Wax Thickness and Distribution Monitoring Inside Petroleum Pipes Based on External Temperature Measurements

[Image: see text] A method to estimate wax thickness inside petroleum pipes from the external pipe temperature measurements is proposed. When wax is deposited inside the pipe, the external pipe surface temperature decreases because the heat resistance of the wax reduces the heat flow from the fluid inside the pipe to the fluid outside the pipe. The decrease in the external pipe temperature can be calculated by solving a heat equation about the heat transfer from the pipe inner fluid to external ambient fluid, and thus the wax thickness can be estimated by measuring the pipe surface temperature. An experiment to validate the method was performed. Crude oil was passed through a pipe with an inner diameter of about 8 mm. Ten thermocouples were installed on the pipe. The pipe was covered by a heat-shrink tube as a substitute for an insulation material. The pipe was cooled by a coolant jacket, and wax about 0.8 mm thick was deposited in the pipe. The wax thickness estimated from the temperature measurements agreed well with the thickness estimated from the pressure rise because of the wax layer and from the final gross weight of the wax. The difference between wax thickness estimated from the temperature measurements and from the final gross weight was less than 0.2 mm.