High pressure safety valve is a kind of safety protection valve. Its opening and closing parts are normally closed under the external force. When the medium pressure in the equipment or pipeline rises and exceeds the specified value, the valve opens automatically. By discharging the medium to the outside of the system Prevent the pipe or equipment media pressure exceeds the specified value. Safety valves are automatic valves, mainly for boilers, pressure vessels and pipes, the control pressure does not exceed the specified value, the personal safety and equipment plays an important protective role. Press the safety valve flap opening height can be divided into micro-Kai-type safety valve and full-valve safety valve, micro-open safety valve opening stroke height: ≤ 0.05d0 (minimum discharge throat caliber); full-Kai safety valve open Height ≤ 0.25d0 (minimum discharge throat caliber). High-pressure safety valve according to the structure of the points, should be divided into vertical hammer, lever, spring and pilot (pulse); according to the valve body structure can be divided into two types of closed and not closed. Closed safety valve that is not excluded from the media, all along the exit to the designated location, generally used in toxic and corrosive media. For air and steam safety valve, multi-use non-enclosed safety valve. For the selection of safety valve products, the actual seal pressure should be determined. For spring-loaded safety valves, springs with several working pressure ratings within a nominal pressure (PN) range should be specified when ordering, in addition to indicating the safety valve model, name, medium, and temperature , Otherwise according to the maximum sealing pressure supply. High pressure safety valve installation and maintenance should note the following: All kinds of safety valves should be mounted vertically. High pressure relief valve outlet should be no resistance, to avoid the phenomenon of compression. Safety valve should be specially tested before installation, and check its official seal. The use of safety valves should be regularly checked. The installation of high-pressure safety valve shall meet the following requirements: (1) Boilers with a rated evaporation greater than 0.5t / h shall be equipped with at least two safety valves: a boiler with a rated evaporation less than or equal to 0.5t / h shall be fitted with at least one safety valve. Separable economizer outlet, steam superheater outlet must be installed safety valve. (2) High-pressure safety valve should be installed vertically in the pot, the highest position of the header. Between safety valve and drum or header, there shall be no steam outlet pipe and valve. (3) Lever safety valve to prevent movement of the hammer to move the device and limit the lever over the guide rails, spring-loaded safety valve to have to enhance the handle and prevent accidentally twist the adjustment screw device. (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) high-pressure safety valve and boiler connection pipe, the cross-sectional area of ​​not less than the safety valve inlet cross-sectional area. If several safety valves are installed together on a short tube connected directly to the drum, the cross-sectional area of ​​the short tube should not be 1.25 times the discharge area of ​​all safety valves. (6) safety valve should be installed generally exhaust pipe, exhaust pipe should be through a safe place, and have sufficient cross-sectional area to ensure that the exhaust gas flow. Safety valve exhaust pipe should be installed at the bottom of the positon has received a safe place of the hydrophobic pipe, the exhaust pipe and the hydrophobic pipe are not allowed to install the valve.