Expired Gauge Calibration and Missing Strand Traceability
An inspector audits a prestressed pile plant producing 400 mm square piles. The plant's stressing gauge calibration is dated 14 months ago; the calibration interval in the quality manual is 12 months. The plant has produced 180 piles since the calibration expired. Strand mill certificates are on file for the current lot, but the heat numbers on the strand tags do not match the certificates for two coils; the plant says the coils are from the same supplier and 'the certificate covers the grade.' Concrete cylinder records for the last 20 piles are complete. The plant wants to ship 60 piles to a bridge project tomorrow. The project specification requires calibration every 6 months and full traceability.
1. Identify the nonconformances and state what can and cannot be shipped.
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There are at least three nonconformances: (1) the stressing gauge calibration is 14 months old, beyond the plant's 12-month interval and far beyond the project's 6-month requirement; (2) two coils lack traceability because the heat numbers on the tags do not match the mill certificates; and (3) the plant is proposing to ship 60 piles while these records are unresolved. The piles cannot be shipped as accepted until the engineer/inspector closes the nonconformances. The calibration issue affects every pile stressed since the calibration expired-180 piles at the plant, not just the 60. The traceability issue affects at least the piles containing the two coils. Complete cylinder records do not cure missing material traceability or invalid force measurement.
2. How should the affected piles be evaluated?
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Recalibrate the stressing gauge and compare it with a master gauge or load cell. Review the stressing records for the 180 piles; if the gauge error is within the allowed force tolerance and the recorded forces can be corrected, the engineer may accept them with documentation. If the gauge error is unknown or large, the force in those piles is unverified and the engineer must decide on additional evaluation, such as re-stressing where possible or rejecting affected units. For the two coils, attempt to reconstruct traceability from receiving records, tags, heat numbers, and supplier certifications. If traceability cannot be established, the strand cannot be accepted under the project specification; piles containing it should be quarantined. Destructive or nondestructive testing may be required, but it does not replace material certification.
3. What immediate actions and documentation are required?
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Place a hold on all piles affected by the expired calibration and the untraceable strand. Do not ship the 60 piles. Recalibrate the gauge before any further stressing. Segregate the two coils and any piles containing them; mark the piles with lot and coil identity. Issue a nonconformance report to the plant and notify the engineer and owner. Review the calibration history and the plant quality manual; if the project requires 6-month calibration, determine whether earlier calibrations were also missed. Verify the heat numbers against mill certificates and receiving logs. Release piles only after the engineer accepts the corrected force records and traceability, and document the basis for acceptance in the inspection file.