Final answer:
Empty cylinders previously in service must be considered as full for safety in storage calculations, due to potential residual gas and overpressure risks at high temperatures. Safety guidelines should be followed, especially regarding maximum storage temperatures to maintain cylinder integrity.
Step-by-step explanation:
Empty cylinders that have been previously in service and stored indoors must be considered as full cylinders when determining the maximum quantities of LP-gas to be stored. This is a safety measure to account for the possible presence of residual gas and to ensure that storage limits are not exceeded, potentially leading to hazardous conditions.
Gas cylinders are often stored at high pressure, and safety factors are used to determine the safe limits to which they can be filled. These safety factors help to prevent failure under normal and extraordinary situations, like in the case of a fire where temperatures and pressures may increase dramatically. Proper storage guidelines, such as avoiding excessive temperatures, are crucial for maintaining the integrity of the gas cylinders and the safety of the storage area. For instance, a gas cylinder should not be stored above temperatures of 120 °F (48.8 °C), as higher temperatures can increase the internal pressure, potentially leading to a dangerous situation.
If an empty cylinder heats up, the pressure can still rise despite it being empty. An example of this is a cylinder designed to contain CO2, which holds liquid CO2 at temperatures below its critical temperature of 31 °C. If the temperature exceeds this point, CO2 cannot be liquefied by pressure, leading to an increased risk of overpressurization and cylinder failure.