What is Check Valve ?

Check valves have many possible uses and can stop the flow of water or air, depending on their design. A check valve for an air compressor stops backflow of air, while a check valve for a water pump stops backflow of water. One water pump check valve application is in a sump pump system. The valve enables water to flow out and keeps it from returning.

In compressor systems, check valves go on the discharge line between the compressor and the air receiver. This component has several uses:

• Preventing backflow: The valve prevents pressurized air from returning to the compressor, helping to protect it from damage and prevent unnecessary cycling.
• Maintaining pressure: If air can flow back out of the receiver, the system will lose pressure when the compressor is off. A check valve ensures air can only flow to downstream equipment, keeping a consistent pressure.
• Enhancing safety and efficiency: This valve promotes safer and more reliable operations by preventing leaks, pressure losses and mechanical wear within the compressor system.

Check valves come in many forms. Here are a few of the most common check valve types:

• Swing: This design uses a hinged disc. It swings open when the flow moves into the tank, but doesn’t open the other way, keeping the flow from reversing. This more basic design works for horizontal piping and general-use applications.
• Lift: This valve type has a disc similar to a swing valve, but the disc lifts out of the way to allow air to pass through from the compressor. When the compressor isn’t running, the disc falls back into place to prevent pressure from escaping. This setup works in vertical or horizontal orientations.
• Ball: A ball inside this valve moves into a wider area to let air through when the compressor is running. When the compressor stops, the ball settles back into place, covering the smaller opening. This design works well for systems with pulsating flow or a need for a quick response.

Piping and instrumentation diagrams (P&ID) and process flow diagrams (PFD) use special symbols to identify different components. These diagrams help in understanding operations and effectively performing repairs or maintenance.

Check valves use a symbol with a circle for the valve body and an internal arrow indicating the flow direction. A line through the circle indicates a nonreturn mechanism. Each type of check valve has a variant of the symbol. Ball valves, for example, have a circle indicating the ball.

Check valves can wear out or become damaged during compressor operations, requiring replacement. Here are a few signs that it might be time to replace this component:

• You notice a slight loss in pressure over time.
• The compressor stops and starts more frequently than usual.
• You hear hissing, humming or rattling sounds near the valve.
• The valve has visible damage, corrosion or buildup.
• The valve leaks during a routine leak test.