Experimental Study Of Pipeline Liquid Loading Ultrasonic Monitoring Technology

While energy use is increasingly tense in the world, the development and utilization of natural gas is favored by many countries, because of its unique advantages of high calorific value, clean and safe. However, people encounter many problems to need to be solved urgently during the development of natural gas. For example, in the course of gas transmission, since the pipe wall transfers heat with the surrounding environment, condensate may be precipitated, at the same time, gas field will outflow water with the exploitation of gas field, resulting in fluid produced in the pipeline. The presence of fluid poses a great threat to the normal operation of the pipeline. Currently, the detection method used at home and abroad are mainly the method of quick closing the valve, fluorescence method, ray method and so on. However, there are shortcomings such as, the scope of some methods is small, some have to be used inside the pipeline, some are radioactive. On the contrary, ultrasonic testing causes widespread concern in domestic and foreign experts on account of on need for correct the speed of sound, not affecting by the parameters such as gas-liquid composition, temperature and pressure, even not having to changing the existing pipeline structure, and you just only need to use a single ultrasonic probe on the outer surface of the pipe to get the fluid level data quickly and accurately.The main principle of fluid level measurement by ultrasonic is, as the ultrasonic wave propagates in the medium, the energy is gradually absorbed, meanwhile, wave amplitude decreases also, we can identify changes of the interface in the internal pipeline by measuring the acoustic attenuation rate, find out the location of gas-liquid interface inside the pipes, determine the fluid level ultimately.In this paper, I take use of ultrasonic inspection system, which is based on UMLQHU-500A ultrasonic detector, that we self-developed, to conduct the experiments of detection of the fluid. I did a lot of ultrasonic testing with air and water as the medium, in the circular pipe in Laboratory of Multiphase Flow, which is in the Yi Fu Laboratory Building on Qingdao Campus of China University of Petroleum (East China). Detected object was a two-phase flow in horizontal channel, and a total of 9 conditions was obtained in different levels and flow rates. The main purpose of this experiment is to observe the changes of the ultrasonic signals reflected back from the inside wall of the pipe, when the ultrasonic probe is moved up and down on the outer surface of the pipe, ultimately determine the location of gas-liquid interface.By regulating the electrically operated valves, and the switching valves before and after the vortex flow meter in the experimental pipeline, we could change the gas flow rate under different fluid level. After that we conduct the adjustment of fluid level in the test pipe by pass pipe, then complete the ultrasonic measurement under different fluid level. We carried out measurements several times for each condition, taking the average of the results and recoding them. At the same time, we collected ultrasonic echo waveform respectively in the positions of solid-gas interfaces, solid-liquid interface, and the three-phase boundary point.Next, it was the manual analysis of ultrasonic echo waveform collected from the detector that had been carried out to determine the impact of the gas flow rate and fluid level on the ultrasonic measurement. Afterwards I analyze the experimental error taking use of Matlab software.Finally, I theoretically analyzed the mechanism of fluid level detection with ultrasonic, and further studied the impact of liquid film, thickness and the tailing on the testing system of ultrasonic.