Lug type butterfly valve, 1½" to 6"

A resilient‑seated butterfly valve in 1½" to 6" (DN40 to DN150), with a cast iron body, a CF8 cast stainless disc on an SS410 shaft, and an EPDM seat liner — in the lug body, drilled to sit inside an ANSI 150# bolt pattern. The same valve is also stocked as a wafer type; inside, the two are identical.

The disc turns a quarter turn inside the body, and its rim presses into the rubber liner to seal. Because it pivots in place instead of lifting clear, the whole valve is only 24 to 28 mm from face to face — against roughly 400 mm for a flanged gate valve at 6". How a butterfly valve works, in full.

• ⚠ Two different rubbers, with opposite compatibility. The seat is EPDM and the shaft O‑ring is NBR. EPDM is poor with mineral oil; NBR is poor with hot water. This is a water and air valve — do not put oil through it, because the seat is the pressure boundary and there is no metal seat behind it. The compatibility table.
• Two pressure figures are published: the specification box states 150 PSI and the test table a nominal of 1.6 MPa (232 PSI), both as printed. Design to 150 PSI unless we confirm otherwise. How to read them.
• The lug body is the one that can end a line. Its tapped holes let each flange bolt on independently, so the downstream pipe can come off with the valve shut and holding pressure — the one practical thing a wafer body cannot do.
• The disc is CF8 — cast 304 stainless — and it is the only part in the flow path that is stainless at all. The body is cast iron. On treated or brackish water, tell us.
• ⚠ Check disc clearance before bolting up. On the smaller sizes the disc swings past the body face as it opens, and against a reducer, a pump flange or a lined pipe it can foul. You will not find out until someone tries to open it.
• No gaskets against the pipe flanges. The EPDM seat has raised faces that seal directly against them; an extra gasket lifts the flange off that face and makes the joint worse.

The stocked valve, photographed. Not renders.

The manufacturer’s sectional drawing. Callout numbers correspond to the parts list above.

• Wafer and lug share one parts list. We checked the two published lists against each other and they are identical part for part and material for material. The bodies differ; nothing inside them does.
• ⚠ The seat is the part to specify, not just the part to know about. EPDM suits water, hot water and air, and is poor with mineral oil. If your fluid needs something else, say so before you order — a different liner is a specification, not a modification. The compatibility table.
• The shaft never touches the fluid path directly. It drives the disc through an SS304 pin and is sealed by the NBR O‑ring, running in polymer bushings that take the side load.
• The lever is ductile iron, not grey. It bends rather than snapping if someone puts a bar on it — though the right answer on the larger sizes is a gearbox, since torque rises sharply through the last part of the stroke.

• Two pressure figures are published. The nominal here is 1.6 MPa (232 PSI) and the specification box says 150 PSI, both as printed — the shell and seal tests are exactly 1.5× and 1.1× the nominal. Design to 150 PSI unless we confirm otherwise, and ask us if your duty falls between the two. How to read them.
• ⚠ Shell and seal tests are proof tests, not working pressures. Do not design to them.
• −30 to 120 °C is the rubber, not the body. Cast iron and a CF8 disc would take far more — the EPDM seat and NBR O‑ring are what stop it. For hot duty use a metal‑seated gate valve, which reaches 425 °C.