Safety valve installation requirements

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The opening pressure often changes with the type of medium, especially when the accumulation state of the medium differs. As the operating temperature increases, the opening pressure generally decreases. Therefore, when it is adjusted at normal temperature for use at high temperatures, the set pressure value at normal temperature should be slightly higher than the required opening pressure value. The extent to which it is high is related to both the valve design and the material used; the manufacturer’s instructions should be followed in this regard. So what is the function of a safety valve? A safety valve is a type of protective valve used primarily in pipelines and various pressure-bearing devices. When the operating pressure of the fluid exceeds the allowable limit, the safety valve opens automatically to release the fluid. As the pressure of the fluid decreases, the safety valve closes again, thereby preventing overpressure hazards in the pipelines and devices. So, what are the installation requirements for safety valves? 1. Key settings: 1) When the container contains a two-phase mixture of gas and liquid, the safety valve should be installed in the gas phase portion. 2) When a safety valve is used to vent flammable liquids, its outlet should be connected to the emergency storage tank. When the material being discharged is a high-temperature flammable substance, the receiving container must be equipped with appropriate protective measures. 3) Ordinary safety valves can be vented locally; the vent opening should be at least 1 meter above the level of the operators, and it must not face any open flames, spark-producing areas, or high-temperature equipment within a distance of 15 meters. The vent outlets of safety valves for indoor equipment and containers shall be led to the roof and extend at least 2 meters above it. 4) When there is a isolation valve at the inlet of the safety valve, it should be in an open position and sealed with lead to prevent errors. 2. Import and export pipelines: 1) The connection pipes and the openings in the fittings between the safety valve and the boiler or pressure vessel must have a cross-sectional area that is not smaller than that of the safety valve’s inlet ； If several safety valves share one inlet pipe, the flow cross-sectional area of the inlet pipe must be no smaller than the sum of the inlet cross-sectional areas of the safety valves. 2) Generally, no shut-off valves or steam extraction pipes shall be installed between the safety valve and the boiler’s drum or header. It is generally not advisable to install stop valves or other outlet pipes between the safety valve and the pressure vessel ； For pressure vessels containing highly toxic, highly hazardous, moderately hazardous, flammable, corrosive, viscous media, or valuable media, a stop valve may be installed between the safety valve and the pressure vessel only with the approval of the technical person in charge of pressure vessels at the user facility, and after reliable preventive measures have been established. During the normal operation of the pressure vessel, the stop valve must remain fully open and sealed or locked with a lead seal. The structure and bore size of the stop valve must not prevent the safe discharge of the safety valve. 3) The spring-loaded safety valve with threaded connection should be connected to a short pipe with threads, while the short pipe shall be welded to the cylinder and the header. 4) The safety valve must be equipped with a discharge pipe. The exhaust pipe should avoid curves and sharp turns as much as possible to minimize resistance. The exhaust pipe must lead to a safe location and have sufficient cross-sectional area to ensure smooth exhaust flow. For safety valves that can interact with each other to produce a chemical reaction, they must not share a common discharge pipe ； When a safety valve is installed on equipment exposed to corrosive or flammable gases, anti-corrosion or fire and explosion prevention measures should also be taken during discharge ； When the equipment equipped with a safety valve contains toxic substances, and the vapor density of these substances is greater than that of air, the substances and vapor discharged from the safety valve must be directed into a closed system, where they can be recovered and reused in production processes. 5) The safety valve discharge pipe must be secured to prevent excessive additional stress on the safety valve or vibration. 6) Safety valves installed outdoors must have reliable measures to prevent the water contained in the medium inside the valve from freezing when the temperature drops below 0°C, thereby avoiding any impact on the valve’s ability to discharge. 7) When the crystallization temperature of the medium in the safety valve is higher than the minimum ambient temperature, the safety valve must be equipped with a thermal insulation jacket and insulated purge steam must be installed to prevent the medium from crystallizing and clogging the safety valve, which could affect its normal operating performance. The inlet and outlet pipes of the safety valve must also be designed with steam insulation jackets or additional insulated steam tracing to prevent the medium from crystallizing and blocking the pipes.