Effect of solid deposition on the risk of pressure surges in closed pipes

Pressure surges in pipes that manifest as wastewater reflux and geysers, overflows, and burst pipes are likely to be related to the development of a solid deposit layer in a closed collector. The mechanisms that lead to the generation of these pressure surges are yet to be fully understood, and therefore require further research. In this work, the effect of solid deposition at the bottom of a closed pipe on the pressure distribution within it was quantified. Assuming uniform and stationary flow, the Exner–Saint Venant equations were applied in pressure variation modeling to explore this effect of solid deposition in a pipe. Analytical and numerical solutions for gravity and pressurized pipes were calculated. Because the solid flow rate is an important parameter in this calculation, the Wang and Graf formulas were separately employed to estimate this parameter. The results obtained using the two formulas were then compared, and the most suitable formula—the one that neither underestimated nor overestimated the deposition-induced pressure modifications in the pipe—was identified. Results showed that the numerical solution provided the most accurate results, while the Wang formula was more accurate than the Graf one. The pressurization of the free surface flow was found to be significantly affected by the development of solid deposits in the pipe. Pressurized conduits may be at particular risk of pressure surges caused by solid deposition. To understand and thus avoid this phenomenon, alterations to the pipe bottom and pressure caused by solid deposition must be evaluated using the most appropriate solid flow formula.