1. IE 366 Chapter 13 Manual Handling

2. IE 366 Overview ● Background ● Manual handling variables ● Pushing and pulling ● Holding, Carrying ● NIOSH Lifting Equation ● Guidelines for manual handling

3. IE 366 Motivation ● 27% of all industrial injuries ● 670,000 injuries/yr in the United States ● 60% of all money spent on industrial injuries ● 93,000,000 lost workdays/yr

4. IE 366 Musculoskeletal Disorders of the Lower Back ● Anatomy – L5/S1 ● Problem – Low-back pain – Low-back impairment – Low-back disability – Low-back compensation ● Risk Factors – Individual physical factors, e.g., ● Weight ● Physique ● Gender – Task demand factors, e.g., ● Horizontal distance to load ● Posture ● Repetition – Environmental factors, e.g., ● Workplace design ● Slippery floors – Psychological factors, e.g., ● Depression ● Anxiety Load H

5. IE 366 Manual Handling Variables / Considerations ● Individual – Stronger usually better – But don’t exclude too many! ● Technique – Posture – Hand orientation – Foot position – Lift training ● Task – Object height – Ease of handling (shape, handles, etc.) – Initial/final height – Advantage: permanent change

6. IE 366 Pushing and Pulling Strength Factors ● Recommendations: see Tables 13.1 – 13.6 (p. 243 ff.) ● Handles – Flat for push, handles for pull ● One hand vs. two hands – 2 > 1 ● Body posture – Standing push: lean toward load – Standing pull: lean away from load – Sitting strength lower – Kneeling strength about same ● Application height – Push at waist – Pull at thigh ● Direction – Generally, | shoulders is best – || shoulders → 50% - 60% of Table values

7. IE 366 Push/Pull Summary ● Two hands are usually better than one. ● Force capability goes down as it is exerted more often. ● Initial force capability is higher than sustained capability. ● Pushing capability is higher than pulling. ● Push at waist level; pull at thigh level.

8. IE 366 Task Modifications ● Measure the force required to move all wheeled equipment; periodically check the forces. ● Install vertical push/pull bars on carts. ● Push rather than pull loads (except over obstruction). ● Avoid muscle-powered pushing and pulling for ramps, long distances, and frequent moves. ● Use mechanical aids and momentum. – e.g., “chiming” a drum (Fig. 13.3) ● Reduce force by reducing friction. ● Use carts with large wheels. ● Remove door sills. ● Use rolling contacts (rollers).

9. IE 366 Holding ● Problems – Holding gives a static load combining body weight and object weight. – Low-back pain arises from spine biomechanics. ● Load-spine lever arm >> spine lever arm ● Means much greater forces ● Low back pain/injury

10. IE 366 Holding (continued) ● Solutions – Reduce the magnitude and duration of the torque. – Use balancers. – Limit high loads to short durations. – Raise conveyor – Provide stools – Platforms for short workers

11. IE 366 Carrying Guidelines ● See carrying method comparison, Table 13.7 (p. 249) ● Replace carrying with pushing or pulling. ● “Everything on wheels.” ● Minimize the moment arm of the load relative to the spine. ● Consider carrying large loads occasionally rather than light loads often (risky → back pain). ● Use teamwork. ● Consider using balancers, manipulators, conveyors, or robots. ● Reduce lifting by raising the initial location. ● Avoid carrying objects up and down stairs.

12. IE 366 NIOSH Lifting Equation: Background ● Created by OSHA, 1970 ● Purpose: – Rank alternatives – Identify and correct problems – Not to rate absolute risk ● Goals –Biomechanical: ≤ 350 kg on L5-S1 –Physiological: ≤ 9.5 kcal/min

13. IE 366 Lifting Guidelines ● 51 lbs is the maximum that can be lifted or lowered (load constant). ● Recommended weight limit (RWL) is load constant multiplied by various factors. ● Lifting index = load weight / RWL

14. IE 366 NIOSH Lifting Equation: Does Not Apply If ● > 1-2 steps ● One-handed lifting ● Seated/kneeling ● Restricted workspace ● Hot/cold/contaminated objects ● Unexpected events (e.g., slips, falls) ● Unstable load ● Carrying, pushing, pulling ● Using tools (e.g., wheelbarrow) ● Slippery floor ● Unfavorable environment (e.g., hot, cold) ● However, sometimes used under these conditions as an approximation.

