In the Pharmaceutical industry, calibration of weighing Balance is done on a monthly basis to check the accuracy of Balance. check the following parameter While performing Weighing balance calibration:
- Accuracy
- Reproducibility
- Eccentricity
Accuracy:
Verify the balances for accuracy with the minimum weight (least count×100 ),5%, 20%, 50%, and 90% capacity of respective balances. Record the displayed weight in respective monthly calibration formats.
Tolerance limit:
The variation, if any, should be ± least count of the balance or ± 0.2 % of the certified value of standard weight used, whichever is higher, and for analytical Balance, the variation should be ± least count of the Balance or ± 0.1 % of the certificate value of standard weight used whichever is higher.
Reproducibility:
Check the Reproducibility by using the minimum standard weight of balance capacity. Place the weight in the middle of the weighing pen and observe the displayed value. Repeat the procedure nine times for the standard weight and record the reading.
Calculate SD and % RSD for both the standard weight by the following formula:
The formula for calculated Standard deviation (SD):
where x= individual value
x̄= mean of the individual value
n= number of value.
% RSD= SD*100/ X
Acceptance criteria: %RSD should not be more than 2.0%.
Record the observations in monthly calibration record as per “monthly calibration record of weighing balance.”
Eccentricity:
Take minimum weight and keep at on specified position as shown below calculate SD and %RSD by the following formula as specified above.
Acceptance criteria:
While calibration % RSD not more than 2.0 %. Record the details of calibration on labels with Marker Pen. Write the identification number of the standard weight used during verification and calibration in the designated place of verification and calibration records. The calibration record shall be verified by a quality assurance by putting a “reviewed by quality assurance” stamp along with initials and date. Calibration of analytical Balance in the quality control department shall be done as per their respective SOP.
Related: SOP on Checking Balance Eccentric Accuracy
Calibration of balances by external agency:
Internal calibration (software calibration) of weighing balances shall be done by external agencies. Calibration certificate received from an external agency shall be reviewed comprising the detail of balance and calibration summary.
Action to be taken if out of calibration:
If the Balance is out of calibration, refer to sop “handling of out of calibration” and rise deviation as per SOP “handling of deviation,” and fix the label “out of calibration” as per SOP (status labeling) and inform to Department Head of Investigation.
Raise maintenance memo and inform the engineering department for rectification action. If required, take a balance of configuration from another section and department for carrying out the weighing activity.
In Such situations, carry out Daily balance verification of transferred Balance and used for Weighing. If the parameter of Daily verification does not meet the specification, monthly calibration should be done. Once rectification of the Balance is done, calibrate the Balance and record the same in respective calibration records. the Balance shall be released for further use only on satisfactory closure of the deviation with a detailed result of Investigation
