Q. Acetylene gas cylinder for gas welding to be erected in upright position

Acetylene gas is normally used for gas welding due to its simplicity in production and transportation and its ability to achieve high temperature in combustion (for example around 5,000^oF). Acetylene is highly flammable and unstable and would explode in elevated pressure when reacting with oxygen in air. Storing acetylene gas in cylinders under pressure is very dangerous. Gas acetylene used for welding purposes is stored in cylinders of liquid acetone comprised in porous material (such as firebrick). This is for cooling purpose in the event of thermal decomposition and to make sure that there is not any free space left for acetylene gas. It also prevents the formation of high-pressure air pockets inside the cylinder. Dissolved acetylene in acetone will no longer be in contact with oxygen and is not subject to decomposition. Acetone is used since it is capable of dissolving large amount of acetylene gas under pressure without changing the nature of gas.

Cylinders for gas welding it implies that oxygen cylinders and acetylene cylinders when not in use must be stored separately since any mixture of these gases resulting from accidental leakage can be highly explosive. When in use, acetylene cylinders must always be kept in upright position. Otherwise, acetone liquid would be drawn from the cylinders with the gas if they are kept horizontally, resulting in substantial leakage of acetone liquid would result. 

Note: Oxygen and acetylene gas cylinders are commonly used in construction sites for gas welding.

Fig: Acetylene gas cylinder erected in upright position