Use and description of air valve! ~~

Oxygen, nitrogen, hydrogen, argon and other gases are often used in physical chemistry experiments. These gases are usually stored in special high-pressure gas cylinders. When in use, the pressure of the gas is reduced to the range required by the experiment through the pressure reducing valve, and then the gas is input into the use system through fine adjustment of other control valves. The most commonly used pressure reducing valve is oxygen valve, referred to as oxygen meter.

1. Working principle of oxygen valve

The appearance and working principle of the oxygen valve are shown in Figure II-2-7 and Figure II-2-8.

The high pressure chamber of the oxygen valve is connected with the steel cylinder, and the low pressure chamber is the gas outlet and leads to the use system. The indicated value of the high pressure meter is the pressure of the gas stored in the steel cylinder. The outlet pressure of the low pressure gauge can be controlled by adjusting the screw.

When in use, first turn on the main switch of the steel cylinder, then turn the pressure adjusting screw of the low pressure gauge clockwise to compress the main spring, and drive the diaphragm, spring pad and ejector rod to open the valve. In this way, the input high-pressure gas enters the low-pressure chamber after throttling and decompression from the high-pressure chamber and leads to the working system through the outlet. Turn the adjusting screw to change the opening height of the valve, so as to adjust the throughput of high-pressure gas and reach the required pressure value.

The pressure relief valve is equipped with a safety valve. It is a device to protect the pressure reducing valve and make it safe to use, and it is also 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 the damage of the trap gasket and valve or other reasons, the safety valve will automatically open the exhaust.

2. How to use the oxygen valve

(1) According to different requirements, oxygen valves have various 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 various specifications for outlet pressure. Generally speaking, the maximum outlet pressure is.

(2) When installing the pressure reducing valve, it should be determined whether the connection specification is consistent with the joint of the gas cylinder and the use system. The pressure reducing valve and steel cylinder are connected by hemispherical surface, and they are completely matched by tightening nuts. Therefore, when in use, the two hemispheres should be kept smooth to ensure good air tightness. Before installation, dust can be blown off with high-pressure gas. If necessary, PTFE and other materials can also be used as gaskets.

(3) The oxygen valve should be forbidden to contact with grease to avoid fire accidents.

(4) When stopping working, the residual gas in the pressure reducing valve should be discharged, and then the adjusting screw should be loosened to avoid long-term compression deformation of the elastic element.

(5) The pressure reducing valve should avoid impact vibration and contact with corrosive substances.

3. Other gas pressure reducing valves

For some gases, such as nitrogen, air, argon and other permanent gases, oxygen valves can be used. However, some gases, such as ammonia and other corrosive gases, need special pressure reducing valves. Common in the market are special pressure reducing valves such as nitrogen, air, hydrogen, ammonia, acetylene, propane and water vapor.

The use methods and precautions of these pressure reducing valves are basically the same as those in oxygen valves. But it should also be pointed out that other gases generally do not use special pressure reducing valves. In order to prevent misuse, some special pressure reducing valves adopt special connection ports between cylinders. For example, both hydrogen and propane use left thread, which is also called reverse thread. Pay special attention when installing.

Figure II-2-7 Schematic diagram of oxygen valve installed on gas cylinder Figure II-2-8 Schematic diagram of working principle of oxygen valve.

1. cylinder; 2. Cylinder switch; 3. Connecting nut 1. Spring pad between cylinder and pressure gauge; 2. Transmission film;

4. High pressure meter; 5. Low-voltage instruments; 6. Low pressure gauge pressure adjusting screw; 3. Safety valve 5. High voltage meter;

7. export; 8. Safety valve 4. Import (connected with gas cylinder);

6. Low-voltage instruments; 7. Compression spring;

8. Exit (connect to the use system); 9. High pressure air chamber;

10. Valve; 12. Push rod 1 1. Low pressure air chamber; 13. Main spring

14. Low pressure gauge adjusting screw.