3.1Thermocouples
Table 3.1.1 Calibration and Replacement Requirements for Thermocouples Used for Control,
Monitoring and Recording.
1. Non-Expendable
2. Thermocouples shall be replaced whenever needed, e.g. failed SAT, or damaged thermocouple;
however, thermocouples shall be replaced minimally as stated above.
3. Base metal thermocouples shall not be recalibrated.
4. Nobel metal thermocouples Type B, R, and S may be recalibrated in lieu of replacement.
5. Does not apply to Load Sensing Thermocouples. See Tables 3.1.4 and 3.1.5
Table 3.1.2 – Calibration and Replacement Requirements for Thermocouples Used for Primary
and Secondary Standards
1. A primary standard thermocouple together with a primary standard instrument shall be used to
calibrate secondary standard thermocouples.
2. Use is limited to the calibration of temperature uniformity, system accuracy, controlling,
recording, monitoring, and load thermocouples.
3. A Type R or S noble metal thermocouple calibrated against a NIST (or equivalent) reference
standard. No error permitted.
4. Base metal thermocouples shall not be recalibrated.
Table 3.1.3 – Calibration and Replacement Requirements for Thermocouples Used for Temperature Uniformity Survey (TUS) and System Accuracy Test (Sat)
1. Base metal thermocouples shall not be recalibrated.
Table 3.1.4 - Calibration and Replacement Requirements for Thermocouple Used for Load
Sensing
1. Base metal thermocouples shall not be recalibrated.
Table 3.1.5 – Allowable Number of Uses for Thermocouples in Specific Applications
1. Includes Load Sensing Thermocouples used as a Control Thermocouple.
2. When a non-expendable base metal thermocouple is used above 980oC (1800oF), the maximum
total number of uses is 90 uses which shall include any previous or subsequent temperature
readings taken with the subject thermocouple.
3. In the absence of documentation of the number of uses for non-expendable base metal
thermocouple used for TUS and SAT, then the thermocouples shall be replaced after 6 months.
4. Expendable base metal thermocouples for load sensing, are allowed more than one use if
thermocouple shows no visual degradation. Documentation is required to show compliance. 5. Non-expendable base metal thermocouples for load sensing, are allowed more than one use if
thermocouple shows no visual degradation. Documentation is required to show compliance.
3.2Instrumentation
TABLE 3.2.1 – INSTRUMENT CALIBRATION REQUIREMENTS
1.Semi-annual calibration is allowed provided that the instrument is calibrated with a primary
standard (multi-point calibration)and the SAT is performed quarterly per Method A (See 3.3.4.1).
See glossary for definitions of single-point calibration and multi-point calibration.
3.3System Accuracy Test (SAT)
EXAMPLE OF ACCEPTABLE SYSTEM ACCURACY TEST (SAT) PROBE METHOD - A
3.3.
4.2 Probe Method B:
EXAMPLE OF ACCEPTABLE SYSTEM ACCURACY TEST (SAT) PROBE METHOD - B
3.3.
4.3 Comparative Method:
EXAMPLE OF ACCEPTABLE SYSTEM ACCURACY TEST (SAT) COMPARATIVE METHOD
Deviation from the initial delta = E – D – C
TABLE 3.3.1 – SYSTEM ACCURACY TEST REQUIREMENTS
1.Maximum value of the Calculated SAT difference (see 3.3.4.1.3 and 3.3.4.
2.5).
2.Maximum deviation from initial delta (see
3.3.
4.3.2)
3.Total offset/bias assigned to the correction of a SAT error shall not exceed 2.0oC (
4.0oF).This
permissible offset/bias is separate from offset/bias assignable to a Calibration error or TUS.
3.4Temperature Uniformity Surveys (TUS)
Table 3.4.1 - TUS Test Thermocouple
(VOLUMETRIC METHOD)
Represents thermocouple locations
Figure 3.4.1 - TUS Test Thermocouple Locations
Table 3.4.2 - Number and Location of the TUS Thermocouples
(PLANE METHOD)