Safety Valve

Introduction
Safety valve is a kind of safety protection valve, its opening and closing parts under the action of external force in the normally closed state, when the medium pressure in the equipment or pipeline rises, exceeds the specified value when the automatic opening, through the discharge of the medium outside the system to prevent the pipeline or equipment in the medium pressure exceeds the specified value. Safety valve belongs to the automatic valve class, mainly used in boilers, pressure vessels and pipelines, control pressure does not exceed the specified value, plays an important role in protecting personal safety and equipment operation.

Main Function
Safety valve plays a protective role in the system. When the system pressure exceeds the specified value, the safety valve opens and drains part of the gas/fluid in the system into the atmosphere/pipeline, so that the system pressure does not exceed the allowable value, so as to ensure that the system does not occur due to high pressure accidents.

Technical Terms
Nominal pressure: indicates the maximum allowable pressure of the safety valve at room temperature. Safety valves are designed and manufactured according to nominal pressure standards.

Opening pressure: also called rated pressure, refers to the inlet pressure when the safety valve disc begins to rise under operating conditions. Under the pressure, there begins to be a measurable opening height, and the medium is a continuous discharge state that can be perceived by vision or sound.

Discharge pressure: the inlet pressure when the disc reaches the specified opening height. The upper limit of discharge pressure shall comply with the requirements of relevant national standards or specifications.

The rated discharge pressure of the safety valve is Pt≤(1.1~1.15)Pk, mostly Pt= 1.1pk

Install
The following points should be paid attention to when setting the safety valve:

When there are gas and liquid two-phase materials in the container, the safety valve should be installed in the gas phase part.

When the safety valve is used to discharge combustible liquid, the outlet of the safety valve should be connected to the emergency storage tank. When the discharged material is high temperature fuel, the receiving container should be equipped with appropriate protective facilities.

Generally, the safety valve can be discharged on the spot, and the opening should be 1 meter (m) higher than the operator and should not be toward the open flame, spark and high-temperature equipment within 15 meters (m). The safety valve opening of indoor equipment and containers should lead out of the roof and be more than 2 meters (m) above the roof.

When the safety valve inlet has a partition valve, the partition valve should be in a normally open state, and to be sealed, so as not to make mistakes.

Import and export pipeline
The cross-sectional area of the connecting pipe and pipe fitting through the hole between the safety valve and the pressure vessel shall not be less than the cross-sectional area at the entrance of the safety valve; If several safety valves share one inlet pipe, the flow cross-sectional area of the inlet pipe is not less than the sum of the inlet cross-sectional area of the safety valve.

During the normal operation of the pressure vessel, the globe valve must be kept fully open. The structure and diameter of the globe valve shall not hinder the safe release of the safety valve.

Safety valves must be fitted with discharge pipes. The discharge pipe should avoid twists and turns as far as possible to minimize resistance. The discharge pipe should go straight to the safe place, and have enough circulation cross-sectional area to ensure the smooth exhaust steam.

The discharge pipe of the safety valve should be fixed to avoid excessive additional stress of the safety valve.

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