Product description
FLOWSIC30 · Operating Instructions · 8020999/173B/V1-4/2020-02 · © SICK Engineering GmbH
15
Su
bj
ec
t t
o
ch
an
ge
w
ith
ou
t n
ot
ice
2.2.2
Determining the sound velocity
Sound velocity c can be calculated by resolving formulas 2.1 and 2.2.
2.2.3
Calculating the volume flow rate a. c.
The volume flow rate in actual condition (a. c.) is calculated from the gas velocity and the
geometric dimensions of the meter body diameter D.
2.2.4
Calculating the methane content
The calculation of the methane content is made by a simple model based on the measured
speed of sound in the medium. It can be used to identify changes in the gas composition
that may require appropriate action by the plant operator. The underlying model has been
created primarily for unconventional natural gas with high contents of methane.
The algorithm is based on the following assumptions:
● The main components are N
2
, CO
2
and CH
4
, all other components exist only in
negligible amounts.
● The portion of N
2
is roughly twice the portion of CO
2
.
● Significant amounts of other substances may lead to deviations.
Application limits of the methane algorithm
-10 °C < T < 85 °C
1 bar (a) < p < 20 bar (a)
The output value is without unit and refers to 1, uncertainty < 0.5%.
L
t
AB
+ t
BA
2
t
AB
· t
BA
(2.4)
c =
·
(
)
Q =
·
(
)
D
2
· π
4
(2.5)
v
