In transient hydraulic software, a check valve slam in a pipeline system is typically modeled via the valve closing time. Utilizing a closing time that is too low or too high may lead to underestimating or overestimating surge pressures due to check valve slam. Therefore, accurately specifying the check valve closing time is essential to predicting any resulting surge pressures. This paper determines the appropriate closing time by using the dynamic characteristics of the check valve and transient characteristics of the system. The methodology is illustrated in an initiating oil terminal with three different pipeline configurations A, B and C. The impact of check valve closing times on transient pressures is demonstrated in Configuration A. The effect of multiple sets of check valves in a chain on transient pressures is analyzed in Configuration B. Finally, the reopening effects of check valves on transient pressures is discussed in Configuration C.
When pipeline flow downstream of a check valve is stopped or interrupted, the check valve will close to prevent back flow as deceleration of the fluid velocity occurs. A check valve slam occurs during this process when the forward fluid flow reverses before the check valve is fully closed. The reverse flow is stopped almost instantaneously by the closing check valve. The valve closure results in pressure increase downstream and pressure decrease upstream. The pressure increase/decrease waves (or positive and negative waves) will propagate upstream and downstream, respectively. The slam (or surge) pressure due to instantaneous valve closure is proportional to the reverse flow velocity at closure and can be predicted by Joukowsky’s equation. Three methods have typically been used to predict check valve slam behavior, a dynamic characteristic curve of the check valve based on experimental testing, a torque or force equation based on a theoretical approach, and a closing time based on regression strategy.
