Low flow check

The Low Flow Check detects when the site being measured is not flowing or is experiencing low flow. This check is performed if the MTR Low Flow Check in the Meter Validation tab is enabled. This check applies to corrected volumes only.

The Low Flow Check is the first validation step to be performed on the data in both pre-and post-calculation validation. The checks and actions taken depend on the setting of the severity level for the Low Flow Check.

The Low Flow Check's tolerance level can be assigned a specific severity:

• Invalid. The record will be designated invalid if the check fails.

• Flagged. The record will be marked, or 'flagged' if the check is unsuccessful.

• Valid. The record will be designated as valid. All other validation checks will be bypassed.

The pre-calculation validation Low Flow Check is performed before the main processing of the data. It only checks the data for low flow if the following criteria are met:

• The severity is valid.

• The volume will not be calculated.

If all these criteria are met and the volume is below the tolerance, the row is marked as Valid and no other validation is done except for the following pre-calculation validation checks:

• The Temperature Operational Check.

• The Pressure Operational Check.

• The Split Record Check.

The post-calculation validation Low Flow Check is performed after the main processing of the data. This includes data that is recalculated because of a gas quality (GQ) ripple or a configuration ripple.

If the severity is valid and the volume is below the tolerance, all post-calculation validation is skipped.

If the severity is flagged or invalid, and the volume is below the tolerance for two consecutive periods, the row is marked with a low flow problematic context record.

The following steps are used to detect when the telemetry flow value is too low.

1. Check if Valt is less than the low flow limit. If this is not the case, then skip the remaining steps.

2. Check if Valt-1 is less than the low flow limit. If not true, then skip the remaining step.

3. Generate Low Flow Problematic Context for this value.

For the purposes of this calculation, assume the following:

• Valt -Volume data at time t.

• Valt-1 - Volume data at time t-1

If the check fails, a low flow problematic context record is generated.