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FLOWSIC100 Flare-XT · Operating Instructions · 8023761/V1-0/2020-10 · © SICK Engineering GmbH
Commissioning FLOWSIC100 Flare-XT
7.5.7
Molar mass
7.5.7.1
Algorithm for calculating the molar mass
▸
Select the desired algorithm for the use of the molar mass:
– Basic
– Hydro Carbon
– Carbon number
– MR113
VOG dependency
When the VOG dependency is activated, different algorithms can be selected for higher and
lower gas velocities.
The field “VOG Limit” serves to define at which gas velocity the algorithm should switch
over.
Basic algorithm
The basic algorithm is suitable for basically flammable gases with a constant composition
and low hydrocarbons content. The basic algorithm is based on the following equation,
which can be used to determine the molar mass for ideal gases
Fig. 84
Basic algorithm formula
The algorithm requires the adiabatic coefficient κ (mean value) as input value, . Velocity of
sound and temperature can be measured by FLOWSIC100 Flare-XT. The algorithm is
suitable for all ideal gases with pressures < 5 bar with constant gas composition.
Hydrocarbon algorithm
The hydro-carbon algorithm is suitable for typical hydrocarbon mixtures with inert gases
proportion < 10%. On the basis of the velocity of sound, the molar mass is calculated with
the assumption of a typical hydrocarbon mixture. Changes in the composition of the
hydrocarbon fractions can be taken into account.
Fig. 85
Hydrocarbon algorithm formula
Carbon number algorithm
The carbon number algorithm is suitable for calculating the molar mass for hydrocarbon
mixtures. During the calculation, the carbon-number algorithm can compensate the
influence of inert gas components CO
2
, N
2
, H
2
O and uncertainty of the molar mass
Mm
R T
VOS
2
-------------------
=
Mm= molar mass
κ = adiabatic coefficient
R = universal gas constant
T = temperature
VOS = velocity of sound
