Calibration procedure for measuring instruments


Purpose :

Purpose of calibration procedure is to ensure that all measuring, test equipment and gauges are maintained in a suitable state and remain capable of measuring to the required accuracy.

Scope :

The applicability of this procedure is for calibration of all monitoring and measuring equipment and gauges used for monitoring/measuring of product and process characteristics within the organization.

Responsibility :

Head QA is responsible for establishing and maintaining this procedure.

Procedure :

Master list of Instruments :

Identify all the Instruments & Gauges for measurement as required for all the stages of production. Prepare a list covering all the instruments & gauges available in the organization and maintain a Master list of instrument & gauges. Provide unique identification number to all monitoring and measuring equipment and gauges.

Calibration Plan :

A “Calibration Plan” is prepared for the instruments and gauges as per the appropriate frequency. The Calibration frequency is based on uses, make & recommendation of manufacture etc. Calibration plan containing the date of calibration, Due date and method of calibration.Calibration is performed by either Internal or by the External agency.

Internal Calibration :

For performing Internal calibration, a proper lab is required and a qualified & experience person is required for doing calibration. Also calibrate the master instrument from NABL approved lab and maintain the record.

External Calibration :

For performing External calibration, the External Agencies used for calibration shall be accredited / approved by National Laboratory (NABL) or ISO / IEC 17025 certified.  Where a qualified laboratory does not exist for a particular equipment, calibration services may be performed by original equipment manufacturer and their names shall be included in approved Supplier list.

Scope of the external agency also check before doing calibration from any agency for checking that the calibration of that equipment is in scope of that agency or not.

The calibration activities are carried out as per the plan and the calibration certificate is verified for the acceptance of the instrument with the defined standard for acceptance criteria. Receipt of Calibration Certificate from external sources and examine the same for adequacy or result under the acceptance criteria.

In case the equipment shows NG values or results found out of acceptance criteria, send back it for repair, if possible. Otherwise put a reject sticker or red paint mark over it and update the relevant records accordingly.

New Instrument :

In case of new / repaired instrument ensure that it is calibrated before bringing it in use. Also update Master List, Calibration plan and individual instrument calibration record (Instrument History card)

Master Instruments :

Keep the Master Instrument in safe and secured condition and ensure that Master Instrument is not used for regular purpose. Cleaning of Master Instrument is ensured and application of preservative as applicable while storing for longer period.

Instruments handling :

Handle and store the calibrated instrument in such a way that their accuracy and fitness for use is maintained. In case the instrument falls down during use or gets damaged, send the same to Standard Room for checking/repairing or re-calibration, if required.

Out of Calibration :

In case the date of calibration is over the grace period of the same will be given of 15 days. Also the material inspected with that gauge shall be identified separately. If possible the calibration of instruments should not be late than due date.

During Calibration following calibration records to be checked:

  • Follow the engineering changes that impact the measurement system.
  • Check that the any out of specifications reading are received from the agency.
  • Check the risk of that out of specification reading on the product.
  • During Calibration, if any instrument is found to be out of calibration (the error exceeding the acceptance criteria), an out of calibration report is to be raised. One of the following actions will be taken on the equipment: a) Recondition and re calibrate b) Replace the equipment and document the validity of previous inspection and the test results.
  • Wherever evidence is available for shipment of suspect product, customer is to be notified.
  • Check & verify the specification after re calibration.
  • Verify the latest software which are used for product & Process and maintained record.
  • Maintain the calibration record of all instrument

Measurement System Analysis (MSA) :

Variable MSA :

  • Identify the instrument & prepare a plan that needed for MSA study.
  • MSA plan is prepared with the appropriate frequency or defined by the customer.
  • Appraiser is selected based on assigned the responsibility of for product inspection and uses of  instruments
  • MSA study is conducted as per plan & Gauge R&R is calculated.
  • Interpretation of Gauge R&R  is conducted and analyzed the results are as :
  1. Measurement System is acceptable if gauge R&R is <10%
  2. Measurement System is may be acceptable if gauge R&R is >10% and <30%
  3. Measurement System is not acceptable if gauge R&R is >30%

Attribute MSA :

  • Prepare Attribute MSA Plan
  • Check Effectiveness
  • Check Miss Rate
  • Check False Alarm
  • Effectiveness of each appraiser should be more than 90%
  • Miss Rate of each appraiser should be less than 2%
  • False Rate of each appraiser should be less than 5%
Calibration process

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