Calibration Process and Equipment Requirements...
Information & Training. | Quality Assurance. Quality Management.
The importance of Calibration. A well managed calibration system is essential in all manufacturing and monitoring operations. It provides confidence in the measured data and consistency in the measuring, test, manufacturing process. It is a requirement of ISO 9000, plus other regulatory standards and is often a customer requirement.What is Calibration?
• Calibration is checking the lack of certainty (uncertainty in measurement) of a measuring instrument.• Is achieved by checking something that has a know value (traceable standard) and noting the output of our measuring instrument.
• The difference between both is the error.
Calibration requirements include the need to…
• Establish and maintain documented procedures.• Determine measurements to be made and accuracy required.
• Select an appropriate measurement instrument capable of measurement accuracy and precision.
• Identify and define measurement instrument for calibration.
• Calibrate to prescribed intervals and to national and international standards. (ILAB, NAMAS, NIST).
• Where no standards exist, document the basis used for calibration. (e.g. Test Fixtures, Autocollimators, etc.)
• Define the calibration process and specify the acceptance criteria.
• Label measurement instruments with a suitable indicator to show calibration status.
• Publish calibration status reports on defined intervals.
• When measurement instruments are not conforming, take appropriate action on same and product affected.
• Maintain calibration records.
• Protect measurement instruments from damage, misuse and deterioration. (Use suitable packaging when not in use)
• Safeguard measurement instruments, including software and hardware, from adjustments which would invalidate the calibration setting.
Calibration terms and definitions:
• Measurement Instrument – Any instrument which monitors or controls a critical parameter of a manufacturing process, controlled environment or used to measure a product or component specification.• Standard – A defined reference tool with traceability to a national standard.
• National standard – A reference tool utilized by an internationally recognized standards laboratory representing the country which operates that laboratory.
• Calibration – Verification of a measurement instrument’s performance against a traceable standard.
• Precision – Or repeatability. Variation in readings obtained when repeating the exact same measurement(s).
• Traceability – Documented reference of calibration results to a recognized standard.
• Accuracy – The relative agreement of a measured value with an accepted standard.
• Loop Calibration – The calibration of measurement instruments “as installed” in a total system and represents calibration of the instruments “as used”.
• Resolution – The power of discrimination of an instrument.
• Range – The breadth or span of an instruments capability of measurement.
Typical calibration user responsibilities in an organization…
• Equipment user shall forward equipment to the calibration coordinator if (say) new batteries are required.• Equipment user shall forward equipment to the calibration coordinator if there is a damaged or non-functional or missing or unreadable calibration label.
• Equipment user shall check equipment calibration due date prior to use to ensure it has not expired.
• Non-portable equipment, equipment user shall inform calibration coordinator if there is a damaged or non-functional or missing or an unreadable calibration label.
• Equipment user shall ensure proper use, handling and storage for assigned test equipment.
Typical calibration representative responsibilities in an organization…
• Department calibration representatives shall attend regular calibration status meetings.• Department calibration representatives shall perform monthly calibration equipment stock check with status reports provided by calibration coordinator.
• Department calibration representatives shall complete & return status reports to the calibration coordinator.
• Department calibration representative shall coordinate search for missing equipment within their respective department.
Identification requirements for calibration…
• Identify and list all measuring instruments including personal measuring devices.• Include all equipment involved with quality control measurements, including test fixtures and software based measuring applications.
• Clearly identify all equipment not to be calibrated with a suitable indicator.
• Quarantine measuring instruments that are not calibrated. If unable to remove, label the item “Do Not Use” and make inoperable if possible.
Selection of suitable equipment…
• Criteria for selection of measuring instruments include appropriate accuracy, precision and resolution.• Test uncertainty ratio of 4:1 or better must apply to accuracy. Documented rational required if (say) a test uncertainty ration of 4:1 cannot be achieved.
• Ease of use – portable, reliable, industry standard.
• Digital display preferred as analogue tends to lend itself to more interpretation during reading results.
Calibration database…
• Must list all calibrated measuring instruments and standards.• Update immediately as new equipment is purchased.
• Indexed by instrument serial number.
Equipment coding system and control…
• Measuring instruments are tracked by original serial number.• Calibration records must identify this unique serial number.
• Code number must be unique and not re-used when instrument is discontinued.
• Should be permanently marked, etched on the equipment.
• Battery replacement must be performed by the calibration department.
• Security seals, anti-tamper labels should be replaced by the calibration department.
• Software used for testing is validated, controlled and protected.
• Manufacture’s user manual, specification and calibration records archived in central area.
Setting calibration intervals…
• A calibration interval is the maximum period between successive calibrations.• Not possible to construct a list of intervals which can be universally applied.
• Based on manufacturers recommendation, extent and severity of use.
• Documented engineering rationale based on usage.
• If none of the above available, interval not greater than 6 months would be a good starting point.
• Apply trend data obtained from previous calibrations.
• Need to consider any tendency to wear and drift with equipment ageing.
• Need to consider the risk and potential impact of an incorrect measured value being accepted.
External calibration…
• Performed by quality assured and approved subcontractors with accreditation for the relevant measuring instrument.• Calibration to be performed to the manufacturers specification across the full instrument range.
• Calibration coordinator should approve calibration certificates.
• Have traceability to a national standard, e.g. NIST, ILAB, NMAS.
Internal calibration…
• Calibration personnel must use application specific procedure.• Fully trained personnel only.
• Environmental conditions must be considered and established.
• Provide instruction on calibration points, required accuracy and precision.
Calibration records & certificates…
• Include measurement instrument ID.• Calibration date and due date.
• Signature of person performing the calibration.
• Identity of standards used and due date.
• Identity of procedure and revision ID.
• Before and after data (if adjusted) for each calibration point.
• Statement of acceptability (pass or fail).
• Tolerances for accuracy and precision.
Misc…
• Measuring instrument owner is responsible for submitting new equipment, equipment due and non-conforming equipment to calibration department.• All measuring instruments require ID and status label.
• Traceability required for internal and external calibration.
Information & Training. | Quality Assurance. Quality Management.
- The Principles of Quality Management
- The Quality Manual
- Quality Standards and Specifications
- The Quality Management System
- Revised requirements of ISO 9001: 2015
- Design Quality – Products & Processes
- Good Manufacturing Practice (GMP)
- Documentation
- CAPA – Corrective And Preventative Action
- Calibration Certification
- Change Management and Control
- Quality Management Training
- Product and Process Validation
- Supplier Quality Assurance
- Audits & Auditing
- Ensuring the Quality Management System is Risk based
- Etc. …. Etc. …. Etc. …
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