My Class

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IE 553 Engineering of Human Work Dr. Andris
Freivalds Class 14
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IE 553 Engineering of Human Work Dr. Andris
Freivalds Class 14
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Manual Materials Handling Limits (Ch. 8)

• 60 low back pain ? overexertion
• LBP lost time ? gt ? out
• Overexertion ? ¼ occupational injuries
• ? overexertion due to lifting
• NIOSH (1981, rev 1991) lifting guidelines
• Epidemiology of injuries
• Biomechanical loading
• Physiological loading
• Psychophysical concepts

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Conflicting Guidelines
Karwowski (1983)
Jung Freivalds (1991)
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Recommended Weight Limit (RWL)

• RWL based on an optimum weight
• With adjustments for task variables
• Resulting in stress limits of
• Fcomp 3,400 N
• Emax 4.7 kcal/min
• Strength requirement achieved by
• 75 of women
• 99 of men
• 90 mixed population

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RWL Limitations

• Smooth lifting, no jerks
• Objects of moderate width
• Hand separation lt 75 cm
• Unrestricted lifting posture
• Good coupling (hands and feet)
• Reasonable temperatures

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RWL LCxHMxVMxDMxAMxFMxCM

• LC 51 lbs
• HM 10/H (10H25)
• VM 1 0.0075V 30 (0V70)
• DM 0.82 1.8/D (10D70)
• AM 1 0.0032A (0A135)
• FM from table
• CM from table

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H, V, D coordinates
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Frequency Multiplier
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Work Duration

• Three categories
• Work 1 hour, rest 1.2 x work
• 1 lt Work 2 hours, rest 0.3 x work
• 2 lt Work 8 hours

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Coupling Multiplier
Coupling Type Vlt30 V30
Good 1.00 1.00
Fair 0.95 1.00
Poor 0.90 0.90
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APPLICATION

• Lifting Index (LI) Load/RWL
• Measure of relative stress
• Compare jobs
• Always two RWL calculations
• 1) origin and 2) destination
• Smallest RWL counts
• Note 0 M 1