Grade/Speed Retard Chart - Komatsu 930E-4SE Operation & Maintenance Manual

Operator Cab And Controls - Section 32
Page 32-4
GRADE/SPEED CHART
Grade/speed chart (8, Figure 32-1 and shown below)
provides the recommended MAXIMUM retarding
limits at various truck speeds and grades with a fully
loaded truck.
This decal in the truck may differ from the decal
below due to optional truck equipment such as:
wheel motor drive train ratios, retarder grids, tire
sizes, etc. Always refer to this decal in the operator's
cab and follow these recommendations for truck
operation.
The operator should refer to this chart before
descending any grade with a loaded truck. Proper
use of dynamic retarding will maintain a safe speed.
Two speed lists are provided, one for continuous
retarding, and the second for short term retarding.
Both lists are matched to the truck at maximum
Gross Vehicle Weight (GVW). The two ratings are
guidelines for proper usage of the retard function on
downhill grades.
The "short term" numbers listed on the chart indicate
the combination of speeds and grades which the
vehicle can safely negotiate for a short duration
before system components reach the maximum
allowable temperature during retarding. These
speeds are faster than the "continuous" values,
reflecting the short term thermal capacity of various
system components.
NOTE: The "short term" rating will successfully
accommodate most downhill loaded hauls.
If the vehicle is operated at "short term" grade and
speed limits for a period of time, it is possible to
reach the thermal capacity of the drive system
components. The Propulsion System Controller
(PSC) will then gradually reduce the retarding effort
from "short term" to "continuous". The "retard @
continuous" indicator light will flash for 15 seconds,
then illuminate steadily alerting the operator of the
reduction in retarding performance and the need for
a reduction in speed. The operator must control the
speed of the truck in accordance to the "continuous
speeds" on the grade/speed chart. The operator
must use the service brakes to quickly slow the
truck to the maximum "continuous" retarding limits
(or less) based on the grade the truck is currently on.
Do not LIGHTLY apply the service brakes when
attempting to slow the truck on a downhill grade.
Overheating of the brakes will result. Apply the
brakes (within safe limits for road conditions) in
order to quickly slow the truck to maximum
"continuous" retarding limits or less.
The "continuous" numbers on the chart indicate the
combination of speeds and grades which the vehicle
can safely negotiate for unlimited time or distance
during retarding.
DO NOT exceed these recommended MAXIMUM
speeds when descending grades with a loaded truck.
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