Technical application | What is the valve opening pressure and how to deal with it correctly?

The output pressure of the Metering Pump is determined by the load and is approximately proportional to the input torque. There are two kinds of faults for abnormal output pressure: the output pressure is too low or the output pressure is too high. Valve opening pressure, which can be described as the pressure difference measured between the valve inlet and outlet when flow is initially detected. Specifically, opening pressure is the minimum pressure difference that the valve will experience during flow.

Check valves are often in fluid environments and are also used to handle various medium such as steam, gas, slurry, and other fluids. The pressure drop is related to the opening pressure and is equal to the pressure difference between the valve inlet and outlet. Once the opening pressure is reached, the valve opens and the medium flows. When the flow rate drops, the valve closes. The opening pressure depends on the design of the Check Valve and is usually measured in pounds per square inch (psi), bar or kilopascal (the corresponding metric units), or both.

Why is opening pressure important?

When selecting a check valve for a specific application, it is important to know the opening pressure of the valve. The valve with the most appropriate internal component design needs to be selected to achieve the desired opening pressure and total pressure difference. Check valves are designed to control flow in one direction and have a certain opening pressure. When fluid flows through the valve and the pressure is higher than the opening pressure, the valve flap leaves the valve seat and the valve opens, compressing the spring. When the check valve is oversized for the expected flow rate, the flow rate will be lower than required. Changing the spring to reduce opening pressure is one way to reduce chatter while improving valve stability.

What will happen if you choose an incorrect opening pressure?

When the opening pressure is too high, there will be a greater pressure drop across the check valve and the valve may not open fully or at all. When the opening pressure is too low, the closing speed of the valve will be reduced, and the valve may not be fully closed in the vertical downward flow position. To ensure consistent flow and avoid premature valve wear, please select a check valve that meets specific application needs.