A hydrate blockage detection apparatus for gas pipeline using ultrasonic focused transducer and its application on a flow loop

Abstract

AbstractThis paper introduces a novel apparatus and the analyzing method for hydrate blockage detection in natural gas pipeline using the ultrasonic focused testing technique. The apparatus mainly consists of three parts: an ultrasonic focused transducer, a supporting guide track and a positioning ruler for the transducer. It can be installed by fixing the guide track onto the pipe outer wall, and the distance of the transducer to the pipe wall can be adjusted with the positioning ruler. The reflection signals of hydrate surfaces can be then received and recorded by an oscilloscope. The hydrate thickness thus can be calculated by multiplying the ultrasonic velocity with the time difference between two reflections. A calibrating test using this apparatus certified that it can provide an accurate measurement of both the pipe wall thickness and the hydrate blockage thickness from outside of the pipe. A maximum hydrate thickness of 50 mm can be measured due to the high penetrability of the ultrasonic. The feasibility of applying this apparatus to the metal pipeline was verified with a carbon steel cylinder with ice attached on the inner wall. A 360° blockage profile around the cylinder was obtained with a step angle of 5°. The accuracy of measured thickness and cross‐sectional area of the blockage can reach 96% and 91%, respectively. Finally, an application test was conducted on a full visible flow loop of 35 mm inner diameter and 49 m length. The test results showed that the hydrate blockage contour measurement can be achieved with this apparatus despite the gas and water flow in the loop. This hydrate blockage detection apparatus can be applied to gas‐dominated pipelines in which hydrate mainly forms on the wall. Early warning of hydrate blockage can be further studied based on the measurement results using this apparatus.