Briefly describe the precautions for safety valve selection


1) According to the calculation, it is determined that the “nominal diameter” of the safety valve must make the discharge capacity of the safety valve ≥ the safe discharge capacity of the pressure vessel.
2) Determine the pressure rating of the safety valve according to the design pressure and design temperature of the pressure vessel.
3) Steam boilers or steam pipelines generally use non-closed full-open safety valves with wrenches. For the safety valve for steam with opening pressure greater than 3MPa or the safety valve for gas with medium temperature over 320℃, the form with radiator (finned) should be selected.
4) Hot water boilers generally use non-closed micro-opening safety valves with wrenches.
5) For non-hazardous media such as air, hot water or steam above 60°C, a safety valve with a wrench should be used.
6) For liquid incompressible media such as water, a closed micro-opening safety valve is generally used, or a safety relief valve is used.
7) High-pressure feed water generally uses closed full-open safety valves, such as high-pressure feed water heaters, heat exchangers, etc.
8) Gas and other compressible media generally use closed full-open safety valves, such as gas storage tanks, gas pipelines, etc.
9) Large-diameter, large-displacement and high-pressure systems generally use pulse-type safety valves, such as temperature reduction and pressure reduction devices, power station boilers, etc.
10) For flammable, extremely toxic or highly hazardous media, a closed safety valve must be used. If a lifting mechanism is required, a closed safety valve with a wrench should be used.
11) When the safety valve may be subjected to a change in back pressure and the change exceeds 10% of the opening pressure or a container or pipeline system that is toxic and flammable, a safety valve with a bellows should be selected.
12) A vacuum negative pressure safety valve is generally used in systems that may generate negative pressure or negative pressure during operation.
13) For systems with a lower freezing point of the medium, thermal insulation jacketed safety valves are generally used.
14) A built-in safety valve should be used for train tankers, automobile tankers, and storage tanks that transport liquefied gas.
15) The top of the oil tank generally uses a hydraulic safety valve, which needs to be used in conjunction with the breathing valve.
16) Pilot-operated safety valves are generally used for underground drainage or natural gas pipelines.
17) A safety return valve is generally used on the liquid phase return pipeline at the outlet of the tank pump in the LPG station.
18) Select the appropriate safety valve material according to the characteristics of the medium. For example, copper or copper-containing safety valves cannot be used in ammonia-containing media; 70% copper-containing or red copper safety valves cannot be used in acetylene.
19) For the working condition with large discharge volume, the full-start type should be used; for the working condition with stable working pressure and small discharge volume, the micro-start type should be used; for the working condition with high pressure and large discharge volume, the indirect start type should be used. , such as pulse-type safety valve. Two or more safety valves should be set up for containers with a length of more than 6m.
20) For E-class steam boilers or stationary vessels with low working pressure Pw, deadweight type (pressure cooker) or lever-weight hammer type safety valve can be used. Mobile equipment should use spring-loaded safety valves.
21) For the medium that is thick and easy to block, it is advisable to use a series-combined relief device of a safety valve and a bursting disc.
22) The working pressure level of the spring is selected according to the nominal pressure of the safety valve. The relationship between the nominal pressure of the safety valve and the working pressure of the spring.

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