ENSURING COTROL OF SAFE FUNCTIONING FOR FACILITIES WITH CRACKS USING ACOUSTIC EMISSION METHOD

Abstract

Each type of equipment for oil and gas technologies can have cracks or crack-like defects of various origin. This fact makes us change the paradigm of the cracked structures are perceived with. It urges to develop design, design-and-experiment, and experiment methods of assessing the risks of their operation. Such an approach is increasingly relevant due to adopted regulatory documents in a number of industrially developed countries including Russia. These documents outline the standards for operation of cracked systems. Methods of linear and non-linear fracture mechanics allow to define the critical size of a crack after reaching which the crack will keep on expanding. Pig inspection allows to detect a fracture, its location and define its dimensions at the same time. However, it is dangerous to operate cracked facilities because the ambient environment may result in accumulating elastic strain energy in the membrane caused by seasonal changes. The most plausible method of relaxation is related to using cracks and crack-like defects as an energy sink through developing fractures and forming a new surface. Since there is still an apprehension that a crack of under-critical size may appear, it is suggested to fill in the detected defects with a composite material. The integrity of the materials is suggested to be controlled with acoustic emission signals. The acoustic emission method is applied to test strain-sensitive coatings that are used for high-hazard facilities when inspecting areas that are difficult to reach with visual inspections. We conducted experiments that showed that it is possible to recover the properties of cracked steel elements by using composite materials. At the same time, we researched a possibility to use acoustic emission method to control the integrity of the composite materials inside the fracture cavity. It is displayed that this method allows to conduct such an inspection and requires further studies. These studies should deal with a possibility to interpret signals related to the composite material deformation by using, for example, a cluster analysis of signals.