Water Cut
Description
This block calculates the uncertainty in Water Cut for a specified Water Cut transmitter. The Water Cut transmitter characteristics should be selected from the drop down boxes.
Transmitter
The Water cut transmitter manufacturer, model and method are selected from the drop down boxes.
In this section, a wide variety of inputs are given based on KELTON’s experiences.
Water Cut Measured
If water cut is measured using a transmitter select Yes, otherwise select No to enter the estimated expanded uncertainty in water cut.
Manufacturer
Select the Manufacturer of the Water cut transmitter from the given list.
Note: if the manufacturer of the transmitter is not shown select unspecified and contact KELTON for further information.
Model
Select the Model of the Water cut transmitter.
Range
Select whether the water cut transmitter is in line calibrated or uncelebrated.
Inputs
The water cut transmitter characteristics are inputted from the manufacturer’s data sheets.
Linearity
Enter the percentage linearity of the results from the water cut transmitter.
Resolution
Enter the resolution percentage in the readings reference to the water cut transmitter.
Fluid Pressure Variation
Enter the change in the pressure of the fluid. (Taken from calibration records where available, otherwise assumed).
Fluid Density Variation
Enter the change in the pressure of the fluid. (Taken from calibration records where available, otherwise assumed).
Calculations
When a transmitter is selected, the relevant uncertainty components from that transmitter’s specification sheet are used for the uncertainty calculation.
Uncertainty Budget
The uncertainty budget table shows a break down of the different components that contribute to the overall calculated uncertainty.
The values input into the uncertainty budget are derived from the transmitter specific values relating to its calibration and specification. These values are taken in as the expanded uncertainties and are divided by a coverage factor to gain the standard uncertainty.
The coverage factor is determined by the probability distribution that best suits that uncertainty component. The standard uncertainty is then multiplied by the sensitivity value then squared. This is done for each component that contributes to the overall uncertainty in Water Cut. The standard absolute uncertainty in water is the square root of the sum of each component variance as shown in the following equation:
Calculated Uncertainty
The Expanded Uncertainty is the Standard Uncertainty multiplied by the coverage factor (k). The coverage factor is defaulted to k = 2 (equivalent to a confidence level of approximately 95%).
References
Standards
ISO 5168:2005 – Measurement of fluid flow – Procedures for the evaluation of uncertainties
ISO Guide 98-3 – Uncertainty of measurement – Part 3: Guide to the expression of uncertainty in measurement (GUM:1995) (2008)
Manufacturer documentation
Transmitters
Water Cut transmitters are available for selection from the following manufacturers: