Numerical analysis of pressure gradients in piping due to hydraulic transients to determine critical axial loads

Resumo

Hydraulic transient or “water hammer” is the sudden pressure variation in a fluid system. In pipelines, it is often associated with closing valves and starting and stopping pumps. In aerial installations, it may produce great axial forces due to the steep pressure differentials that may occur. To correctly dimension pipe supports, stress analysis studies must consider these loads, which, in turn, require hydraulic simulations. Often this data is unavailable given the required deadlines. The work presented here aims to provide data on dynamic forces generated in hydraulic transients in a wide range of cases found in the oil industry. Hydraulic simulations were performed considering various pipeline diameters, flow velocities, and different fluids, analyzing the rapid closure of a ball valve. These simulations provided the pressure gradients that occur across multiple pipe lengths. Quadratic interpolations were then performed with the data obtained by the simulations, and it was verified that they were adequate to get pressure gradients for scenarios of flow velocities and density values intermediate to those of the simulated cases without the need to carry out new simulations. It was also verified that a fifth-order polynomial could perfectly describe the pressure gradient curves of each scenario, allowing the results to be obtained by simple equations.