The stated circumstance is the main cause of the increase of scope and extent of accuracy in calculated assessment of the stressed state of pressure vessels during their designing, the introduction of the system of check calculations on the basis of which the additional limitations of structure loading conditions, the increase of metal quality control by NDT techniques as well as the increase of requirements to the correctness of performance of all basic technological procedures are determined.

Nevertheless, as it has been stated above, in the manufacture practice of large scaled structures it can be found that single breaks of metal quality were missed (mainly, production defects of crack type, which are most dangerous in view of failure appearance and development).

In this case a timely detection of failure developing by structure operations becomes of a great importance. The acoustic emission techniques are a most effective means to reveal developing defects, and it permits to record sound oscillations of metal, occurring by relief of internal energy of stressed structure owing to the proceeding of plastic strain processes or the formation of new free surfaces (crack jumped up). Coming to metal surface sound oscillations can be recorded by a piezoreceiver, and it permits to give warning of fracture development in structure elements.