DR Solver options for missing flow detection

To set the DR Options for Missing Flow Detection:

• From within the AVEVA Production Accounting GUI, click Tools>Option, and then click the DR Solver tab.

  

The missing flow detection feature is applied only when the Auto Correction for Missing Flow option is checked in the DR Solver tab.

Note that there are five checkboxes that control missing flow detection and correction.

• The first checkbox is on the Missing Flow Detection(MFD) frame (above, left), called Auto Correction for Missing Flows. It determines whether DR Solver performs missing flow detection. This means AVEVA Production Accounting will find the balance points with missing flows and alters the results of reconciliation to assume that the detected missing flow(s) were real and of the predicted size.

• If the Limit MFD to Tanks Only option is checked, only missing flows for tank balance points can be detected. AVEVA Production Accounting will not, in this case, assign a missing flow to a node or process. If, in your plant, missing flows most often happen around tanks because the oil movement data on the tanks are missing, it is recommended to check this option.

To detect missing flows, AVEVA Production Accounting uses a proprietary and complex method that considers the imbalance and tolerance of the balance points around the suspected missing flow. The tolerance of the balance point is defined as the following.

The tolerance of the balance point

The tolerance used depends on which options you check in the Missing Flow Detection (MFD) frame.

You have two choices:

1. Use the tolerance assigned to the stream that the missing flow would belong to. This is the default.

2. Use the overall Confidence Level to calculate the tolerance as 100%-Confidence Level. This derived tolerance is then applied to each balance point. (E.g. A Confidence Level of 95% would result in 100-95=5% being used as the tolerance for each flow.) To force the use of the overall Confidence Level, check the Use System Defined Tolerance in MFD checkbox. We recommend that you check this checkbox since the missing flow on a given balance point is not highly related to the tolerance of input and output flows on that balance point.

Alternative

If you want to simply detect the missing flow with the user defined tolerance assigned to the balance point to which the suspected missing flow belongs, you check the Forced Balance checkbox. If this Forced Balance option is used, DR Solver detects a missing flow whenever the balance point in question has a measured imbalance larger than the tolerance of the balance point. The measured imbalance of any balance point is the sum of the measured values of input flows minus the sum of the measured values of output flows. The tolerance of each balance point is assigned using the GUI, and passed to the DR Solver engine.

The DR Solver dialog contains a Confidence Level which you may edit.

The GUI generates the input data of balance points to define the absolute tolerance of each balance point. Any relative tolerances defined the AVEVA Production Accounting GUI are converted to and passed as absolute.

In the following image, the tolerance value of this balance point is 100,000. DR Solver detects this balance point with missing flow, since the imbalance (2,249,951) is larger than the tolarance value (100,000) and excludes this balance point from the balance.

If the Use Reduced Balance checkbox is checked, the Forced Balance executes on the reduced balance points (balance envelopes) instead of the individual balance points.