I’d like some advice: how should liquefied gas storage tanks be classified?
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There is a liquid ammonia storage tank at room temperature without any insulation measures; its volume is 10 cubic meters. What category does it fall into? I’m not sure. According to the regulations on fixed containers, it should be classified as Category 2, but some people say it’s Category 3. I’m waiting for an answer right now – it’s quite urgent
In principle, check the nameplate of the tank equipment; it indicates the category. Generally, liquefied gas is flammable and explosive, so it should be classified as a category 3 pressure vessel
In the absence of any insulation measures, it is necessary to take into account the saturated vapor pressure of liquid ammonia at 50 degrees Celsius; thus, the design pressure is 2.16 MPa, with a volume of 10 m3, classifying it as Category II
Without any insulation measures, the pressure inside the equipment changes with temperature. Considering the saturated vapor pressure of liquid ammonia at 50 degrees Celsius, which is 2.03 Mpa (absolute pressure), the gauge pressure is 1.93 Mpa; therefore, the design pressure is typically set at 2.16 Mpa. The volume is 10 m3, and the medium belongs to Group 1. According to TSG 21-2016, it should be classified as Category II.
It should be listed on the equipment nameplate of that tank. There are certain categories, and it’s not up to you to decide which categories they are; pressure vessels are generally designed by design firms, taking into account factors such as pressure, temperature, the type of medium used, and the toxicity of that medium. Liquid ammonia storage tanks should be classified as category three, as the upper part of such tanks is filled with ammonia gas. A mixture of ammonia gas and air in certain proportions can lead to explosions, which shows just how hazardous they are; their risk level is even half a tier higher than that of liquefied gas storage tanks. That is why Class III pressure vessels are required