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Installation and Configuration Manual 61
Principles of Operation Certified System DrawingsReturn PolicyPerformance Optimization
Appendix B
Principles of Operation
B.1 Theory of specific gravity measurement
By definition:
The relative density is numerically equal to specific gravity when the supercompressibility factors of
both the gas and the standard air at the measurement conditions are taken into consideration.
Therefore:
Now let the density of the gas sample measured be
ρ
1
, again by definition:
By comparing the density of the sample gas with the density of a fixed quantity of a reference gas
contained in a fixed volume:
Gas specific gravity = Molecular weight of gas/Molecular weight of standard air
(1) for example, G = M
G
/M
A
where M
A
is taken as 28.96469
Relative density = Density of gas/Density of air
(2) for example,
ρ
r
= ρ
G
/ρ
A
at the same conditions of temperature and pressure.
(3)
G
ρ
G
Z
G
ρ
A
Z
A
---------------=
(4)
ρ
1
P
1
M
1
Z
1
RT
1
------------------=
(5) where
ρ
2
P
2
M
2
Z
2
RT
2
------------------=