LCH Consulting Associates, LLC

Stack Temperature Thermocouple Calibrations

On a recent stack test I witnessed a unique and effective way of calibrating the stack thermocouples. Section 10.3.1 of Method 2 calls for the thermocouple to be calibrated within 10% of absolute average stack temperature. I have typically calibrated TC’s with the 2 point ice bath and boiling water standards. However this isn’t necessarily within 10% of absolute stack temperature.  Also the method calls for calibrations after each field use, which is another caveat that isn’t necessarily satisfied.  To satisfy these requirements, Pete Tomas of PSE&G’s Maplewood Test Lab developed the following procedure.

1.  Before starting the final port of a test, attach a NIST traceable thermocouple and thermometer.
2. At each traverse point record the standard test and the NIST temperature data.
3. Collect the NIST data on a seperate data and submit with calibration records.
4. Field data is considered valid if the NIST and sample train thermocouples agree within 1.5% of absolute.
5. Should the agreement be greater than 1.5% data can be corrected at the approval of the administrator