Units

ISA S75.01 has several standard conversion factors for unit conversion. The program enforces two conventions:

1. The flow units are mass flows.

2. The units are conventional practical metric units.

   Flow:	kg/h
   Pressure:	kPa
   Density:	kg/m3
   Valve/Pipe diameter:	mm
   Valve size:	Cv factors
   Viscosity:	mPa.s (same as centipoise)

For this purpose, ISA 75.01 has provided N factors in tables 1 and 2.

In the program, we define the same factors with the same name except in lower case as global variables, namely:

n2 = 0.00214

n4 = 76000

n5 = 0.00241

n6 = 2.73

Should it be desired to change the units, for example to imperial units, then using the factors in tables 1 and 2 of ISA 75.01 would be a convenient way to do it.

It is strongly recommend that units of flow remain in mass units rather than volumetric units. Volumetric units, especially when gases are involved, can lead to confusion.