Industrial range
Butterfly valves
Quarter-turn valves with a disc that turns in a rubber-lined body: light, short and low cost for water, air, mud tank, fuel and process lines at low pressure.
A butterfly valve controls flow with a disc that turns a quarter turn on a stem across the bore. In a concentric, resilient-seated valve, the disc closes against a rubber seat that lines the body, giving tight shut-off at low pressure in a short, light valve. We supply wafer and lug butterfly valves of this type to API 609 Category A and EN 593, with EPDM, NBR or FKM seats, operated by lever, gear, or pneumatic or electric actuator.
Wafer and lug
| Wafer | Lug | |
|---|---|---|
| Body | Thin ring clamped between flanges | Body with threaded lugs around it |
| Bolting | Through bolts pass around the valve | Each flange bolts to its own set of lugs |
| Dead-end service | No | Yes, within the maker's stated limit |
| Weight and cost | Lowest | Higher |
Construction and materials
| Part | Common materials |
|---|---|
| Body | Cast iron or ductile iron; WCB carbon steel or CF8M stainless to order |
| Disc | Ductile iron (coated), CF8 or CF8M stainless, aluminum bronze |
| Stem | Stainless steel |
| Seat | EPDM, NBR or FKM, chosen for the fluid and temperature |
Face-to-face dimensions follow the short series for wafer and lug valves, so a valve fits the space between standard flanges. The flange drilling, ASME B16.5 Class 150 or EN 1092 PN 10 or 16, is stated on the order.
Levers with a notched plate suit small sizes and frequent operation; gear operators with a handwheel suit larger sizes; an ISO 5211 top flange takes a pneumatic or electric actuator. Larger valves need more torque, so tell us the line pressure and the fluid when you ask for actuated valves.
Testing
Each valve is shell and seat tested to API 598 or EN 12266-1 and marked with size, pressure rating, body material and seat material.
Ordering
Butterfly valve, lug type, NPS 6, ASME B16.5 Class 150 drilling, ductile iron body, CF8M disc, EPDM seat, gear operated, tested to API 598, 4 pcs
Butterfly valve, wafer type, NPS 4, PN 16 drilling, ductile iron body, ductile iron coated disc, NBR seat, lever operated, 10 pcs
Frequently asked questions
Wafer or lug?
A wafer valve is clamped between two flanges by bolts that pass around its body; it is light and cheap, but the line must be taken apart to remove it. A lug valve has threaded lugs, so each flange bolts to the valve on its own side and one side of the line can be disconnected while the valve holds pressure on the other, within the limits its maker states.
Which seat material?
EPDM for water, glycol and many mild chemicals; nitrile (NBR) for oils, fuels and hydrocarbons; fluoroelastomer (FKM) for higher temperatures and aggressive chemicals. State the fluid and temperature and we confirm the seat.
Can a butterfly valve throttle?
Within limits. It controls flow reasonably between about 30% and 80% open, but long periods at small openings erode the seat and disc edge. For tight control or high pressure drops, use a valve made for throttling.
Which flanges does it fit?
Wafer and lug valves are made for the flange drilling you name: ASME B16.5 Class 150, or EN 1092 PN 10 or PN 16. Lug threads are tapped to the matching bolt size.