Why the Right Size of Check Valve Is Important

Check valves serve an important function; they are primarily used to prevent reverse flow of media - typically liquids, gases and vapors - but can also be used for vacuum breaching, low pressure relief, line isolation, manifolds, media injection and many other applications. By allowing only one-way flow, check valves can prevent destructive backflow and some models can also prevent hydraulic shock.

There are different items to consider when sizing a media actuated check valve versus other types of flow control valves that utilize external actuation methods. When check valves are correctly sized, systems operate more efficiently and reliably. Correctly sizing valves protects them from preventable problems, such as premature wear or rupture, which can disrupt the flow and cause damage to other equipment and components.

Single Plate Check Valve

Oversizing Problems

Oversized valves can significantly shorten their service life due to premature wear, potentially leading to complete failure. If they fall apart, they can damage or destroy more expensive components upstream or downstream - usually downstream of the check valve - resulting in far higher costs than a simple valve replacement. A sign of oversizing is when the check mechanism rattles and chatters because it does not open and close completely and properly.

Undersized problems

An undersized check valve creates an obstructed flow condition, which means a process cannot obtain the required media flow or pressure downstream of the check valve. When a valve is too small, it will interfere with the intended function. Because the system cannot operate efficiently, it puts more stress and burden on the flow source (e.g., the pump).

In addition, when the check valve is undersized or too heavily sprung, the check mechanism may not perform as intended. Even if the valve is sized to match the line size, its flow rate will be lower than required by the application, causing flow blockage. As a result, it will not produce the required media flow downstream to accomplish the desired function.

Swing Check Valve

Correct sizing

- Improve valve operation and promote longer service life

- Minimize the frequency, cost and time of valve maintenance, repair and replacement

- Reduce downtime due to valve failure and potential equipment damage or destruction

- Enable adequate flow and pressure to operate at optimum performance

How to Size Correctly

Sizing depends heavily on the type of valve. For most flow control valves (gate valves, globe valves, ball valves, etc.), it is simply based on the size of the piping. In addition, these valve types are manually throttled. With the turn of a handle, the opening mechanism of a ball or gate valve can be manipulated as needed to achieve the desired pressure loss and/or flow coefficient.

Check valves, on the other hand, are automatic and are activated by flow conditions. This makes accurate valve sizing even more important. Specific to spring-loaded check valves, proper spring selection is critical for optimum valve performance.

The spring setting (also known as the spring break pressure) is equal to the minimum differential pressure required to initially open the valve. To fully open the valve, some additional differential pressure and flow is required.

Ductile Iron Body and Disc Tilting Check Valve

LIWEI now produces a series of butt butterfly valves, flange butterfly valves, gate valves, globe valves, check valves, ball valves, liquid control valves, etc. We have successfully passed the ISO9001 international quality system certification. Our valves are widely used in food, medicine, electric power, smelting, construction, petroleum, chemical and other industries. If you want to know more, please contact us.