PSI - Issue 16

Borys Paton et al. / Procedia Structural Integrity 16 (2019) 176–183

179

Borys Paton et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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The system was mounted on pipeline of 630 mm pipe diameter with 25 mm wall thickness. Pipe material was 15Kh1M1F steel. Altogether 16 AE transducers were mounted (on two pipeline runs of 120 m each). Considering the high operating temperature of the pipeline, transducers were mounted on 500 mm wave guides (Fig. 3).

Fig. 2. Tensile testing of 15Kh1M1F steel sample at 560°C temperature.

Fig. 3. Mounting AE transducers (a) on pipeline: transducer 1 in a special box, placed on waveguide 2 welded to pipeline; connecting cable in flexible insulation 3 (b), in rigid box 4 (c).

AE transducer spacing is 20 m. In addition, transducers 15 and 16 monitor the connecting pipeline of 370 mm diameter with 17 mm wall thickness, made of 12Kh1MF steel. In keeping with technical requirements and schematics given in technical assignment, mounting of continuous monitoring system, its connection to the mains and company intranet were performed. Required preparatory measures were taken to put the system into trial operation. Instrumentation and control blocks were connected to common control network; continuous monitoring system was put into trial operation mode. The main objectives during trial operation period of continuous monitoring system are establishing optimum parameter settings, system operation modes, and special features associated with system operation in the given facility, as well as elimination of detected malfunctions. Monitoring during trail operation is periodic-continuous. This means that the system should be periodically put in continuous monitoring mode, and one-time testing of objects of control is performed periodically. Monitoring, both continuous and periodic, was performed, in particular, in pipeline operating modes, in particular, at steam pressure in the pipe equal to 22 atm., and steam temperature of 542°C. During testing the monitoring system automatically determined higher damage areas and performed prediction of breaking load (Nedoseka (2007, 2008)). Work on putting the mounted system into operation was started from sounding the pipeline sections to be monitored by pulsed signals from a special generator so as to determine the required sensitivity of the system and presence of acoustic coupling between adjacent AE transducers. Preliminary testing demonstrated high sensitivity of the system that enabled arranging the so-called locating antennas from groups of transducers, mounted on adjacent pipeline sections, which provided the required acoustic coupling. Thus, three acoustic antennas were formed, which include the following transducers (channel numbers in the diagram of connection to AE instrument): antenna 1 – numbers from 1 to 7; 2 – from 8 to 14; 3 – 15 and 16. Considering the configuration of transducer arrangement, linear location mode was selected for all the three antennas. Cluster analysis is envisaged for incoming information classified as AE events, which allows combining the events by coordinate and a number of other characteristics. Application of such an approach for actual structures, especially those with complex geometry of the objects and in the presence of interference, is highly effective (Paton et al. (2012), Nedoseka et al. (2012)). In the case of significant scatter in certain event coordinates, which with a high degree of probability belong to one and the same process in the material, combining them in a cluster allows the most accurate location of their origin source. This is particularly important for those pipeline sections, the access to which is impossible for technical reasons. It should be taken into account that industrial enterprise equipment is a source of acoustic and electromagnetic interference that may affect the quality of information transmitted during