Elements of Ergonomics Programs A Primer Based on Workplace Evaluations of Musculoskeletal Disorders

NIOSH researchers conducted initial and follow-up evaluations of musculoskeletal disorders of the upper limbs and back at a motorcycle manufacturing company. The objectives of this evaluation were to identify the job tasks in the flywheel milling department thought to cause musculoskeletal injuries and to provide recommendations to decrease and prevent such injuries. NIOSH researchers reviewed OSHA Form 200 logs and workers' compensation data and conducted an ergonomic evaluation of four jobs in this department (two flywheel milling jobs, one flywheel truing job, and one flywheel balancing job). Data gathered on the initial site visit in the flywheel milling area showed that repeated manual transport, placement, and removal of the flywheels between milling processes resulted in more than 28,000 lb handled per 8-hour shift. In addition, repeated use of a handheld power grinder to remove metal burrs from milled flywheels proved to be inefficient and presented other accident risks. Analysis of data from the flywheel truing job showed that impact forces from the 5-lb brass hammer repeatedly striking the flywheel ranged from 25,000 to 92,000 lb. Using the NIOSH 1993 lifting equation to analyze the flywheel balancing job showed potential risk for back injury. NIOSH recommended engineering controls to reduce risk factors for musculoskeletal disorders, and the company effected a number of them through establishment of a management/labor ergonomic committee. The engineering controls included the following:

• Upgrading forging and milling machine processes and improving product flow to reduce the burden of flywheel handling from 28,000 to 17,500 lb per 8-hour shift

• Installing a customized 40-ton press to eliminate the use of brass hammers for truing the flywheels

• Using an overhead lift to eliminate manual handling of the 35-lb assembled flywheel unit, further reducing the total weight that had to be handled each day

During a 5-year period from 1989 through 1993, the efforts of the plant's management, engineers, and workers resulted in a reduction of WMSDs involving lost or restricted workdays from 27.6 per 100 workers in 1989 to 12.5 per 100 workers in 1993. The severity of musculoskeletal disorders decreased from 610 lost or restricted-activity workdays per 100 workers in 1989 to 190 workdays in 1993 [HETA 91-0208-2422].