The difference between safety valve and relief valve

Time：2022/2/10 22:05:38 Category：TECHNICAL ARTICLE Source： Click：

In a broad sense, safety valves include relief valves. From the perspective of management rules, they are directly installed on steam boilers or a class of pressure vessels. The necessary condition is that they must be approved by the technical supervision department. Commonly referred to as a relief valve. The safety valve and the relief valve are very similar in structure and performance. Both of them automatically discharge the internal medium when the opening pressure is exceeded to ensure the safety of the production device. Due to this essential similarity, people often confuse the two when using them. In addition, some production devices also stipulate which one can be used in the rules. Therefore, the differences between the two are often overlooked. As a result, many problems have arisen. If you want to make a clearer definition of the two, you can understand it according to the definition stated in the first part of the "ASME Boiler and Pressure Vessel Code":

(l) Safety Valve is an automatic pressure relief device driven by the static pressure of the medium in front of the valve. It is characterized by a protruding full opening action. For gas or steam applications, see Figure 1.

(2) Relief valve, also known as overflow valve, is an automatic pressure relief device driven by the static pressure of the medium in front of the valve. It opens proportionally as the pressure exceeds the opening force. Mainly used for fluid occasions. as shown in picture 2.

(3) Safety relief valve (Safet Relief Valve), also known as safety relief valve, is an automatic pressure relief device driven by medium pressure. It can be used as both a safety valve and a relief valve depending on the application. Taking Japan as an example, there are few clear definitions for safety valves and relief valves. Generally, safety devices used for large-scale energy storage pressure vessels such as boilers are called safety valves, and those installed on pipelines or other facilities are called safety valves. It is the relief valve. However, according to the provisions of the "Technical Standards for Thermal Power Generation" issued by the Ministry of International Trade and Industry of Japan, the important part of the safety guarantee on the equipment is designated to use safety valves, such as boilers, superheaters, reheaters, etc. In the case where the lower side of the pressure reducing valve needs to be connected to the boiler and the turbine, it is necessary to install a relief valve or a safety valve. In this way, the safety valve requires more reliability than the relief valve. In addition, from the high-pressure gas management regulations of the Ministry of Labor of Japan, the regulations of the Ministry of Transport and shipping associations at all levels, from the point of view of the identification and regulation of safe emissions, we call those that guarantee emissions a safety valve, but do not guarantee The valve that discharges the volume is called a bleed valve. In China, whether full-opening or micro-opening is collectively referred to as a safety valve.