TEMPERATURE TRANSMITTER TEMPE TEMPERATURE TRANSMITTER
- 2. 1. THE IMPORTANCE OF TEMPERATURE MEASUREMENTS The ability to measure temperature accurately is a critical requirement • for earth energy balances and to the understanding of macrosystems • for an understanding of global warming • for successful scientific analysis • critical to all chemical and physical scientific research • includes life systems of all kinds, global heating and cooling processes, weather, and oceanography • any analysis that includes energy exchange must have precise and accurate temperature measurement to be successful • because the thermodynamics of equilibria and the kinetics of processes usually depend exponentially on temperature.
- 3. 2. WHAT IS TEMPERATURE? • Temperature is the level of thermal energy. Thermal energy transfer only occurs spontaneously from a high temperature to a low temperature, never the reverse. So temperature is the driving force for heat transfer. Temperature measurement Thermometers Probes Non-contact
- 4. 3. THERMOMETERS 3.1 Glass tube thermometers • Principle Liquid in glass thermometer works on the principle that liquid expands as the temperature increases and contracts as the temperature decreases. • Application at field Temperature indicator of motor 715-G02S • Verification with thermobath
- 5. 3.2 Bimetal thermometers - 1 • Principle When a temperature is sensed by the element, the metallic components want to expand. • Application at field Temperatur indicator of crankshaft oil 712G01 • Verification/calibration with thermobath, see WI-018 THERMOMETER-Rev3
- 6. 3.2 Bimetal thermometers - 2 (Work Instruction) • INSPECTION / CHECK LIST - L1 1) Check/inspect the tag no. For possible damage or missing. 2) Check/inspect front glass, dial plate and pointer/needle for possible damage. Replace if damage. 3) Check/inspect sensing element for possible mechanical damage (i.E. Bimetal, capillary tubing and gear train ). 4) Check/inspect thermowell or protective tube for possible leak 5) Clean the thermometer for possible dirt or foreign material deposits. • INSPECTION / CHECK LIST - L2 1) This inspection covers all the list specified in L1 preventive maintenance. 2) Check/inspect indication of thermometer compare to thermometer standard, do calibration if 3) Check/inspect cable gland, cable and cable termination. 4) Check the function of proximity or limit switch including str 918 card. If any • Procedure calibration the local thermometer 1) Clean the thermometer for possible dirt or foreign material deposits. 2) Prepare and operate the temperature calibrator or thermobath as per manufacturer opeting instruction 3) Select the appropriate thermowell dimension which fit to local thermometer stem. Install it to the temperature calibrator 4) Set the calibrator at room temperature or 25% of measuring range, increase it stepweise in increment 5) Set calibrator to room temperature ( measure with thermometer standar ) and adjust the pointer needle 6) Repeat steps 4 and 5 until calibration response error is within acceptable tolerance.
- 7. 3.2 Bimetal thermometers - 3 (Troubleshooting) WHAT SHOULD WE DO ABOUT IT?
- 8. 4. PROBE 4.1 THERMISTOR • Principle The thermistor is a device that changes its electrical resistance with temperature. • Application at field Heat detector at MCC building • Verification, see WI-018 THERMOMETER-Rev3
- 9. 4.2 RESISTANCE TEMPERATURE DETECTOR (RTD) - 1 • Principle Rtds work on a basic correlation between metals and temperature. As the temperature of a metal increases, the metal's resistance to the flow of electricity increases. • Application at field Temperature element of 722T71 • Verification/Calibration, see WI-072 THEMPERATURE transmitter-Rev3
- 10. 4.2 RTD - 2 (Work Instruction) • Inspection / check list - l1 1) Identify all sensor correctly. Override the interlock or perform "cal mode" to avoid any tripping. 2) Check/inspect the tag no. For possible damage or missing. 3) Check/inspect wiring termination, cable and cable gland for possible damage or loose connection 4) Check/inspect thermowell or protective tube for possible damage or leak. 5) Check/inspect thermohead seal and metal insulator for possible damage or liquid entry. • Inspection / check list - l2 1) This inspection covers all the list specified in L1 preventive maintenance. 2) Measure output temperature sensor resistance and convert to table or compare with standard 3) Compare indication on procedure 3.1.2 to control panel reading or DCS reading. Calibrate if error • Procedure calibration the local thermometer 1) Clean the thermometer for possible dirt or foreign material deposits. 2) Prepare and operate the temperature calibrator or thermobath as per manufacturer opeting instruction 3) Select the appropriate thermowell dimension which fit to local thermometer stem. Install it to the temperature calibrator 4) Set temperature calibrator from initial value or room temperature, increase it stepwise in increment of 25 % 5) Decrease the setting temperature calibrator step wise in decrement of 25% from full scale value up to 25 % 6) If error >2.5% replace temperature sensor with new unit.
- 11. 4.2 RTD - 3 (Troubleshooting) WHAT SHOULD WE DO ABOUT IT?
- 12. 4.3 THERMOCOUPLE • Principle • If there is a difference in temperature between the hot junction and cold junction, a small voltage is created. • Application at field Temperature Boiler 738 • Verification, see WI-018 THERMOMETER-Rev3
- 13. 5. NON-CONTACT DEVICES 5.1 INFRARED THERMOMETER • An infrared thermometer is a thermometer which infers temperature from a portion of the thermal radiation sometimes called blackbody radiation emitted by the object being measured.
- 14. 6. THERMOWELLS Thermowells for temperature instruments are recommended for all process systems where pressure, velocity or viscous, abrasive and corrosive materials are present individually or in combination.
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