The original equipment manufacturer (OEM) of the shovel, Hitachi, has an onboard data
logging system called the machine information center (MIC) that logs, among other
things, engine running time, front end operating time*, travel time, and engine load factor.
MIC data from January 1 to July 12, 2010 was downloaded from the shovel for this
study. After careful review, the research team used shift averages of engine running time,
front end operating time, travel time, and engine load factor for data analysis. Since MIC
does not log fuel consumed, Hitachi data on fuel consumption and load factors were used
to establish the relationships described in Equation (1), which relates engine load factor
to fuel consumption for the two shovel models analyzed in this study.
EX1900 fuel consumption [gals/hr] = 52.971 Load factor 0.0133
EX2500 fuel consumption [gals/hr] = 71.304 Load factor 0.0059
(1)
Additionally, researchers conducted time and motion studies of the shovel loading
operation to obtain cycle times. Shovel productivity was obtained by correlating time
stamps on the data with the truck OEM data logging system (discussed in the next
section).
Statistical correlation analysis, at 95% confidence, was used to examine the correlation
between load factor (a proxy for fuel consumption) and engine running time, front end
operating time, front end utilization (ratio of time the front end was active in the shift),
travel time, and ratio of time the shovel traveled in the shift. The decision to use time
ratios in correlation analysis was to enable extension of results to different shift lengths.