Help: Safety valve and vent valve

Safety valves are important safety accessories on boilers, pressure vessels, and other pressurized equipment. They are installed directly on steam boilers or Class 1 pressure vessels, and it is a necessity that they be approved by the technical supervision authorities. The nominal pressure of the safety valve is determined by the operating pressure, its operating temperature range is determined by the operating temperature, the pressure setting range of the spring or lever is determined by the calculated pressure setting value of the safety valve; the material and structural type of the safety valve are chosen based on the medium used, and the throat diameter of the safety valve is calculated based on its discharge capacity. http://bbs.hcbbs.com/viewthread.php?tid=521870 This forum thread discusses the function of relief valves

2.0.1 Safety valves: Safety valves that are operated by a spring or controlled by a pilot valve. It is a safety relief valve that opens when the static pressure at the outlet exceeds the set pressure, allowing the valve disc to rise in order to release excess pressure from the protected system; it automatically closes again once the pressure drops to the reset pressure. 2.0.2 Pilot valve: An auxiliary pressure relief valve that controls the operation of the main valve. 2.0.3 Fully open safety valve: When the static pressure at the inlet of the safety valve reaches its set pressure, the valve disc rises rapidly to its maximum height, thereby discharging the excess pressure material to the greatest extent possible. It is generally used for compressible fluids. The maximum lift height of the valve disc shall be not less than 1/4e of the throat diameter. 2.0.4 Slightly opening safety valves: When the static pressure at the inlet of the safety valve reaches its set pressure, the position of the valve disc increases proportionally as the inlet pressure rises, thereby minimizing the amount of material that needs to be discharged. It is generally used for incompressible fluids. The maximum lift height of the valve disc shall be not less than 1/2 of the throat diameter. 1/40. 2.0.5 Spring-type safety valve: A safety valve that operates due to the action of a spring. Its set pressure is controlled by a spring, and its operating characteristics are affected by back pressure. 2.0.6 Back-pressure balanced safety valve: A safety valve that operates using a spring. Its set pressure is controlled by a spring, and a piston or bellows is used to reduce the impact of back pressure on its operating performance. 2.0.7 Pilot-operated safety valve: A safety valve controlled by a pilot valve. Its set pressure is controlled by a pilot valve, and its operating performance is essentially unaffected by back pressure. When the pilot valve fails, the main valve can still open automatically without exceeding the relief pressure, thereby releasing the full rated amount of discharge. 2.0.8 Main Safety Valve: The main safety valve is the primary safety relief device for the system being protected, and its discharge area is determined based on the amount of flow that must be released under the most severe possible accident conditions. 2.0.9 Auxiliary Safety Valves: Auxiliary safety valves (sometimes more than one) are devices that complement the main safety valve, providing an additional discharge area in addition to that of the main safety valve. Used for overpressure relief under conditions other than the maximum possible accident scenario. 5 Installation of safety valves 5.0.1 Safety valves are suitable for clean, particle-free, low-viscosity fluids. In locations where a safety pressure relief device must be installed but where a safety valve is not suitable, a burst disc or a combination of a safety valve and a burst disc should be used. 5.0.2 Safety valves must be installed on containers in any of the following situations: 5.0.2.1 Independent pressure systems (separated from other systems by isolation valves). This system refers to fully gas-phase, fully liquid-phase, or gas-connected systems; 5.0.2.2 Cases where there is no safety valve at the source of pressure in the container; 5.0.2.3 Containers and pipes whose design pressure is lower than that of the pressure source; 5.0.2.4 Outlet pipes of positive-displacement pumps and compressors; 5.0.2.5 Containers subjected to overpressure due to the accumulation of non-condensable gases; 5.0.2.6 When a shut-off valve or control valve is installed on the outlet pipe of a heating furnace, a safety valve should be installed upstream of such valve; 5.0.2.7 Areas where overpressure occurs as a result of process accidents, automation failures, power failures, fires, or utility failures; 5.0.2.8 Areas where liquids experience thermal expansion due to valves being closed at both ends; 5.0.2.9 Steam outlet pipes of condensing turbines; 5.0.2.10 In some cases, a safety valve is installed on the inlet pipe of a pump due to leaks in the pump’s outlet check valve; 5.0.2.11 Other locations where safety valves should be installed. The relief valve seems to be manually operated in general; the details are not very clear.

The safety valve is described in detail, what about the vent valve?

The vent valve has high-point venting and low-point condensate drainage. The vent valve is essentially a regular gate valve; it is used during startup or shutdown for venting or draining condensate. During normal operation, a blind flange is installed on it, so it cannot be used to relieve pressure. Safety valves, on the other hand, serve to ensure the safety of equipment and personnel during normal operation; when the pressure in the equipment rises, the valve opens automatically under that high pressure to release the excess pressure.

Safety valves are considered to be safety accessories for equipment, and vent valves should be equipped with corresponding vent pipes. The function of the relief valve is to manually release pressure when it exceeds the specified safe pressure.

Safety valves and relief valves are usually present together. Where there is a safety valve, there is almost always a bypass relief valve as well. A safety valve comes into action when the pressure in a pressure vessel rises without being detected in time, or when the relief valve has not been opened to release pressure. Once the pressure reaches the set point of the safety valve, it activates automatically to release pressure. However, once the safety valve activates, it is generally considered an operational incident