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Safe operation: During long-term operation, pressure vessels are subject to the combined effects of various complex factors such as pressure, temperature, and medium corrosion, which can lead to abnormal conditions or defects in certain parts. The operation of pressure vessels involves the safe control of process parameters during operation, with the aim of minimizing or avoiding such abnormalities or defects. Process parameters include temperature, pressure, flow rate, liquid level, and material ratios. Temperature control: Temperature is one of the key control parameters for pressure vessels and their systems. Excessively high temperatures can lead to intense reactions that result in a sudden increase in pressure, causing material to be ejected or the pressure vessel to explode, or it can lead to the decomposition and ignition of the reactants. At the same time, excessively high temperatures can weaken the mechanical properties of pressure vessel materials (such as high-temperature strength), reduce their load-bearing capacity, and cause the pressure vessels to deform. Too low a temperature can cause the reaction rate to slow down or come to a halt. When the temperature returns to normal levels, excessive unreacted material may lead to intense reactions that result in explosions. Low temperatures can also cause certain materials to freeze, leading to blockages or ruptures in the pipelines, which in turn can cause flammable substances to leak and result in fires and explosions. To strictly control the temperature, measures should be taken in the following areas: ① Prevent sudden interruption of heat exchange during the reaction. ②The heat transfer medium should be selected properly; common heating media include steam, water, mineral oil, triphenyl, molten salts, soft molten metals, flue gas, etc. Choosing the right heating medium is of great importance for the safety of the heating process; substances that are incompatible with the properties of the reaction materials should be avoided as heating media as much as possible. ③Enhance insulation measures. Proper insulation is beneficial for controlling process parameters, reducing fluctuations, and stabilizing production. It also prevents high-temperature equipment and pipelines from posing a fire or explosion risk to surrounding flammable and explosive materials. When providing insulation, it is advisable to use leak-proof and impermeable metal sheets as the outer cover, thereby preventing external flammable substances from leaking into or accumulating within the insulation layer and creating potential hazards. Feed control ① Feed amount control. For devices involving exothermic reactions, the amount and rate of feed must not exceed the heat transfer capacity of the equipment; otherwise, the temperature of the material will rise sharply, leading to decomposition of the material and bumping, which can result in accidents. If the feeding temperature is too low, it often leads to an excessive accumulation of material; once the temperature becomes appropriate, the reaction intensifies. Moreover, since heat cannot be removed in time, both temperature and pressure exceed normal levels, resulting in accidents. ②Feed sequence control. Especially in the petrochemical industry, the order of feeding materials is determined based on the properties of those materials and the reaction mechanisms; reversing this order can very likely lead to an explosion. Fluctuation range control ① Control of the fluctuation range of pressure and temperature. Pressure vessels may suffer fatigue failure under repeatedly varying loads. Fatigue failure begins in the high-stress areas of pressure vessels. Local peak stresses exist at the nozzles, welds, openings, corners, and support points of pressure vessels. Intermittent startup operations in the manufacturing process can cause significant fluctuations in pressure and temperature. Especially for lined pressure vessels, extra care must be taken during operation. ②Temperature and filling volume control. For pressure vessels filled with liquefied gas, the filling quantity must be strictly controlled to ensure that there is a gaseous phase inside the vessel at the design temperature. This is because in such vessels, liquefied gas exists in a two-phase state of gas and liquid, maintaining dynamic equilibrium at a certain temperature; in other words, the temperature of the medium determines its pressure. Only by strictly controlling the amount of gas filled can safe operation at the highest temperatures be ensured.