Liquid-in-glass thermometers not meeting the requirements shall be discarded or returned to the manufacturer. 4.2.2 Portable Electronic Thermometers (PET) Portable electronic thermometers (PET’s) and thermometer assemblies, including the thermometer portion of closed system measurement devices shall be as specified in the latest edition of “API MPMS Chapter 7.2 – Temperature Determination: Portable Electronic Thermometers” or equivalent Energy Institute or ISO standard. They are subject to the following verification protocols: • Calibration before initial use and annually thereafter.
4.2.1 Liquid-in-Glass Thermometers
4.2.2.2 Monthly Verification On a monthly schedule, the PET should be checked at two or more temperatures near the ends of its range against a traceable reference thermometer, along with the following physical checks • The junction between the cable and the probe should be checked for mechanical damage. • The cable insulation should be checked for cuts, breaks, or abrasions.
Liquid-in-glass thermometers and thermometer assemblies shall be as specified in the latest edition of “API MPMS Chapter 7.1 – Temperature Determination: Liquid-in- Glass Thermometers” or equivalent Energy Institute or ISO standard. Newly purchased calibrated liquid-in-glass thermometers must be verified at a single point and inspected to ensure that the glass is not broken or cracked, that the liquid column has not separated or degraded, and that all markings are legible. Thermometers that are used for intermittent service, such as tank gauging, shall be inspected before each use or once per day, whichever is less frequent, to verify the thermometer is not broken and the liquid column is still intact. On a quarterly basis, the thermometer shall be verified against a traceable master thermometer of suitable resolution and accuracy at a single point, such as ambient temperature, or in a temperature- controlled source (e.g. temperature bath). Annually, a liquid-in-glass thermometer with organic liquids shall require at least a multipoint verification. A multipoint verification establishes whether a thermometer is reading within specification throughout its scale. Typically, the checkpoints are approximately 10 %, 50 %, and 90 % of the temperature range in which the thermometer is expected to be used.
• Grounding cable should be checked for damage.
• The case body should be checked for cracks or damage.
If any of the damage above is noted, the PET shall be removed from service until repaired. If the thermometer readings differ more than the tolerance stated in “API MPMS Chapter 7.2” the thermometer should be re-standardized.
• Monthly verification and inspection.
• Field verification before each use, or once a day, whichever is less frequent.
4.2.2.3 Daily (Prior to Use) Verification
Before each use, or once per day (whichever is less frequent), PET’s should be spot -checked by comparing the ambient reading against a reference standard thermometer in liquid. If the reading differs by more than 0.25 ° C or 0.5 ° F the PET should be re-calibrated before being used for custody transfer.
4.2.2.1 Annual Calibration
Before initial use, and at least once a year thereafter, each PET shall be re-standardized in a laboratory or other qualified calibration facility. The PET shall be compared at three or more temperature points, near the midpoint and ends of the range against a traceable certified reference thermometer.
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