Valve issues: What is the main difference between a safety valve and a pressure relief valve?

Personal understanding: Pressure relief valves are generally used in long-distance pipelines, with the main difference lying in the amount of pressure released; safety valves are typically used for providing protection against small amounts of pressure buildup, such as protecting against pressure increases due to temperature rise； Pressure relief valves are generally used for discharge protection in high-flow applications, such as overpressure protection for the outer pipes of long-distance pipelines. It’s just my personal understanding; I haven’t come across any more authoritative statements either. I look forward to getting advice from experts! ! !

1: The principle of a pressure relief valve is that when the pressure in the pipeline exceeds the set pressure of the valve, the oil will flow out through it, thereby preventing the pressure in the pipeline from rising above a certain limit. The needle-type pressure relief valve regulates the clamping force by adjusting the length of the spring inside the valve. When the pressure in the pipeline exceeds the set value, the spring is compressed in the opposite direction, causing the sealing needle to open and allowing oil to leak out; this mechanism serves to protect the equipment and regulate the system pressure. II: In a broad sense, so-called safety valves include relief valves. From the perspective of regulatory requirements, they are valves that must be installed directly on steam boilers or pressure vessels of category 1, and it is necessary for them to be approved by the technical supervision authorities; in a narrow sense, these are referred to as safety valves, while the others are generally called relief valves. 3: Safety valves and relief valves are very similar in structure and performance; both discharge the fluid inside automatically when the set pressure is exceeded, thereby ensuring the safety of the production equipment. Due to this fundamental similarity, people often confuse the two when using them; furthermore, some manufacturing equipment also allows either one to be used as per the regulations. Therefore, the differences between the two are often overlooked. As a result, many problems have arisen. If a clearer definition for both is to be provided, it can be understood in accordance with the definition outlined in Part 1 of the ASME Boiler and Pressure Vessel Code: (l) Safety Valve – an automatic pressure relief device driven by the static pressure of the medium in front of the valve. It is characterized by a sudden, full-opening start action. Used for gas or steam applications. (2) Relief Valve, also known as a pressure relief valve, is an automatic pressure release device driven by the static pressure of the medium in front of the valve. It opens proportionally as the pressure exceeds the opening force. It is mainly used in fluid applications.

A relief system must be provided to prevent over-pressurization of the equipment and piping within the operating unit during abnormal operating conditions, and to ensure the safe and efficient removal of flammable, toxic, or other hazardous materials to a location where they can be safely disposed of through burning, neutralization, or other methods. The component used in a relief system is called a relief valve; a pressure safety valve is also a type of relief valve.

What was said on the 3rd floor is detailed and reasonable. According to the 4th floor, is a safety valve a type of relief valve? The more I look at it, the more confused I get.

Overview, definitions, and differences between safety valves and relief valves. I. Overview Safety valves are important safety accessories installed on boilers, pressure vessels, and other pressurized equipment. The reliability of its operations and its performance are directly related to the safety of equipment and people, and are also closely connected to energy conservation and environmental protection. And some users and design departments always choose the wrong model when making selections. To this end, this paper analyzes the selection of safety valves. II. Definition: In a broad sense, a safety valve includes relief valves. From the perspective of regulatory requirements, it is a valve that must be installed directly on steam boilers or pressure vessels of category 1, and it is necessary for such a valve to be approved by the technical supervision authorities. In a narrow sense, it is referred to as a safety valve; other similar valves are generally called relief valves. Safety valves and relief valves are very similar in structure and performance; both discharge the fluid inside automatically when the set pressure is exceeded, in order to ensure the safety of the production equipment. Due to this fundamental similarity, people often confuse the two when using them; furthermore, some manufacturing equipment also allows either one to be used as per the regulations. Therefore, the differences between the two are often overlooked. As a result, many problems have arisen. If a clearer definition for both is to be provided, it can be understood in accordance with the definition outlined in Part 1 of the ASME Boiler and Pressure Vessel Code: l) Safety Valve – An automatic pressure relief device driven by the static pressure of the medium in front of the valve. It is characterized by a sudden, full-opening start action. Used for gas or steam applications. (2) Relief Valve, also known as a 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. It is mainly used in fluid applications. (3) Safety Relief Valve: Also known as a safety overflow valve, it is an automatic pressure relief device driven by the pressure of the medium. It can be used as either a safety valve or a relief valve, depending on the application. Taking Japan as an example, there are few clear definitions for safety valves and relief valves. Devices used as safety mechanisms in large pressure vessels such as boilers are generally referred to as safety valves, while those installed on pipes or other equipment are called relief valves. However, according to the \"Thermal Power Generation Technology\" guidelines issued by Japan’s Ministry of International Trade and Industry, safety valves are specified as an essential component for ensuring safety in equipment such as boilers, superheaters, and reheaters. Where the lower side of the pressure relief valve needs to be connected to a boiler and a turbine, a drain valve or safety valve must be installed. From this perspective, safety valves are required to have greater reliability than relief valves. Furthermore, based on the regulations regarding high-pressure gas management set by Japan’s Ministry of Labor, as well as the rules established by the Ministry of Transport and various ship associations concerning the determination of safe discharge amounts, we refer to valves that ensure such discharge amounts as safety valves, while those that do not guarantee such discharge amounts are called relief valves. In China, both fully open and slightly open types are collectively referred to as safety valves.

Pressure relief valves are generally used in long-distance pipelines; the main difference lies in the amount of pressure that can be released. Safety valves, on the other hand, are valves designed to protect equipment by releasing pressure when it exceeds the rated pressure； Pressure relief valves are generally used for discharge protection in high-flow applications, such as overpressure protection for the outer pipes of long-distance pipelines.

It’s actually very simple: a pressure relief valve is used for manual pressure release, while a safety valve serves as a protection mechanism; most pressure vessels are equipped with one

Safety valves are installed on the equipment, while pressure relief valves are installed on the pipelines

I’ve also never been able to figure this out – for example, in my pressure-reducing water supply pipeline, should a safety valve be installed after the pressure regulator, or just a regular pressure relief valve?