Working principle of oxygen valve
The high pressure chamber of the oxygen valve is connected with the cylinder, and the low pressure cavity is the gas outlet and leads to the use system. The indication of the high pressure meter is the pressure of the gas in the cylinder. The outlet pressure of the low pressure meter can be controlled by the adjusting screw.
When used, the main switch is opened first, then the low pressure gauge adjusting screw is rotated clockwise, so that it compresses the main spring and drives the membrane, spring pad and ejector rod to open the valve. The high pressure gas imported from the high pressure chamber enters the low pressure chamber through the throttling pressure reduction and passes through the exit to the working system. The adjusting screw is rotated to change the height of the valve opening so as to adjust the passing amount of the high pressure gas and reach the required pressure value.
The oxygen valve is equipped with a safety valve. It is a device to protect the pressure relief valve and make it safe to use. It is also a signal device for the failure of the pressure relief valve. If the outlet pressure rises or exceeds a certain allowable value due to the damage of the valve gasket or valve, or because of other reasons, the safety valve will automatically open the exhaust.
The use of oxygen valves
(1) the oxygen pressure relief valve has many specifications according to the different requirements. Most of the highest import pressure is, the minimum import pressure is not less than 2.5 times that of the export pressure. There are more pressure specifications for export, generally, the maximum outlet pressure is.
(2) when installing the pressure relief valve, it should be determined whether the connection specification is consistent with the joint of the cylinder and the use system. The pressure relief valve and the cylinder are connected by the hemispherical surface, and the two are fully anastomosed by the tightening nut. Therefore, two hemispherical surfaces should be kept in use to ensure good air tightness. The dust can be blown away by high pressure gas before installation. If necessary, polytetrafluoroethylene and other materials can be used as gaskets.
(3) oxygen valve should be strictly forbidden to contact oil, so as to avoid fire accidents.
(4) when the work is stopped, the residual gas in the pressure relief valve should be cleaned and the adjusting screw is loosened to avoid the long compression deformation of the elastic element.
(5) the oxygen valve should avoid impact vibration and should not contact with corrosive substances.
Other oxygen valves, gas pressure relief valves
The use of these pressure relief valves and matters of attention are basically the same as the oxygen valve. However, it should also be pointed out that the special pressure relief valve is generally not used for other gases. In order to prevent misuse, special joints are used between some special pressure relief valves and steel cylinders. For example, both hydrogen and propane use the left tooth thread, also called the reverse thread, and should be paid special attention when installing.
Analysis of the cause of combustion and explosion of oxygen valve
1. the rust, dust, slag in the pipe and the friction between the inner wall of the pipe or the valve mouth produce high temperature combustion
This situation is related to the type, particle size and airflow speed of impurities. Iron powder is easy to burn with oxygen, and the smaller the particle size is, the lower the ignition point. The faster the gas speed, the easier it is to burn.
2. in the pipe or in the valve, there are low burning substances such as oil and rubber, which are ignited at the local high temperature.
The high temperature produced by 3. adiabatic compression causes the combustion of the combustibles. Before the valve is 15MPa, the temperature is 20 DEG C, the valve for atmospheric 0.1MPa, if the valve block speed open the valve after the oxygen temperature according to adiabatic compression formula can reach 553 DEG C, which has reached or exceeded certain substances.
4. the burning point of combustibles in high pressure pure oxygen is the cause of the combustion of oxygen pipeline valves. The risk of oxygen pipeline and valve in high pressure pure oxygen is very large. The test proves that the detonation of fire can be inversely proportional to the square of pressure, which poses a great threat to oxygen pipeline and valve.
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