MIL-PRF-21038F
3.21 Marking. Transformers shall be marked with the military PIN, manufacturer's PIN, code symbol,
terminal identification (terminals shall be identified by appropriate numbers unless otherwise specified (see 3.1),
and date code in accordance with MIL-STD-1285, method 1. The marking may be applied to more than one
side of the case if the required marking necessitates more space than is available on the one side. Where the
surface areas are insufficient for all of the required information, as many as possible of the markings shall be
applied using the order of priority as listed above. Markings shall remain legible after all tests.
3.22 Workmanship. Transformers shall be processed in such a manner as to be uniform in quality and shall
meet the requirements of this specification and be free from any defects that will affect life and serviceability.
4. VERIFICATION
4.1 Classification of inspections. The inspection requirements specified herein are classified as follows:
a.
Qualification inspection (see 4.4).
b.
Retention of qualification (see 4.5).
c.
Conformance inspection (see 4.6)
4.2 Test equipment and inspection facilities. Test and measuring equipment and inspection facilities of
sufficient accuracy, to permit performance of the required inspection shall be established and maintained by the
contractor. The establishment and maintenance of a calibration system to control the accuracy of the
measuring and test equipment shall be in accordance with ANSI/NSCL Z540-1, ISO 10012-1 or an equivalent
system approved by the qualifying activity.
4.3 Inspection conditions. Unless specified herein, all inspections shall be performed in accordance with the
test conditions specified in the "GENERAL REQUIREMENTS" of MIL-STD-202.
4.3.1 Test frequency. When a nominal test frequency is specified herein, the frequency used shall be within
± 2 percent of the nominal value.
4.4 Qualification inspection. Qualification inspection shall be performed at a laboratory acceptable to the
Government on sample units produced with equipment and procedures normally used in production.
4.4.1 Sample size. The number of sample units comprising a sample of transformers to be submitted for
qualification inspection shall be as specified in the appendix to this specification.
4.4.2 Test routine. Samples shall be subjected to the qualification inspection specified in table I in the order
shown.
4.4.3 Failures. One or more failures shall be cause for refusal to grant qualification approval.
4.4.4 Qualification by similarity. Qualification by similarity for qualification of similar transformer types is
specified in the appendix. The manufacturer also has the option of recommending additional qualification by
similarity proposals for approval by the qualifying activity.
4.5 Retention of qualification. To retain qualification, the manufacturer shall provide verification to the
qualifying activity of the following items every 12 months:
a.
Design of the transformer has not changed.
b.
Conformance inspections (e.g., group A and group B) have been performed on inspection lots supplied
to the requirements of this specification.
c.
The manufacturer retains the capability to manufacture and test transformers to this specification.
In the event that no production has occurred in this period, the manufacturer shall verify to the qualifying activity
that the capability to manufacture and test the QPL transformer still exists and that the manufacturer wants to
remain on the QPL.
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