Summary
Widely used as it is, pipeline pigging still holds ambiguities in its mechanisms. In this paper we explore the nature of the wax removal process with a unique pigging facility. Solid wax content, yield stress, viscoelasticity, and microscopic characteristics of wax samples are thoroughly studied with differential‐scanning‐calorimetry (DSC) trials, rheological tests, and microscopic observations. We found that the relative solid wax content is approximately linearly dependent on temperature, and yield stress can be well‐fitted with wax content in an exponential format. An investigation on wax‐breaking force indicates that it increases with solid wax content. Wax removal efficiency increases with wax thickness and pipe‐wall temperature, decreases with a wax‐mixing ratio and solid wax content, and it varies irregularly vs. the scraping‐element hardness in the pig. Furthermore, a prediction model of wax removal efficiency was developed on the basis of nondimensional analysis. The absolute average deviation of verification experiments against this model is 5.22%. This model might benefit in estimating the wax‐scouring capacity of the wax‐in‐oil slurry and, therefore, helps to avoid wax blockage and to arrange the pigging program.
