In physical chemistry experiments, gases such as oxygen, nitrogen, hydrogen, and argon are often used. These gases are generally stored in specialized high-pressure gas cylinders. When in use, the gas pressure is reduced to the required range for the experiment through a pressure reducing valve, and then finely adjusted through other control valves to input the gas into the system. The most commonly used pressure reducing valve is the oxygen pressure reducing valve, abbreviated as the oxygen meter.

1. Working principle of oxygen pressure reducing valve

The high-pressure chamber of the oxygen pressure reducing valve is connected to the steel cylinder, and the low-pressure chamber is the gas outlet and leads to the usage system. The high pressure gauge indicates the pressure of the gas stored in the cylinder. The outlet pressure of the low-pressure gauge can be controlled by an adjusting screw.

When using, first turn on the main switch of the steel cylinder, and then turn the pressure regulating screw of the low-pressure gauge clockwise to compress the main spring and drive the film, spring pad, and top rod to open the valve. The high-pressure gas imported in this way enters the low-pressure chamber after being throttled and depressurized by the high-pressure chamber, and then passes through the outlet to the working system. Rotate the adjusting screw to change the height of the valve opening, thereby adjusting the amount of high-pressure gas passing through and reaching the required pressure value.

Pressure reducing valves are equipped with safety valves. It is a device that protects the pressure reducing valve and ensures its safe use, as well as a signal device for the failure of the pressure reducing valve. If the outlet pressure rises by itself and exceeds a certain allowable value due to damage to the valve pad, valve, or other reasons, the safety valve will automatically open for exhaust.

2. Usage of oxygen pressure reducing valve

(1) According to different usage requirements, there are many specifications for oxygen pressure reducing valves. The maximum inlet pressure is mostly, and the minimum inlet pressure is not less than 2.5 times the outlet pressure. There are many specifications for outlet pressure, generally, with a maximum outlet pressure of.

(2) When installing the pressure reducing valve, it should be determined whether its connection specifications are consistent with the joints of the steel cylinder and the system used. The pressure reducing valve is connected to the steel cylinder with a hemispherical surface, and the two are completely matched by tightening the nut. Therefore, both hemispherical surfaces should be kept smooth and clean during use to ensure good airtightness. Before installation, high-pressure gas can be used to blow away dust. When necessary, materials such as polytetrafluoroethylene can also be used as gaskets.

(3) Oxygen pressure reducing valves should be strictly prohibited from coming into contact with grease to avoid fire accidents.

(4) When stopping work, the remaining air in the pressure reducing valve should be completely discharged, and then the adjusting screw should be loosened to prevent the elastic element from being compressed and deformed for a long time.

(5) The pressure reducing valve should avoid impact and vibration, and should not come into contact with corrosive substances.

3. Other gas pressure reducing valves

Some gases, such as permanent gases such as nitrogen, air, argon, etc., can use oxygen pressure reducing valves. But there are also some gases, such as corrosive gases such as ammonia, that require dedicated pressure reducing valves. Common specialized pressure reducing valves on the market include nitrogen, air, hydrogen, ammonia, acetylene, propane, water vapor, etc.

The usage and precautions of these pressure reducing valves are basically the same as those of oxygen pressure reducing valves. However, it should also be pointed out that specialized pressure reducing valves are generally not used for other gases. To prevent misuse, some specialized pressure reducing valves use special connection ports between them and steel cylinders. For example, both hydrogen and propane use left-hand threads, also known as reverse threads, and special attention should be paid during installation.