SOP for Top Pan Balance

1.0 PURPOSE

To lay down the procedure for the operation and calibration of Top Pan Balance.

2.0 SCOPE

It is applicable to top pan balance installed in Quality Control.

3.0 RESPONSIBILITY

Microbiology personnel

4.0 ACCOUNTABILITY

Head of Department

5.0 PROCEDURE

5.1 Pre-operational checks

5.1.1 Check the power cord is connected properly.
5.1.2 Check the cleaning of the balance.
5.1.3 Check for daily calibration completion before use.
5.1.4 Check the position of the balance.

5.2 Operation of balance

5.2.1 Connect the power supply cord and plug the other terminal into the socket in back of the balance.
5.2.2 To switch the balance on press the switch ON/OFF after the main power supply of balance has been switched on.
5.2.3 Check the position of the weighing balance. If required adjust it with the screws at the bottom of the balance.
5.2.4 Place the sample to be weighed on the top of the pan balance.
5.2.5 Observe the display for value.
5.2.6 Enter the balance usage details.

5.3 Cleaning of the balance

5.3.1 Use a moistened soft cloth or tissue paper to clean the weighing pan.
5.3.2 To switch the balance by ON/OFF button on the side of the balance.

5.4 Calibration of balance

5.4.1 Calibrate the balance daily with the standard weights of 10 gm, 100 gm and 250 gm individually.
5.4.2 Record the observations.

5.5 Monthly Calibration of balance

5.5.1 Ensure that the standard weights used are within the validity period of its calibration.
5.5.2 The weights selected for uncertainty measurement for 10 gm, 100 and 500 gm, 1000 gm
5.5.3 Weigh 10 gm of standard weight, for 10 times and note down the observation.
5.5.4 Calculate mean and standard deviation (S.D.) for the weights taken above.
5.5.5 Calculate the uncertainty for all the selected weights by using following formula:
                                                                  2 x S.D.
Calculation for uncertainty = ----------------------------------------
                                             Standard weight (g) (as per certificate)

5.5.6 Follow the same procedure for other selected weights.
5.5.7 Acceptance criteria: Not more than 0.10 %. (Uncertainty)
5.5.8 Record the observations in the respective monthly calibration data sheet.

5.6 External calibration

5.6.1 Perform the calibration of Balance against Standard Weights: Calibrate the balance with the standard weights of 10 gm, 50 gm, 100 gm, 250 gm, 500 gm, 750 gm, and 1000 gm individually.
5.6.2 Acceptance criteria: 0.1 % of the mass of the standard weight.
Note: The balance should display the weight within the tolerance limits specified for each of the standard weight range. In the case of non-conformance, clean the standard weight with lint free cloth and re-weigh, if the problem persists then call the service engineer for rectifying the problem. Do not use the balance, until the problem is rectified. Recalibrate the balance after maintenance before use.
5.7 After calibration if the balance is not showing correct weight then perform this activity.

6.0 ABBREVIATIONS

6.1 SOP – Standard operating procedure
6.2 gm – gram
6.3 SD – Standard deviation
6.4 % – Percentage

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