40 • ROCK products • March 2018 www.rockproducts.com
Charleston Stone
days. According to Tarble, the reduction in downtime is
expected to be the most beneficial outcome to result from
the conversion.
13
Mike Vaughn, who manages the operation at the quarry,
estimates that the cost to Charleston Stone is "$2,000 to
$3,000 per hour in maintenance performed, wages, and
lost productivity" when the primary crusher is down.
14
The company was experiencing 80 to 120 hours of down-
time annually, so eliminating this could save $160,000 to
$360,000 each year.
Product quality is critical for all manufacturing processes
and was an important factor in the decision to convert to an
electric rock crusher. The impact crusher is very effective
at separating the shale from the limestone in the rock. The
screening process is then able to collect more of the high
quality limestone out of the raw material.
Diesel prices have been relatively low in the last few years,
but quite volatile over the last decade. Figure 7 shows retail
diesel prices (including road tax) over the last decade.
15
Charleston Stone does not have to pay road tax for the
diesel used in the crusher, but would still experience the
same volatility.
FIGURE 6: Mike Vaughn of Charleston Stone shows
electrical connections to Sam Adair of CMEC.