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A gas cylinder, compressed gas cylinder or gas tank is a pressure vessel used to store gases at above atmospheric pressure.
Gas cylinders are cylindrical shaped metal items, fitted with a pressure/release valve at one end. They have thick metal walls, which makes them heavy. Gas cylinders are often made of carbon steel or steel alloys, while stainless steel cylinders are rarer, but do exist. For cylinders designed to store corrosive chemicals, nickel, copper or (rarer) aluminium alloys are used. Gas cylinders can release their content through a valve, located at one end of the tube. Same valve can be used to fill the tank.
Small gas cylinders, mostly used in labs are called lecture bottles.
Liquefied petroleum gas tanks
Commonly used in camping, kitchen, or as a convenient flame source, they have a short cylindrical form and are fitted with a circular handle and a release valve in the middle. LPG gas tanks can be either single use or refillable.
High pressure gas tanks
Since acetylene cannot be compressed as it explodes, special storage tanks are required. These tanks are filled with acetone or dimethylformamide inside a porous material, called Agamassan. Acetylene tanks must always be kept in a vertical position when used.
- See Lecture bottle
Labels are used on gas cylinders to indicate the type of gas, composition, flammability, storage conditions, etc.
Color coding is commonly used to differentiate between gasses.
To determine the amount of gas a cylinder can provide per the amount you need per operation, you will first need to determine the amount of gas from the cylinder (volume of cylinder if it's full), output flow and gauge pressure, for each type of gas you use. A calculator for oxygen gas can be found here.
Gas cylinders can be bought or rent from a variety of hardware and industrial stores. Renting a cylinder it's generally cheaper than buying one. Cylinders smaller than 20 l tend to be cheaper than larger ones and it may worth buying one, though they don't last as long.
Some pet stores will sell refillable CO2 gas tanks, though purging all the gas from inside the cylinder and refilling it with another is dangerous.
DIY gas cylinder
While it's possible to make a gas cylinder if you have sufficiently advanced technical knowledge, due to extreme hazards of handling a home made pressure vessel and high cost, it's best to simply buy or rent a gas cylinder. It's just not worth the risk.
- Heat source (LPG)
- Cut materials (acetylene)
- Inert atmosphere (argon, carbon dioxide)
Gas cylinders are heavy and moving them around is risky. The tank valve needs to be often inspected for any signs of malfunctioning, damage, corrosion or other tampering.
Gas cylinders should be kept in cool places, away from heat and light. They should also be kept away from corrosive chemicals.
NEVER USE COPPER SEALING ON ACETYLENE TANKS!
Many industrial stores won't sell gas cylinders or refill them to individuals, due to the hazardous nature of a pressurized vessel. Likewise, in some places only certain entities are legally allowed to refill gas tanks.