What is the weight limit for DOT cylinders that must always be filled by weight?

In the context of the NFPA Liquefied Petroleum Gas Code (NFPA 58), the requirement that dictates a weight limit for Department of Transportation (DOT) cylinders that must always be filled by weight is established for safety and precision during the filling process. The code specifies that any cylinder that has a water capacity greater than 100 pounds must be filled by weight, rather than by volume.

This standard is based on ensuring that the filling process takes into account the maximum safe weight of liquid propane that the cylinder can hold, which prevents overfilling and associated hazards, such as pressure build-up and the risk of leaks. The fill by weight approach provides a more accurate measurement, especially for larger cylinders, where volume ratios can lead to significant variations in the amount of gas contained.

Thus, the correct limit that requires these larger DOT cylinders to be filled by weight aligns exactly at 101 pounds, as it is the threshold that marks the transition to this filling method. It's important to recognize that filling smaller cylinders, which have a water capacity of 100 pounds or less, can typically be done by volume without posing the same level of risk, as long as proper procedures are followed.