OBJECTIVE
To provide a standard operating procedure for the calibration of Mercury mercury-filled glass thermometer.
SCOPE
This procedure applies to all thermometers used in plants.
RESPONSIBILITY
Doing: Technical Assistant/Executive
Checking: Executive /Manager
ACCOUNTABILITY
Head of the Department
PROCEDURE
Frequency: Once in a six month
- Assign a Q.C Report No to each thermometer as per the following logic XXX/0000
Where
XXX = Abbreviation of Company
0000 = serial number.
- Keep the thermometer which is to be calibrated at room temperature till room temperature is achieved.
- Visually inspect the thermometer for cracks, gaps, clear correct markings, chipped or distorted glass, and separation in the mercury column.
- If separation in the mercury (liquid) column, is found then take the following corrective action.
- Immerse the bulb portion of the thermometer in a block of dry ice until the meniscus has stopped moving. Ensure not to freeze the mercury (liquid) in the bulb.
- If the separation remains, gently tap the bulb on a soft object and swing the thermometer in a small arch until the mercury (liquid) is united.
- Thermometers with measurement ranges above 50℃ are calibrated by a third party.
- Calibration Procedure for thermometer having measuring range up to 50℃.
- First, keep all 50℃ range thermometers at room temperature till room temperature is achieved.
- After achieving room temperature, keep all thermometers in an ice bath with reference thermometers.
- Ensure the thermometer is immersed to the proper immersion depth.
- When the meniscus has stopped moving gently tap the thermometer, as some amount of the meniscus may adhere to the wall of the thermometer.
- View the 0℃ mark and compare the test thermometer with the reference thermometer.
- Record the value of the test and reference thermometer in Annexure-I.
- Use a low-temperature water bath for calibration.
- For the first temperature point use the following procedure.
- Set the water bath at 10℃ ± 1℃ temperature. After achieving the temperature of 10℃ ± 1℃, keep the reference calibrated thermometer and test thermometer inside the water bath.
- After 5 minutes observe the temperature of the reference and test thermometer.
- Record the value of the test and reference thermometer in Annexure-I.
- For the second temperature point use the following procedure.
- Set the water bath at 25℃ ± 1℃. After achieving the temperature of 25℃ ± 1℃, keep the reference calibrated thermometer and test thermometer inside the water bath.
- After 5 minutes observe the temperature of the reference and test the thermometer.
- Record the value of the test and reference thermometer in Annexure-I.
- For the third temperature point use the following procedure.
- Set the water bath at 40℃ ± 1℃. After achieving the temperature of 40℃ ± 1℃, keep the reference calibrated thermometer and test thermometer inside the water bath.
- After 5 minutes observe the temperature of the reference and test the thermometer.
- Record the value of the test and reference thermometer in Annexure-I.
- Ensure the results are within the tolerance limit.
- If values are out of tolerance, keep the thermometer for 72 hrs. For stabilization and then recalibrate it . Remove it from the services and destroy the thermometer if it is out of the limit.
- Maintain the issue record of the thermometer as per Annexure II.
ANNEXURE
Annexure-I: THERMOMETER
CALIBRATION RECORDS
Annexure-II: THERMOMETER ISSUE RECORDS
ABBREVIATIONS
℃: Degree centigrade
REVISION HISTORY
Nil
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