What calculation is needed to determine the proper scale setting before filling a cylinder by weight?

To determine the proper scale setting before filling a cylinder by weight, the correct calculation is the water capacity of the cylinder multiplied by the conversion factor (0.42 for propane) plus the tare weight of the cylinder and the weight of the filling hose.

This is essential because propane, when in liquid form, expands when it is vaporized, and its weight in the cylinder when filled should reflect the liquid volume accurately. By using the water capacity figure and multiplying it by the appropriate conversion factor (0.42 for propane) gives you the equivalent weight of propane that can be accommodated in the cylinder.

Then, adding the tare weight accounts for the empty weight of the cylinder itself, and including the hose weight ensures that any additional equipment used during the filling process does not result in an overfill, which is critical for safe handling and adherence to regulations outlined in NFPA 58.

Thus, the formula captures all necessary components to arrive at a safe and accurate scale reading before the cylinder is filled.