Standard Temperature & Pressure Effects on Volume

Since gas is compressible, the volume displayed is dependent on the temperature and pressure that the gas is at. In metric, we assume that the gas is at a different standard temperature and pressure (STP) than an imperial volume. Our assumptions for STP are based on SI units and North American field practices.

These are the default settings in Harmony, which are based on:

• International standard metric conditions for natural gas and similar fluids: 288.15 K (15.00°C; 59.00°F) and 101.325 kPa.
• STP – commonly used in imperial (US system of units): air at 60°F (520°R) and 14.696 psia (15.6°C, 1 atm)

Because gas is a compressible fluid, Harmony needs volume to be relative to temperature and pressure. There is no way to change how Harmony handles STP volume conversions for data; you can only change how Harmony handles the data on import.

These assumptions apply:

• Harmony assumes that if you enter volume in metric units (m3), those measurements are at the standard conditions of 101.325kPa(a) and 15C
• Harmony assumes that if you enter volume in field units (ft3), those measurements are at the standard conditions of 14.65psi(a) and 60F
• that at either of these standard conditions, gas behaves similar to that of a noble gas (that is, the Z compressibility factor is 1).
• When converting between metric and imperial, the molar mass is the same.