During calibration it is typical to record “As Found” data that reflects the condition of the unit under test (UUT) prior to any adjustment. If there is an adjustment made to the UUT, “As Left” data is recorded to reflect the condition when the calibration was complete.
In some cases, the “As Found” data will indicate that the UUT did not meet the tolerance assigned during the initial assessment of the UUT. This may be a significant event depending on the criticality of the UUT and how far out of tolerance (OOT) the UUT was determined to be. There are two cases where this might be significant: 1) The UUT is a calibration standard, used to verify the accuracy of other equipment and/or 2) The UUT is used to perform measurements that are critical for some other reason (e.g. product release).
If the OOT UUT is a calibration standard, then it is possible the OOT may be significant enough to affect the integrity of calibrations performed using this UUT as a standard, and a Standard Traceability Report is run to identify any equipment that may have been calibrated using the standard since the last time the standard was calibrated. Each item that has been calibrated using the OOT standard should be evaluated to determine if the OOT condition of the standard may have adversely affected the calibration performed using that standard.
If the OOT UUT is used to perform measurements that are critical for any other reason, then it is required to identify and contact the owner to alert them (typically with an Out of Tolerance Notification so an evaluation may be performed. The owner can evaluate the specifics of the OOT condition to determine if it might have adversely affected data collected since the last successful calibration. With a properly designed tolerance system, the tolerance is usually such that small excursions would not have a significant effect on the quality of product as a result of the measurement.
Some of the specifics to consider in assessing the effect of an OOT may include the following:
Once the OOT condition has been evaluated and the effect determined. Appropriate corrective measures may be taken. In addition to adjusting or replacing the UUT, the following may be considered:
After the OOT and corrective actions have been performed, documented, and approved by quality assurance ongoing monitoring will, over time, prove if the corrective actions have been effective.