MANUAL MATERIAL MANUAL MATERIAL HANDLINGHANDLING

PREPARED BY:PREPARED BY:

Dr. R. ALKADEEMDr. R. ALKADEEM

THIRD YEAR THIRD YEAR

PRODUCTION ENGINEERING DEPT.PRODUCTION ENGINEERING DEPT.

HUMAN FACTORS ENGINEERINGHUMAN FACTORS ENGINEERING

Manual Material Handling Manual Material Handling ( low back pain & back ( low back pain & back

disorder)disorder)• Manual material handling (MMH) tasks, Manual material handling (MMH) tasks,

which include unaided which include unaided liftinglifting, l, loweringowering, , pushingpushing, , pullingpulling, , holding activitiesholding activities, , are the principle source of work injuries are the principle source of work injuries affecting low back pain.affecting low back pain.

• According to the National Safety Council According to the National Safety Council 28% of all work injuries involving 28% of all work injuries involving disability are caused by overexertion, disability are caused by overexertion, lifting, throwing, carrying, pushing or lifting, throwing, carrying, pushing or pulling loads that weigh under 50lb.pulling loads that weigh under 50lb.

Manual Material HandlingManual Material Handling

• The act of manually lifting, pushing, The act of manually lifting, pushing, or pulling an object has been of or pulling an object has been of continual concern to :continual concern to :

1.1. Efficient use of a workforceEfficient use of a workforce

2.2. Unnecessary injury and illness in Unnecessary injury and illness in industry prevention.industry prevention.

Though automation is difficult Though automation is difficult in service industries;in service industries;

• Building & constructionBuilding & construction• Mechanical repair of Mechanical repair of equipment (maintenance) equipment (maintenance)

• Baggage & package handlingBaggage & package handling• Health care servicesHealth care services• Fire fighting ……………..Fire fighting ……………..etc.etc.

Lifting ActivitiesLifting Activities

Lower Back Lower Back DisordersDisorders

Risk Factors of Low Back Risk Factors of Low Back Pain LBPPain LBP

• Risk factors of low back pain LBP and low back Risk factors of low back pain LBP and low back disorders LBD include the following:disorders LBD include the following:

1.1. General heavy physical workGeneral heavy physical work

2.2. Static workloadStatic workload

3.3. Dynamic workload: heavy MMH, Dynamic workload: heavy MMH, lifting, lifting,

4.4. Repetitive workRepetitive work

Low Back InjuriesLow Back Injuries

• OneOne out of every out of every threethree industrial overexertion industrial overexertion injuries attributed to MMH.injuries attributed to MMH.

• These injuries include shoulder and hip injuries These injuries include shoulder and hip injuries and lower back injuries, such as ;and lower back injuries, such as ;

1.1. Disc herniation Disc herniation

2.2. Disc degenerationDisc degeneration

3.3. Fracture of the vertebral bodyFracture of the vertebral body

4.4. Tears in the muscles & ligamentsTears in the muscles & ligaments

Types of Disc Problems Types of Disc Problems

Biomechanical Aspect of Biomechanical Aspect of MMHMMH

The SpineThe Spine

Biomechanical Aspects of Biomechanical Aspects of MMHMMH

• Torso linkage system:Torso linkage system:

the figure demonstrates the the figure demonstrates the forces on the lumbosacral forces on the lumbosacral discdisc

Low Back Static ModelLow Back Static Model

Forces acting on the Forces acting on the L5/S1 disc L5/S1 disc

• FFAA is the force is the force created by the created by the abdominal abdominal pressure.pressure.

• Reaction force Reaction force components at the components at the lumbosacral disc:lumbosacral disc:

1.1. FFcompcomp=compressio=compression forcen force

2.2. FFshearshear=shear force=shear force

Forces & Moments on SpineForces & Moments on Spine

• Figure shows the Figure shows the simple biomechanical simple biomechanical model of the model of the lumbosacral disc.lumbosacral disc.

