AIR & WATER

MONITORING NEWSLETTER  

March 2013
No. 401

Cone DP Meters Are Popular But Have Calibration Issues

The cone meter is a simple and robust generic differential pressure (DP) meter. It has been shown to be remarkably resistant to the effects of both asymmetric and swirling flow. The cone meter is often the meter of choice when there is a limited straight pipe length available for a flow meter. Therefore, cone DP meters are becoming increasingly popular gas flow meters. Casey Hodges and William Johansen, writing in Pipeline & Gas Journal, explored the calibration issues for DP meters.

Cone meters are generic DP meters and must be calibrated across an application’s full Reynolds number range for the calibration to be valid for that application. This requirement means it is often inappropriate to calibrate a cone meter in a water flow facility if the application has high Reynolds numbers. Extrapolation of cone meter calibration data is not advisable. Each individual cone meter has a unique performance and must be individually calibrated.

Once calibrated, the cone meter’s performance will stay constant until the meter’s geometry is altered by adverse flow conditions. Periodic recalibration is only required if the operator suspects contamination or damage. It is not yet possible for industry to accurately know a cone meter’s performance without calibrating the meter. However, a properly-calibrated cone meter can have a flow rate uncertainty of 0.5 percent.

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