Download occupational ergonomics a practical approach pdf

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Proper design depends not only on whether the worker is standing or sitting, but also on what type of work is being performed. Table 4 suggests proper work-surface heights for standing operators. Table 5 gives suggestions for seated operators. The optimal work-surface height is slightly below the elbow. When the work surface is too high or the worker is positioned too low , Applied Ergonomics Table 4.

Human Factors ; 15 3 Adapted by permission. This can cause shoulder-muscle fatigue and on a long-term basis can contribute to cervicalmuscle loading, involving the upper trapezius and levator scapulae muscles. The work space should allow adequate room for the task being performed. Controls, materials, and so forth should be within easy reach, not too close and not too far.

Think of the task of writing. The paper is not positioned at the very edge of the table; it is placed slightly forward. A clearance of approximately 6 inches from the trunk or about 5 inches from the edge of the table is recommended. Occasional stretching beyond the area of the measured arc s is acceptable. Keep in mind that a task that requires gripping will decrease the reach capacity by 2 inches or more. Backward reaching should be avoided.

Workers should not sit at jobs that do not allow the legs to be placed under the workstation. By trying to "cuddle" into a workstation with no leg clearance, the worker either will end up straddling the chair and sitting in a stooped position or will sit sideways, necessitating twisting of the torso.

Workstation depth is suggested to be a minimum of 25 inches to allow adequate leg clearance. Source: Ayoub MM: Work place design and posture. In addition to height, also consider adjustable depth and height for the backrest and adjustable width of the armrests. Tool Design Hand and arm positions can significantly influence the development of cumulative trauma disorders.

Tools should therefore be designed with this in mind: the tool does the bending and not the worker. The wrist should be maintained in a neutral position as much as possible. When repetitive wrist bending is required, it should remain within 0 to 40 degrees.

For example, a pistol-grip drill handle is indicated when the work is oriented vertically in front of the worker ideally at elbow height or when horizontally oriented and positioned at knuckle height. A pistol grip should have a degree bend. Well-known angled tools include the Western Electric bent pliers with a degree bend, Bennett's degree curved-handle golf clubs, soldering irons with degree bends, and hammers with a degree bend.

One of the most common errors in handtool design is the diameter ofthe handle. When using a power grip, the distal joint of the thumb should fully overlap the distal joint of the middle or ring finger.

A diameter of 1. Ayoub 7 has cited additional design considerations: 1. Precision tools should be designed so that they can be operated primarily by the radial side of the hand, due to its sensory and motor capabilities. The recommended diameter for these tools is 0. Flexion of only the distal phalanges should be avoided. Trigger handles, for example, should be designed so that both the middle and distal joints can be flexed together in order to better distribute the load.

A trigger that is long enough to accommodate all four fingers further enhances this. In order to keep the wrist neutral, the tool should be designed so that it is an extension of the axis of the forearm motion required, i.

Compliant handle coverings should be used. The handle surface should be nonporous and slip-resistant. A friction covering is preferred over flutes or ridges, which may not fit all hand sizes.

Loads should be supported by the palm of the hand and not by the poorly protected extensor surface. Spring openings on scissors and pliers will eliminate this problem.

Sharp edges of tools should be rounded to avoid stress concentrations in the palm of the hand. Avoid side loading of the fingers and stress concentrations at the base of the palm in particular. These surfaces are relatively unprotected by bulky tissue. Handles that can be grasped rather than pinched are preferred when the task allows.

This enables stronger muscles to be used. Tools should be designed to be used by either hand. This not only will accommodate differences in hand dominance, but A cylindrical shape for the tool handle is preferred since it provides a more natural contour in the hand. Handle length should be at least 4 inches with an additional 0.

Shorter handles place a stress concentration in the palm of the hand. Stress or force to the center of the palm should be avoided because it is a neurovascularly rich area. When force is to be exerted along the handle, as in a pump screwdriver, a well-sized guard at the forward end of the handle will reduce grip-force requirements and will be less fatiguing. Distribute the load forces over as large an area of the hand as possible, again to minimize stress concentrations.

T-shaped handles generally provide greater torque capacity with less grip strength required. Tools with a handle span, such as pliers, should have a maximum distance between the handles of 3. Work-Methods Design The overall design of the job must also be considered in order to avoid unsound practices. These principles should be kept in mind in order to minimize the effects of repetitive or forceful work.

All static work postures should be avoided. Special attention should be given to those involving neck flexion, arm abduction, trunk flexion, and holding of, or otherwise applying force to, objects. Work should be dynamic and allow for frequent changes in position.

