Reasons for Depressurization of a High-Pressure Cylinder

Abstract

High-pressure cylinders are vessels for storing and transporting compressed gases under high pressure, which are necessary for use in various technological processes. These vessels are mainly made of steel or aluminum and have significant strength to withstand high (more than 400 kgf/cm2) pressure. Such cylinders have a wall of sufficiently large thickness and are used in various industries. The object of the study is a one-piece forged cylinder made of 38ХН3МФА steel. The purpose of this study is to determine the causes of cylinder depressurization, which occurred during filling the cylinder with helium at a speed of 7.5 m3/h at an operating pressure of 365 kgf/cm2. As is known, when operating process equipment operating under excess pressure, damage may occur due to the structure of the material and the features of its mechanical properties. This damage can lead not only to the failure of the vessel itself, but also to damage to other units and parts located nearby. And if people are working nearby, the cost of such an accident will be even higher. Therefore, the study in this article of the causes of destruction of a high-pressure cylinder is very relevant. A set of studies (visual and measuring control, factographic, metallographic and spectral analysis) was carried out, which helped to establish the cause of the destruction of the vessel body at the neck of the cylinder. The main conclusion on the causes of depressurization of the vessel in question is the presence of a stress concentrator, namely, a depression of the folds of the cylinder, which was formed during the formation of the neck of the cylinder in the transition area from the cylindrical part to the neck. During long-term operation, under the influence of residual technological stresses, a crack was formed, which spread from the inner surface of the cylinder to the outer one, up to its through damage, which led to depressurization.