🔍 Key Concepts

• Look at how the disc is mounted on a hinge or pivot and how it moves with the flow (see the dashed positions). • Think about what kind of valve automatically prevents backflow without a handwheel or stem visible in the drawing. • Compare the body shape and flow path with typical globe, gate, and butterfly valves you’ve studied.

💭 Think About

• Does the moving element in this illustration slide straight up and down, rotate around a central shaft, or swing like a door on a hinge? • If flow reverses, what will this disc naturally do based on the way it is supported—will it close by swinging back into the seat or by lifting/dropping? • Which of the answer choices describes a valve that works automatically with flow direction, rather than being operated by a handwheel or actuator?

✅ Before You Answer

• Verify whether there is any stem/handwheel shown; if not, ask which type of valve normally operates without manual actuation. • Check if the seat is arranged so the disc swings into place to seal, rather than being pressed by a rising/lowering stem. • Match the movement of the disc shown by the dashed outlines with the verb in the name: “swing,” “lift,” “gate,” or “butterfly.”