Gas Cylinder

Content
1. What is gas cylinder?
2. Types of gas cylinder
    2.1 Gas cylinder classification by manufacturing method
    2.2 Gas cylinder classification by the physical state of the filled medium
3. Use of gas cylinder
    3.1 Gas cylinder charging
    3.2 Safety use of gas cylinder
    3.3 Periodic inspection of gas cylinders
4. How to buy gas cylinder?

Gas cylinder refers to the main structure of the bottle, generally filled with gas (can be compressed gas, liquefied gas, dissolved adsorption gas, etc.) that can be moved to a class of pressure vessels. Gas cylinders are very widely used. Both the production field and the field of life cannot be separated from the gas cylinder.

Gas cylinder is a pressure equipment, with the risk of explosion, and its filling medium generally has flammable, explosive, toxic, strong corrosion, and other properties, the use of the environment and because of its mobile, repeated filling, operation, and use of personnel not fixed and the characteristics of the changing environment, more complex than other pressure vessels, harsh. Once the cylinder explosion or leakage, often fire or poisoning, or even causes catastrophic accidents, bringing serious property damage, casualties, and environmental pollution.

To ensure the safe use of gas cylinders, in addition to requiring them to meet the general requirements of pressure vessels, but also need to have some special provisions and requirements.

Welded gas cylinders are made of cylindrical cylinders welded with thin steel plates and headers at both ends. Welded gas cylinders are mostly used for low-pressure liquefied gases, such as liquefied sulfur dioxide, etc.

Controlled gas cylinder is a seamless cylinder made of seamless steel pipe. The head at both ends is formed by heating the steel pipe on a special machine by spinning or extruding.

Punching and drawing gas cylinders are made by heating the ingot and then punching out the concave head, then drawing it to make an open-top cylinder, and then making the top head and interface pipe according to the method of controlling gas cylinders.

The winding gas cylinder is composed of an aluminum inner tube and a certain thickness of alkali-free glass fiber wound outside the inner tube. The role of the aluminum inner tube is to ensure the gas tightness of the cylinder. The pressure strength of the cylinder relies on the glass fiber shell wall (with epoxy phenolic resin and other adhesives) wound into one outside the inner cylinder. The shell fiber material is easily aged, so the service life is generally inferior to that of steel cylinders.

The gas whose critical temperature is lower than -10℃ is called permanent gas, and the gas cylinders containing permanent gas are called permanent gas cylinders. For example, cylinders for oxygen, nitrogen, air, carbon monoxide, and inert gases are all in this category. The common standard pressure series are 15 MPa, 20 MPa, and 30 MPa.

The critical temperature is equal to or higher than -10℃ for various gases, which are in a gaseous state at room temperature and pressure, but become liquid after being pressurized and cooled. Among these gases, some have a higher critical temperature (higher than 70℃), such as hydrogen sulfide, ammonia, propane, liquefied petroleum gas, etc., which are called high critical temperature liquefied gases, and also called low-pressure liquefied gases. The gas cylinders for storing these gases are low-pressure liquefied gas cylinders. At ambient temperature, low-pressure liquefied gas is always in the state of co-existence of gas and liquid phases, and the pressure of its gas phase is the saturation vapor pressure of the gas at the corresponding temperature. Considering the maximum working temperature of 60℃, the saturated vapor pressure of all liquefied gases with high critical temperature is below 5 MPa, so these gases can be filled with low-pressure cylinders. The standard pressure series are 1.0 MPa, 1.6 MPa, 2.0 MPa, 3.0 MPa, and 5.0 MPa.

Dissolved gas cylinders are specially used to fill acetylene cylinders. As acetylene gas is extremely unstable, especially under high pressure, it is easy to polymerize or decompose, and a slight vibration of liquefied acetylene will cause an explosion, so it cannot be filled in a compressed gas state, and acetylene must be dissolved in solvent (commonly used acetone) and filled with porous material (such as calcium silicate porous material, etc.) as an absorbent inside. Dissolved gas cylinders of the highest working pressure generally do not exceed 3.0 MPa, its safety issues have special characteristics, such as acetylene cylinders within the acetylene spray, will cause acetylene cylinders with static electricity, resulting in combustion, explosions, acetone consumption increases and other hazards.