15. IE 366 NIOSH Lifting Equation RWL = LC × HM × VM × DM × FM × AM × CM ● LC = Load constant ● HM = Horizontal multiplier ● VM = Vertical multiplier ● DM = Distance multiplier ● FM = Frequency multiplier ● AM = Asymmetry multiplier ● CM = Coupling multiplier

16. IE 366 Multiplier Formulas Horizontal multiplier HM = BIL / H BIL = Body interference limit = 10” H = Horizontal location Large HM (small H) better (load close to body) Vertical multiplier VM = 1 – VC × | V – KH | VC = Vertical constant = 0.0075 in. V = Vertical location KH = Knuckle height (for typical lifter = 30 in.) Large VM (V close to KH) better (load closer to optimal lifting height)

17. IE 366 Multiplier Formulas (cont.) Distance multiplier DM =.82 + DC / D DC = Distance constant = 1.8 in. D = Vertical travel distance

18. IE 366 Multiplier Formulas (cont.) Frequency multiplier See Table 13.9. Lifting frequency = mean number of lifts in a 15-minute period Lifting duration /session in hours may be: – Short =.001 h to ≤ 1 h with recovery time of ≥ 1.2 × duration – Moderate = >1 h ≤ 2 h with recovery time of ≥.3 × duration – Long = >2 h but ≤ 8 h

19. IE 366 Multiplier Formulas (cont.) Asymmetry multiplier AM = 1 – 0.0032 × A A = Angle of symmetry (≤ 135°) 30% penalty for 90° angle Coupling multiplier See Tables 13.10, 13.11; Fig. 13.13 ● Depends on: – Height of initial and final hand–container coupling – Whether coupling is good, fair, or poor

20. IE 366 NIOSH Lifting Equation Example 1 from Waters et al (1994)

21. IE 366 Job Analysis Parameters ● Object weight – L = 40 lbs. ● Hand location – Origin ● H = 18 in. ● V = 15 in. – Destination ● H = 10 in. ● V = 36 in. ● Vertical Distance – D = 21 in. ● Asymmetry – Origin: A = 45° – Destination: A = 45° ● Frequency – 1 – 12 times/shift – > 1.2 Recovery Time/Work Time ratio – F < 0.2 lifts/min. ● Duration – < 1 hour ● Object Coupling – C = Fair

22. IE 366

23. Multiplier Calculations Horizontal multiplier HM = BIL / H = 10/18 = 0.56 Vertical multiplier VM = 1 – VC × | V – KH | = 1 – 0.0075 |15 – 30| = 1 – 0.0075(15) = 0.89 Distance multiplier DM = 0.82 + DC / D = 0.82 + 1.8 / 21 = 0.91 Frequency multiplier FM = 1.0 (from Table 13.9) Asymmetry multiplier AM = 1 – 0.0032 × A = 1 – 0.0032(45) = 0.86 Coupling multiplier CM = 0.95 (from Table 13.10)

24. IE 366 Final Calculations RWL = LC × HM × VM × DM × FM × AM × CM = 51 x 0.56 x 0.89 x 0.91 x 1.0 x 0.86 x 0.95 = 18.9 lb. LI = load weight / RWL = 40 / 18.9 = 2.1

25. IE 366 NOTE: Multipliers appear in different order here! Significant control not required at destination, so RWL not computed.

26. IE 366 Hazard Assessment ● Lifting Index = 2.1 (> 1.0) – hazardous job ● Note smallest multipliers – HM = 0.56 – AM = 0.86 – VM = 0.89 ● Recommendations? – Bring load closer to increase HM. – Reduce angle to increase AM. – Raise origin to increase VM.

27. IE 366 NIOSH Lifting Equation Example 2

28. IE 366

29. NIOSH Lifting Equation Example 3

30. IE 366

31. Guidelines for Manual Handling ● Select Individual – Select strong people based on tests. ● Teach Technique – Bend the knees. – Don’t slip or jerk. – Don’t twist during the move. – Get a good grip. – Keep the load close to the body. ● Design the Job – Use machines. – Move small weights often. – Put a compact load in a convenient container. – Work at knuckle height.

32. IE 366 Summary ● Background ● Manual handling variables ● Pushing and pulling ● Holding, Carrying ● NIOSH Lifting Equation ● Guidelines for manual handling