DX4 - Reconciled Difference Indicator

The DX4 - Reconciled Difference Indicator is a fundamental data quality index that indicates the amount of distortion between the reconciled and measured flows. This index is expressed as a percentage. Reconciled Difference is normally expected to be slightly negative (-0.1%) if all measurement errors are only Gaussian white-noise. Meter bias, losses, and missing or misinterpreted flows are possible causes of reconciled difference. Misinterpretation of flows can occur if piping or meter placement changes made during plant maintenance are not reflected in the P&IDs and the Sigmafine flow model. It is a serious data quality issue if the reconciled flows are greatly out of line with the measured flows.

A way to represent this value graphically is to visualize the index as the vector sum of the measured and reconciled vectors as shown below.

DX4 is calculated by the following equation:

DX4 = RMS (Reconciled Flows) / RMS (Redundant Flows) - 1

Where:

I = ith flow/transfer/inventory that is in service.

QT = value of the measurement that is redundant.

QRec = value of the reconciled mass or a measurement.