Understand the maximum reasonable reverse flow rate

Note: This setting does not apply if the source rate record is configured as an Analog input.

The Max Reasonable Reverse Flow Rate (vol/h) reflects the maximum possible flow rate going in the opposite direction on a unidirectional pipeline.

In typical use, the value of this setting will be less than the Max Reasonable Flow Rate (vol/h) since reverse/back flow is a rare scenario on a unidirectional pipeline.

The value cannot be negative. The Max Reasonable Reverse Flow Rate (vol/h) is designed to compare negative delta changes reported at the meter to the reported volume reading. If the delta indicates a negative flow rate greater than the Max Reasonable Reverse Flow Rate (vol/h), the delta will be regarded as an anomalous condition and the volume of the accumulator will stay the same.

If the delta indicates a negative flow rate that is less than or equal to the Max Reasonable Reverse Flow Rate (vol/h), it will not be regarded as an anomalous condition, but whether it affects the accumulator volume depends on the configuration being used:

If the Volume Accumulation Mode is Positive Only, the Virtual Flow Computer (VFC) will enter a Catch-Up state. In this state, there will be no volume change (though the change is tracked internally). The volume will not go up until the rate providing the volume has re-accumulated the volume it "lost" due to the negative flow. When the previously read accumulation value is reached again, the VFC will automatically exit the Catch-Up state. The following diagram provides an example:

Note: In rare situations, it may be desirable to manually exit the Catch-Up state to account for a legitimate backward jump. For more information on how to manually exit the Catch-Up state, refer to the AVEVA Pipeline Operations for Liquids Controller Guide documentation.

If the volume's Accumulation Mode is Positive and Negative, the volume will be decremented by the amount indicated by the delta.

If Max Reasonable Reverse Flow Rate (vol/h) is zero and Max Reasonable Flow Rate (vol/h) is non-zero, then any backwards flow will be counted as an anomalous condition and a bad delta will be submitted. If it is zero but Max Reasonable Flow Rate (vol/h) is also zero, all negative flows will be treated as valid.