Equipment Calibration Status
The Navy calibration program has a series of distinctive labels and tags for indicating the calibration or serviceability status of all Navy test and measuring equipment. All calibration personnel and equipment users should be familiar with each label and tag and its meaning. Labels of different nomenclature, color combinations, and shapes have been designed to help users identify the calibration status. These labels and tags should be used by all participants in the Navy METCAL Program and should be affixed to all Navy standards and test/measuring equipment. NAVAIR 17-35MTL-1/NAVELEX 0969-LP-133-2101/ NAVSEA OD 45845, Metrology Requirements List (METRL), lists Navy calibration procedures and intervals for all laboratory standards and test/measuring equipment. Only equipment actually used for quantitative measurements requires calibration. The lettering Department of the Navy Metrology and Calibration (METCAL) Program (NAVELEX Instruction 4355.2) permits the custodians of test and measuring equipment to obtain and affix CALIBRATION NOT REQUIRED and INACTIVE labels to test/measuring equipment. The METRL also identifies test and measuring equipments that are known to require calibration. Assistance in identifying other test/measuring equipment in this category is available from the respective METCAL group, from the systems commands' designated representatives, or from the Metrology Engineering Center (MEC). Examples of all labels and tags used m the METCAL Program are described and illustrated in the following paragraphs.
CALIBRATED.- The CALIBRATED label (fig. 13-13, black lettering with a white background) comes in two different sizes and is the most commonly used
Figure 13-13.-CALIBRATED labels.
Figure 13-14.-CALIBRATED-REFER TO REPORT labels.
label in the Navy METCAL Program. It indicates that the instrument to which it is affixed is within its applicable tolerance on all parameters. If there are any qualifying conditions for use of the instrument, one of the other labels should be used.
CALIBRATED-REFER TO REPORT.- The CALIBRATED-REFER TO REPORT label (fig. 13-14, red lettering with a white background) also comes in two sizes. It is used when you must know actual measurement values and associated uncertainties to use the instrument.
SPECIAL CALIBRATION.- There are two SPECIAL CALIBRATION labels (fig. 13-15, black with a yellow background), differing in size and content. There is also a SPECIAL CALIBRATION tag, which is used with the smaller of the two labels. The SPECIAL CALIBRATION label is to be used whenever there is some unusual or special condition in the calibration that should be drawn to the attention of the user and/or calibrating activity. Examples of special conditions are deviations from usual calibration tolerances, multiple calibration intervals, or a requirement for in-place calibration. The special condition that resulted in the special calibration should
Figure 13-15.-SPECIAL CALIBRATION labels and tag.
be described directly on the large label where sufficient space is available to mount the label on the instrument. When there is only enough spats for the small label on the instrument, this condition should be described on the tag. The following paragraphs briefly describe the situations that may require the use of the SPECIAL CALIBRATION label.
Deviation from Specifications.- In cases where the user does not require full-instrument capability, the calibration could be performed to reduce tolerances or cover less than all ranges and parameters. This approach is often used when the instrument does not meet Ml-calibration tolerances on certain ranges or parameters but can still meet user requirements. On the other hand, the special calibration may be for higher accuracy than usual on a short-term basis upon the specific request of the user. In many cases, users should be requesting special calibration because of deviation from specifications. For example, the user sends an instrument in for full calibration but will never use it over its full range. The user should have requested special calibration of the instrument to cover only the ranges needed. If this is accomplished Navywide, thousands of calibration hours and dollars could be saved.
Multiple Calibration Intervals.- Some instruments have components that require calibration less frequently than the rest of the instrument. For example, the attenuator in a signal generator may require calibration every 12 months, whereas the rest of the instrument parameters should be calibrated every 4 months. Since the attenuator calibration is time-consuming and may require unavailable standards, use of the multiple-interval approach can save many man-hours and can permit the more frequent calibration
to be performed at a lower level laboratory. When a specific instrument has been designated for multiple calibration intervals, such information is provided in the applicable calibration procedure. The SPECIAL CALIBRATION label or tag should be annotated as Multiple Interval, and the type of calibration performed should be indicated (i.e., partial 1 of 2, 2 of 2, or complete calibration). The calibration due date reflects the due date of the next partial or complete calibration, as the case may be.
Calibrated in Place.- Some instruments should be calibrated in place. Annotation on the SPECIAL CALIBRATION label or tag and MEASURE format should alert both the user and the calibration activity that the instrument should not be removed but should be calibrated where it is actually installed.
Figure 13-16.-USER CALIBRATION label.
USER CALIBRATION.- The user should calibrate some test/measuring equipments instead of referring the instruments to a calibration facility. For example, some instruments, such as hardness testers and densitometers, are provided with their own standards and should be calibrated each time they are used or at least on a frequent basis. Instruments, such as oscillographic recorders, may require calibration before, during, and after each use. Some automatic instruments have self-calibration tests that should be performed each time they are used. Still other instruments may require calibration as part of check-out procedures performed daily or weekly. These calibrations should be recorded in maintenance logs. Whenever recognized, the requirement for calibration by the user and the calibration interval are indicated in the METRL. The USER CALIBRATION label (fig. 13-16, black lettering with a white background) is affixed when the calibration is performed by the user. This label is not replaced at each calibration. When the label is first affixed to the instrument, it is annotated as to the appropriate calibration intervals. Records of calibrations performed (when calibration is performed other than each time the instrument is used) should be by normal maintenance practices, such as maintenance logs and maintenance action forms.
INACTIVE.- If an individual instrument due for recalibration will not be used for sometime in the future, the user may indefinitely postpone the recalibration by affixing an INACTIVE label (fig. 13-17, green lettering
Figure 13-17.-INACTIVE label.
with a white background) to the instrument. The INACTIVE label remains on the instrument until it is recalibrated. The instrument should not be used while it is bearing an INACTIVE label. The inactivation of test equipment occurs most commonly when a ship is in an overhaul status and the test equipment has been removed from the ship and stored in an environmentally safe location.
CALIBRATION NOT REQUIRED.- Standards and test/measuring instruments not requiring calibration are shown as NCR in the Metrology Requirements List (METRL). The CALIBRATION NOT REQUIRED label (fig. 13-18, orange letters with a white background) is affixed on the instrument and should remain there indefinitely unless its calibration requirements are changed. If an instrument is not listed in the METRL, you should use the following criteria (as listed in the METRL) to decide if the instrument should be placed in the CALIBRATION NOT REQUIRED
The instrument does not make quantitative measurements nor does it provide quantified outputs.
The instrument is "fail-safe" in that any operation beyond the specified tolerances will be apparent to the user.
All measurement circuits are monitored during use by calibrated instruments or are dependent on external known or calibrated sources of performance within required limits.
When you determine that an instrument falls into the CALIBRATION NOT REQUIRED category, you should annotate the label as to the authority for the decision, such as METRL, the applicable technical manual, and letters or messages from higher authority.
REJECTED.- If an instrument fails to meet the acceptance criteria during calibration and cannot be adequately repaired, a REJECTED label (fig. 13-19, black letters with a red background) is placed on the
Figure 13-18.-CALIBRATION NOT REQUIRED label.
Figure 13-19.-REJECTED label and tag.
instrument and all other servicing labels are removed. In addition to the REJECTED label, a REJECTED tag, giving the reason for rejection, is attached to the instrument. This rejection is also entered onto the MEASURE format of the instrument. The REJECTED label and tag remain on the instrument until it is repaired and recalibrated. The instrument should not be used while bearing a REJECTED label.