Cone DP Meter Calibration Issues |
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| Casey Hodges, Charles Britton, William Johansen, Richard Steven |
- Abstract:
- Cone DP flow meters are becoming increasingly popular for natural gas flow metering. A cond DP meter operates according to the same physical principles as other DP meters but it is not as yet included in the ISO 5167 report on DP meters. In this paper, thirty one cone DP meter single phase data sets from CEESI independent research, a wet gas research Joint Industry Project, and multiple third party cone DP meter calibrations are reviewed. The meters discussed have diameters ranging from 2” to 14”, beta ratios ranging from 0.45 to 0.85, Reynolds numbers ranging between 5e4 and 5e6, and pressures up to 75 bars. This paper discusses:
Performance comparisons between pairs of nominally identical cone DP meters built to the same specifications. These include pairs of meters built by to same manufacturer and built by different manufacturers. Conclusions are drawn on the prospects of similar meters having the same performance.
The discharge coefficient vs. Reynolds number relationship. The potential for exposure to biases, caused by calibrating cone DP meters with low Reynolds number water flows and then extrapolating the resulting data fit for high Reynolds number gas flow applications, will be explained. Multiple meter data sets logged from various test facilities will be used in this discussion.
The practice of periodic re-calibration of cone DP meters will be discussed. Conclusions will be drawn on whether this practice is necessary after examining the repeat calibration data sets of several different meters.
All data sets are plotted on one graph to view the discharge coefficient spread.
There is potential for cone assemblies to suffer some plastic deformation in service (e.g. due to slug strikes, excessive flow rates, etc). Therefore, the effect on a 4” 0.75 beta ratio cone DP meter’s calibration of shifting the cone alignment by 1° off the calibration position has been investigated. The experimental results showed some surprising and important conclusions.
A potential serious flaw in a common meter sizing methodology will be discussed that can leave a cone DP meter not fit for its purpose. A detailed worked example is given. The simple remedy is also given.
Comments are made on the prospects of cone DP meters being eligible for inclusion in ISO 5167. - Keywords:
- Cone DP Meters, Calibration of Cone Meters
- Download:
- IMEKO-TC9-2010-036.pdf
- DOI:
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