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PTI INVOLVEMENT
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During 1982, Powder Technology
Inc. (PTI) began production of fine and coarse test
dusts. PTI obtained raw material from the same Arizona
supplier used by AC Spark Plug to avoid chemical composition
differences. PTI processed test dust by using jet milling
and air classification to control particle size. In
1982 the published SAE J726 Specification described
fine and coarse test dust using the Roller Table. PTI
therefore began production of SAE Fine and Coarse Test
Dusts using particle size limits specified by the Roller
Table and a Coulter Counter Model TAII instrument as
means of particle size measurement.
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During the following decade,
popularity of PTI produced test dusts grew due to product
consistency, lower cost, and immediate availability.
Some test dust users reported differences in testing
performance when comparing AC Spark Plug and PTI produced
test dusts.
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A task force to investigate differences
between PTI and AC Spark Plug produced test dusts was
formed by the SAE Air Filter Test Code Subcommittee.
A report submitted by the task force dated June 1988
compared particle size of three samples each of AC
Spark Plug Fine Test Dust, AC Spark Plug Coarse Test
Dust, PTI Fine Test Dust, and PTI Coarse Test Dust.
Several samples were analyzed by PTI using a Coulter
Counter TAII instrument. The following table compares
differential content of PTI Test Dusts with AC Spark
Plug Test Dusts. Numbers below are expressed in percent
by volume.
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AC
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PTI
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Category
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AC
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PTI
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Coarse
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Coarse
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Difference
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(microns)
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Fine
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Fine
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Difference
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6.4
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5.3
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-1.1
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0 - 2.5
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20.0
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19.7
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-0.3
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11.9
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11.5
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-0.4
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0 - 5.0
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34.0
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37.3
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+3.3
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8.7
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11.6
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+2.9
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5 - 10.0
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16.7
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18.2
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+1.5
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14.6
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14.9
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+0.3
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10 - 20.0
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18.6
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17.7
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-0.9
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23.2
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22.4
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-0.8
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20 - 40.0
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19.9
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16.6
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-2.3
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26.4
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28.7
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+2.3
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40 - 80.0
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11.0
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9.9
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-1.1
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15.2
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10.9
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-4.3
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80.0+
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0.7
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0.4
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-0.3
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Although no formally conducted performance
comparison effort was organized, controversy involving
differences in performance of test dusts manufactured
by AC Spark Plug and PTI continued until March of 1992
when AC Spark Plug informed it's customers and SAE
Committees it would cease production of test dust.
AC Spark Plug indicated the equipment used to manufacture
test dust was wearing out and continuing formulation
of test dusts was not profitable.
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AC SPARK PLUG CEASES PRODUCTION
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With a backlog of orders and inability
to produce test dust, AC Spark Plug hired PTI to produce
several batches of fine and coarse test dust to satisfy
existing orders. AC Spark Plug asked PTI to produce
test dusts that would comply with AC Spark Plug particle
size specification using the Leeds & Northrup Microtrac
analyzer AC Spark Plug had been using since 1979. Three
batches of AC Spark Plug Fine Test Dust, numbers 4396,
4401, and 4414, were produced. Three batches of AC
Spark Plug Coarse Test Dust, numbers 4385, 4386, and
4412, were produced. Due to differences in production
methods, the six batches of fine and coarse test dust
listed above should be expected to perform differently
than prior test dust batches produced by either AC
Spark Plug or Powder Technology Inc.
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