© 2019 Department of Petroleum Resources. All rights reserved Department of Petroleum Resources (DPR) PROCEDURE GUIDE

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1.15.9 Associated flow computer 
The associated flow computer must be installed to correct the volume rate and 
accumulated volume for pressure, temperature and compressibility, and to provide 
necessary data retention for audit trail.  
1.15.10 Density measurement 
A densitometer/ Gas chromatograph should be installed downstream of the UM to take 
density measurements.  
1.15.11 Orientation of Meters  
The metering package should be oriented during flow calibration to match the field 
installation.  
1.15.12 Meter Tube Inspection and Cleaning Ports  
Meter tube inspection ports should be located a minimum of 3 ND downstream and/or 
upstream of the ultrasonic flow-meter body flanges. Inspection ports for the flow 
conditioner should be located 3 ND upstream of the flow conditioner. The port diameter 
should not exceed 6% of the pipe diameter for meters larger than 1 2” and 0 .750” for meters 
12” and smaller. 
1.15.13 Flow conditioner 
Installation of flow conditioners shall be as recommended in AGA Report No.9 2017 – 
Measurement of Gas by Multipath Ultrasonic Meters. 
1.15.14 Flow Computer Calculations 
The necessary calculations are summarized in the following expressions 
𝑄𝑏= 𝑄𝑓(𝑃𝑓
𝑃𝑏
⁄ )(𝑇𝑏𝑇𝑓
⁄ )(𝑍𝑏𝑍𝑓
⁄ ) 
𝑉𝑏= ∫𝑄𝑏𝑑𝑡 
 
Where Qb = flow rate at base conditions 
 
Qf = flow rate at flowing conditions 
 
Pf = absolute static pressure of gas at flowing conditions 
 
Pb = base pressure, typically atmospheric pressure (101.325Kpa) 
 
Tb = base temperature 
 
Tf = absolute temperature of gas at flowing conditions 
 
Zb = compressibility factor of gas at base conditions 
 
Zf = compressibility factor of gas at flowing conditions 
 
Vb = accumulated volume at base conditions 
 
dt = integration increments of time (per second)