Understand how anomalous flows affect downstream applications

The Virtual Flow Computer (VFC) can handle a variety of different anomalous conditions. In some cases, applications using the Gross Standard Volume (GSV) provided by the VFC can be affected as well. Applications that commonly use the VFCs as input are Pipeline Monitor (PLM), Batch Tracking, and Batch Transfer.

It is recommended for any VFC being used by a downstream application to be configured with Positive Only accumulation mode, a non-zero Maximum Reasonable Flow Rate (vol/h) and a zero Maximum Reasonable Reverse Flow Rate (vol/h) to prevent spurious negative flows from affecting applications using the GSV of the VFC. At this time, negative volume changes are not supported in other AVEVA Pipeline Operations for Liquids applications.

In the case where an anomalous flow that exceeds the Maximum Reasonable Flow Rate (vol/h) occurs, the VFC will filter out the spike. Downstream applications will not be affected in this case.

The same applies for anomalous flows that exceed the Maximum Reasonable Reverse Flow Rate (vol/h). The change will be filtered out, and downstream applications will not be affected.

If a reset occurs on the field device, the VFC volume will not change, and it will continue incrementing as normal. Downstream applications will not be affected.

If a non-zero Maximum Reasonable Reverse Flow Rate is configured, negative volume changes will be reflected in downstream applications. This configuration is not recommended for any VFC being used by a downstream application.

• If the Positive Only accumulation mode is used, negative volume changes will not be reflected in the VFC or in downstream applications. However, it may take the VFC some time to continue counting upwards again while it works through the negative spike. This can result in unexpected results in downstream applications as the volume stays stuck in place, even though the field devices are still counting upwards.

• If the Positive and Negative accumulation mode is used, negative volume changes will be reflected in the VFC and in downstream applications. This scenario will result in unexpected behavior. This configuration is not supported for any VFC being used by a downstream application.