SOP for Maintenance and Calibration of Heating Block : Pharmaguideline

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SOP for Maintenance and Calibration of Heating Block

Standard operating procedure of maintenance and calibration of heating block used for endotoxin testing.


To lay down a Procedure is to provide guidelines for Operation, Maintenance & Calibration of Heating Block.


This procedure is applicable for Heating Block which is installed in microbiology laboratory of Quality Control Department.




Head QA & QC


5.1 Connect the 230V AC power supply to the power connection properly and Switch ON the Mains.
5.2 Open the lock of control panel situated on the front side of equipment with the help of the key.
5.3 Switch “ON” the red switch situated at the control panel, which is indicated by glowing of the red lamp.
5.4 The equipment temperature ranges from 0°C–100°C, so adjust the temperature at 37°C ± 1°C of the equipment by pushing the SET button and rotating clockwise or anti-clockwise temp. set knob of the equipment placed on the control panel.
5.5 Confirm the temperature that is displayed on the digital display and then releases the SET button.
5.6 Now the heater will start.
5.7 After attaining the SET temperature the heater gets automatically “OFF”.
5.8 Observe again after 30 minutes of attending the set temperature. If the displayed temperature is stable at the set temperature, then the equipment is ready for use.
5.9 Maintenance/Cleaning: Daily
5.9.1 Clean the outer surface of the Heating block with a lint-free cloth soaked in a mild soap solution, followed by wiping with a dry lint-free cloth.
5.10 Maintenance/Cleaning: Monthly
5.10.1 Switch OFF the Main switch of the equipment and then switch OFF from Main Supply.
5.10.3 Remove the heating blocks and transfer to washing area.
5.10.4 Wipe out the outside surface of the equipment with liquid detergent and then wipe out the base of the heating block.
5.10.5 Place the blocks in hot WFI for 30 minutes and then wash with a liquid detergent solution. Use nylon brush if there is any stain.
5.10.6 Again wash with WFI to remove the detergent traces and allow drying at room temperature.
5.10.7 After drying fix the blocks in their respective place and remove the label “UNDER MAINTENANCE/UNDER CLEANING”.
Related: SOP for Heating Block Validation

5.11 Calibration

5.11.1 Internal Calibration frequency once in six months & External Calibration frequency once in a year.
5.11.2 Internal Calibration carried out by Microbiology department and External Calibration carried out by engineering department or approved outside party.

5.12 Internal Calibration

5.12.1 Operate the Heating block as per SOP for operating instruction for the heating block.
5.12.2 Insert five BET tubes in a different location of wells and then add 200 ml SWFI with the help of micropipette.
5.12.3 Now insert a calibrated thermometer into the tubes containing 200 ml WFI.
5.12.4 Set the Heating block at 37°C temperature.
5.12.5 After attaining the heating block temperature, note down the temperature for 1 hour at the interval of 02 minutes for each set temperature points.
5.12.6 Compile the data and find out the temperature uniformity throughout the 1 hour period. It should be ± 1°C.
5.12.7 After calibration, immediately put the “CALIBRATION” tag duly filled with necessary information.

5.13 External Calibration

5.13.1 Temperature mapping.
5.13.2 When 37°C temperature achieves, insert thermocouple in the test tube filled with water.
5.13.3 Connect the thermocouple with the data logger. Record the thermocouple reading for 1 hour at an interval of 1 minute.
5.13.4 Determine the heat distribution studies by analyzing the temperature profile data.

5.14 Acceptance criteria

5.14.1 Temperature recorded by each probe at different locations must be in the range of 37°C ± 1°C.


SOP: Standard Operating Procedure
QA: Quality Assurance
QC: Quality Control
NA: Not Applicable
SS: Stainless steel
WFI: Water for Injection
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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  1. Hello! This is a very nice SOP, but I cannot find any literature used. Could you please indicate the sources?


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