Environmental Engineering Reference
In-Depth Information
Ta b l e 2 . 1 0
Asymmetric Multiplier
A
deg
AM
0
1.00
15
0.95
30
0.90
45
0.86
60
0.81
75
0.76
90
0.71
105
0.66
120
0.62
135
0.57
>
135
0.00
minimal risk and required no further analysis (although continuous monitoring
would be recommended in case task conditions changed). The revised NIOSH
guide (Waters et al. 1994, p. 35) stated that job risk increased as the RWL
increased, and that “nearly all workers will be at an increased risk of work-related
injury when performing highly stressful lifting tasks (i.e., lifting tasks that would
exceed a LI of 3.0).” Since the MPL was calculated to be three times the AL
and the LI range of 1 to 3, the parallels can be seen between the original and
the revised lifting guides.
To date, NIOSH has not presented any further revisions to the revised lift-
ing guide (Waters et. al. 1994). Therefore, the revised guide represents the best
analytical tool for the ergonomic evaluation of manual materials handling tasks.
The
Applications Manual for the Revised NIOSH Lifting Equation
(Waters et al.
1994) goes into significantly more detail in the background and calculations for
the revised guide and should serve as a reference to the ergonomist conducting
manual materials handling analyses. The manual provides numerous examples
and provides details regarding jobs involving multiple lifting tasks (i.e., man-
ual palletizing or depalletizing, where the objects being handled are stacked on
multiple layers, so the
H
and
V
values change for each row and layer).
Commercial software packages are available that can perform the calculations.
However, as with any software package, the analyst should validate and verify
the software before making recommendations based on the software analysis.
2.4.6 What about Nonlifting Manual Materials Handling Tasks?
Lifting is the most prevalent manual materials handling task. As such, it has
received the most attention by NIOSH and researchers. However, there are many
additional materials handling activities that can lead to worker injuries. NIOSH
incorporated
lowering
into its analysis in the revised lifting equation by simply
stating that lowering activities could be analyzed as lifting activities, which is a
Search WWH ::
Custom Search