Yokogawa 415 Steam and Gas - Manual (Page 24)

3.2.1 Ideal Gas Law
If the effects of compressibility on a gas can be ignored, then Z
B
and Z
F
can be set
to 1.00 in equations 1 to 8. This can make calculations much simpler,
particularly when the properties of a gas are not known or, over small ranges of
pressure and temperature, where the effects of compressibility are often
negligible.
Example 4
A vortex meter is used to measure oxygen in a 2" pipe at 25° C and
200 kPa (abs). The flowmeter produces 9500 pulses/m
3
and the
flowrange is 100 to 1000 m
3
/h. Determine the flow parameters
which need to be programmed into the instrument for it to display
the flowrate and total flow as both mass and corrected volume to
Standard Conditions.
From the table, the Molecular Weight of oxygen is 31.9988. From
equation (1)
G =
31.9988
28.9625
= 1.105
According to ISO5024, Standard Conditions are 15° C (59° F) and
101.325 kPa (14.69595 psia). Hence, the following are
programmed into the instrument:
Scaling Factor (K-factor) = 9500 pulse/m
3
Specific Gravity G = 1.105
Base Temperature = 15 °C
Base Pressure = 101.325 kPa
Timebase of Rate = Hours
Other parameters can be programmed as required.
The instrument will now display the corrected volume and mass
flowrates of the gas.
22 Operation