The Calibration Certificate That Does Not Cover the Range Used
During an API Q1 audit of a pressure-testing station, you sample five calibration certificates for pressure gauges used to hydrotest bodies at 1.5x rated working pressure. Four gauges are rated to 10,000 psi and tested at 6,000 psi. The fifth gauge, used on the largest body size, is rated 15,000 psi and is used at 11,250 psi. Its calibration certificate covers only 0 to 10,000 psi and states an uncertainty of ±0.5% of full scale. The client's procedure requires gauges be calibrated over the range of use and that measurement uncertainty be considered against a 1% product tolerance. The calibration provider is on the client's approved supplier list. The quality manager says the gauge 'reads fine' and shows you three passing test records.
1. Is this a nonconformity? Against what requirement, and what is the objective evidence?
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Yes. The objective evidence is documentary and unambiguous: the certificate's accredited range (0–10,000 psi) does not cover the point of use (11,250 psi), and the client's own procedure requires calibration across the range of use. This is a nonconformity against the client's documented procedure and against API Q1/ISO 9001 requirements for control of monitoring and measuring resources - the equipment must be suitable and calibrated for the measurement being made.
Do not be moved by 'reads fine' or passing product records. Passing results do not demonstrate that the measurement was valid; a gauge reading outside its calibrated range has unknown error and the passing records are themselves of uncertain validity. That is the point to make in the report.
State the evidence factually: certificate number, range, point of use, procedure clause. Avoid characterizing intent.
2. What should the corrective action request require, and how would you verify it?
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The CAR should require root-cause analysis addressing why the range-of-use check failed at the planning stage (not just 'recalibrate the gauge'). Expect: a review of all gauges against their points of use, revision of the calibration specification to state required range, a check of records produced with the out-of-range gauge, and consideration of impact on product already released.
Verification: sample the corrected gauge list against certificates, confirm the procedure now specifies range of use, and check the impact assessment disposition for the affected bodies. Effectiveness is confirmed only when a later sample shows no recurrence - not when the recalibrated certificate is presented.