ENM 426

Homework #4 Solution

2. An assembly worker is required to reach out and lift coils from an incoming conveyor and then places the coils on a workbench to complete preparation work on the coil as shown in the figures with recorded task variables below.

Significant control of the object is required at the destination. The coil is lifted by several wires which make it difficult to power grip and handle. The frequency is 0.5 lifts per minute and duration of lift is 2-8 hours. The load weight is 20 lbs.

a) Calculate the RWL for the task performed. Interpret the result.

b) Is improvement required? Redesign the task if necessary. Calculate the new RWL after improvement according to your redesign suggestions.

Interpret all results.

Solution:

a) RWL= LC x HM x VM x DM x AM x CM x FM

RWL origin = 51 x 0.40 x 0.87 x 1 x 1 x 0.90 x0.81 = 12.94 lb(s)

RWL destination= 51 x 1 x 0.90 x 1 x1 x0.90 x0.81 =33.46 lb(s)

Overall risk of task

LI= 20 / 12.94 = 1.55 > 1 the task is dangerous for worker health. It causes WMSDs.

b) Yes, since the overall risk of task lifting index value LI > 1 and the RWL at origin is smaller than the actual load weight (20 lb(s)) so the task should be redesigned. Besides, at destination part, the LI < 1 (RWL at destination is larger than the actual load weight). So, the task should be redesigned at origin.

Many suggestions can be provided based on NIOSH redesign suggestion principles that we discussed and ordered in the class.

One of suggestion is to reduce horizontal distance from 25 inch to 12 inch. After redesign, HM value increases from 0.40 to 0.83. RWLorigin=26.85 lb(s). LI = 0.74 < 1.