What are the basic requirements for the safe operation of pressure vessels?

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Proper and reasonable operation and use of pressure vessels are important measures to ensure their safe operation; the basic requirements are to operate them smoothly and to prevent overpressure, overheating, and overload. Stable operation mainly refers to performing loading and unloading slowly, as well as maintaining a relatively stable load during operation. When loading a pressure vessel, the speed should not be too high, especially to prevent sudden increases in pressure. Because too high a loading speed may cause containers with minor defects to suffer brittle fracture under rapid pressure impacts. Heating and cooling during startup, shutdown, and operation should be carried out slowly to avoid sudden changes in the shell temperature and to reduce thermal stress on the shell. When the pressure at the source of pressure is higher than the operating pressure of the container, overpressure occurs mostly due to operational errors. For example, the outlet valve of the pressure vessel is accidentally closed, yet the medium continues to be fed into the vessel ； Or accidentally opening a valve that should not be opened ； Or, due to a malfunctioning pressure relief valve, media at a higher pressure may enter the container. Vessels in which pressure is generated by chemical reactions of the medium inside them often experience overpressure due to uncontrolled chemical reactions caused by excessive charging or impurities mixed into the raw materials. In containers designed to hold liquefied gases, if the container is overfilled or exposed to heat accidentally, the entire interior space may be filled with the liquid phase. As the temperature continues to rise, the expansion of the liquid leads to a sharp increase in pressure inside the container, which is one of the main causes of explosions in such pressure vessels. The effects of overheating on the safety of pressure vessels are just as severe as those of overpressure; prolonged operation at elevated temperatures can directly or indirectly lead to vessel failure. For lined containers, if the cooling and depressurization rates are too rapid, it may cause the liner to “bulge”. For fixed tube sheet heat exchangers, sudden and significant temperature changes may cause damage to the joints between the tubes and the tube sheet, or to the tubes themselves. To ensure smooth operation and prevent the container from experiencing overpressure, overheating, or overload during use, the following points should be noted: a. Strictly follow the safety operating procedures, maintain proper process conditions, and enhance responsibility in carrying out operations ； b. Install safety operation tags on certain key valves and control devices, or equip them with safety interlock systems to prevent accidental operations ； c. When filling liquefied gases, strict measurement must be observed; overfilling is strictly prohibited to prevent accidental heating ； d. Install reliable safety relief devices and overpressure alarm devices ； e. Gaps in the operating process, as well as start-up and shutdown operations, can cause significant fluctuations in pressure and temperature. However, from an operational perspective, it is necessary to strive for a steady increase or decrease in pressure and temperature, and to avoid unnecessary start-ups and shutdowns as much as possible.