Choosing a safety valve in this way ensures greater safety

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　　A safety valve is an automatic pressure release device used on pressurized equipment, containers, or pipelines. When the pressure within the protected system rises above the allowable level, the valve opens automatically to release some of the excess fluid, thereby preventing further increases in system pressure. When the system pressure drops to a specified level, the valve closes automatically again, ensuring the normal operation of the system. The main performance indicators of a safety valve are: 1) Safety. Upon leaving the factory, the valves undergo strength tests and sealing tests in accordance with **relevant standards, to ensure that their mechanical properties meet the requirements of those standards. 2) Sensitivity. The opening pressure and closing pressure of the valve are within the **standard ranges and those specified by the user; the opening pressure is accurate and rapid, while the closing pressure remains stable. 3) Sealing performance. After the valve returns to its seat, it exhibits excellent sealing performance with no leakage. 4) Safety valves with emission requirements: after the valve operates, its emission level meets the mechanical specifications specified by the standards; moreover, the valve’s sealing performance and other characteristics remain stable and do not change. How to properly select a safety valve is directly related to the economic efficiency of the using entity, as well as the safety of operators and equipment. The following outlines the general rules for selecting safety valves: 1) Determine the \"nominal diameter\" of the safety valve based on calculations, ensuring that its discharge capacity is ≥ the safe release capacity of the pressure vessel. 2) Determine the pressure rating of the safety valve based on the design pressure and design temperature of the pressure vessel. 3) Steam boilers or steam pipes generally use unenclosed, full-opening safety valves with wrenches. For safety valves used for steam with a starting pressure greater than 3 MPa, or for gases with a temperature exceeding 320°C, a model equipped with a radiator (fins) should be selected. 4) Hot water boilers generally use unenclosed, wrench-operated slightly-opening safety valves. 5) For non-hazardous media such as air, hot water above 60°C, or steam, a safety valve equipped with a wrench should be used. 6) Incompressible media such as water generally use closed micro-tilt safety valves, or safety relief valves. 7) For high-pressure feed water, closed full-open safety valves are generally used, such as in high-pressure feed water heaters and heat exchangers. 8) Compressible media such as gases generally use closed full-opening safety valves, such as in gas storage tanks and gas pipelines. 9) Pulse-type safety valves are generally used in large-diameter, high-displacement, and high-pressure systems, such as temperature and pressure reduction devices and power plant boilers. 10) For flammable media with extremely or highly hazardous toxicity, closed safety valves must be used; if a valve equipped with a lifting mechanism is required, then a closed safety valve fitted with a wrench should be employed. 11) In cases where the back pressure that a safety valve may be subjected to is variable and the variation exceeds 10% of the opening pressure, or in systems involving toxic or flammable substances, safety valves equipped with bellows should be used. 12) Systems that may experience negative pressure or negative pressure during operation generally use vacuum safety valves. 13) For systems with a low freezing point of the medium, insulated jacketed safety valves are generally used. 14) Tank cars, road tankers, and storage tanks used for transporting liquefied gas should be equipped with internal safety valves. 15) Hydraulic safety valves are generally used on the top of oil tanks, and they need to be used in conjunction with breather valves. 16) Pilot-operated safety valves are generally used for underground drainage or gas pipelines. 17) A safety reflux valve is generally used on the liquid-phase reflux pipeline at the outlet of the tank pump in LPG stations. 18) Select an appropriate safety valve material based on the medium properties. If an ammonia-containing medium is present, copper or valves containing copper cannot be used ； Acetylene cannot use safety valves made of copper containing 70% copper or red copper. 19) For conditions with high discharge rates, a fully open type should be selected ； For operating conditions with stable working pressure and low leakage rates, a slightly open type is advisable ； For conditions involving high pressure and large discharge volumes, a non-direct-acting type, such as a pulse safety valve, is recommended. For containers with a length of more than 6 meters, two or more safety valves should be installed. 20) For Class E steam boilers or fixed vessels with a low operating pressure Pw, static weight-type (pressure cooker) or lever-weight type safety valves can be used. Mobile devices should be equipped with spring-loaded safety valves. 21) For media that are thick and prone to clogging, a discharge device consisting of a safety valve in series with a burst disc is advisable. 22) The spring operating pressure grade is selected based on the nominal pressure of the safety valve. Relationship between the nominal pressure of a safety valve and the spring operating pressure.