Manual Handling is Associated with

1
Manual Handling is Associated with

• 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

2
Approaches to Recommendations

• Biomechanical
• Physiological
• Psychophysical

3
Manual Handling Variables

• Individual
• Technique
• Task

4
Pushing and Pulling Strength Factors

• Handles
• One hand vs. two hands
• Body posture
• Application height
• Direction

5
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.

6
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.
• Avoid muscle-powered pushing and pulling for
  ramps, long distances, and frequent moves.
• Use mechanical aids and momentum.
• Reduce force by reducing friction.

7
Holding

• Problems
• Holding gives a static load combining body weight
  and object weight.
• Low-back pain arises from spine biomechanics.
• Solutions
• Reduce the magnitude and duration of the torque.
• Use balancers.
• Limit high loads to short durations.

8
Carrying Guidelines

• Replace carrying with pushing or pulling.
• Minimize the moment arm of the load relative to
  the spine.
• Consider carrying large loads occasionally rather
  than light loads often.
• Use teamwork.
• Consider using balancers, manipulators,
  conveyors, or robots.
• Reduce lifting by raising the initial location.
• Avoid carrying objects up and down stairs.

9
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

10
NIOSH lifting example

• At initiation,
• Horizontal location, H1 10 in.
• Vertical location, V1 40 in.
• Vertical location, V2 51 in.
• Angle of asymmetry, A 0
• Frequency, F 12 /min.
• Load 14 lbs.
• Duration 2 hr.
• What is the RWL?
• What is the Lifting Index, LI?

11
Basic NIOSH Lifting Formula (pg. 269)

• RWL LC HM VM DM FM AM CM
• RWL recommended weight limit
• LC load constant (51 lbs.)
• HM horizontal multiplier
• VM vertical multiplier
• DM distance multiplier
• FM frequency multiplier
• AM asymmetry multiplier
• CM coupling multiplier

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Multiplier Formulas

• Horizontal multiplier
• HM BIL / H
• BIL Body interference limit
• H Horizontal location
• Vertical multiplier
• VM 1 VC V KH
• VC Vertical constant
• 0.0075 for inches, 0.003 for cm.
• V Vertical location
• KH Knuckle height (assume 30 in.)

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Multiplier Formulas (cont.)

• Distance multiplier
• DM .82 DC/D
• DC Distance constant
• 1.8 for inches, 4.5 for cm.
• D Vertical travel distance
• Asymmetry multiplier
• AM 1 .0032A
• A Angle of symmetry

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Multiplier Formulas (cont.)

• Frequency multiplier
• See Table 15.9.
• 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 gt1 h 2 h
• with recovery time of .3 duration
• Long gt2 h but 8 h

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Multiplier Formulas (cont.)

• Coupling multiplier
• See Table 15.10, 15.11, Fig. 15.13
• Depends on
• Height of initial and final handcontainer
  coupling
• Whether coupling is good, fair, or poor

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Force Limits

• FL A F DIST
• A Age factor
• F Frequency factor
• DIST Distance factor
• Differences between force limits and NIOSH
  guidelines.
• Different factors
• Different criteria
• FL permissible load 1.8 times that of NIOSH

17
Resources

• Manual Handing Guide (Mital et al.)
• Biomechanical software
• ErgoIntelligence MMH
• 2D Static Strength Prediction Program
• 3D Static Strength Prediction Program

18
Guidelines for Manual Handling

• Three categories
• Select individual
• Select strong people based on tests.
• Teach technique
• Bend the knees.
• Dont slip or jerk.
• Dont twist during the move.
• Design the job
• Use machines.
• Move small weights often.
• Get a good grip.
• Put a compact load in a convenient container.
• Keep the load close to the body.
• Work at knuckle height.

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Examples to discuss