Appendix B - Measuring The Internal Diameter - ABB AquaProbe FEA100 User Manual

AquaProbe FEA100 / FEA200
Electromagnetic flowmeter
Appendix B – Measuring the Internal Diameter
When a standard full-bore electromagnetic flowmeter is manufactured, it is usually supplied in a nominal
bore size of a round figure anywhere between 15 and 2000 mm (for example 600 mm, 700 mm). Rarely are
flowmeters precisely this nominal size, but it is not important as the wet flow calibration (performed on
ABB's UKAS-approved and traceable flow rigs in the UK) compensates for small deviations in size. In the
case of a probe, clearly it can't be tested in the pipe in which it is to be finally installed. It is therefore not
possible to take account of the difference between the nominal or expected internal diameter of the pipe
and its actual value.
Since the relationship between the point velocity measurement and the flow depends on the area of the
cross section of the pipe ( x the radius squared), an error in the value of the internal diameter of the pipe
causes a much greater error in the volume flow measurement due to the 'square effect'. Therefore it is
essential, whenever possible, to measure the internal diameter accurately to eliminate this extra source of
errors. ABB supply an internal pipe-measuring probe (Pipe-bore Gauging Tool) for this purpose. The tool is
used as follows:
1. Fit the tool into the back of the valve, so that the red line on top of the fitting and the handle of the
tool is in line longitudinally with the centre line of the pipe.
2. Open the valve and push the tool in gently until it touches the other side of the pipe.
3. Back off the tool a small amount and rotate the handle through 180° so it is again in line with the
longitudinal axis of the pipe.
4. Push the tool down again carefully until it touches the wall of the pipe. Now, slide the small collar on
the tool down to touch the top of the fitting.
5. Pull the tool back carefully until it touches the top of the pipe. During this withdrawal, take care not to
touch the sliding collar. This distance between the top knife-edge of the sliding collar and the top of
the fitting is the internal diameter of the pipe. Measure this distance using a good quality tape rule.
6. Once the diameter has been measured and recorded, push the measuring tool back into the pipe a
little then turn it through 180° so that the handle is once more in line with the longitudinal axis of the
pipe and in the same direction as the red line on the top fitting.
7. Retract the probe fully into its fitting and close the valve fully.
Fig. B.1 Pipe-bore Gauging Rod
OI/FEA100/200–EN Rev. D
Pipe Alignment
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