• The line of action of The line of action of the erector spinae the erector spinae muscles of the muscles of the lower lumbar back lower lumbar back is parallel to the is parallel to the normal force of normal force of compression on compression on L5/S1 disc.L5/S1 disc.

Disc Herniation Disc Herniation

• Large spinal disc Large spinal disc compression forcescompression forces can can be produced by muscular be produced by muscular exertion, especially when exertion, especially when lifting. The resulting lifting. The resulting values if repeated, values if repeated, increase the risk of disc increase the risk of disc degeneration.degeneration.

• Shear forcesShear forces, whether in , whether in flexion, extension, or torso flexion, extension, or torso twisting are resisted by the twisting are resisted by the (annulus fibrosus) of the (annulus fibrosus) of the disc.disc.

Disc Herniation Disc Herniation

Predicted L5/S1 Disc Predicted L5/S1 Disc Compression Forces for Compression Forces for

different positions from the different positions from the bodybody

Squatting Versus Stooping Squatting Versus Stooping Lifting MethodsLifting Methods

• H should be minimized to minimize the H should be minimized to minimize the compression forcecompression force

• Torso should be kept more vertical to decrease Torso should be kept more vertical to decrease the shear forcethe shear force

1. Stooped posture 2. Squatted posture

Squatting Versus Stooping Squatting Versus Stooping Lifting Methods and their Lifting Methods and their

effect on Vertebral Columneffect on Vertebral Column

Prevention of Musculoskeletal Prevention of Musculoskeletal Disorders Related to MMHDisorders Related to MMH

• These factors which define a MMH system, were These factors which define a MMH system, were grouped as follows;grouped as follows;

1.1. Worker characteristicsWorker characteristics

2.2. Load characteristics Load characteristics

3.3. Task characteristics Task characteristics

4.4. Work practices Work practices

Worker Characteristics Worker Characteristics

1.1. Physical:Physical: include general worker measures, e.g. include general worker measures, e.g. age, sex, anthropometry….etc.age, sex, anthropometry….etc.

2.2. Sensory:Sensory: measures of worker sensory processing measures of worker sensory processing capabilities, e.g. visual, auditory, tactual, ……etccapabilities, e.g. visual, auditory, tactual, ……etc

3.3. Motor:Motor: measures of worker motor capabilities, measures of worker motor capabilities, e.g. strength, endurance, range of movement, e.g. strength, endurance, range of movement, kinematic characteristics ,….etckinematic characteristics ,….etc

4.4. Psychomotor: Psychomotor: e.g. reaction/response time, e.g. reaction/response time, coordination, information processing.coordination, information processing.

5.5. PersonalityPersonality6.6. Training/experience Training/experience 7.7. Health statusHealth status

Material/container Material/container Characteristics Characteristics

1.1. Load:Load: measures of force, weight, pushing, pulling measures of force, weight, pushing, pulling force requirements, mass moment, inertiaforce requirements, mass moment, inertia

2.2. Dimensions:Dimensions: measures of size of unit workload, measures of size of unit workload, e.g. height, width, breadth when indicating the e.g. height, width, breadth when indicating the form as rectangular, cylindrical, …..etcform as rectangular, cylindrical, …..etc

3.3. Distribution of load:Distribution of load: location of CG w.r.t. worker location of CG w.r.t. worker for one hand or two hands.for one hand or two hands.

4.4. Coupling:Coupling: measure of devices used to aid grasping, measure of devices used to aid grasping, e.g., texture, handle size, shape, and location.e.g., texture, handle size, shape, and location.

5.5. Stability of load:Stability of load: measures of CM location measures of CM location consistency, as a concern in handling liquids and consistency, as a concern in handling liquids and bulk materials.bulk materials.

