Safety relief valve - definition and difference between safety valve and relief valve

July 12, 2021

Safety Relief Valve, also known as Safety Relief Valve, is an automatic pressure relief device driven by medium pressure. It is suitable for both safety valves and bleed valves depending on the application. In Japan, for example, the safety valve and the relief valve are clearly defined. Generally, the safety device used as a large-scale energy storage pressure vessel such as a boiler is called a safety valve, and is installed on a pipe or other facility. It is a relief valve. However, according to the "Technical Standards for Thermal Power Generation" of the Ministry of International Trade and Industry of Japan, important parts of the safety guarantee on the equipment are 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, a relief valve or a safety valve is required. In this way, the safety valve requires more reliability than the relief valve. In addition, from the high-pressure gas management rules of the Ministry of Labour of Japan, the regulations of the Ministry of Transport and the associations of ships at all levels, we refer to the definition and regulation of safety emissions, we call the safety valve guaranteed, not guaranteed The valve for emissions is called a bleed valve. In China, whether it is full-open or micro-open, it is collectively called a safety valve.

I. Overview

Safety valves are important safety accessories for boilers, pressure vessels and other pressure-bearing equipment. Its operational reliability and performance are directly related to the safety of equipment and people, and are closely related to energy conservation and environmental protection. Some users and design departments always choose the wrong model when selecting the model. To this end, this paper analyzes the selection of safety valves.

Second, the definition

The so-called safety valve includes a bleed valve in a broad sense. From the perspective of management rules, it is directly installed on a steam boiler or a type of pressure vessel. The necessary condition is that it must be approved by the technical supervision department, which is called a safety valve in a narrow sense. Others are generally referred to as bleed valves. The safety valve and the relief valve are similar in structure and performance, both of which automatically discharge the internal medium when the opening pressure is exceeded to ensure the safety of the production unit. Since there is such an essential similarity, people tend to mix the two when they are used. In addition, some production devices also stipulate which ones can be used in the rules. Therefore, the differences between the two are often overlooked. As a result, many problems have arisen. If a clear definition of the two is to be made, it can be understood in accordance with the definitions set out in the ASME Boiler and Pressure Vessel Code*:

(l) Safety Valve An automatic pressure relief device that is driven by static pressure in front of the valve. It is characterized by a full opening action with a sudden opening. For gas or steam applications.

(2) Relief Valve, also known as the relief valve, is an automatic pressure relief device driven by the static pressure of the medium before the valve. It opens proportionally as the pressure exceeds the increase in opening force. Mainly used for fluid applications.

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Mr. Zheng

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zheng@rmiplast.com

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