Section 6: Meter operation

Reference, Installation, and Operations Manual

June 2013

3-9000-743 Rev S

 

 

6.1.9Volumetric flow rate

The Daniel Mark III Ultrasonic Gas Flow Meter meter provides three volumetric flow rate values: raw, (expansion-corrected and/or profile-effect corrected) flow-condition, and base-condition. Note that a positive volumetric flow rate indicates flow in the forward direction whereas a negative volumetric flow rate indicates flow in the reverse direction.

Raw volumetric flow rate

The “raw” volumetric flow rate is calculated from the average gas flow velocity (wet-calibration gas flow velocity) as shown in Equation 6-12.

Equation 6-12 Raw volumetric flow rate

Q

 

 

=

V

 

 

πDin2

 

⋅ 3600 s hr

 

 

 

 

 

Raw

WetCal

-----------

 

 

 

 

 

4

 

 

where

 

 

 

 

 

 

 

 

 

 

QRaw

=

“raw” volumetric flow rate (m3/h) (QMeter)

VWetCal

=

wet-calibration gas flow velocity (m/s) (AvgFlow)

π

=

geometric constant, pi (dimensionless) (3.14159...)

Din

=

pipe inside diameter (m) (PipeDiam)

Flow-condition volumetric flow rate

The flow-condition volumetric flow rate is the result of applying expansion correction and flow- profile correction to the raw volumetric flow rate as shown in Equation 6-13subject to the low- flow cut-off. If the resulting value is below the low-flowcut-off value, it is set to zero. The low-flow cut-off volumetric flow rate (CutRate) is the specified low-flow velocity threshold (ZeroCut) converted to a volumetric flow rate.

196

Volumetric flow rate