Maintenance of Temperature Measurement in Process Plants

Thumb rules for Maintenance of Temperature Measurement in Process Plants temperature instrumentation can inform a plant's maintenance department that a problem exists
1.0) Thumb rules for Maintenance of Temperature Measurement
Mount Themowells opposing Flow. Generally to be mounted in high turbulence area.
Good idea to mount Thermowells on Pipe elbows.
Thermowells should be inserted up to the center of the pipeline.
Thermowells must be manufactured from bar stock & should be Schedule 160 as a minimum. Can be welded or threaded.
Choose material as per Application.
It is most economical to have Head mounted Transmitter.
Buy Twin Thermocouples in the well. Generally, Non-Grounded & Mineral Insulated.
When Inspecting, Check characteristics by putting reference junction at ice point ( 0 degrees Celsius).
For critical Temperature measurements replace Element every two to three years to maintain Characteristics.
Follow Standards to match Element Characteristics with Input card.
If the element is exposed to vibrations, Thermocouple is a good choice.
Wire wound RTDs have better accuracies than thin film RTDs.However thin film RTDs have better tolerance to Vibrations.
RTDs are more repeatable, have more sensitivity, have Excellent linearity & their long-term drift is predictable. Thermocouple drift is Erratic.
RTD can achieve a precision of 0.1 degrees Celsius. Good where tight control or precise trip is required.
Given a choice, RTDs are desirable over Thermocouples. Their cost of ownership is less as compared to Thermocouples.
Visit manufacturers site while Inspection & check how it is manufactured. There are the lot of things to learn & improve there.

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