SOP for Operation and Calibration of muffle Furnace

This document details the procedure for the Operation and Calibration of the Muffle Furnace or Muffle furnace calibration

It is the policy of Xyz Pharmaceuticals Limited that a written procedure shall be followed the Operation and Calibration of Muffle Furnace and its use monitored in order to ensure smooth operation  to obtain consistent and reproducible results and minimize downtime  and meet regulatory requirements           

This procedure is to be applied at the time of Operation and Calibration of the Muffle Furnace.


Persons along with their responsibilities and accountability are given below:

Executive - Corporate Quality Assurance:- To prepare the SOP

Trainee Analyst/ Jr. Analyst/ Analyst/ Sr. Analyst:- To follow the SOP accordingly

Manager  -  Technical:- To ensure implementation of SOP.

Muffle furnace Calibration Procedure


5.1.1 Clean the outside surface of the instrument with a Clean Cloth.


5.2.1 Keep the instrument clean and dust-free.

5.2.2 Temperature in the muffle furnace is too high so always use long arm tongue.

5.2.3 Do not keep the door of the instrument open for a long period when the temperature is in “ON” condition


5.3. Switch “ON” the main power supply of the instrument.

5.3.2 The required temperature can be set by a thermostatically controlled knob, by rotating it in a clockwise or anti-clockwise direction.

5.3.3 Ensure that the temperature indicator/controller is in working condition i.e. the set temperature should be maintained/retained properly.

5.3.4 Put the objects /crucibles that required ignition by using a long arm tongue and close the door.

5.3.5 Ensure that the door of the muffle furnace is properly closed and does not loosen during operation.

5.3.6  Maintain the logbook of Muffle Furnace on XYZ/CQA/SOP-067/FR-01, Logbook for Muffle Furnace (Appendix I).


6.0.1  Calibration Frequency: Half Yearly.

6.0.2  Calibrated Platinum resistance thermometer(Range 0-1000°C) with sensor and digital temperature indicator is used for the calibration of the instrument.

6.0.3  Insert the sensor of the reference/calibrator sensor (PRT) in the muffle furnace as near as possible to the sensing tip or sensor of the temperature controller/indicator of the laboratory.


6 0.5 When the temperature is stable note down the temperature reading as displayed by the muffle furnace and Reference PRT Thermometer simultaneously

6.0.6  Record the temperature readings at   2 hours and 4 hours.

6.0.6 Correlate the readings observed with the reference standards and apply corrections, if necessary. 

6.0.7 For the calibration of the Muffle furnace having a range of 800˚C follow the steps6.0.2 to 6.0.6.

6.0.8 Record all the calibration data on XYZ/CQA/SOP-067/FR-02, Calibration Data Sheet  Appendix II (Page 1 of 1)

6.0.9 After the calibration of the instrument, affix the calibration tag on the instrument and fill all the required details as per SOP No. XYZ/CQA/SOP-006, Labelling Policy.

6.0.10 Report any discrepancy observed during operation and calibration of instrument to Section. In charge or his representative for corrective and preventative action (as per XYZ/CQA/SOP-030)

6.0.11 Section In charge or his representative will take the necessary action and report the same to Manager-Quality Assurance.

6.0.12 Affix “ Out of Order” label on the Muffle Furnace.


Generate the instrument calibration number on the calibration datasheet as INSCALXXYYZZZ where INS denotes instrument, CAL denotes calibration, XX denotes the year, YY denotes month and ZZZ denotes sequence number.


XYZ       Xyz Pharmaceuticals Limited

SOP      Standard Operating Procedure

QC         Quality Control

CQA       Corporate Quality Assurance  

(B) 1.0     OBJECTIVE

1.1 To lay down the procedure for MUFFLE FURNACE operation.

2.0    SCOPE

2.1 This procedure applies to Quality Control Department.


3.1  QC chemists to prepare and follow the SO.

3.2   Head – QA & QC for implementation of SOP.



4.1.1 Load the testing material in the furnace and shut down the door.

4.1.2 Before switching on the main, the knob of the energy regulator should be at the “OFF” position.

4.1.3   Switch ON the instrument.

4.1.4   Set the desired temperature with the help of the Digital temperature controller.

4.1.5 Note the time, when the temperature reaches the desired temperature.

4.1.6  Run the instrument for the required period of time.

4.1.7   Unload the testing material and shut down the door.

4.1.8   Switch off the furnace, if not in use.

Calibration of muffle Furnace

4.2       PRECAUTION:

4.2.1 Ensure that the instrument is cleaned before and after use.

4.2.2 Metal oxides, hardening, and reducing agent, salt-like substances which should not get in touch with the muffle.

4.2.3 The material to be treated should not occupy more than 50-70% of the heating space.

4.2.4   All the repair work on the furnace must be done only with the power main being switch off.

4.2.5   Do not disturb the thermostat knob once the temperature is set.

4.2.6   Avoid touching the instruments with a wet hand.


            SOP:           Standard Operating Procedure

            QA:           Quality Assurance

            QC:           Quality Control        

6.0       REFERENCE: NIL

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