Double-offset valves, also known as high-performance butterfly valves, have the shaft mounted slightly offset from the pipe centerline, and the shaft is mounted behind the sealing band of the Water Pump Control Valvesseat. The seat is a Water Power Control Valvesnarrow resilient band is clamped in the body and must be resilient. PTFE is resilient enough to seal, and the disc only wipes the seat for a few degrees of travel at seating. So there is Oil pumpsa lot less friction, the seats can last longer, and the seats can be made from materials that are capable of dealing with higher temperatures than the rubber seats of the lined valve. Metal seatsfire pumps are available for HP Butterfly valves allowing operation to around 1200F. SInce the disc is offset from the shaft, there is a lot of metal in the flow stream in the Split case pumpswide-open position, and double-offset valves have somewhat less maximum capacity than flat-disc, non-offset valves. These valves are also position-seated. Unlike the lined valves, these valves can actually damage the seats if they are overstroked so they almost all have a travel-stop pin in the body.

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