"Does a gauge fall under the category of \"safety accessories\" for pressure vessels?

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In TSG 21-2016, the \"safety accessories\" and \"instruments\" of pressure vessels are listed separately; that is, \"instruments\" do not fall under the category of \"safety accessories\". The revision notes for TSG 21-2016 explain that this revision (compared to the 2009 version of the regulations) distinguishes between the concepts of safety accessories and instruments. Safety accessories are those that can automatically initiate corresponding actions in the event of abnormal conditions, thereby protecting pressure vessels ； The instrument merely serves to indicate certain parameters, and no protective action is taken in the event of abnormal conditions. In the past, the concept of safety accessories, including instruments, was too broad, making it difficult to specify certain technical requirements and to ensure that those requirements were met. This revision redefines the safety accessories and instruments: the safety accessories of pressure vessels include safety valves, rupture disc devices, fusible plugs, emergency shut-off devices, and safety interlock devices that are directly connected to the pressure vessel ； The instruments include pressure, temperature, level, and other measuring devices that are directly connected to the pressure vessel. The safety accessories specified in the current GB 12337-2014 \"Steel Spherical Storage Tanks\" include instruments, which is consistent with the old regulations; this should also be changed in future revisions.