145 Cubic Foot Cylinder

The #4 designation is the trade shorthand for the 145 cubic foot acetylene cylinder size, part of a numbering system suppliers use alongside cubic feet. A #4 and a 145 cf acetylene tank are the same cylinder. Smaller sizes carry lower numbers, with the portable MC and B sizes at the bottom of the range.

Acetylene cylinders run from the small portable MC and B sizes through 40, 75, 100, and 145 cubic feet, with 145 cf (#4) being the largest commonly stocked size. Larger cylinders mean fewer refill trips but are too heavy to carry and belong on a cart. The gas and its 15 PSI working limit are identical across all sizes.

Duration depends on torch tip size and whether the work is cutting, heating, or welding, with heating tips consuming gas fastest. A 145 cf cylinder is chosen by shops doing production work who find smaller bottles emptying weekly. Acetylene also has a maximum safe withdrawal rate, which sets a practical ceiling on how fast it can be drawn.

Acetylene is dissolved in acetone inside a porous filler rather than stored as a free compressed gas, and drawing it too quickly pulls acetone out with it. The accepted guidance is to withdraw no more than about one seventh of the cylinder’s capacity per hour. Exceeding that damages equipment and degrades the flame.

The acetone that stabilises the dissolved acetylene will migrate to the valve if the cylinder lies on its side, and can then be drawn into the hoses and torch. Store, transport, and use acetylene cylinders upright. If one has been laid down, stand it upright for at least an hour before opening the valve.

Acetylene must never be used above 15 PSI at the torch, because it becomes unstable above that pressure. Acetylene regulators are built with this limit marked on the gauge. The limit is the same on a 145 cf cylinder as on the smallest portable size.

It uses a CGA510 valve, the standard connection for acetylene in the United States, so it needs an acetylene regulator with a matching CGA510 inlet. The regulator is a separate purchase. Never adapt an oxygen or inert gas regulator to a fuel gas cylinder.

Cutting consumes oxygen much faster than acetylene, so a 145 cf acetylene cylinder is normally paired with a considerably larger oxygen cylinder such as a 250 or 300 cf. Matching them by equal cubic feet means running out of oxygen repeatedly. A supplier can advise the pairing for a specific torch and duty cycle.

No, it ships empty with the CGA510 valve installed. Acetylene is a hazardous material and cannot move by standard carrier, so the cylinder is filled at a local welding gas supplier on arrival.

Store it upright and chained or strapped so it cannot fall, with the cap fitted when the regulator is off, in a ventilated area away from heat and ignition sources. Acetylene cylinders must be kept separated from oxygen cylinders in storage by distance or a fire-resistant barrier. Never store acetylene in a confined or unventilated space.