The following NIOSH Lifting Equation Example is from the NIOSH Lifting Equation Applications Manual and has been adapted to show the proper use of the NIOSH Lifting Equation inside the ErgoPlus Platform.
In addition, this example shows how this tool can be used to evaluate body mechanics recommendations and ergonomic redesign suggestions.
To help you follow along, here are links to download our free guides to recommended ergonomic assessment tools and to create a free ErgoPlus Platform account to use the NIOSH Lifting Equation software tool inside.
Now let’s get to work on the example:
Job Description
This job consists of a worker inspecting compact containers for damage on a low shelf, and then lifting them with both hands directly in front of the body from shelf 1 to shelf 2 at a rate of 3 per minute for a duration of 45 minutes. For this analysis, assume that (1) the worker cannot take a step forward when placing the object at the destination, due to the bottom shelf, and (2) significant control of the object is required at the destination. The containers are of optimal design, but without handles.
Job Analysis
The task variable data are measured and recorded using the ErgoPlus Platform:
To conduct ergonomic assessments using the ErgoPlus Platform, you can create a free account here.
Data Collection
The horizontal distance at the origin of the lift is 10 inches and the horizontal distance at the destination of the lift is 20 inches. The height of shelf one is 22 inches and the height of shelf two is 59 inches. Since the container is of optimal design, but does not have handles or handhold cutouts, the coupling is defined as “fair” (i.e., C=2). No asymmetric lifting is involved (i.e., A = 0). Since the lifting pattern is continuous over the 45-minute work session, the lifting frequency is not adjusted. Significant control of the load is required at the destination of the lift. Therefore, the RWL is computed at both the origin and the destination of the lift.
Hazard Assessment
The RWL for this activity is 34.8 lb. at the origin and 15.3 lb. at the destination. The weight to be lifted (26 lb.) is less than the RWL at the origin (34.8 lb.) but greater than the RWL at the destination (15.3 lb.). The LI is 26/34.8 is .75 at the origin, and the LI is 26/15.3 or 1.70 at the destination. These values indicate that the destination of the lift is more stressful than the origin, and that some healthy workers would find this task physically stressful.
Redesign Suggestions
The multipliers with the smallest magnitude (i.e., those that provide the greatest penalties) are .50 for the HM at the destination, .78 for the VM, .87 for the DM, and .88 for the FM at the destination of the lift. The following job modifications are suggested:
- Bring the destination point closer to the worker or modify the task to eliminate significant control at the destination to increase the HM value.
- Lower the height of shelf 2 to increase the VM value.
- Decrease the vertical distance between origin and destination of lift to increase the DM value.
- Reduce the lifting frequency rate to increase the FM value.
Comments
As the modified worksheet above shows, if the H is reduced to 14” and the destination V is lowered to 39”, the RWL would now be 27.7 lb. and the LI would be .94. This ergonomic design improvement would significantly lower the injury risk to healthy employees.
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