Comparing Dual Plate and Swing Check Valves and the Importance of Minimum Flow for Dual Plate Check Valves

Abstract

Check valves are automatic valves that open with forward flow and close against reverse flow. The main function of a check valve is to protect mechanical equipment in a piping system by preventing fluid reversal. A swing check valve is an economic type of check valve, but it has a high slamming effect. Dual plate check valves are more popular than swing check valves in Norwegian offshore industry [16] because they have a low slamming effect. Additionally, the total cost of a dual plate check valve—initial cost, maintenance cost, and energy cost—is less than a swing check valve. In fact, swing check valve makes more pressure drop and energy consumption in pumping system. However, the minimum flow capacity may not produce enough pressure during the usage of dual plate check valves, which results in two operational problems. The valve loses more pressure when it is not in a fully open position, and in addition to a rise in energy consumption, insufficient flow velocity can wear the valve. A case study of minimum flow capacity and velocity calculation for fully opening a 22Cr duplex dual plate check valve in ASME pressure class 300 is discussed in this paper. The minimum flow in the example is lower than minimum critical flow required to fully open the valve. Thus, to avoid operational problems, it is recommended to not operate the valve with minimum flow. The other recommendation is to avoid installing the valve on the vertical line. Reducing the size of the valve and spring torque behind the disk are two other solutions to mitigate operational risks due to a minimum flow condition.