Spring Loaded Safety Valves

What is a spring loaded safety valve?

Spring loaded safety valve refers to locking the valve or plunger and other seals of the valve by relying on the elastic pressure of the spring. Once the pressure of the pressure vessel is abnormal, the high pressure generated will overcome the spring pressure of the safety valve, so the locking device is pushed open to form a pressure relief channel to release the high pressure. According to the different opening height of the valve disc, it is divided into full lift type and micro lift type. The full lift type has large discharge capacity and good resilience. It is suitable for liquid and gas media, and the micro lift type is only suitable for liquid media.

Working principle of spring loaded safety valve

According to the analysis of the opening action characteristics of the spring loaded safety valve, it can be concluded that under the action of the external force FW, the change law of the external force FW in the whole process of a safety valve from closing to opening, and then from opening to closing, when the additional force gradually increases from zero, it is consistent with the internal pressure pl × When the sum of S is just the spring preload, the valve slightly opens, increasing the medium action area s, resulting in a sharp increase in the internal pressure force used to overcome the spring preload, resulting in an instantaneous reduction in the external force. Thus, the first characteristic peak a appears. When the external additional force gradually decreases and reaches the closing point, due to the sudden reduction of the medium action area, in order to maintain the balance relationship of the force, the external additional force will rise instantaneously, that is, the second characteristic peak point B. The above two characteristic peaks A and B are the technical basis for detecting the opening pressure and reseating pressure of the safety valve under on-line conditions.

Structure of spring loaded safety valve

Safety valves are divided according to their structural forms, including vertical hammer type, lever type, spring type and pilot type (pulse type); According to the structure of the valve body, it can be divided into closed type and non closed type. Closed safety valve means that the excluded medium will not leak out, and all will be discharged to the designated place along the outlet. It is generally used in toxic and corrosive media. For air and steam safety valves, non closed safety valves are mostly used. The selection of safety valve products shall be determined according to the actual sealing pressure. For spring-loaded safety valves, springs with several working pressure levels within a nominal pressure (PN) range. When ordering, in addition to indicating the model, name, medium and temperature of the safety valve, the sealing pressure of the valve body shall also be indicated, otherwise they shall be supplied according to the maximum sealing pressure.

Installation and maintenance of spring loaded safety valve

• Various safety valves shall be installed vertically.
• There shall be no resistance at the outlet of the safety valve to avoid pressure.
• Before installation, the safety valve shall be specially tested and its tightness shall be checked.
• The safety valve in use shall be inspected regularly.

The installation of spring loaded safety valve shall meet the following requirements:

• (1) Boilers with rated evaporation capacity greater than 0.5t/h shall be equipped with at least two safety valves: Boilers with rated evaporation capacity less than or equal to 0.5t/h shall be equipped with at least one safety valve. Safety valves must be installed at the outlet of separable economizer and steam superheater.
• (2) The safety valve shall be installed vertically at the highest position of the drum and header. The outlet pipe and valve for steam shall not be installed between the safety valve and the drum or header.
• (3) The lever type safety valve shall be equipped with a device to prevent the weight from moving by itself and a guide frame to limit the lever deviating from the track. The spring loaded safety valve shall be equipped with a lifting handle and a device to prevent the adjustment screw from being screwed casually.
• (4) For boilers with rated steam pressure less than or equal to 3.82MPa, the throat diameter of safety valve shall not be less than 25mm; for boilers with rated steam pressure greater than 3.82MPa, the throat diameter of safety valve shall not be less than 20mm.
• (5) The cross-sectional area of the connecting pipe between the safety valve and the boiler shall not be less than the inlet cross-sectional area of the safety valve. If several safety valves are installed on a short pipe directly connected to the drum, the passage cross-sectional area of the short pipe shall not be 1.25 times of the exhaust area of all safety valves.
• (6) Generally, the safety valve shall be equipped with steam exhaust pipe, which shall be directly connected to the safe place and have sufficient cross-sectional area to ensure smooth steam exhaust. There shall be a drain pipe connected to a safe place at the bottom of the exhaust pipe of the safety valve. Valves are not allowed to be installed on the exhaust pipe and drain pipe.

China spring loaded safety valve manufacturer www.pilgrimpipeline.com supplies spring loaded safety valve for industrial use, in kinds of materials such as carbon steel, stainless steel, alloy steel, etc.