Page 130 - Advances In Productive, Safe, and Responsible Coal Mining

114 Advances in Productive, Safe, and Responsible Coal Mining

The iPD system uses this method to continuously track the position of multiple miners
around the mining machine with a high degree of accuracy.
The achievable accuracy of the position triangulation is limited by the stability and
repeatability of magnetic readings. A given magnetic-field strength reading should be
associated with a distinct shell around the machine. However, normal variation in the
electromagnetic proximity system causes the same reading to be observed over a
range of distances at any given point on that shell. This variability is influenced by
several operational and environmental variables. NIOSH researchers quantified
iPD system accuracy in the laboratory by taking thousands of shell measurements
while varying these conditions, with variability of up to 12in. (30.5cm) observed.

7.5.2 Development of zones and selective shutdown

Once the position of a miner has been calculated, the iPD system provides protection
against striking and pinning accidents by disabling all machine motions that could
cause a collision between the machine and a miner. The decision of which machine
motions to disable is accomplished by comparing the calculated position of the miner
to a preprogrammed set of zones around the mining machine. Each of these zones is
associated with a set of potentially dangerous machine functions. When a person is
detected in a zone, the functions associated with that zone are disabled. For example,
the zone to the right of the conveyor boom would be associated with conveyor swing
right and all tram functions that would move the conveyor boom to the right. If a miner
were standing in this zone, these motions would be disabled, but the miner would still
be able to tram forward and run the cutter drum.
To gain insight into the safety potentially afforded by different proximity detection
zone configurations, NIOSH researchers conducted an analysis of 39 fatalities that
occurred between 1984 and 2015 in which a miner was struck or pinned by a contin-
uous mining machine in an underground US mine [17]. The objectives of this analysis
were to estimate the number of cases for which a proximity detection system may have
prevented the accident, and identify the potential safety benefits of iPD systems com-
pared to conventional proximity detection systems. Fatality investigation reports from
MSHA were reviewed and analyzed for each accident to determine whether a conven-
tional proximity or iPD system could have prevented the fatality.
Although it is mandated that all machine tram and conveyor boom functionality is
shut down when a miner enters any stop zone around a CMM, for the purposes of this
analysis, it was assumed that all machine functions would be shut down on a commer-
cial proximity detection system based on proximity detection manufacturer designs.
Additionally, it was assumed that iPD systems would selectively disable machine
functions as previously described. In considering conventional proximity detection,
it is assumed that all machine motion would be blocked when a miner is detected
in any stop zone, while iPD systems would selectively disable machine functions
as previously described.
Two iPD zone configurations were examined. Neither configuration is intended to
be a recommendation, but rather both are presented as examples for comparing factors
associated with establishing zone definitions. The first is shown in Fig. 7.7, and will be