What type of valve is a flow-regulating device that uses a disc-shaped flow-control element to increase or decrease flow?
A) Ball check valve
B) Lift check valve
C) Swing check valve
D) Gate valve
Answer: C
Explanation: A) Incorrect. A ball check valve is a ball- or sphere-shaped flow-control element is used. Forward flow pushes the ball off the valve seat; backflow pressure causes the ball to drop back down onto the seat, sealing the valve.
B) Incorrect. A lift check valve is a disc-shaped flow-control element controls the flow of the fluid. The disc is lifted off its seat to allow flow in one direction. It rests back on its seat to prevent flow in a backward direction.
C) Correct. A swing check valve is forced closed if the fluid changes directions.
D) Incorrect. A swing check valve is forced closed if the fluid changes directions.
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