MIL-PRF-9954D
4.3 Sampling For Quality Conformance Test. For purposes of inspection, a lot shall consist
of media of the same chemical composition and size. If production is continuous, a lot shall be
the product of not more than eight hours of continuous production and it is not to exceed 20,000
pounds. Alternatively, Statistical Process Control Methods may be used to monitor the quality of
the product so that it meets the requirements of the applicable detail specification. Two
representative samples of the 1500 grams each shall be selected from separate containers chosen
at random. Each sample shall be used in the following tests.
4.4 Test Methods.
4.4.1 Silica Content. The silica content shall be determined in accordance with ASTM
Method C 169 or a generally accepted instrumental method with traceable standards.
4.4.2 Scored, Broken, Un-fused Angular Particles and Roundness. For each representative
sample, three random samples will be taken and an actual count of a field of approximately 100
beads each. A microscope, or similar magnification device with 20X magnification or greater,
shall be used to make the count. The average count of each specimen shall be reported as
percent true spheres. An automated method is acceptable provided it correlates to the optical
method or a generally accepted instrumental method with traceable standards.
4.4.3 Coating. For each representative sample, the test for silicone coating shall be performed as
follows: slowly pour 50 grams of the glass beads into a 250 ml beaker containing 200 ml of
distilled water. Any air entrainment causing the beads to coagulate into discrete lumps is an
indication of silicone. The glass beads should disperse when poured into the water; however, a
small number of beads floating on the water are permissible.
4.4.4 Specific Gravity. A 60 gram sample of glass beads, previously dried, shall be placed in a
100 ml graduated cylinder containing 50 mls of distilled water. The total volume, minus 50, will
give the volume or the beads. The specific gravity shall be computed as follows or with a
generally accepted instrumental method with traceable standards.
Sp. Gr. = Weight of sample (grams)
Water level (mls) after
Addition of Sample -50 mls
4.4.5 Magnetic Iron Particles. For each representative sample, approximately 500 grams of
beads shall be obtained per Section 4.3 and shall be sprinkled on an inclined magnetic plane
consisting of four 10,000 gauss strength magnets. The magnets shall be centered directly behind
the plane as depicted in Figure 1. After sprinkling the glass beads, carefully brush any magnetic
particles into a tarred, weighing dish. The glass beads are to be re-sprinkled until no magnetic
particles are retained on the magnetic plane. When no more particles are visible on the magnetic
plane, weigh the magnetic iron particles and compute the percentage. No more than 0.1% by
weight of free magnetic iron particles shall be permissible.
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