Meter Audit Review
• Flowmetrix Technical Services is an industry leader in conducting liquid flow metering audits, identifying adequate sizing and accuracy validation from primary to secondary converter to data repository; an end-to-end check. Our expertise focuses on liquid flow measurement for all mechanical water meters to non-mechanical flow meter types. A complete assessment of the meter type, size, age, and physical installation is reviewed. Display, signal outputs, and totalization registration is reviewed, and data repository is validated.
I calibrate all my process/billing meters each year. Does an audit need to be done as well?
An audit is required for many reasons.
- when there is a balance error where the contribution of error could be directly related to metering,
- when an IWA/AWWA water balance/audit is being done where a level of confidence in the calibration techniques needs to be defined,
- when a current calibration program is not adequate enough to prove performance,
- when a more detailed approach to understanding the metering process is required identifying all aspects of metering type, installation, flow throughput, calibration, outputs, registration, etc
What levels of verification/calibration is there?
Although there are many ways to provide a better level of confidence, there is only one true way to calibrate – compare one flow reading against another to a level of confidence outlined in the testing practice to achieve the level of accuracy for each meter.
Typical instrumentation programs for annual certificate of approvals doesn’t truly yield a “verification” nor “calibration” since the flow meter is not being challenged against a know value of throughput.
manufacturers “flow tube simulatators” only validate the electronics converter for display, outputs, and volumetric registration. This does not prove the overall performance or accuracy statement of the meter being verified.
Can a meter be accurate but still register inaccurately?
As mentioned in out meter-sizing menu. If a meter is not properly sized, it might be accurate for the range of flows it is designed for however, it might be inaccurate at the flow rates it is trying to measure. This is certainly true for a meter that is oversized.
What are the effects of an incorrectly "zeroed" electromagnetic" flow meter?
When an electro-magnetic flow meter is installed, it should be pressurized with the process liquid and then “zeroed” for any inconsistency related to the installation effects. If this is not done, the value being read during true zero flow will be additive (+ or -) to the actual readings causing great errors during a no flow condition or at least during low flow conditions above the low flow cut-off filter.
This is reviewed during any audit but not necessarily during an annual calibration.