Civil Engineering Reference
In-Depth Information
46.7.1.5 Comments
The horizontal distance (H) is a significant factor that may be difficult to reduce because the size of the
paper rolls may be fixed. Moreover, redesign of the machine may not be practical. Therefore, elimination
of the manual lifting component of the job may be more appropriate than job redesign.
46.7.2 Dish-Washing Machine Unloading, Example 2
46.7.2.1 Job Description
A worker manually lifts trays of clean dishes from a conveyor at the end of a dish-washing machine and
loads them on a cart as shown in Figure 46.9. The trays are filled with assorted dishes (e.g., glasses, plates,
bowls) and silverware. The job takes between 45 min and 1 h to complete, and the lifting frequency rate
averages 5 lifts
min. Workers usually twist to one side of their body to lift the trays (i.e., asymmetric lift)
and then rotate to the other side of their body to lower the trays to the cart in one smooth continuous
motion. The maximum amount of asymmetric twist varies between workers and within workers;
however, there is usually equal twist to either side. During the lift the worker may take a step toward
the cart. The trays have well designed handhold cutouts and are made of lightweight materials.
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46.7.2.2 Job Analysis
The task variable data are measured and recorded on the job analysis worksheet (Figure 46.10). At the
origin of the lift, the horizontal distance (H) is 20 in., the vertical distance (V) is 44 in., and the angle
of asymmetry (A)is30
. The trays
normally weigh from 5 to 20 lb, but for this example, assume that all of the trays weigh 20 lb.
Using Table 46.6, the coupling is classified as “good.” Significant control is required at the destination
of the lift. Using Table 46.5, the FM is determined to be 0.80. As shown in Figure 46.10, the RWL is 14.4 lb
at the origin and 13.3 lb at the destination.
8
. At the destination of the lift, H is 20 in., V is 7 in., and A is 30
8
46.7.2.3 Hazard Assessment
The weight to be lifted (20 lb) is greater than the RWL at both the origin and destination of the lift (14.4
and 13.3 lb, respectively). The LI at the origin is 20
14.4 or 1.4 and the LI at the destination is 1.5. These
results indicate that this lifting task would be stressful for some workers.
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44
INCHES
ORIGIN
30°
SAGITTAL LINE
DESTINATION
30°
7 INCHES
FIGURE 46.9 Dish-washing machine unloading, example 2.
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