Simplified approach for sizing surge tank in long-distance pipeline systems

The cross-sectional area of a surge tank (CAST) is a key factor for protecting pipelines from harm by hydraulic transients. However, for long-distance pipeline systems (LDPS), the water level fluctuations in the surge tank and valve closure water hammer normally share a coupling relationship. Traditionally, this coupling relationship renders difficulty in determining the CAST. This study focused on the influence of water level fluctuation and water hammer, and proposed a simplified approach for sizing surge tanks. First, a water hammer formula that considers the coupling effect was derived. Subsequently, formulae for sizing the CAST were deduced. Finally, a case study of an actual LDPS was conducted to verify the accuracy of the presented formulae. In addition, the calculation errors caused by the theoretical assumptions are discussed. The results indicate that the theoretical calculation values and time-domain simulation results match well, thereby demonstrating the great convenience of designing surge tanks.