Task Characteristics Task Characteristics

1.1. Workplace geometry:Workplace geometry: movement distance, movement distance, direction and extent of path, obstacles, nature of direction and extent of path, obstacles, nature of destination.destination.

2.2. Frequency/duration/pace:Frequency/duration/pace: measures of time measures of time dimensions of the handling task.dimensions of the handling task.

3.3. Complexity:Complexity: manipulation requirements of manipulation requirements of movements, precision of motion, tolerance.movements, precision of motion, tolerance.

4.4. Environment:Environment: temperature, humidity, lighting, temperature, humidity, lighting, noise, vibration, foot traction. noise, vibration, foot traction.

Work Practices Work Practices Characteristics Characteristics

1.1. Individual:Individual: speed and accuracy in moving objects, speed and accuracy in moving objects, postures in moving objects.postures in moving objects.

2.2. Organizational:Organizational: plant size, staffing of plant size, staffing of medical/hygiene/engineering/ and safety functions, medical/hygiene/engineering/ and safety functions, and utilization of team work.and utilization of team work.

3.3. Administrative:Administrative: safety training and control, long safety training and control, long work shifts, rotation, personal protective devices.work shifts, rotation, personal protective devices.

Definition of Lifting Hazard Definition of Lifting Hazard LevelsLevels

• NIOSH (national institute for safety & NIOSH (national institute for safety & health) recommendations are based on health) recommendations are based on two levels of hazard:two levels of hazard:

1.1. Action LimitAction Limit (AL) (AL)

2.2. Maximal Permissible LimitMaximal Permissible Limit (MPL)(MPL)

AL Based OnAL Based On1.1. Epidemiological data Epidemiological data indicating that some indicating that some

workers would be at increased risk of injury on workers would be at increased risk of injury on jobs exceeding the AL.jobs exceeding the AL.

2.2. Biomechanical studiesBiomechanical studies indicating that L5/S1 indicating that L5/S1 disc compression forces can be tolerated by most disc compression forces can be tolerated by most people at about the 3400 N level.people at about the 3400 N level.

3.3. Physiological studiesPhysiological studies disclosing that the disclosing that the average metabolic energy requirement would be average metabolic energy requirement would be 3.5 kcal/min for jobs performed at AL.3.5 kcal/min for jobs performed at AL.

4.4. Psychophysical studiesPsychophysical studies show that over show that over 75%75%

women & women & 99%99% of men could lift loads at AL. of men could lift loads at AL.

MPL Based OnMPL Based On1.1. Epidemiological data Epidemiological data indicating that indicating that

musculoskeletal injuries rates and severity rates are musculoskeletal injuries rates and severity rates are significantly higher for most workers placed on jobs significantly higher for most workers placed on jobs exceeding the MPL.exceeding the MPL.

1.1. Biomechanical studiesBiomechanical studies indicating that L5/S1 disc indicating that L5/S1 disc compression forces cannot be tolerated by most compression forces cannot be tolerated by most people over 6400 N level, which is created at MPL.people over 6400 N level, which is created at MPL.

2.2. Physiological studiesPhysiological studies disclosing that the average disclosing that the average metabolic energy requirement would exceed 5 metabolic energy requirement would exceed 5 kcal/min for workers frequently lifting loads at MPL.kcal/min for workers frequently lifting loads at MPL.

3.3. Psychophysical studiesPsychophysical studies show that only about show that only about 25%25% of men, and less than of men, and less than 1%1% of women have the muscle of women have the muscle strength to be able to lift above MPL.strength to be able to lift above MPL.

Hazard Categories Hazard Categories

• The Al and MPL permit lifting tasks to be classified The Al and MPL permit lifting tasks to be classified into three hazard categories for control planning:into three hazard categories for control planning:

1.1. Above MPLAbove MPL should be considered as unacceptable, should be considered as unacceptable, and engineering controls should redesign the lifting and engineering controls should redesign the lifting conditions.conditions.

