MIL-PRF-24790A (SH)
4.6.2 Packing and fluid compatibility. Packing shall be immersed in the control fluids specified in table I for
the applicable type & class for 1000 hours at ambient temperature (see 3.3.2).
4.6.2.1 Flexibility and fluid compatibility. The flexibility test (see 4.6.1) shall be performed after immersion
and the results compared to pre-immersion tests (see 3.3.2.1).
4.6.2.2 Dimensional stability and fluid compatibility. Prior to immersion in the control fluids, cross-
sectional measurements shall be taken along a 3-inch length of packing and averaged. Three additional cross-
sectional measurements shall be made at 90 degrees to the first measurements and averaged. Following the 1000-
hour immersion, the same measurements shall again be made. Pre- and post-immersion averaged cross-sectional
measurements shall be compared for swelling or shrinkage (see 3.3.2.2).
4.6.2.3 Tensile strength and fluid compatibility. Tensile strength shall be measured in accordance with
method A of ASTM F 152. Tensile strength of the individual packing strands shall be measured rather than the
tensile strength of the cross-section of the braided packing material. Packing shall be unbraided, with three 6-inch
long strands removed from the braid for each of the control fluids for which the material is to be tested. Three
strands shall be used for reference. The tensile strength of the immersed strands shall then be compared to that of
the reference strands (average of 3 breaks)(see 3.3.2.3).
4.6.3 Thermogravimetric analyzer (TGA) analysis. Use ASTM D 3850 standard test method (see 3.3.3).
4.6.4 Detrimental materials. Acceptable test methods and procedures are provided as guidance; however,
testing methods are not limited to these exact procedures. Any standard test method to determine total
concentrations may be used, as long as each element in all forms can be determined to levels below 250 (ppm) (see
3.4).
4.6.4.1 Halogen concentration. Any standard test method may be used (suggested: use oxygen combustion
bomb along with ASTM D 129 and ASTM E 144, ignite approximately 0.5 grams of the sample under 30
atmospheres of oxygen pressure and dilute to a final volume of 100 mL with the carbonate/bicarbonate buffer
required for analysis by ion chromatography) (see 3.4.1).
4.6.4.1.1 500 ºF leach test.
(a)
Cut two specimens from the selected sample, weighing approximately 20 grams, record their exact weight
to 0.1 gram, and identify them as specimens A and B. This identification shall be maintained throughout
the test.
(b)
Each test specimen shall be transferred to a suitable pressure vessel (parr reaction vessel, or equivalent),
covered with enough distilled water to obtain a final volume of 500 mL and simmered at 500 ± 10 ºF for a
minimum of 6 hours. The leach water shall then be separated by filtration and the filter rinsed. A control
filtrate shall be run using similarly cleaned equipment and distilled water from the same source.
(c)
Using aliquots from the control filtrate and filtrates A and B, the concentration of bromide, chloride, and
fluoride ions in each filtrate shall be determined by an appropriate method of ASTM D 1246, ASTM D
512, and ASTM D 1179, respectively, or by equivalent methods. The concentration of water-leachable
halide in the material shall be determined as follows:
Bromide, Chloride, or Fluoride, ug/g (ppm) = C multiplied by 500/M
Where:
C=
bromide, chloride, or fluoride concentration of filtrate, in milligrams per liter; and
M=
grams of the test specimen, prepared per (a) above.
(d)
The total leachable halogen concentration is the sum of leachable bromide, chloride and fluoride
concentrations. The halide concentrations for filtrates A and B shall be corrected by the results of the
control filtrate.
4.6.4.2 Total sulfur concentration. Any standard test method may be used (see 3.4.2).
4.6.4.3 Other detrimental materials. Any standard test method may be used (suggested: use oxygen
combustion bomb digestions for metal analysis; analyze digestates of cadmium and lead by direct aspiration atomic
absorption spectroscopy) (see 3.4.4).
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