Charge Factor

A cylinder must have space for vapor as well as liquid. As the temperature rises, the liquid expands. The space filled with vapor decreases. At a certain point, there will only be liquid in the cylinder. Beyond this, even a slight increase in temperature causes a large amount of pressure to build up in the cylinder as the liquid attempts to continue expanding despite the absence of the necessary space. The forces that result are strong enough to rupture the cylinder. To prevent a cylinder from being overfilled, the regulations regarding compressed gases specify how many kilograms of refrigerant may be added to a cylinder per liter of internal volume. The product of multiplying this charge factor by the internal volume of the cylinder is the permissible capacity. The figure for refrigerant used in vehicles is 1.15 kg (2.54 lbs) / liter.