АНАЛІЗ ФАКТОРІВ, ЯКІ ВПЛИВАЮТЬ НА ЯКІСТЬ ГІДРОСТАТИЧНИХ ВИПРОБУВАНЬ ТРУБ НАФТОГАЗОВОГО СОРТАМЕНТУ

The key factors affecting the quality and reliability of hydrostatic testing of oil and gas pipes, which is the final and 100 % mandatory method of checking product compliance with operational characteristics, are analysed. Pipe production is regulated by a number of international and national standards (e.g. DSTU EN ISO 13679:2022, API 5 CT, DSTU GOST 3845:2019), with the latter standard defining the method for calculating the test pressure depending on the ratio of wall thickness to pipe diameter (S/D) and the permissible stress of the material (R). The study focuses on analysing the operation of hydraulic presses installed in pipe finishing areas and their hydraulic systems, which consist of low-pressure, high-pressure and oil control circuits. The main criterion for assessing the quality of the test is the stability of pressure maintenance during a specified holding time – the technological ''pressure strip''. Four main groups of negative factors that reduce the quality of hydraulic tests have been identified: the presence of air in the pipe, which causes waves on the pressure diagram; leaks through shut-off valves or technological collars, leading to a drop in pressure; uneven movement of the hydraulic multiplier piston, which causes a change in the rise speed or pressure overload; inaccurate operation of the pressure adjustment and limitation system. A set of technical solutions has been proposed to eliminate these factors, including the introduction of diagnostic and leakage compensation systems, the use of linear displacement sensors to control the multiplier stroke, and automation of the process based on programmable logic controllers with feedback from pressure sensors. Further research directions have been identified, consisting in modelling the dynamic characteristics of hydraulic systems.