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IE 553 Engineering of Human Work Dr. Andris Freivalds Class #14

IE 553 Engineering of Human Work Dr. Andris Freivalds Class #14. IE 553 Engineering of Human Work Dr. Andris Freivalds Class #14. Manual Materials Handling Limits (Ch. 8). 60% low back pain → overexertion LBP & lost time → > ⅔ out Overexertion → ¼ occupational injuries

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IE 553 Engineering of Human Work Dr. Andris Freivalds Class #14

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  1. IE 553 Engineering of Human Work Dr. Andris Freivalds Class #14 IE 553

  2. IE 553 Engineering of Human Work Dr. Andris Freivalds Class #14 IE 553

  3. Manual Materials Handling Limits (Ch. 8) • 60% low back pain → overexertion • LBP & lost time → > ⅔ out • Overexertion → ¼ occupational injuries • ⅔ overexertion due to lifting • NIOSH (1981, rev 1991) lifting guidelines • Epidemiology of injuries • Biomechanical loading • Physiological loading • Psychophysical concepts IE 553

  4. Conflicting Guidelines Karwowski (1983) Jung & Freivalds (1991) IE 553

  5. 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 IE 553

  6. RWL Limitations • Smooth lifting, no jerks • Objects of moderate width • Hand separation < 75 cm • Unrestricted lifting posture • Good coupling (hands and feet) • Reasonable temperatures IE 553

  7. RWL = LCxHMxVMxDMxAMxFMxCM • LC = 51 lbs • HM = 10/H (10≤H≤25) • VM = 1 – 0.0075|V – 30| (0≤V≤70) • DM = 0.82 + 1.8/D (10≤D≤70) • AM = 1 – 0.0032A (0≤A≤135) • FM = from table • CM = from table IE 553

  8. H, V, D coordinates IE 553

  9. Frequency Multiplier IE 553

  10. Work Duration Three categories: • Work ≤ 1 hour, rest = 1.2 x work • 1 < Work ≤ 2 hours, rest = 0.3 x work • 2 < Work ≤ 8 hours IE 553

  11. Coupling Multiplier IE 553

  12. 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 IE 553

  13. Ex. Lifting Box into Car RWLor = 51(10/H)(1-.0075|V-30|)(.82+1.8/D)(1-.0032A)FMxCM RWLdest = 51(10/H)(1-.0075|V-30|)(.82+1.8/D)(1-.0032A)FMxCM IE 553

  14. Effect of Multipliers - 1 IE 553

  15. Effect of Multipliers - 2 IE 553

  16. Effect of Multipliers - 3 Frequency Multiplier IE 553

  17. Multi-Task Lifting • Multi-task lifting ↑ LI over single-task • ↑ LI from worst case, as marginal effect • Calculate Composite LI (CLI) from: • Single task RWL (STRWL) • Frequency independent RWL (FIRWL), FM=1 • Single task LI (STLI) • Frequency independent LI (FILI) • CLI = STLI1 + FILI2x(1/FM1,2 – 1/FM1) IE 553

  18. Ex. Multi-Task Lifting IE 553 CLI = 1.6 + 1.0x(1/.88–1/.94) + 0.67x(1/.7–1/.88) = 1.9

  19. Frequency Multiplier IE 553

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