Design of Repetitive Work

7/31/2019 Design of Repetitive Work

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ERGONOMICS

Design of Repetitive Tasks

A Presentation By:

Richa Sharma (17)

Sandeep Kumar (19)

Shloka Raaj (21)


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Repetitive tasks is defined as doing thesame task over and over again withinshort intervals.

The premise of Ergonomics is to reducephysical strain by designing or modifyingthe work station, work methods, and toolsto eliminate excessive exertion andawkward postures and to reduce repetitivemotion.

Introduction


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The early identification of a repetitive motionproblem, increases the chance of taking correctiveaction on time:

Attention should be paid to any warning signs

such as pain or soreness. Symptoms like numbness, tingling and apparent

loss of strength of muscles should not be ignored.

Cumulative Trauma Disorders (CTD's) are

becoming more commonplace in the work worldand are caused by repetitive movements overlong periods of time, vibration from machinery andimproper arm or body support.

Identification of Repetitive Motion

Problem


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Fatigue or tiredness in muscles and /or joints is the body's wayof telling a person to change the pattern of working.

Tendinitis - inflammation of the tendons. Can be caused byperforming repeated motions incorrectly or in an awkward

position. Tenosynovitis - a condition in which both the tendon and its

covering become inflamed. Can be caused by improper orrepetitive bending of the wrist.

Carpal Tunnel Syndrome - painful squeezing of the median

nerve in the wrist. Causes loss of grip, muscle pain,weakness, and numbness in the thumb and first two fingers. Ifafter an appropriate period of time, test and medication do notwork, surgery may be necessary.

Introduction to work-related

musculoskeletal disorders


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The main occupational factors associated

with musculoskeletal conditions at work are

Force

Posture

Repetition

Duration

Factors associated with adverse

outcomes


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Human muscle has excellent endurance

capacity for loads less than 15% of the

muscles maximum voluntary contraction

Above this threshold, rest periods are

needed, if acute or chronic problems are

to be avoided.

Effects of Repetitive Task: Muscle

Pain


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Tendons have a tensile strength of 50100

MPa (megapascals).

Under further tension, the fibrils elongate

by 15% of their length.

This results in inflammation of

tendons(tendinitis) and impaired blood

supply to the tendons.

Pain in Tendons


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Rapid,repetitive movements of hand or

fingers can cause the sheaths surrounding

tendons to produce excess synovial fluid.

The resultant swelling causes pain andimpedes movement of the tendon in the

sheath. This is known as tenosynovitis.


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The head and neck should not be flexed

forwards by more than 15 degrees if

undue postural stress is to be avoided.

frequent or sustained flexion of the head

and neck beyond this is related to chronic

neck and shoulder pain.

Control of Neck Problems


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Elbow rests appear to be beneficial for

both sitting and standing workers by

stabilising and supporting the arms, they

reduce the load on the shouldermusculature.

More upright postures are obtained if the

monitors are raised such that the middle ofthe monitor is at eye height rather than at

1525 degrees below eye height as is

usually recommended.

Contd..


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If possible work with the hands near waist level and close tothe body.

If the hands have to be positioned above shoulder level, theirelevation above the shoulders should be no more than 35degrees. Hand loads should not exceed 0.4 kg and the

posture should be held for no more than 20 seconds for eachminute of work.

Shoulder flexion >90 degrees should be avoided

Taller workers should be selected for workplaces that cannotbe modified.

Regular rest breaks should be provided. Hand-held weights need to be minimized.

External support should be provided for the weight of thearms

Work objects have to be within the zone of convenient reach.

Wrist rests must be provided for keyboard workers.

Methods of Reducing Shoulder

Stress


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1.Tool Design and Posture

Bend the handle (510 degrees) not the wrist.

Avoid excessive use of pinch grip (thumb andfingers).

Maintain neutral wrist posture. Reduce required grip forces:

Use high-friction materials for handles.

Longer handles increase mechanical advantage.

Maximum allowable grip force (holds for less than 3seconds)

Add handles for carrying tool and resisting reactiontorque.

Damp vibration from powered tools.

Encourage use of large muscle groups.

Prevention of WMSD of Upper

Limbs


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Damp jerk and impact forces.

Position work objects so as to eliminatestatic neck postures.

Eliminate static shoulder elevation orprovide elbow rests or slings.

Provide vices, clamps or other aids to

minimise the need for sustained holding ofwork objects.

Use arm supports in the form of slings orbalancers to lower EMG activitiy in thetra ezius and deltoid muscles.

Workstation design


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Limit repetitive movements to 2000 per hour or less.

Eliminate highly repetitive (


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Avoid repetitive work in cold conditions.

Use ergonomic criteria when making

equipment procurement decisions.

Redesign tasks before a discomfort

becomes a disorder.

Eliminate excessive overtime working.

Management of working

conditions and worker exposure


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Work Practices should include a program with key elements such as properwork techniques, employee conditioning, inspections, feedback, andmaintenance.

Proper work techniques include training on the correct lifting proceduresand

correct use of ergonomically designed work stations, fixtures, and tools. Employee conditioning should include employees gradually being worked

into a full workload as appropriate for their specific job.

Employees reassigned to new jobs should also have a break-in trainingperiod.

Inspections shall be conducted periodically to ensure safe operatingprocedures

are being followed.

Feedback will provide a system for employees to notify supervisors about

conditions with potential ergonomic hazards.

Employees should be instructed to report ergonomically related symptomsto their supervisors immediately.

Maintenance should be the preventive program for monitoring mechanicalequipment and tools to ensure they are in proper working condition.

Training


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Work area should be adjusted to fit the body.

There should be comfortable work environment.

Stretching every few hours relieves physicaltension and body aches and increases the

productivity. The work pattern should be changed so that the

operators are not doing the same motion over andover.

If you can, lean or sit rather than stand for longperiods of time.

Wrists should be straight while work.

Use legs, arms for lifting. Bend your knees andkeep your head, back and hips in a straight line.Never bend over to pick anything up without first

Conclusion


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Thank You

Documents

Design of Repetitive Work