Civil Engineering Reference
In-Depth Information
hand couplings, or unstable footing. Professional judgment should be used to determine weight limits
under these conditions.
If any of the conditions in the following list are present, then professional judgment should be used to
reduce weight limits below those recommended in the TLVs:
.
Lifting at a frequency higher than 360 lifts per hour
.
Extended work shifts: lifting performed for longer than 8 h per day
.
High asymmetry: lifting more than 30
8
away from the sagittal plane
.
One-handed lifting
.
Lifting while seated or kneeling
.
High heat and humidity
.
Lifting unstable objects (e.g., liquids with shifting center of mass)
.
Poor hand coupling: lack of handles, cut-outs, or other grasping points
.
Unstable footing (e.g., inability to support the body with both feet while standing)
The lifting TLV does incorporate relatively complex data into a format that is quick, easy to use, and easy
to interpret; hence, it is a very useful tool to quickly assess many lifting tasks. The results can also direct
the user to job redesign strategies. For example, if the lifting conditions exceed the TLV, the user can then
find cells in the table that would not exceed the TLV, and then redesign the job accordingly. Since the
results are presented in a straightforward, intuitive format, the TLV also can be useful when requesting
support from management for resources to institute ergonomic interventions.
50.3.2 Instructions for Determining the Lifting TLV
1. Understand the limitations and basis of the TLVs
2. Determine if the task duration is less than or equal to 2 h per day or greater than 2 h per day
3. Determine the lifting frequency as the number of lifts a worker performs per hour
4. Use the TLV table that corresponds to the duration and lifting frequency of the task (Table 50.3
can be used to determine the appropriate TLV table given the frequency and the duration.)
5. Determine the lifting zone height based on the location of the hands at the beginning of the lift
(Figure 50.2.)
6. Determine the horizontal location of the lift by measuring the horizontal distance from the
midpoint between the inner ankle bones to the midpoint between the hands at the beginning
of the lift
7. Determine the TLV for the lifting task, as displayed in the table cell that corresponds to the lifting
zone and horizontal distance in the appropriate table, based upon frequency and duration
50.3.3 If a Lifting Task Exceeds the TLV
If the weight being lifted in the task exceeds the TLV, then changes must be made to the task to ensure that
the weight is within the limit. Factors such as the characteristics of the task, type of industry, and
TABLE 50.3 TLV Table Corresponding to Specified Levels of Lifting
Frequency and Lifting Duration
Duration of Task per day
Lifts per hour
2h
.
2h
60
Table 50.4
12
Table 50.4
.
12 and 30
Table 50.5
.
60 and 360
Table 50.6
.
30 and 360
Table 50.6
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