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What Welders Need to Know About Gas Cylinders

Gas Cylinders

In the simplest sense of the word, gas cylinders are pressurized vessels used to store gas above atmospheric pressure. Bottled gases or cylinder gases are most commonly stored in steel treated with anti corrosives.

Regulations on Cylinders

In the US, the Department of Transportation regulates gas transport. Design and quality standards are further influenced by Underwriter’s Laboratory. Manufacturers also seek out third-party quality agents for required inspection. Common tests include hydrostatic, burst and tensile strength.Impact and pressure cycling is also tested.

Essential for proper use, handling, and storage is the information you’ll find stamped on the cylinder. Permanently indicated (with some variations) will be the cylinder type, working/service pressure, serial number, manufacture date, register code, and test pressure. Reusable high-pressure cylinders should be hydrostatically or ultrasonically tested every few years. Visual inspections should be done regularly. Depending on the cylinder and its use,the US requires testing every five or ten years.


Stop angle valves are usually found at the end of long, narrow cylinders. When not in use, caps may be placed over the valve to protect it from damage. Other cylinders have a protective collar, making them easier to store and transport. US valves are sometimes called CGAs. The Compressed Gas Association outlines what connections work with which products. Valves in different industries will have varying sizes and types. This makes accidental misuse less likely.

In use, pressure regulators are attached to the valve. Pressure gauges allow calculations for use. Liquid gas’s pressure doesn’t fall until the cylinder nears empty.


Color codes, though not always standard or regulated, can be helpful in identifying gases. One should never rely on this method alone. The label should always be checked.

Gas Safety

Many gases are hazardous and they are all under pressure. Bottles should be stored in a way that ensures they won’t fall over. Proper ventilation, signage, and training are essential. Cylinders should only be handled by trained individuals.

In case of fire, gas pressure will rise with the temperature. If the pressure exceeds the cylinder’s strength, the vessel will fail. If the gas is flammable, specifically if the contents are liquid, a Boiling Liquid Expanding Vapor Explosion can occur. Burst discs or Wood’s metal seals allow pressure release. The CGA publishes information on safe handling. This would be good reading for those regularly working with potentially dangerous gases.


Packaged gas is a costly investment. Transactional history, gas use, and related numbers can prove invaluable in keeping manufacturing costs down. When users know their gas usage by cylinder type, on-hand quantities, and age of cylinders, management can make better stocking decisions resulting in lower costs. Bar coded cylinders are now available. This accounts for who used what, watches expiration dates, and will tell you where your cylinders are.

It is easy to take for granted, the common gas cylinder. Take a few minutes to appreciate the design and regulations that help keep you safe.And strive to maintain a healthy fear and respect for the potential danger associated with working around these bottles. Don’t forget to read the label every time you pick up a vessel. And consult the CGA for more information.



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