2.2. Between Al and MPLBetween Al and MPL are unacceptable without are unacceptable without administrative or engineering controls, thus requiring administrative or engineering controls, thus requiring careful employee selection. Placement and training, careful employee selection. Placement and training, and /or job redesign.and /or job redesign.

3.3. Below the ALBelow the AL are believed to represent nominal risk are believed to represent nominal risk to most workers. to most workers.

Size of the Lifted Object Size of the Lifted Object • Both limits are sensitive to the object Both limits are sensitive to the object

size. size. • Varying V, D, H, or F will influence Varying V, D, H, or F will influence

the weight maximum values for the the weight maximum values for the task.task.• V :is the location of the object CM V :is the location of the object CM

or hand grip centreor hand grip centre• D: is the vertical travel distance of D: is the vertical travel distance of

hands from origin to destination of hands from origin to destination of the objectthe object

• H: is the location of CM or hand H: is the location of CM or hand grip measured horizontally from grip measured horizontally from point on the floor midway between point on the floor midway between the ankles.the ankles.

• F: is the frequency of lifting F: is the frequency of lifting (lifts/min) averaged over the (lifts/min) averaged over the period of lifting.period of lifting.

Al & MPL CalculationAl & MPL Calculation

Lifting Index Composite Lifting Index

L.I = L/RWL (RWL= LC*HM*VM*DM*AM*FM*CM)

CLI = LI A,1 + (LI B,1 – LI B,2)

National Institute of Occupational Safety and Health

RWL RWL Recommended Weight LimitRecommended Weight Limit

LCLC Load ConstantLoad Constant

HMHM Horizontal MultipliersHorizontal Multipliers

VMVM Vertical MultipliersVertical Multipliers

DMDM Distance MultiplierDistance Multiplier

AMAM Asymmetric MultiplierAsymmetric Multiplier

FMFM Frequency MultiplierFrequency Multiplier

CMCM Coupling MultiplierCoupling Multiplier

LILI Lifting IndexLifting Index

LL Actual LoadActual Load

CLICLI Composite Lifting IndexComposite Lifting Index

AbbreviationsAbbreviations

To Control the Overexertion To Control the Overexertion InjuriesInjuries

• To control the injuries caused by MMH tasks the To control the injuries caused by MMH tasks the following alternatives are suggested:following alternatives are suggested:

1.1. Eliminate the need for strenuous MMH jobsEliminate the need for strenuous MMH jobs

2.2. Reduce MMH demandsReduce MMH demands

3.3. Eliminate stressful body postures or movementsEliminate stressful body postures or movements

4.4. Use mechanical equipment to move materialsUse mechanical equipment to move materials

5.5. Train workers in proper MMH techniquesTrain workers in proper MMH techniques

6.6. Design MMH jobs that can be performed by Design MMH jobs that can be performed by workers without undue risk of overexertion workers without undue risk of overexertion injuriesinjuries

Aiding lifting devicesAiding lifting devices

Scissor lift Scissor lift

Aiding lifting devicesAiding lifting devices

Electric power jackMechanical lifting deviceWork positioner

Patient lifting devicePatient lifting device

MMH Job Design Procedure MMH Job Design Procedure

• One of the popular approaches to designing MMH jobs One of the popular approaches to designing MMH jobs is based on the capabilities of a certain percentile.is based on the capabilities of a certain percentile.

• The procedure involves dividing the job into basic MMH The procedure involves dividing the job into basic MMH activity elements, e.g. lifting, lowering, pushing….etc.activity elements, e.g. lifting, lowering, pushing….etc.

• Elements with a risk potential greater than 1 are Elements with a risk potential greater than 1 are considered stressful and must be redesigned.considered stressful and must be redesigned.

• The formula to determine risk potential is:The formula to determine risk potential is:

Risk Potential (LI) = required work rate/desired work rateRisk Potential (LI) = required work rate/desired work rate

lifting Indexlifting Index