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Islamic University of Gaza - Palestine
Chapter 13: Manual Handling
Islamic University of Gaza - Palestine
Learning Outcomes:
1. Define the term manual handling,2. Know the activities involve manual handling,3. Know types of injuries caused by manual handling,4. Know the risk factors of manual handling that can lead to
injuries,5. Be aware of manual handling as an important
occupational health and safety issue,
2
Islamic University of Gaza - Palestine
Learning Outcomes (cont.):
6. Outline ways of minimizing manual handling risk,
7. Identify the hazards and explain the precautions andprocedures to ensure safety in the use of lifting andmoving equipment with specific reference to fork-lifttrucks, manually operated load-moving equipment (sacktrucks, pallet trucks), lifts, hoists, conveyors and cranes.
Islamic University of Gaza - Palestine
3
Islamic University of Gaza - Palestine
Islamic University of Gaza - Palestine
Wrong way! I’m using my back instead of my legs
Using a trolley is the way to
go!
5
Islamic University of Gaza - Palestine
Islamic University of Gaza - Palestine
Manual Handling
Manual handling tasks are any activity at the work place that require the use of force by a person.
Primarily lifting but includes pushing, pulling, grasping, throwing, striking, restraining, lowering, holding etc.
6
Islamic University of Gaza - Palestine
Manual Handling
Manual Materials Handling (MMH): The use of human power to move loads by lifting, lowering, pushing, pulling, and/or carrying.
•Dynamic Effort: The muscle acts as a local pump in the circulatory system. Compression squeezes blood out of the muscle and the subsequent relaxation releases a fresh flow of blood into it several times greater than normal. In fact, the muscle may receive between 10 and 20 times as much blood as when it is resting.
( A muscle performing dynamic work is therefore constantly flushed out with blood and returns the energy-rich sugar and oxygen balance contained in it, while at the same time waste products are removed. )
Islamic University of Gaza - Palestine
Manual Handling
•Static Effort: During static effort the muscle is not allowed to extend, but remains in a state of heightened tension, with force exerted over an extended period. ( During static effort the blood vessels are compressed by the internal pressure of the muscle tissue, so that blood no longer flows through the muscle. )
* Waste Product Accumulation: A muscle that is performing heavy static work is receiving virtually no sugar or oxygen from the blood and must depend upon its own reserves.Moreover - and this is by far the most serious disadvantage - waste products are not being excreted. Quite the reverse, the waste products are accumulating and produce the acutepain of muscular fatigue.
7
Islamic University of Gaza - Palestine
Is the job repetitive
Are the loads handled heavy at times
Are awkward postures used
Do you feel tired at the end of the shift
Manual handling checklist
Islamic University of Gaza - Palestine
Risk factors in manual handling
− Individual physical factors, e.g.,l Weightl Physiquel Gender
− Task demand factors, e.g.,l Horizontal distance to loadl Posturel Repetition
− Environmental factors, e.g.,l Workplace designl Slippery floors
− Psychological factors, e.g.,l Depressionl Anxiety
8
Islamic University of Gaza - Palestine
• Prolonged poor posture
• Repeated heavy lifting
• Manual handling in a poor posture,
• Sudden unexpected movements
• Work on unstable or slippery surfaces
Common causes of injury
Islamic University of Gaza - Palestine
Types of injuries
Fractures to limbs, ribs, hands, arms caused by slips, falls and dropped objects,
Torn or over- stretched muscles, ligaments, tendons due to unnatural movement,
Injuries to the discs due to bending, twisting,
9
Islamic University of Gaza - Palestine
Example Statistics on Manual Handling
Manual handling is associated with:• 27% of all industrial injuries• 670,000 injuries/year in the United States• 60% of all money spent on industrial injuries• 93,000,000 lost workdays/year
Islamic University of Gaza - Palestine
MH Criteria Categories
• BiomechanicalEmphasizes the forces and torques of manual handling and
their effects on the body. (the back is the weakest link)
• PhysiologicalEmphasizes the energy requirements of the task and the
effects on the cardiovascular system.
• Psychosocial – combines biomechanical and physiological
Under controlled conditions, individuals perform tasks to determine ‘real’ rates for workers.
10
Islamic University of Gaza - Palestine
Manual Handling Variables
l Individual
l Technique− People are not machines− People forget− People make mistakes− People fail to learn
l Task− Permanent change by task modification
Islamic University of Gaza - Palestine
Manual Handling Variables (cont.)l Individual
− What can be done so a small person can do the job?− Stronger usually better− But don’t exclude too many!
l Technique− Posture− Hand orientation− Foot position− Lift training
l Task− Object height− Ease of handling (shape, handles, etc.)− Initial/final height− Lift symmetry
11
Islamic University of Gaza - Palestine
Pushing and Pulling Strength Factors
• Handles (Switches, Grips)• One hand vs. two hands• Body posture• Application height• Direction
Islamic University of Gaza - Palestine
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.
