Slide 1Slide 2Manual Materials Handling Limits (Ch. 8)Conflicting GuidelinesRecommended Weight Limit (RWL)RWL LimitationsRWL = LCxHMxVMxDMxAMxFMxCMH, V, D coordinatesFrequency MultiplierWork DurationCoupling MultiplierAPPLICATIONIE 5531IE 553 Engineering of Human WorkDr. Andris FreivaldsClass #14IE 5532IE 553 Engineering of Human WorkDr. Andris FreivaldsClass #14IE 5533Manual Materials Handling Limits (Ch. 8)•60% low back pain → overexertion•LBP & lost time → > out⅔•Overexertion → ¼ occupational injuries• ⅔ overexertion due to lifting•NIOSH (1981, rev 1991) lifting guidelines–Epidemiology of injuries–Biomechanical loading–Physiological loading–Psychophysical conceptsIE 5534Conflicting GuidelinesKarwowski (1983)Jung & Freivalds (1991)IE 5535Recommended 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 populationIE 5536RWL Limitations•Smooth lifting, no jerks•Objects of moderate width •Hand separation < 75 cm•Unrestricted lifting posture•Good coupling (hands and feet)•Reasonable temperaturesIE 5537RWL = 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 tableIE 5538H, V, D coordinatesIE 5539Frequency MultiplierIE 55310Work DurationThree categories:1) Work ≤ 1 hour, rest = 1.2 x work2) 1 < Work ≤ 2 hours, rest = 0.3 x work3) 2 < Work ≤ 8 hoursIE 55311Coupling MultiplierCoupling TypeV<30 V≥30Good 1.00 1.00Fair 0.95 1.00Poor 0.90 0.90IE 55312APPLICATION•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 ≤
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