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Chapter 11 Safety Accessories and Related Requirements: In accordance with the Pressure Vessel Regulations and relevant standards, the safety accessories for pressure vessels include safety valves, pressure gauges, rupture disc devices, manometers and temperature measuring instruments, as well as safety interlock devices for quick-opening pressure vessels. I. Safety devices for pressure vessels are classified into three categories based on their function: (1) Indicating devices: various types of pressure gauges, thermometers, level gauges, etc. (2) Controlled display control device. Such devices can adjust themselves according to the set process parameters, ensuring that these parameters remain stable within a certain range. Such as pressure relief valves, control valves, electric contact pressure gauges, electric contact thermometers, automatic hydraulic gauges, emergency shut-off valves, overflow valves, and safety interlock devices. (3) The safety pressure relief device allows for the automatic release of some or all of the gas when the pressure of the medium inside the container or system exceeds the rated pressure. To prevent continuous increases in pressure from threatening the normal use of the container and causing damage. A. Valve-type safety pressure relief device. (i.e., various types of safety valves) B. Frangible safety relief devices. (Cracking discs, bursting caps, etc.) C. Melting-type safety pressure relief devices, fusible plugs, fusible sheets. (D for cylinders and tank trucks) D, combined safety pressure relief device. (Composed of two types of safety pressure relief devices, such as a safety valve and a rupture disc; the rupture discs are connected in series, with the rupture disc at the inlet of the safety valve being connected in series to the one at its outlet. ) II. Main requirements for safety accessories of pressure vessels (1) Manufacturers of safety accessories and protective devices for pressure vessels must obtain permission from the department in charge of supervision and management of special equipment under the State Council before they can engage in such activities. The design and manufacture of safety accessories shall comply with the requirements of the “Pressure Vessel Regulations” as well as relevant **standards and industry standards. (2) For the various valves on each pressure vessel, the manufacturer shall hold a manufacturing license for the corresponding category, and provide a certificate of conformity as well as technical documents. (3) The safety accessories shall be equipped with labels indicating the main technical parameters. (4) The safety interlock devices for quick-opening pressure vessels must meet the following functional requirements; they should be subjected to trial use and technical validation before they can be widely used. The quick-opening door (cover) of fast-opening pressure vessels shall be equipped with a safety interlock device and shall have the following functions: A. An interlock control function that prevents pressurization until the quick-opening door reaches its predetermined closed position. B. The interlock function for opening the quick-opening door can be activated only after the internal pressure of the pressure vessel has been completely released and the safety interlock device has been disengaged. C. It has an alarm function that is synchronized with the above. III. Inspection cycle for safety devices: The inspection of safety accessories is divided into two types: ① Operational inspection: refers to the inspection of safety accessories while they are in operation. Under normal circumstances, it can be carried out by personnel on the production front line. It mainly checks the appearance and operating condition of the safety accessories. Pressure gauge is malfunctioning or not calibrated ； The shut-off valve between the pressure vessel and the safety valve is closed ； Safety valves can become corroded or clogged; especially with media that have high viscosity, this can cause the safety valves to get stuck ； After long-term use, pressure relief valves develop a time effect, resulting in inaccurate burst pressure ； The liquid level indication of the level gauge is inaccurate, and so on. ②Shutdown inspection: refers to the inspection of safety accessories by professionals when the equipment is not in operation. Operational inspections can be carried out simultaneously with external container inspections, while shutdown inspections can be performed in conjunction with a comprehensive inspection of the container or independently. Safety valve ①: Before installing a new safety valve, it must be tested and adjusted according to the conditions of use before it can be installed and put into use. ②Safety valves should generally be calibrated at least once a year; when it is difficult to remove them for calibration, on-site calibration (in-line calibration) should be used. Blowout discs: Blowout disc assemblies should be replaced regularly; those that have not ruptured despite exceeding the maximum design burst pressure must be replaced immediately ； Blowout valve devices used under harsh conditions should be replaced annually ； Generally, burst disc assemblies should be replaced within 2 to 3 years (except where the manufacturer specifies that the service life can be extended). Pressure gauge: Pressure gauges and temperature measuring instruments shall be calibrated within the period specified by the user organization. The calibration and maintenance of pressure gauges shall comply with the relevant regulations of the **metrology authorities. The pressure gauge should be calibrated before installation; a red line indicating the maximum operating pressure should be marked on the dial, along with the date for the next calibration. After calibration, the pressure gauge should be sealed with a lead seal. Emergency shut-off device: The emergency shut-off device must be removed from the pressure vessel in order to be disassembled, inspected, repaired, and adjusted. Tests for pressure resistance, sealing performance, and emergency shut-off functionality must be conducted; it can only be put back into use after passing these tests and being re-sealed with a seal. Before installation and use of the level gauge ①, level gauges for low- and medium-pressure vessels shall undergo a hydrostatic test at 1.5 times the nominal pressure of the gauge, while level gauges for high-pressure vessels shall be tested at 1.25 times the nominal pressure of the gauge ； ②The specified maintenance interval for level gauges shall not exceed the overall inspection interval for pressure vessels ； ③The level gauge should be flushed regularly every quarter. Thermometers should be calibrated within the period specified by the user organization. Newly installed temperature measuring instruments must be certified as qualified by the **Quality Department. Selection of safety accessories: (1) The discharge capacity of safety valves and rupture discs must be greater than the safe discharge capacity of the pressure vessel. (2) For pressure vessels containing flammable, explosive, or highly toxic and hazardous media, a lever-type glass level gauge or an automatic level indicator should be used. (3) The pressure gauges, level gauges, etc. of pressure vessels should be selected appropriately based on the medium contained in the vessel, as well as its maximum operating pressure and temperature. (4) Safety accessories: In any of the following situations, they shall not be used. ①Without product certification and nameplate ； ②Performance does not meet requirements ； ③Failing to conduct inspections or verifications upon expiration ；