SOP for Calibration of Mercury Filled Glass Thermometer
1.0 OBJECTIVE
To provide a standard operating procedure for the calibration of Mercury filled glass thermometer.
2.0 SCOPE
This procedure is applicable to all thermometer use in plant.
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3.0 RESPONSIBILITY
3.1 Doing : Technical Assistant/Executive
3.2 Checking : Executive /Manager
4.0 ACCOUNTABILITY
Head of the Department
5.0 PROCEDURE
Frequency : Once in a six month
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5.1 Assign a Q.C Report No to each thermometer as per following logic PL/0000 Where,
PL= Abbreviation of Company and 0000 = serial number.
5.2 Keep the thermometer which are to be calibrated at room temperature till room temperature is achieved.
5.3 Visually inspect the thermometer for cracks, gaps, clear correct markings, chipped or distorted glass, and separation in the mercury column.
5.4 If separation in the mercury (liquid) column, found then take following corrective action.
5.4.1 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.
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5.4.2 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.
5.5 Thermometer with measurement range above 50°C are calibrated by third party.
5.6 Calibration Procedure for thermometer having measuring range up to 50°C.
5.6.1 First keep all 50°C range thermometer at room temperature till room temperature is achieved.
5.6.2 After achieving room temperature, keep all thermometer with reference thermometer in a ice bath.
5.6.3 Ensure the thermometer is immersed to the proper immersion depth.
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5.6.4 When meniscus has stopped moving gently tap the thermometer, as some amount of the meniscus may adhere to the wall of the thermometer.
5.6.5 View the 0°C mark and compare test thermometer with reference thermometer.
5.6.6 Record the value of test and reference thermometer in Annexure-I.
5.6.7 Use low temperature water bath for calibration.
5.7 For first temperature point use following procedure.
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5.7.1 Set the water bath at 10°C + 1 °C temperature. After achieving the temperature 10°C + 1 °C, keep reference calibrated thermometer and test thermometer inside the water bath.
5.7.2 After 5 minutes observed the temperature of reference and test thermometer.
5.7.3 Record the value of test and reference thermometer in Annexure-I.
5.8 For second temperature point use following procedure.
5.8.1 Set the water bath at 25°C + 1 °C. After achieving the temperature 25°C + 1 °C, keep reference calibrated thermometer and test thermometer inside the water bath.
5.8.2 After 5 minutes observed the temperature of reference and test thermometer.
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5.8.3 Record the value of test and reference thermometer in Annexure-I.
5.9 For third temperature point use following procedure.
5.9.1 Set the water bath at 40°C + 1 °C. After achieving the temperature 40°C + 1 °C, keep reference calibrated thermometer and test thermometer inside the water bath.
5.9.2 After 5 minutes observed the temperature of reference and test thermometer.
5.9.3 Record the value of test and reference thermometer in Annexure-I.
5.10 Ensure the results are within the tolerance limit.
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5.11 If values are out of tolerance, keep thermometer for 72 hrs. For stabilization and then recalibrate it. If it is out of limit, remove from the services and destroy the thermometer.
5.12 Maintain the issue record of thermometer.
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6.0 ABBREVIATIONS
6.1 SOP= Standard Operating Procedure
6.2 °C= Degree centigrade
