Check Valve Properties

The question describes a valve that exhibits specific behavior related to the operation of a pump:

• It opens when the pump is running (operated).
• It closes automatically when the pump is suddenly stopped.

Let's analyze the properties of the given valve types:

Check Valve

A check valve, also known as a non-return valve (NRV), is a mechanical device that allows fluid (liquid or gas) to flow through it in only one direction. It has two ports, one for incoming flow and one for outgoing flow. The main purpose of a check valve is to prevent backflow in a system.

How it works with a pump:

• When the pump is running, it creates pressure and flow in the forward direction. This pressure pushes the internal mechanism (like a disc, ball, or swing gate) of the check valve, causing it to open and allow fluid to pass through.
• When the pump is suddenly stopped, the forward flow ceases. The pressure differential across the valve changes. The weight of the fluid in the discharge line or back pressure from the system pushes the valve mechanism back to its closed position, preventing any fluid from flowing backward through the pump. This automatic closing action prevents issues like water hammer or draining of the discharge line back through the pump.

This behavior perfectly matches the description provided in the question.

Other Valve Types

• Scour valve: This type of valve is typically located at the lowest point of a pipeline or tank to drain or flush out accumulated sediment. Its operation is usually manual or controlled by an actuator, not automatic based on flow direction from a pump.
• Butterfly valve: A butterfly valve uses a disc mounted on a rotating shaft to regulate or isolate flow. It is usually operated manually with a lever or handwheel, or automatically with an actuator. It does not automatically close when flow stops or reverses; it stays in the position it was set to unless actively changed.
• Sluice valve (Gate valve): A sluice valve, or gate valve, uses a gate-like barrier that is lowered or raised to block or allow flow. Like the butterfly valve, it is typically operated manually or by an actuator and does not automatically close upon cessation of forward flow.

Based on the analysis, the valve type that automatically opens with forward flow and closes when the flow stops is the check valve.