search.noResults

search.searching

saml.title
dataCollection.invalidEmail
note.createNoteMessage

search.noResults

search.searching

orderForm.title

orderForm.productCode
orderForm.description
orderForm.quantity
orderForm.itemPrice
orderForm.price
orderForm.totalPrice
orderForm.deliveryDetails.billingAddress
orderForm.deliveryDetails.deliveryAddress
orderForm.noItems
CALIBRATION BE MORE CERTAIN OF UNCERTAINTY


Dr Bruno Pinguet, Multiphase Domain senior advisor at TÜV SÜD National Engineering Laboratory, outlines how to deal with uncertainty in flow meter calibration


W


hile flow meters are


calibrated under ideal laboratory conditions, the environments into which they are installed vary greatly. It is therefore incredible to see today in the billion-dollar oil and gas industry that most flow measurement systems are reporting flow rates with no consideration of measurement uncertainty. Uncertainty analysis is essential to determine whether measurement systems can meet required performance targets. It is a popular misconception that measurement is an exact science. In fact, all measurements are merely estimates of the true value being measured and the true value can never be known. The terms ‘accuracy’ and ‘uncertainty’ are also misused in the oil and gas industry.


Accuracy refers to the agreement between a measurement and an expected true value. Therefore, accuracy requires two measurements with two different meters.


Uncertainty is an interval defined around the average, which is based on data collected over a given period that is considered a stable flow condition. The true value can be expected to be within the interval defined during the measurement. The size of the interval is described as a confidence interval or in terms of sigma (i.e. standard deviation from a statistical point of view).


So, how can oil & gas operators effectively allow for this uncertainty? The ideal approach would be to calibrate every individual flow meter device for the specific conditions it will encounter. However, this is not financially realistic and to establish a flow meter’s performance, an uncertainty budget must be constructed, considering additional uncertainties arising from interpolation and extrapolation from calibration conditions. Firstly, calibration against a single-phase meter at least three to four times better than


‘BUY A FLUKE, GET A FREE FLUKE’ OFFER RENEWED


Installation, maintenance, troubleshooting and repair engineers can continue to ‘Buy a Fluke, get a free Fluke’ this Autumn with a broad range of safe, reliable, and easy to use Fluke tools, network testers and calibration equipment available between 1 September and 15 December 2021. Fluke’s Autumn seasonal promotion encourages customers to claim a free product when they purchase a Fluke tool. A broad range of industrial and electrical tools, network testers and calibration equipment for residential and commercial use is available Customers who purchase Fluke tools through authorised Fluke distributors can use their original


invoice to claim their free product through Fluke’s website. The ‘Buy a Fluke, get a free Fluke’ offer is divided into six levels depending on the value of the


qualifying purchase. The minimum purchase for customers to claim a free product is £100. A qualifying purchase includes Fluke’s electrical and industrial test tools, Fluke Networks and Fluke Calibration products. Customers can then choose a second product from a selection of free tools available, including clamp meters, digital multimeters, advanced testers, and accessories such as equipment cases. For more information on how to claim a free product, view the range of tools available, and for full terms and conditions, go to: www.fluke.co.uk/freefluke


the device in question is needed. This is done in a third-party flowloop facility, the best being a primary calibration facility. Secondly, the repeatability performance of the flow meter must be established (effectively this is the closeness of agreement between successive measurements made under the same conditions) in its estimation of the overall uncertainty of the calibration. Reproducibility is another essential parameter from the end-user’s point of view. This is established by moving from a given condition, such as pressure or choke opening etc., to different conditions and then returning to the previously given conditions. Meter drift is a systematic uncertainty that should also be accounted for, as this determines how the error in the


measurement process will change over time. Bias is very well documented and addressed in ISO 21748 and it could also be a source of uncertainty.


Stability is another parameter to consider, as if there have been multiple calibrations of the same flow meters over the years, this will be the standard deviation of the calibration results. The standard uncertainty and the associated stability on the reference measurement should be taken into account. To establish the performance of an installed flow meter against a reference flow meter, some prerequisites are necessary. For example:


• Both devices must be physically as close as possible, so changes between them in line pressure and temperature are minimal. • Both devices must record data at the same time.


• Both devices must use the same 8 OCTOBER 2021 | PROCESS & CONTROL


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66