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Time：2022/6/5 11:27:13 Category：TECHNICAL ARTICLE Source： Click：
Common safety valves generally have the following types.
1. according to the overall structure and loading structure of the form can be divided into heavy hammer lever type safety valve, spring type and control type.
2. according to the ratio of the flap type opening height to the valve flow diameter can be divided into 2 types of micro-opening and fully-opening safety valves.
3. according to the way the gas discharge can be divided into fully closed, semi-closed and open type 3.
Usually referred to as safety valves, generally refers to the more common spring-type safety valves.
The selection of safety valves should be considered from the following aspects.
1, the structure form, mainly depends on the process conditions of the equipment and the working medium, characteristics. General boilers, pressure vessels more spring-type safety valves. If the equipment medium is toxic, flammable and explosive, the safety valve should be selected closed.
2, boilers, high-pressure vessels, safety discharge volume and wall thickness corrosion margin is not large, low-pressure vessels should be selected fully open safety valve.
3, pressure range, each safety valve has a certain range of working pressure. Selection should be used in accordance with the maximum allowable working pressure of the equipment to choose the appropriate safety valve.
4, the discharge, must be greater than the safety of the equipment release, so as to ensure that when the overpressure, the safety valve opens in time to discharge part of the media, to avoid continued pressure rise. For boilers, the total discharge volume of the safety valve must be greater than the maximum continuous evaporation. For pressure vessels, the displacement of the safety valve must be greater than or equal to the safety relief of the pressure vessel.
Safety valve is an important safety accessory on special equipment, its installation also has the corresponding requirements, the following list of some common matters.
1, rated evaporation greater than 0.5t / h boiler, at least two safety valves installed: rated evaporation less than or equal to 0.5t / h boiler, at least one safety valve. Can be divided at the exit of the coal conservator, steam superheater outlet must be installed at the safety valve.
2, the safety valve should be installed vertically in the pot business, the highest position of the set box. Between the safety valve and the pot or set box, shall not be equipped with the export pipe and valve for taking steam.
3, lever safety valve should have a device to prevent the weight from moving on its own and limit the lever to cross the guide frame, spring safety valve to have a lifting handle and prevent the casual unscrewing of the adjusting screw device.
4, for rated steam pressure less than or equal to 3.82MPa boiler, safety valve throat diameter should not be less than 25mm: for rated steam pressure greater than 3.82MPa boiler, safety valve throat diameter should not be less than 20mm.
5, the safety valve and the boiler connection tube, its cross-sectional area should not be less than the cross-sectional area of the safety valve inlet. If several safety valves are installed together in a short pipe directly connected to the pot, the short pipe pathway cross-sectional area should not be more than 1.25 times the area of all safety valve steam discharge.
6, the safety valve should generally be installed in the exhaust pipe, the exhaust pipe should go straight to the safety location, and there is sufficient cross-sectional area to ensure the smooth flow of steam. The bottom of the safety valve exhaust pipe should be installed with a safe place to receive the water pipe, in the exhaust pipe and water pipe are not allowed to install the valve.