A large-scale equipment of a famous refining and chemical company of China had to be temporarily shut down for repairing, because one of its fractionation bottom reboiler tubes was suspected to leak. These tube bundles are densely distributed, and the outer casing of the reboiler is the fixed structure which can not be opened to check these tubes unless it is cut. The outer casing cutting for checking is very time-consuming (about 1–2 months) and costly. Possible pipe guided wave technology or endoscope method also can not be used because of acoustic attenuation from dense fins and severe corrosion of tubes or being inaccessible, so Acoustic Emission testing became the only choice for finding out the leaking tube in that time. Also due to the significant acoustic attenuation, the traditional Acoustic Emission linear positioning method is difficult to find out leaked tubes, so the zonal localization method of acoustic sources was predominant in this test. The hydraulic test of pipelines was used to stimulate acoustic signals from leaking sources. However, the water from leaking holes will be splashed to the adjacent pipes and then drop onto pipes below, which will cause false leaking signals. For finding out the leaked tube, logic method is adopted to infer the real leaked tube complementarily. The spatial positions of all tubes and the sequences, frequencies, amplitudes and total hits of acoustic signals from all tubes monitored are considered in the analysis. Finally, the leaked tube was successfully found out in half a day by the combination of Acoustic Emission testing and logic analysis, the leaked tube was replaced and the production was resumed in the next three days.

By comparing acoustic emission (AE) online inspection results of vertical tank floors with validation testing results by other methods including magnetic flux leakage (MFL), visual examination (VT), Magnetic Particle Testing (MT) or Penetrant Testing (PT), vacuum leak detection or destructive cutting, the dependability and precision of AE inspection results are analyzed, and the successful experience of AE online testing of atmospheric tank floors is summarized.

Acoustic emission (AE) technique has been widely applied to pressure vessel and piping inspection, such as local abrasion or corrosion, growing fatigue cracks. Sound source location analysis plays an important role in the whole AE inspection and evaluation process, how to improve the location precision to an extent is the research focus all over the world. For AE sound source location of pressure vessels, the arrival-time difference location method is mainly used, i.e. compute arrival-time difference which sound source signals arrive at different sensors to determine the sound source location. If an active sound source is on the internal surface or in the wall not on the external surface of thick-wall pressure vessels, the location error obviously exists because of the wall thickness influence. In this paper the sound source error for thick-wall pressure vessels is deduced in detail, the sound source location error formulas are founded and the change law of location error with the wall thickness is analyzed and discussed too. Furthermore, it is proposed that about 200 mm radius area around the source location should be rechecked by normal nondestructive testing methods to determine the actual source location when inspecting thick-wall pressure vessels by AE technique.

In China, the management and inspection of metal atmospheric storage tanks are still in a self-discipline or post-mortem mode. Therefore, the effective inspection is not carried out for most metal atmospheric storage tanks especially those being on service for more than 20 years. The potential leakage risk and environmental pollution are serious. In order to reduce the operating risk of metal storage tanks, effective inspection for metal atmospheric storage tanks is needed. Based on the practical situation of their management in China and the development process of the standard, an effective inspection method is proposed in this paper in which magnetic flux leakage testing and acoustic emission testing technologies are adopted. The method is used to verify the inspection results and the treatment for inspected defect is also put forward. The inspection results show that this method can be adopted in practical application.

In china, atmospheric storage tanks are not included in the management of special equipment, and therefore they are not required to be inspected compulsorily. There is larger difference between China and developed countries on atmospheric storage tank inspection technique than the other techniques on the inspection of pressure vessels. It is widely believed that the strength worsening and perforation of the tank is mainly caused by the serious corrosion at the bottom surface of tank floor. The present development of nondestructive testing on atmospheric storage tank was analyzed systematically in this paper, in which the principle, standard present status, the usage of inspection equipments and the application of the acoustic emission testing and magnetic flux leakage testing techniques on atmospheric storage tanks were mainly introduced. The problems existing in the inspection equipments usage were discussed. A practice for inspecting and evaluating atmosphere storage tanks using these testing methods was proposed.