BOOK_CONTENT
From Valve Selection Handbook: Engineering Fundamentals for Selecting the Right Valve Design for Every Industrial Flow Application, Fifth Edition

FUNCTION OF CHECK VALVES

The prime function of a check valve is to protect mechanical equipment in a piping system by preventing reversal of flow by the fluid. This is particularly important in the case of pumps and compressors, where back flow could damage the internals of the equipment and cause an unnecessary shutdown of the system and in severe cases the complete plant.

Generally speaking check valves have no requirement for operators, and so the valve is operated automatically by flow reversal; however, in very special circumstances this uni-directional facility has to be overridden. Check valves either can be fitted with a device that allows the closure plate(s) to be locked open or alternatively can have the closure plate(s) removed. The latter alternative requires dismantling the valve, removing the plates, and re-installing the valve.

Check valves are automatic valves that open with forward flow and close against reverse flow.

This mode of flow regulation is required to prevent return flow, to maintain prime after the pump has stopped, to enable reciprocating pumps and compressors to function, and to prevent rotary pumps and compressors from driving standby units in reverse. Check valves may also be required in lines feeding a secondary system in which the pressure can rise above that of the primary system.

Grouping of Check Valves

Check valves may be grouped according to the way the closure member moves onto the seat. Four groups of check valves are then distinguished:

  1. Lift check valves. The closure member travels in...

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Products & Services
Check Valves
Check valves are self-activating safety valves that permit gases and liquids to flow in only one direction, preventing process flow from reversing. They are classified as one-way directional valves. 
Air Valves
Air valves allow metered fluid flow in one or both directions. They are used in pneumatic circuits to regulate the rate of activation or exhaust of cylinders and other pneumatic devices.
Water Valves
Water valves are designed to handle and control hot water, cold water, ground water, potable water, salt water and/or wastewater. They are made from metal or plastic.
Industrial Valves
Industrial valves are classified in many different ways. They can be distinguished by material of construction, media handled, and/or application.
Plastic Valves
Plastic valves are made from plastic materials and are used in applications that require corrosion resistance and/or chemical handling.

Topics of Interest

PRINCIPAL TYPES OF PRESSURE RELIEF VALVES Pressure relief valves are designed to protect a pressure system against excessive normal or subnormal pressure in the event of positive or negative...

GROUPING OF VALVES BY METHOD OF FLOW REGULATION Manual valves may be grouped according to the way the closure member moves onto the seat. Four groups of valves are thereby distinguishable:...

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Experience has proven the need for check valves in piping where reverse flow could be detrimental to the system. A valve which closes quietly and eliminates water hammer is obviously desirable. A need...

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