a resilient EPDM liner with a coated ductile iron or stainless steel disc. Steam, high temperatures and tight gas shut-off need metal-seated designs such as triple-offset valves.
What to put in the enquiry
DN, PN, medium and temperature, body style, flange standard, operator (lever, gearbox, electric actuator) and whether the valve will be at the end of a line. TAZ engineers will advise where a butterfly valve can replace a gate valve without losing reliability.
Checklist
- DN and PN
- medium and temperature
- wafer, lug or double-flanged
- liner and disc material
- operator type
- end-of-line service or not