VALVE AND TESTING PDF

What is a valve?

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• A device for controlling the passage of fluid or air through a pipe, duct, etc., especially an automatic device allowing movement in one direction only.

Reference Codes and Standards

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• API STD 598: Valve inspection and testing

• API STD 600: Steel gate valve

• API STD 594: Check valve

• API 608: Ball valve

• API 609: Butterfly valve

• API RP 621: Valve repair

• ASME 16.34: Valves (flanged, threaded and welding end)

Gate Valve

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• A gate valve consists of a body that contains a gate that interrupts flow. This type of valve is normally used in a fully open or fully closed position. Gate valves are generally used in systems where low flow resistance for a fully open valve is desired and there is no need to throttle the flow.

Advantages:

- It has good shutoff characteristics.

- The pressure loss through the valve is minimal.

Disadvantage

- It is not suitable for throttling applications.

- It is prone to vibration in the partially open state.

- It is more subject to seat and disk wear than a globe valve.

- Repairs, such as lapping and grinding, are generally more difficult 

to accomplish.

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