Gas cylinder is a high-pressure closed container specially used for storing and transporting all kinds of compressed gases, liquefied gases or dissolved gases. With the features of pressure resistance, sealing and portability, it is widely used in many fields such as industrial production, scientific research and experimentation, medical and health care, food processing and so on, and it is the key carrier connecting the production of gases and the end-use. Its safe use is directly related to the personal safety of personnel, equipment integrity and the order of production and scientific research, so it is important to master the basic knowledge of gas cylinders and the use of norms.
(I) Classification of gas cylinders: by nature of gas
The core classification of gas cylinders is based on the physical and chemical properties of the stored gases, and there are significant differences in the materials, pressure resistance standards and usage requirements of different types of cylinders, which are commonly categorized as follows:
1. Compressed gas cylinders
The gases stored in such cylinders are gaseous at room temperature and pressure, and are compressed at high pressure and loaded into containers, which remain gaseous when stored, and the pressure is usually high (generally 10-30MPa). Common examples include oxygen, nitrogen, hydrogen, argon, helium and so on. Among them, oxygen cylinders are mostly used for medical emergencies, welding and cutting; nitrogen cylinders are widely used for food preservation and chemical inert protection; hydrogen cylinders are used for scientific research experiments, fuel cells and other fields. These cylinders are mostly made of high quality carbon steel or alloy steel, and need to have very high pressure resistance and sealing reliability.
2. Liquefied gas cylinders
The stored gas will be liquefied under high-pressure or low-temperature conditions, using the high density of the liquid to achieve a large number of storage, the gas-liquid two-phase equilibrium will be formed in the cylinder at room temperature, and the pressure is relatively stable (generally in 1-10MPa). Common examples are carbon dioxide, propane, butane, liquefied petroleum gas (LPG) and so on. Carbon dioxide cylinders are mostly used for welding protection, food carbonation, and artificial rainfall; LPG cylinders are commonly used for home cooking and small-scale industrial heating. These cylinders need to have good corrosion resistance, and some of them also need to be equipped with a level meter, so that it is easy to observe the remaining volume of gas.
3. Dissolved Gas Cylinders
This type of cylinder storage gas needs to be dissolved in a specific solvent in order to stabilize the existence, to avoid its dangerous reaction under high pressure, the most typical is acetylene cylinder. Acetylene itself is flammable and explosive, can not be directly compressed and stored at high pressure, it needs to be dissolved in acetone, filled with porous materials (such as activated charcoal) within the cylinder, so as to achieve safe storage and transportation. Acetylene cylinders are mainly used for welding, cutting and other metal processing scenarios, the use of which requires strict control of the flow rate to prevent acetone with acetylene together with the outflow of danger.
4. Corrosive gas cylinders
Cylinders are used to store gases with strong corrosiveness, such as chlorine, ammonia, hydrogen fluoride, etc. These gases are easy to corrode ordinary metals. Such gases are easy to corrode ordinary metals, so the cylinder material should be corrosion-resistant alloy (such as stainless steel) or special coating treatment, seals also need to use corrosion-resistant materials (such as polytetrafluoroethylene). When using the gas, personal protection should be done to avoid the gas leakage contacting the skin and respiratory tract, and the storage environment should be kept ventilated, dry and away from acidic or alkaline substances.
