Butterfly valves are ordered in two dominant body styles: wafer and lug. They share the same disc, seat and stem — the difference is entirely in how they mount between pipe flanges, and it matters more than most buyers expect.
A wafer butterfly valve is clamped between two pipe flanges by long through-bolts. It is the lightest and cheapest configuration and works perfectly for the most common duty: isolating flow in a continuous, pressurized line. Its limitation is that the valve cannot hold pressure with the downstream flange removed — the through-bolts need both flanges to carry the load.
A lug body has threaded inserts (lugs) around its circumference; each flange bolts to the valve independently. That allows dead-end service — removing downstream piping while the valve holds pressure — and lets maintenance crews drop one side of the line without disturbing the other. For pump discharge isolation, tank outlets and pipeline ends, specify lug type.
Above roughly DN600, or when axial pipe loads are high, a double-flanged body carries loads better than either. For zero-leakage high pressure and temperature, step up to a triple-offset metal-seated design in wafer, lug or flanged pattern.
Both styles are available across our butterfly valve range from DN50 to DN2000 with EPDM, PTFE or metal seats.