Environmental Engineering Reference
In-Depth Information
1.0
0.9
Occasional,
bench height and above
0.8
0.7
0.6
Continuous,
bench height and above
occasional,
low lifting
0.5
0.4
0.3
Continuous,
low lifting
0.2
0.1
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18
Average Lifts per Minute
Figure 2.4
Frequency factor graph
MPL
=
3
(
AL
)
(4)
See Figures 2.1, 2.2, 2.3, and 2.4.
2.3
Example Using 1981 NIOSH Guide
For two hours per day, an employee lifts objects off a feed conveyor and places
them in a packing carton after a visual inspection. The objects are 25 cm cubes
and arrive at a rate of four per minute. The conveyor is 70 cm high and the
bottom of the packing station is 80 cm from the floor. Assume that the objects
on the conveyor are very close to the person lifting them (assume that
H
is
15
W/
2).
Identify the variables:
Load constant
+
=
40 kg
H
=
15
+
W/
2
=
15
+
25
/
2
=
27
.
5cm
V
=
70 cm
D
10
However, based on the limitation for
D
,
D
=
(
80
−
70
)
=
=
25 cm for the calculation:
F
=
4 lifts/minute
F
max
12 lifts/min
AL
(
kg
)
=
=
40
(
15
/
27
.
5
)(
1
−
0
.
004
|
70
−
75
|
)(
0
.
7
+
7
.
5
/
25
)(
1
−
4
/
12
)
AL
(
kg
)
=
40
(
0
.
545
)(
0
.
98
)(
1
.
0
)(
0
.
667
)
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