The disc stays in the flow stream even when fully open, mounted on a shaft that turns through 90 degrees. Concentric, rubber-lined designs handle water and HVAC duty cheaply, double-offset high-performance valves add PTFE or metal seats for higher pressures, and triple-offset valves give metal-to-metal tight shutoff. Short face-to-face length and low weight make them the standard choice in large water lines.
The 24 inch butterfly valve on the condenser water return won't close all the way, I think the liner's swollen.
Check that the disc can swing into the adjacent pipe or fitting; a disc that hits a lined spool or a check valve will not open.
Also heard as
- BFV
- butterfly
Related terms
BFV
Butterfly valve: the clipped form used on valve tags, takeoff sheets and HVAC and fire protection drawings.
Triple-offset butterfly valve
A metal-seated butterfly valve whose geometry lets the seal touch the seat only at the end of closure, for tight, rub-free shutoff.
Wafer
A thin valve body clamped between two pipe flanges by long bolts passing outside it.
Ball valve
A quarter-turn valve that opens and closes by rotating a ball with a bore through it.