1. Classification by manufacturing method
According to the manufacturing method, gas cylinders can be divided into the following four categories.
(1) Welded gas cylinder
The welded gas cylinder is made of a cylindrical cylinder body welded with a thin steel plate and the heads at both ends are welded together. Welded gas cylinders are mostly used to hold low-pressure liquefied gases, such as liquefied sulfur dioxide.
(2) Controlled gas cylinders
Gas cylinders are seamless gas cylinders made of seamless steel pipes. The heads at both ends are formed by heating the steel pipe on a special machine tool by spinning or extrusion.
(3) Drawing and drawing gas cylinders
It heats the steel ingot and punches out the concave head first, then draws it into an open preform, and then makes the top head and the interface tube according to the method of controlling the gas cylinder.
(4) Winding gas cylinder
This gas cylinder is composed of an aluminum inner cylinder and an alkali-free glass fiber wound with a certain thickness outside the inner cylinder. The function of the aluminum inner cylinder is to ensure the air tightness of the gas cylinder. The compressive strength of the gas cylinder depends on the glass fiber shell wall (using epoxy phenolic resin, etc. as a binder) that is wound into one piece on the outside of the inner cylinder. The shell fiber material is prone to "aging", so the service life is generally not as good as that of steel cylinders.
2. Classification according to the physical state of the medium
Gas cylinders can be divided into the following three categories according to the physical state of the medium.
(1) Permanent gas cylinders
The gas whose critical temperature is lower than -10℃ is called permanent gas, and the gas cylinder containing permanent gas is called permanent gas cylinder. For example, cylinders containing oxygen, nitrogen, air, carbon monoxide and inert gases belong to this category. The commonly used standard pressure series are 15 MPa, 20 MPa and 30 MPa.
(2) Liquefied gas cylinders
Various gases whose critical temperature is equal to or higher than -10°C are gaseous at normal temperature and pressure, but become liquid after pressurization and cooling. Among these gases, some have high critical temperature (above 70°C), such as hydrogen sulfide, ammonia, propane, liquefied petroleum gas, etc., which are called high critical temperature liquefied gas, also known as low pressure liquefied gas. The cylinders that store these gases are low-pressure liquefied gas cylinders. At ambient temperature, the low-pressure liquefied gas is always in a state of coexistence of two phases of gas and liquid, and the pressure of its gas phase is the saturated vapor pressure of the gas at the corresponding temperature. Considering that the maximum working temperature is 60 °C, the saturated vapor pressure of all high critical temperature liquefied gases is below 5 MPa, so such gases can be filled with low-pressure gas cylinders. Its standard pressure series are 1.0 MPa, 1.6 MPa, 2.0 MPa, 3.0 MPa, 5.0 MPa.
(3) Dissolved gas cylinders
This gas cylinder is a gas cylinder specially used to hold acetylene. Because acetylene gas is extremely unstable, especially under high pressure, it is easy to polymerize or decompose. The liquefied acetylene will explode if it vibrates a little, so it cannot be filled in a compressed gas state, and acetylene must be dissolved in a solvent (commonly used acetone) It is filled with porous material (such as calcium silicate porous material, etc.) as an absorbent. The maximum working pressure of the dissolved gas cylinder is generally not more than 3.0 MPa, and its safety issues are special. For example, the acetone in the acetylene cylinder will be sprayed, which will cause static electricity in the acetylene cylinder, resulting in combustion, explosion, and increased acetone consumption. .