The correct filling of the gas cylinder is one of the keys to ensuring the safe use of gas cylinders. Improper filling, such as gas mixing, and overfilling is dangerous.

Gas mixing refers to the same gas cylinder filled with two gases or liquefied gases. The most common phenomenon of mixing is oxygen and other combustible gases and combustible gases, such as the original filling of gas (such as hydrogen, methane, etc.) of the cylinder, not after replacement, cleaning, and other processing, and there is residual gas in the bottle, and used to fill the oxygen. If these two media are in the right conditions the chemical reaction will cause serious explosive accidents. Therefore, never allow the gas to mix.

Overfill is also a common cause of gas cylinder rupture and explosion. Overfilled cylinders are affected by the ambient temperature, especially in the summer, the cylinder of liquefied gas because of the rapid expansion of the volume of warming, so the pressure inside the bottle increases sharply, causing the cylinder to rupture and explode.

To prevent the overfilling of gas cylinders, the following aspects should be done Filling work should be the responsibility of a person, filling personnel should receive regular safety education and assessment; filling personnel should operate carefully and should not leave their posts without permission while paying attention to emptying the remaining liquid and verifying the weight of the bottle. The weighing apparatus used for liquefied gas filling should be calibrated at least once every three months, and the maximum weighing value of the weighing apparatus used should be 1.5~3 times the usual value. Establish cards by the bottle and record carefully. Filled cylinders should be responsible for repeated weighing. Installation of automatic measuring equipment, the excess amount can automatically alarm and cut off the valve.

a. Prevent the gas cylinder from being heated. Gas cylinders in use should not be placed in the hot sun, do not be close to the fire and high-temperature areas, from the open flame, should not be less than 10 m; do not use high-pressure steam to directly spray gas cylinders; prohibit the use of hot water thawing and open fire baking, strictly prohibited with a temperature of more than 40 ℃ heat source to the cylinder heating.

b. Gas cylinders should be placed in standing measures to prevent tipping; open the valve slowly to open, to prevent the attachment of fast pressure to produce high temperature; cylinders of combustible gases, cannot use steel tools and other knocking cylinders to prevent sparks; oxygen cylinder valve and its accessories shall not be stained with grease, hands or gloves stained with oil, shall not operate the oxygen cylinder.

c. Gas cylinders should be left with residual gas at the end of use, mainly to prevent accidents caused by mixing with other gases or impurities. Gas cylinders used for the occasion of possible backflow (backflow), there must be devices to prevent backflow, such as a one-way valve, check valve, buffer tank, etc. LPG gas cylinder residual oil and gas, the application of safety measures to recover the facilities, do not deal with their own.

d. Strengthen the maintenance of gas cylinders. The paint layer on the outside of gas cylinders is both an anti-corrosion and identification mark, which can prevent misuse and mixing, and keep the paint surface intact and the mark clear. Bottles mixed with water will accelerate the corrosion of the cylinder wall, before filling must be the dry treatment of gas cylinders. The use of gas cylinders shall not change the variety of gas filling units, or unauthorized replacement of the cylinder color logo. Do need to replace the application should be made by the gas cylinder inspection unit is responsible for the modification of gas cylinders. Responsible for the modification of the unit according to the cylinder manufacturing steel mark and safety conditions, to determine whether the cylinder is suitable for the gas to be changed. Retrofitting, the cylinder should be thoroughly cleaned inside, inspected, hit the steel seal and painted inspection mark, change the corresponding accessories, replace the modified gas wording, color ring, and color.

The inspection cycle for all types of the gas cylinder has the following provisions.

a. Cylinders containing corrosive gases need to be inspected once every 2 years.

b. Gas cylinders containing general gases need to be inspected every 3 years.

c. The service life of LPG gas cylinders is 15 years. This type of gas cylinder needs to be inspected every 4 years, and the last inspection for 3 years.

d. Cylinders containing inert gases need to be inspected once every 5 years.

e. Cryogenic cylinders need to be inspected every 3 years.

f. Automotive LPG cylinder inspection every 5 years, automotive compressed natural gas cylinder inspection every 3 years. Car scrapped, car gas cylinders in the process of use found to have serious corrosion, damage, or doubt about their safety and reliability, should be tested in advance. Inventory and out-of-use for more than one inspection cycle of gas cylinders, before the start of the inspection.

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