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Evaluation of Face Dust Concentrations at Mines Using Deep-Cutting Practices (Paperback)
Loot Price: R354
Discovery Miles 3 540
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Evaluation of Face Dust Concentrations at Mines Using Deep-Cutting Practices (Paperback)
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Loot Price R354
Discovery Miles 3 540
Expected to ship within 10 - 15 working days
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Dust surveys were conducted at six underground mines to determine
if deep-cut mining practices expose face workers to higher levels
of respirable dust by comparing levels during the first 20 ft of
advance (regular-cut depth) during the deep cut to levels during
the final 10 to 20 ft of advance (deep-cut depth). The studies were
conducted at mines where the Mine Safety and Health Administration
(MSHA) had approved an extended curtain setback distance with
operation of a flooded-bed scrubber to permit taking deep cuts of
up to 40 ft. In general, all of the selected mines exercised good
dust control practices by maintaining water sprays, scrubber
airflows, proper curtain setback distances and providing sufficient
airflow to the active faces. These practices minimized variability
in dust levels related to factors other than the depth of cut. To
ensure proper scrubber functioning, the scrubber screen was
back-flushed before commencing each cut. Both exhausting and
blowing face ventilation configurations were studied. All of the
operations surveyed for this study were able to successfully
implement deep-cutting methods without significantly increasing the
dust exposures of face workers during the cutting and bolting
cycles. For exhausting face ventilation, field data indicate that
scrubber airflow is the most important factor for controlling dust.
Clogging of the scrubber screen can result in lower airflows;
therefore, the screen must be periodically tapped and back-flushed.
Data collected for this study indicate that 20-mesh screens should
be cleaned for every 40 ft of advance because 22% of the deep-cut
sequences surveyed for this study experienced a 20% to 35% decrease
in scrubber airflow over the course of the cut. For blowing face
ventilation, field and laboratory data indicate that maintaining a
proper curtain-to-scrubber airflow ratio of 1.0 and a curtain
setback distance that allows the miner operator to stand at the
mouth of the curtain helps control dust. Curtain airflows should be
measured before activation of the scrubber regardless of
ventilation type (exhausting or blowing) to avoid erroneously
overinflating the ratio. The curtain setback variance should be
greater than the maximum cutting depth to allow miner operators to
maintain their position at the mouth of the curtain when the miner
is fully extended into the cut. Greater curtain setback distances
associated with deep-cutting methods may result in cuts that do not
require ventilation curtain, such as the initial heading
developments beyond the last open crosscut. For these cuts, dust
levels were generally lower during development of deep cuts when
compared to regular cuts. However, adequate ventilation of cuts
without ventilation curtain is dependent on a properly functioning
scrubber. Dust levels on the bolting faces did not appear to be
affected by the longer cycles associated with deep-cut mining
practices when curtain airflow was measureable and the curtain was
periodically advanced in sync with the bolting machine.
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