What does a marking of 4E240 on a cylinder signify?

The marking of 4E240 on a cylinder signifies that it is constructed from aluminum using a welded and brazed method. This specific marking indicates that the cylinder complies with certain specifications for design and fabrication of aluminum cylinders, which are crucial for ensuring safety and structural integrity during storage and transport of propane and other gases.

Understanding the context of the marking is important; it informs users that the cylinder is made from aluminum, which is known for its lightweight properties and corrosion resistance, making it suitable for gas storage. The reference to welded and brazed construction indicates the technique used in the manufacturing process, which helps bind the aluminum parts together, assuring strength and reliability in various pressure conditions.

The other options refer to different characteristics or types of cylinders. For example, composite materials would refer to a different class of cylinders made from advanced materials, rather than aluminum. The refillable nature of cylinders is also a separate attribute, which can apply to various types of cylinders, not just those marked with 4E240. Lastly, containers over 120,000 gallons pertain to large storage tanks rather than standard cylinders, which are typically much smaller in capacity.