onsite checks of coriolis meters 1

[jae3806]

Could I get some feedback/debate on the following proposal.
I want to save money and not send my coriolis meters away for recalibration (remote, non custody measurement site).

1. Pull the meter out of line and blind off one end and fill with water and
A. Compare the temperature on the display with a certified temperature device.
B. Send a sample of the water away for density measurement to be compared with the density reading recorded from the display.
C. Check electronics

My reasoning is that if the density & temperature are within acceptable tolerances (to be determined). Then there is no damage to the internal tubes and so the meter factor should not have shifted. SO no need to send away for recalibration. ???

 

[jmw]

I deduce from your question that you expect some form of errosion, is this the case?
two factors that can throw your performance off are errosion and deposition. Both could lead to an imbalance in a twin tube device.
If errosive materials are resent then bent tube designs may be more vulnerable than straight tube. Essentially if it is errosion or deposition that is suspected, then there is, with some devices, a calculation that can be performed to estimate the errosion. This requires the resonant frequency in air at a known temperature. For this sort of data you will need to address the manufacturer for the specific characteristics of your meter. If the dtata and/or equation is not available then the thing to do is remove the meter, clean it and dry it, measure the resonant frequency in air and monitor this value. You need to know the temperature as the resonant frequency in air will vary with the change in Youngs Modulus. Even small temperature changes can be significant if you want to get an accurate measure of what changes are occuring. Bets is if you can set up the test in a temperature controlled laboratory where you reproduce the temperature each time you test.
What you hope to see is that over a period of time, the resonant frequency results create a scatter around a mean value. What you might see is a trend due to a change e.g. errosion.
Something else is to use and endoscope to visually inspect the tubes paying particular attention to welds, to the flow splitter and to the tube a short distance after each bend.

 

[dcasto]

In custody transfer applications, the coriolis meters are calibrated with a portable piston prover and a picnometer (sic). After the meter is calibrated, a meter factor can be applied in the totalizer.