Proposing new correlations to improve the accuracy of hydrostatic tests for buried steel pipelines

Abstract

This study proposes an efficient and effective method to estimate the water temperature inside buried gas pipelines during hydrostatic tests. The goal is to develop appropriate correlations that can easily calculate the pipeline’s water temperature, taking into account the adjacent soil temperature variations, pipeline size, thickness, and coating properties. The study first presents a mathematical model of the problem, introducing relevant non-dimensional parameters. Then, the unsteady problem is numerically analyzed, considering all significant variables, and next, the effects of each non-dimensional parameter on the water temperature are carefully examined and evaluated. The numerical simulations show that the difference between the pipeline water temperature and the adjacent soil temperature can be up to 80%, particularly for large-diameter pipelines. The proposed correlations are able to estimate the pipeline water temperature during the hydrostatic test with around 1% deviation from the direct numerical solutions. Additionally, the results indicate that for typical test cases, the pipeline size is the main influential parameter, while the pipeline thickness and material coating with conventional properties do not significantly affect the water temperature variations.