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|  MIL-T-18847C(AS)
4.6.2.3.4 Stringer discontinuity. A stringer discontinuity is defined,
for the purpose of x-ray interpretation, as a void, an oxide stringer, or a
series of voids and/or stringers in a linear distribution when the ratio of
the major dimension to the minor dimension of an individual discontinuity is
5:1 or greater. The stringer discontinuity shall be considered a single
stringer where the adjacent discontinuities are not separated by a length
equal to or greater than 15 percent of "T". A stringer discontinuity is
permissible if the summation of all connected, elongated, or aligned voids or
inclusions do not exceed a total area of 0.060 square inches in any 6.0 inch
length of weld and occurs in the weld bead reinforcement area (root and face).
4.6.2.3.5 Undercutting. Undercutting shall be cause for rejection if it
is in excess of 1/10 "T" in depth. Undercutting of any depth less than
1/10 "T" shall be not greater than one inch of weld length.
4.6.3 Internal surface conditioning. The cleanness of all tanks (see
3.13) shall be judged by a visual examination and wiping all accessible
suspect areas with a clean, white, lint free cloth. This examination shall be
made before liner proof pressure test.
4.6.4 Liner proof pressure test. All metal liners shall be proof pressure
tested for five minutes to the requirements of 3.14.6. There shall be no
leakage.
4.6.5 Tank liner diameter. While pressurized in accordance with 4.6.4,
the tank liner diameter shall be measured in four locations to verify
compliance to the applicable drawings. These measured dimensions shall be
recorded.
4.6.6 Liner preparation. All metallic liner materials abraided, cleaned,
etched, or primed for bonding or overwrap shall demonstrate that the surface
is clean by a water-break-free test using de-ionized water in accordance with
ASTM-F22.
4.6.7 Tank contour. The outside diameter of the tank liner shall be
measured for conformance with the appropriate drawing.
4.6.8 Composite construction.
4.6.8.1 Tank Iiner bond. Test specimens simulating tank materials,
construction, and surface preparation, and completed at the time of tank
winding and Identified with the tank and serial number, shall be tested to the
requirements of 3.14.7.
4.6.8.2 Filament winding inspection. The filament winding machinery and
process shall comply to the requirements of 3.14.8.1 and receive continuous
Inspection during the winding operation either by controlled operator
instructions or an attending qualified inspector. Cleanliness of the
atmosphere, machinery, and operator will be maintained. Any item previously
cleaned and prepared for bonding shall be handled with white throw away gloves
or clean rubber gloves. Any item being improperly handled or otherwise
contaminated shall be recleaned by the approved process cleaning requirement
(see 3.13).
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