Diagnosis, Modelling and Assessment of Transient Pressure Events Based on Observed In-Field Evidence

Intermittent pipe movement due to transient pressure events including vapor column collapse or water hammer events can impart large strains into the pipe, cause damage to the support structure, damage coatings, and cause damage or failure of the pipe. This paper will present a method that has been used with success for determining the pipe stresses and strains and possible cause associated with a transient pressure event based on coating damage evidence gathered from in-field assessments. After constructing a hydraulic model of the piping system, various transient events were modelled to obtain resulting pressure over the transient event’s period at key points along the piping system, such as valves and elbows. A second, more refined finite element model was created to incorporate the pressure values to determine the resulting displacements and stresses to relate to the in-field measurements of the region in question. By comparing the displacements in the model to the field evidence, the models were calibrated, and evaluation of the likely cause of coating damage found in the field was able to be performed. Moreover, the stresses in the pipe during the event are able to be assessed which allows for damage assessments to be conducted and allows for corrective actions to take place. Transient events assessed ranged from valve openings and closures, pump start up, and vapor column collapse.