Regarding the substitution of fully open safety valves and slightly open safety valves

Slightly open type is used for incompressible fluids

It doesn’t hit the mark; in principle, it only states that the slightly-open type is suitable for incompressible fluids. It’s simpler to relieve pressure in incompressible fluids, as once the safety valve opens a little, the pressure drops immediately, which helps to reduce waste from fluid discharge. If fluid discharge volume is not considered and there is a recovery device for the discharged fluid, can an fully open type replace a slightly open type in this case?

Looking forward to experts solving this difficult problem~~~ Thank you~~~~

Full-opening safety valves are suitable for releasing gases, steam, and liquefied gas media, while slightly opening safety valves are generally suitable for releasing liquid media.

What you’re saying is all based on what’s in books. Is there any evidence to support the claim that full-opening safety valves cannot be used for releasing liquids?

Spring-loaded safety valves are classified based on the ratio of the maximum opening height of the valve disc to the diameter of the valve’s flow passage; they can be divided into spring-loaded slightly-opening safety valves and spring-loaded fully-opening safety valves. The main difference between fully open safety valves and slightly open safety valves lies in the different discharge volumes resulting from their different flow channel diameters, as well as in their different discharge coefficients; the discharge volume of slightly open safety valves is smaller than that of fully open safety valves. 　　1. Spring-loaded slightly open safety valve: The opening height of the valve disc in a spring-loaded slightly open safety valve is less than 1/4 of the diameter of the flow channel; it is usually between 1/40 and 1/20 of the flow channel’s diameter. The outlet diameter is equal to the inlet diameter. The operation of this type of safety valve is proportional in nature, and it is primarily used in liquid applications; it is sometimes also used in situations involving gases with very low flow rates. 　　2. Spring-loaded full-open safety valve The opening height of a spring-loaded full-open safety valve is greater than or equal to 1/4 of the diameter of the flow channel; the outlet diameter is one size larger than the inlet diameter. For example, if the inlet diameter is DN25, then the outlet diameter is DN32. The discharge area of a fully open safety valve is the minimum cross-sectional area at the valve seat throat. Its operating mechanism is of a two-stage type; it requires the use of a lifting mechanism, namely a recoil disc, in order to reach the fully open position. Fully open safety valves are primarily used in applications where there is a high demand for flow rate, such as with gas media. Summary: Full-open safety valves and slightly-open safety valves can be used interchangeably as long as the required discharge volume is met.

Spring-loaded safety valves are classified based on the ratio of the maximum opening height of the valve disc to the diameter of the valve’s flow passage; they can be divided into spring-loaded slightly-opening safety valves and spring-loaded fully-opening safety valves. The main difference between fully open safety valves and slightly open safety valves lies in the different discharge volumes resulting from their different flow channel diameters, as well as in their different discharge coefficients; the discharge volume of slightly open safety valves is smaller than that of fully open safety valves. 　　1. Spring-loaded slightly open safety valve: The opening height of the valve disc in a spring-loaded slightly open safety valve is less than 1/4 of the diameter of the flow channel; it is usually between 1/40 and 1/20 of the flow channel’s diameter. The outlet diameter is equal to the inlet diameter. The operation of this type of safety valve is proportional in nature, and it is primarily used in liquid applications; it is sometimes also used in situations involving gases with very low flow rates. 　　2. Spring-loaded full-open safety valve The opening height of a spring-loaded full-open safety valve is greater than or equal to 1/4 of the diameter of the flow channel; the outlet diameter is one size larger than the inlet diameter. For example, if the inlet diameter is DN25, then the outlet diameter is DN32. The discharge area of a fully open safety valve is the minimum cross-sectional area at the valve seat throat. Its operating mechanism is of a two-stage type; it requires the use of a lifting mechanism, namely a recoil disc, in order to reach the fully open position. Fully open safety valves are primarily used in applications where there is a high demand for flow rate, such as with gas media. Summary: Full-open safety valves and slightly-open safety valves can be used interchangeably as long as the required discharge volume is met. No evidence was found; it’s from Baidu. Can we take a look?

As long as the minimum cross-sectional area of the valve seat throat meets the requirements, that should be sufficient, and by calculating the thrust and ensuring proper piping design, safety can be achieved, right?

It cannot be used universally; a slightly open valve can only be used for liquids, while a fully open valve can be used for gases as well as liquids. However, when used for liquids in fully open mode, its operating characteristics become those of a slightly open valve. The inner diameter of its nozzle should correspond to that of a slightly open valve, and the flow coefficient of the slightly open safety valve provided by the manufacturer should be used.

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