12
Islamic University of Gaza - Palestine
Push/Pull Summary (cont.)
l Application height− Push at waist (between elbow and hip)
− Pull at thigh (between hip and knee)
l Direction− Generally, | to the shoulders is best
− || to shoulders → 50% - 60% of Table values
•Overall, pushing & pulling is better than lifting & lowering; generally pushing is better than pulling.
Islamic University of Gaza - Palestine
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.
13
Islamic University of Gaza - Palestine
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.
Islamic University of Gaza - Palestine
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.
• (You should sometimes carry heavy boxes instead of carrying light loads often)
14
Islamic University of Gaza - Palestine
Carrying Guidelines (cont.)
• Use teamwork.
• Consider using balancers, manipulators, conveyors, or robots.
• Reduce lifting by raising the initial location.
• Avoid carrying objects up and down stairs.
• Students often carry back bags, 10% of the body weight is a recommended maximum (especially for children).
• (A convenient locker can reduce the load carried)
Islamic University of Gaza - Palestine
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
15
Islamic University of Gaza - Palestine
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
Islamic University of Gaza - Palestine
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?
16
Islamic University of Gaza - Palestine
Basic NIOSH Lifting Formula
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
• The RWL protects about 85% of women and 95% of men.(Recommended Weight Limit: RWL)
Islamic University of Gaza - Palestine
Multiplier Formulas
Horizontal multiplierHM = BIL / H• BIL = Body interference limit• H = Horizontal location
(BIL = 10 inches = 25 cm)HM = BIL / H = 10 / 10 = 1)
Vertical multiplierVM = 1 – VC × | V – KH |• VC = Vertical constant
= 0.0075 for inches, 0.003 for cm.
• V = Vertical location• KH = Knuckle height (assume 30 in.)
17
Islamic University of Gaza - Palestine
Multiplier Formulas (cont.)
Distance multiplierDM = .82 + DC ÷ D• DC = Distance constant• D = Vertical travel distance
Asymmetry multiplierAM = 1 – .0032 × A• A = Angle of symmetry
(D = V2 – V1 = 51 – 40 = 11DM = 0.82 + (1.8/11) = 0.9836)
Islamic University of Gaza - Palestine
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
18
Islamic University of Gaza - Palestine
Multiplier Formulas (cont.)
Frequency multiplier(See Table 13.9)
Frequency multiplier
• 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– (F = 12/min à > 1 but < 2 hrs (in this case, 2 hrs.) à V> 30 in. à FM = 0.21)
Islamic University of Gaza - Palestine
Multiplier Formulas (cont.)
Coupling multiplier(See Table 13.10)
• Depends on:– Height of initial and final hand–container coupling– Whether coupling is good, fair, or poor
19
Islamic University of Gaza - Palestine
Guidelines for Manual Handling
• Select strong people based on tests.
• Bend the knees.• Don’t slip or jerk.• Don’t twist during the
move.• 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.
Islamic University of Gaza - Palestine
Guidelines for Manual Handling (cont.)
• Three categories:– Select individual
1. Select strong people based on tests.
– Teach technique2. Bend the knees.3. Don’t slip or jerk.4. Don’t twist during the move.
– Design the job5. Use machines.6. Move small weights often.7. Get a good grip.8. Put a compact load in a convenient container.9. Keep the load close to the body.10. Work at knuckle height.
20
Islamic University of Gaza - Palestine
Examples to discuss
Islamic University of Gaza - Palestine
Resources
• Manual Handing Guide (Mital et al.)• Biomechanical software• 2D Static Strength Prediction Program• 3D Static Strength Prediction Program
21
Islamic University of Gaza - Palestine
End of Chapter 13
Islamic University of Gaza - Palestine
Example
• Cartons weighing 30 lbs are to be picked up from the floor and placed on a roller conveyor 24" above floor level. Hand holds are located 18" above the floor and 12" forward of the midpoint of the worker's ankles. The average frequency of lifting is .2 lifts per minute and the task duration is more than an hour.
Note: The table value for Fmax for this task is 12.
