Oxygen valves Oxygen, nitrogen, hydrogen and oxygen valves are often used in physical chemistry experiments. In physical chemistry experiments, these gases are usually stored in special high-pressure gas cylinders. When used, the gas pressure is reduced to the required range of the experiment through the reducing valve, and then fine-tuned by other control valves, so that the gas is input into the use system. The most commonly used pressure reducing valve for oxygen pressure reducing valve, referred to as oxygen table.
The working principle of oxygen valve
The high pressure chamber of the oxygen valve is connected to the cylinder, and the low pressure chamber is the gas outlet and leads to the service system. The high pressure gauge shows the pressure of the gas stored in the cylinder. The outlet pressure of low pressure meter can be controlled by adjusting screw.
When in use, first open the main switch, and then clockwise turn the low pressure meter pressure adjustment screw, so that it compresses the main spring and drives the film, spring pad and ejector rod and opens the valve. The imported high-pressure gas enters the low-pressure chamber after being throttled and decompressed, and leads to the working system through the outlet. Rotate the adjusting screw to change the opening height of the valve, so as to adjust the passage of high pressure gas and achieve the required pressure value.
Oxygen valves are equipped with relief valves. It is the device to protect the reducing valve and make it safe to use, but also the fault of the reducing valve signal device. If the valve pad, valve damage or other reasons cause the outlet pressure to rise and exceed a certain allowable value, the safety valve will automatically open the exhaust.
Methods of using oxygen valves
（1）According to the use of different requirements, oxygen pressure reducing valves have many specifications. The maximum inlet pressure is mostly, and the minimum inlet pressure is not less than 2.5 times of the outlet pressure. There are many outlet pressure specifications. Generally, the highest outlet pressure is.
（2）When installing the reducing valve, ensure that the connection specifications are consistent with the connections of the cylinder and service system. The reducing valve and the cylinder are connected by hemispherical surface, and the nut is tightened to make them fit perfectly. Therefore, the two hemispheres should be kept smooth when in use to ensure good air tightness. Dust can be blown off by high pressure gas before installation. Polytetrafluoroethylene and other materials can be used as washers when necessary.
（3）Oxygen valve should be strictly prohibited from contact with grease to avoid fire accidents.
（4）When you stop working, the remaining gas in the reducing valve should be released, and then loosen the adjusting screw to prevent the elastic element from being compressed and deformed for a long time.
（5）The oxygen valve shall avoid impact and vibration, and shall not contact with corrosive substances.
Other oxygen valves, gas relief valves
The use methods and precautions of these reducing valves are basically the same as those of oxygen valves. However, it should also be pointed out that special pressure reducing valves are generally not used for other gases. In order to prevent misuse, some special reducing valves have special connections between them and the cylinder. For example, hydrogen and propane use left thread, also known as reverse thread, should pay special attention to installation.
Cause analysis of oxygen valve combustion explosion
1.The rust, dust and welding slag in the pipeline friction with the inner wall of the pipeline or the valve port produces high temperature combustion
This situation is related to the type of impurities, particle size and airflow speed, iron powder and oxygen combustion easily, and the finer the particle size, the lower the ignition point; The faster the gas velocity, the more likely combustion occurs.
2.There are grease, rubber and other low ignition point substances in the pipeline or valve, igniting at local high temperature.
3.The high temperature of adiabatic compression causes the fuel to burn. Before the valve is 15MPa, the temperature is 20℃, after the valve is 0.1MPa atmospheric pressure, if the valve block speed is opened, the oxygen temperature after the valve can reach 553℃ according to the adiabatic compression formula, which has reached or exceeded the ignition point of some substances.
4.The ignition point reduction of fuel in high pressure pure oxygen is the inducement of oxygen pipeline valve combustion. Oxygen pipes and valves are very dangerous in high pressure pure oxygen. The test proves that the ignition energy of fire is inversely proportional to the square of pressure, which poses a great threat to oxygen pipes and valves.
