Grooved end butterfly valves are attached to the pipes and pipeline systems using standard clamping couplings. The valves are rated to 21 bar or 300 PSI but each size and type has their own ratting
Lug styled butterfly valves function in much the same way as wafer butterfly valves which you can read about here.
A butterfly valve is a valve which can block the flow. The closing mechanism is a disk that rotates by means of a stem running through it's center and connected to the handle.