• AL (lb) = 90(6/H)(1-.01|V-30|)(.7+3/D)(1-/Fmax)• MPL (lb) = 3(AL)(AL: Action Limit, MPL: Maximum Permissible Limit)
22
Islamic University of Gaza - Palestine
• Discuss with class … CM = 1, 0.95, 0.9 ? (looking at fig 13.13, I estimate “fair”, so since V=40 in., CM = 1)
• Then • RWL = LC × HM × VM × DM × FM × AM × CM• = 51*1*0.925*0.9836*0.21*1*1 = 9.7443
• LI = LW / RWL = 14/ 9.7443 = 1.44
Islamic University of Gaza - Palestine
Example
• AL (lb) = 90(6/H)(1-.01|V-30|)(.7+3/D)(1-F/Fmax)• H Factor = (6/H) = (6/12) = .50• V Factor = (1-.01|V-30|) = (1-.01|18-30|) =.88• D Factor = (.7+3/D) = (.7+3/24) = .825• F Factor = (1-F/Fmax) = (1-.2/12) = .983• AL = 90(.50)(.88)(.825)(.983) = 32 lbs• MPL = 3(AL) = 3(32) = 96 lbs
• Conclusion:• The weight lifted is below the AL. This task represents an
acceptable risk for most workers.
1
Islamic University of Gaza - Palestine
Chapter 13: Manual Handling
Islamic University of Gaza - Palestine
Learning Outcomes:
1. Define the term manual handling,2. Know the activities involve manual handling,3. Know types of injuries caused by manual handling,4. Know the risk factors of manual handling that can lead to
injuries,5. Be aware of manual handling as an important
occupational health and safety issue,
2
Islamic University of Gaza - Palestine
Learning Outcomes (cont.):
6. Outline ways of minimizing manual handling risk,
7. Identify the hazards and explain the precautions andprocedures to ensure safety in the use of lifting andmoving equipment with specific reference to fork-lifttrucks, manually operated load-moving equipment (sacktrucks, pallet trucks), lifts, hoists, conveyors and cranes.
Islamic University of Gaza - Palestine
3
Islamic University of Gaza - Palestine
Islamic University of Gaza - Palestine
Wrong way! I’m using my back instead of my legs
Using a trolley is the way to
go!
5
Islamic University of Gaza - Palestine
Islamic University of Gaza - Palestine
Manual Handling
Manual handling tasks are any activity at the work place that require the use of force by a person.
Primarily lifting but includes pushing, pulling, grasping, throwing, striking, restraining, lowering, holding etc.
6
Islamic University of Gaza - Palestine
Manual Handling
Manual Materials Handling (MMH): The use of human power to move loads by lifting, lowering, pushing, pulling, and/or carrying.
•Dynamic Effort: The muscle acts as a local pump in the circulatory system. Compression squeezes blood out of the muscle and the subsequent relaxation releases a fresh flow of blood into it several times greater than normal. In fact, the muscle may receive between 10 and 20 times as much blood as when it is resting.
( A muscle performing dynamic work is therefore constantly flushed out with blood and returns the energy-rich sugar and oxygen balance contained in it, while at the same time waste products are removed. )
Islamic University of Gaza - Palestine
Manual Handling
•Static Effort: During static effort the muscle is not allowed to extend, but remains in a state of heightened tension, with force exerted over an extended period. ( During static effort the blood vessels are compressed by the internal pressure of the muscle tissue, so that blood no longer flows through the muscle. )
* Waste Product Accumulation: A muscle that is performing heavy static work is receiving virtually no sugar or oxygen from the blood and must depend upon its own reserves.Moreover - and this is by far the most serious disadvantage - waste products are not being excreted. Quite the reverse, the waste products are accumulating and produce the acutepain of muscular fatigue.
7
Islamic University of Gaza - Palestine
Is the job repetitive
Are the loads handled heavy at times
Are awkward postures used
Do you feel tired at the end of the shift
Manual handling checklist
Islamic University of Gaza - Palestine
Risk factors in manual handling
− Individual physical factors, e.g.,l Weightl Physiquel Gender
− Task demand factors, e.g.,l Horizontal distance to loadl Posturel Repetition
− Environmental factors, e.g.,l Workplace designl Slippery floors
− Psychological factors, e.g.,l Depressionl Anxiety
8
Islamic University of Gaza - Palestine
• Prolonged poor posture
• Repeated heavy lifting
• Manual handling in a poor posture,
• Sudden unexpected movements
• Work on unstable or slippery surfaces
Common causes of injury
Islamic University of Gaza - Palestine
Types of injuries
Fractures to limbs, ribs, hands, arms caused by slips, falls and dropped objects,
Torn or over- stretched muscles, ligaments, tendons due to unnatural movement,
Injuries to the discs due to bending, twisting,
9
Islamic University of Gaza - Palestine
Example Statistics on Manual Handling
Manual handling is associated with:• 27% of all industrial injuries• 670,000 injuries/year in the United States• 60% of all money spent on industrial injuries• 93,000,000 lost workdays/year
Islamic University of Gaza - Palestine
MH Criteria Categories
• BiomechanicalEmphasizes the forces and torques of manual handling and
their effects on the body. (the back is the weakest link)
• PhysiologicalEmphasizes the energy requirements of the task and the
effects on the cardiovascular system.