It is ideal to alternate sitting and standing, for example. Standing for over an hour is not recommended as this increases whole-body fatigue. While work should be dynamic, the motions should be smooth and flowing, avoiding sudden movements or jerking.

Work should be designed so that the object being manipulated is held close to one's center Applied Ergonomics of gravity. The arms should be kept close to the sides and the elbows flexed, preferably at an angle that positions them slightly above the wrists. By designing for operations to be kept close to the center of gravity, abduction of the arms is minimized, since under static demands it results in muscle loading of the neck, upper back, and shoulders.

This is very common and is a cause of neck, upper-back, and arm pain as is overhead work. Ideally, for seated operators, the arms should be supported either by the work surface or by armrests on the chairs at a height that does not cause shoulder elevation or depression. Lifting with the arms in full supination or pronation is not recommended.

Also, lifting with the elbows fully extended is contraindicated since it puts the bicep muscle at a mechanical disadvantage. As previously mentioned, wrist-bendingflexion, extension, or radial or ulnar deviation, for example-should be kept in mid-range to minimize stress.

Any of these motions carried to an extreme will increase the risk of cumulative trauma disorder because of stretching and pressure on the tissues. Also, when two or more of these motions are paired, or when the motion s are combined with forceful, rapid, or repetitive work, the chance for developing cumulative trauma is further increased. For example, wrist flexion and ulnar deviation, when combined with repetitive pinch, cause an increase in pressure in the carpal tunnel. Likewise, wrist flexion combined with finger flexion increases carpal tunnel pressure.

A jig is a device that holds an object or material while it is being worked on. Lead-ins and tool-entry points decrease the demands of vision and coordination, as when a worker is loading a part into a machine, and also help to minimize general fatigue. In assessing the job sequence, look for prolonged static contractions.

Tasks requiring this 35 should be broken up or otherwise redesigned. Forceful repetitions should also be avoided. Can other muscle groups be used? By adding foot pedals, some of the demand on the upper extremities may be lessened. Administrative controls should not be overlooked.

These include approaches such as jeb rotation, presorting materials, employee training, use of functional-capacity testing to determine physical capacities, and scheduling of breaks. Jobs might be recombined so that steps are added that require differing musculoskeletal demands and motions, thus reducing the amount of repetition.

The rate of work can also be addressed through recombining jobs. Training is available at the university level and through professional seminars, books, and journals. A resource list is included at the end of this article. The trained therapist can apply this knowledge to evaluate the "transfer potential," answering the question, "Will the new tool design produce the desired effect, or will it simply transfer the biomechanical stress from, for example, the wrist to the shoulder or from one worker to another?

In recommending ergonomic changes, you will be assuming a professional liability and should be careful to practice within the confines of the knowledge you have acquired, being prepared to call in an engineer or other professional when the situation requires it. Primarily for safety reasons, regulatory factors exist that place constraints on the job's design or operation.

Examples of these include use of protective eye wear during certain operations and where machine guards or palm buttons are placed. States may have their own version of OSHA standards, which, at minimum, must meet the federal standards and often go above and beyond these in ensuring worker safety.

State Workers' Compensation laws could be another impacting factor. Be aware of these factors before making recommendations on job redesign or modification. Finally, ergonomic job redesign should not be used as the only method of addressing workrelated injuries. It should be a component of a larger program educating administrators, supervisors, and laborers in causes, solutions, and prevention of musculoskeletal injuries and illnesses.

Such a program involves all the key players and is far more likely to have effective and long-lasting results than a one-time ergonomic analysis. Ergonomics is a very common-sense approach. Often our bodies will tell us how we fit the work, if we will only listen, look, and feel. If we observe workers in the performance of their jobs, many risk factors can be easily identified.

Ostrom, PhD, has worked in the fields of risk assessment, industrial safety, ergonomics, and human factors for over thirty-five years. He has authored or co-authored two other books on ergonomic and risk topics and has authored over 75 papers and conference proceedings. Cheryl A. She has been the director of the Industrial Technology BS degree program.

In her thirty year career, she has conducted hundreds of ergonomic assessments and risk assessments from offices to nuclear hot cells. Buy this book! By jaadaut Well written and easy to follow. Packed with helpful images and examples. Highly recommended for anyone looking to apply ergonomics in the workplace or study for the CPE. Wilhelmsen Kindle. Posting Komentar. Rabu, 01 Agustus [A Wilhelmsen Exactly what should you believe a lot more? Most helpful customer reviews 0 of 0 people found the following review helpful.

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