flow meter calibration

Flow Meter Calibration Tips: Titan Enterprises

Flowmeters have become ubiquitous. There is hardly any part of modern life that is not touched by these devices and because, or in spite of this, the flow meter calibration procedures are increasingly important. Today engineers and scientists rely on flow meters to maintain or improve the financial viability, quality and safety of a product / process and as such require regular calibration to ensure they are operating within acceptable limits. What are the key points to consider when calibrating or re-calibrating a flowmeter?

1. How often should I re-calibrate my flowmeter?

Flowmeters will not hold their calibration indefinitely and the calibration interval will be dependent on the type of meter and the application. Mechanical meters will wear and electronic ones can suffer minor degradation in the electronics or mechanical damage from impact or corrosion.

2. Should I return the flowmeter to the manufacturer for re-calibration?

This is a good course of action as the manufacturer is best placed to ensure that the meter is serviced and returned to an acceptable standard.

3. Is calibration in-situ with a reference standard in-line with the device on test practical?

Full installation criteria must be observed to ensure that one flowmeter is not corrupting the data produced by another flowmeter. There are several suppliers who will hire the required equipment and give installation recommendations e.g.www.Flowhire.co.uk.

4. Can I carry out flow meter calibration myself?

This can be quite simple with small flowmeters (12mm diameter and below) but with larger meters is often impractical. However there are some factors (detailed below) that you need to consider before you continue down this route.

5. Do you have a traceable reference standard?

This requires either a secondary flowmeter or a standard that is approaching an order of magnitude better accuracy than the errors you wish to measure. For example if you have a set of scales and you wish to measure 100Kg with an accuracy of ±1% the scales should be accurate to ±0.1Kg.

6. Is your reference standard traceable to national standards?

Taking the example in ‘5’ above, when were the scales last calibrated? Do you have a certified reference weight to check the mass recorded?

7. If you are recording flow rate do you have an accurate timing method?

The same resolution requirements are desirable for time as mass. With a linear flowmeter this is less important and becomes a second order effect but for non-linear devices such as the differential pressure meters it is very important.

8. Are you calibrating your flowmeter with actual fluid used in the process?

This guarantees that the answers are correct for your fluid.

9. Are your flow meter calibration and process operating conditions identical?

A lot of flowmeters are parameter specific and if the temperature, viscosity, density or flow rate changes the calibration will shift. Ensure that the calibration conditions, not just the fluid, are representative of the actual running conditions.

10. Is your process flow rate constant?

If the flow rate of your process is not constant – calibration must be performed over the entire operating range. This is particularly important if the meter is not installed in line with the manufacturer’s recommendations. Often it is not possible to conform to the installation instructions and in this case calibration in-situ is essential to ensure optimal flow meter performance.

At Titan Enterprises we employ commercial piston provers which use the displacement of a known volume by a piston as the reference to calibrate our flowmeters. These calibration devices are calibrated regularly against a traceable standard and retain their original ±0.05% repeatability. To learn more about flow calibration at Titan Enterprises please contact us.