• Psychosocial – combines biomechanical and physiological
Under controlled conditions, individuals perform tasks to determine ‘real’ rates for workers.
10
Islamic University of Gaza - Palestine
Manual Handling Variables
l Individual
l Technique− People are not machines− People forget− People make mistakes− People fail to learn
l Task− Permanent change by task modification
Islamic University of Gaza - Palestine
Manual Handling Variables (cont.)l Individual
− What can be done so a small person can do the job?− Stronger usually better− But don’t exclude too many!
l Technique− Posture− Hand orientation− Foot position− Lift training
l Task− Object height− Ease of handling (shape, handles, etc.)− Initial/final height− Lift symmetry
11
Islamic University of Gaza - Palestine
Pushing and Pulling Strength Factors
• Handles (Switches, Grips)• One hand vs. two hands• Body posture• Application height• Direction
Islamic University of Gaza - Palestine
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.
12
Islamic University of Gaza - Palestine
Push/Pull Summary (cont.)
l Application height− Push at waist (between elbow and hip)
− Pull at thigh (between hip and knee)
l Direction− Generally, | to the shoulders is best
− || to shoulders → 50% - 60% of Table values
•Overall, pushing & pulling is better than lifting & lowering; generally pushing is better than pulling.
Islamic University of Gaza - Palestine
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.
13
Islamic University of Gaza - Palestine
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.
Islamic University of Gaza - Palestine
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.
• (You should sometimes carry heavy boxes instead of carrying light loads often)
14
Islamic University of Gaza - Palestine
Carrying Guidelines (cont.)
• Use teamwork.
• Consider using balancers, manipulators, conveyors, or robots.
• Reduce lifting by raising the initial location.
• Avoid carrying objects up and down stairs.
• Students often carry back bags, 10% of the body weight is a recommended maximum (especially for children).
• (A convenient locker can reduce the load carried)
Islamic University of Gaza - Palestine
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
15
Islamic University of Gaza - Palestine
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
Islamic University of Gaza - Palestine
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?
16
Islamic University of Gaza - Palestine
Basic NIOSH Lifting Formula
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
• The RWL protects about 85% of women and 95% of men.(Recommended Weight Limit: RWL)
Islamic University of Gaza - Palestine
Multiplier Formulas
Horizontal multiplierHM = BIL / H• BIL = Body interference limit• H = Horizontal location
(BIL = 10 inches = 25 cm)HM = BIL / H = 10 / 10 = 1)
Vertical multiplierVM = 1 – VC × | V – KH |• VC = Vertical constant
= 0.0075 for inches, 0.003 for cm.
• V = Vertical location• KH = Knuckle height (assume 30 in.)
17
Islamic University of Gaza - Palestine
Multiplier Formulas (cont.)
Distance multiplierDM = .82 + DC ÷ D• DC = Distance constant• D = Vertical travel distance
Asymmetry multiplierAM = 1 – .0032 × A• A = Angle of symmetry
(D = V2 – V1 = 51 – 40 = 11DM = 0.82 + (1.8/11) = 0.9836)
Islamic University of Gaza - Palestine
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
18
Islamic University of Gaza - Palestine
Multiplier Formulas (cont.)
Frequency multiplier(See Table 13.9)
Frequency multiplier
• 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– (F = 12/min à > 1 but < 2 hrs (in this case, 2 hrs.) à V> 30 in. à FM = 0.21)
Islamic University of Gaza - Palestine
Multiplier Formulas (cont.)
Coupling multiplier(See Table 13.10)
• Depends on:– Height of initial and final hand–container coupling– Whether coupling is good, fair, or poor
19
Islamic University of Gaza - Palestine
Guidelines for Manual Handling
• Select strong people based on tests.
• Bend the knees.• Don’t slip or jerk.• Don’t twist during the
move.• 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.
Islamic University of Gaza - Palestine
Guidelines for Manual Handling (cont.)
• Three categories:– Select individual
1. Select strong people based on tests.
– Teach technique2. Bend the knees.3. Don’t slip or jerk.4. Don’t twist during the move.
– Design the job5. Use machines.6. Move small weights often.7. Get a good grip.8. Put a compact load in a convenient container.9. Keep the load close to the body.10. Work at knuckle height.
20
Islamic University of Gaza - Palestine
Examples to discuss
Islamic University of Gaza - Palestine
Resources
• Manual Handing Guide (Mital et al.)• Biomechanical software• 2D Static Strength Prediction Program• 3D Static Strength Prediction Program