If this is going to an appliance like a boiler or furnace, then typically there are jurisdictional fuel utilization codes that specify (among many other things) line sizes for various loads, equivalent length of piping run and inlet pressures. Any of the ones I've seen are tables included in the applicable code book. You'll likely save yourself a lot of grief from the local inspection authority if you just go with the pipe size shown.
When you mention a fluid to transport, you should identify its phase. There's a difference. Just like there is a difference between the Fanning Equation and the Darcy-Weisbach Equation (the Darcy friction factor = 4 x Fanning FF). If you are handling a gas or vapor instead of a liquid, the same basic Darcy-Weisbach relationship can be employed if the pressure drop is less than 10% of the initial pressure. This is to stay within reasonable accuracy. If you're handling a mixed, 2-phase fluid then you've got a worse problem. It gets really sticky and inaccurate.
Vaporized LPG is calculated for pressure drop just like any other pure vapor - with an appropriate gaseous calculation equation. Or, if the pressure drop is less than 10%, then you can use the D-W equation with reasonable accuracy. Otherwise, use an appropriate gas computer program or spreadsheet to calculate the pressure drop.
Allright Art - yes theres a difference between Fanning and Darcy - i just assumed that people wathing these page would either check or know...
Apart from that i agree with your comments re. knowing wich phase your dealing with is important and if there is a phase trancition and that multiphase is nmore difficult than single phase (at least for hand calc. allthough it take the same time when using a suited simulation tool).
