We have a building with a large propane cylinder that distributes propane to different sources within the building. When the cylinder is filled, the propane is compressed to a liquid, and our bill is therefore in liters of liquid propane. It is then converted to a vapor in the pipes due to lower pressure.
After the cylinder there is a pressure regulator that regulates the pressure in the line down to 10 PSI. In the line there is a gas meter that measures consumption in units of 100 cubic feet (2831.68 liters). Finally before the appliance is another regulator which regulates the final output pressure to 0.5 PSI for the appliance.
I am trying to calculate the consumption of liquid propane by a tenant relative to the consumption measured on the gas meter. In several sources online (for example), I see that the ratio of liquid to gas propane is 1:270, however I would assume that this is probably at STP. If the temperature is 25°C and the pressure is 10 PSI, how would I determine this ratio in order to accurately charge the tenants for their consumption?
Note, I am unfamiliar with gas regulator terminology, but I would assume that this would mean pressure above atmospheric pressure, because if it was only 10 PSI, gas would flow into the pipe instead of out of it since atmospheric pressure is 14.7 PSI. So 10 PSI would actually mean 24.7 PSI. Please correct me if I'm wrong.