Elements of a Material Handling Ergonomics Program

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Elements of a Material Handling
             Ergonomics Program
Analyze management operations

We must first recognize that materials handling is often one of the largest cost
components of a product, operation or service. Unnecessary handling of
materials costs time and money.

We must understand the relationship between workstation design and the jobs
workers are expected to perform. People responsible for designing work methods
must pay particular attention to details of the task involved to ensure the greatest
possible harmony between the work method and the worker.

Make purchasing agents an important part of the materials handling program.
Have them pay attention to details, such as size, weight, packaging and
convenience for handling. Use sold to/ship to arrangements to eliminate in-plant
handling wherever possible. Products being shipped to your company for
distribution may be more efficiently transported from your supplier to the
customer, saving freight and handling. Reduce overall work-in-process
quantities. Failure to do so often results in overcrowding problems-- extra
handling, use of larger containers or parts stacked higher. Housekeeping
problems may develop, increasing possibilities of materials handling vehicle
accidents and damage to materials and finished goods. To reduce work-in-
process quantities, it is necessary to tighten controls and shorten forecasting for
inventory, scheduling, ordering and shipping. Manufacture products on an as-
ordered basis, instead of stockpiling for anticipated use.

Perform product analysis. Changes in the product sometimes result in reduced
materials handling. Consider lightening the product, and allowing a worker or
conveyor to handle more pieces at one time. Plan to expand or change.
Production usually suffers under crowded conditions. Much of this material is
dependent upon management's policies and procedures.

But even in the absence of management analysis, you personally can analyze
and implement change in the following ways. Establish disposal and storage
methods, and ways to improve material flow for scrap, waste materials,
containers, tools and equipment. Each workstation must be analyzed.

Material flow

It is usually not enough to simply observe and study a specific manual materials
handling task. Key questions arise regarding how the material is routed through
the facility or work site that can only be answered by looking at the bigger picture.
Eliminate unnecessary materials handling by combining operations or shortening
the distances that the materials must be moved. Look for crossing paths, loops,
backtracking and a lack of direction during production. One benefit of short
distances is the ability to link workstations by conveyors and reduce carrying
distances. Also, less mechanical handling can mean fewer opportunities for
forklift accidents. Walk through your operations with an employee. Make
immediate simple changes. (Make written suggestions for observed cost-saving
and people-saving changes that need approval or further evaluation.)

Simplify, rearrange or change the process. Often, processes that are handled
differently can be performed in a similar fashion to simplify the material flow. Plan
adequate aisleways for intended material flow, and emergency access and exit.
Personnel must be able to evacuate quickly in an emergency. Cramped
aisleways may restrict exits and cause panic. Emergency vehicles also must be
able to quickly gain access. Adequate aisleways and exits facilitate the orderly
movement of materials. Avoid the necessity of working in aisleways.

Workplace

Check floor surfaces. Repair cracks, depressions, holes, damaged flooring and
surfaces. Starting forces for carts can double or triple on poor surfaces. Worn-out
or damaged wheels also can increase the required force. Insist on good
housekeeping. Keep floor surfaces clean. Water, oil, grease and material scrap
reduce traction and increase the force required to push or pull carts. Poor
housekeeping only increases materials handling obstacles.

Review plant design to remove building obstructions that interfere with materials
handling.

In materials handling, "what goes down must come up." To prevent repeated
stooping and bending, the goal is to bring both incoming and outgoing materials
at each process to a suitable work height. We recommend at least a minimum of
20 inches from the floor, but ideally to knuckle height of about 30 inches. Reduce
the need to raise or lower materials from above shoulder height. If you must raise
or lower materials above shoulder height, store lighter objects on top shelves.

Remove constraints that prevent materials from being positioned close to the
body. Allow enough space for feet to get under tables and conveyor belts.
Provide clear access to shelves and adequate space around pallets. Reduce
height differences during load travel. Keep loads between knuckle and shoulder
height from origin to destination. Slide objects rather than lifting and lowering
them.

Provide adjustable chairs for all operations. Chairs should swivel for side-lifting,
whether they are located in the company president's office or on the small-parts
assembly line.
Load Guidance

Some specific considerations when handling loads would include:

      Small is better than big.

Generally speaking, when it comes to the manual handling of loads, small is
better than big. Large, awkward loads present the handler with a variety of
potential problems including added stress and strain to the upper extremities and
the back. Containers should not be so tall that they obstruct vision or, conversely,
bump annoyingly against the legs
as they are carried. Loads that will be lifted should be packaged in containers
narrow enough to fit between the knees during a squat lift (knees and hips bent,
and the back more or less straight). This design will allow the load to be
positioned close to the spine, thereby reducing the load's compressive forces on
the spine.21

      Loads should not be too light.

 Loads that are too light may encourage the handler to lift a number of units at a
time, creating an unstable load that is more likely to fall. Conversely, loads
should sometimes be made so heavy that people will not attempt to lift the load
without the help of another person or will get mechanical assistance. Whenever
possible, packages should be labeled with the content's weight so people who
handle them will immediately know how heavy a load they are dealing with.

      Containers should be designed to prevent their contents from shifting.

Loads that shift in their containers may move the center of gravity away from the
handler, suddenly and traumatically increasing the load on the lower back.
Likewise, loads that are unevenly distributed in their container (a nonsymmetric
center of gravity) place torsion on the spine. Therefore, it is recommended that
packaging "capture" the contained items, to prevent movement within the
container and hold the items in as symmetric an orientation as possible. For
nonsymmetric loads, the heavier portion of the container should be
closest to the handler in order to keep the center of gravity as close to the spine
as possible.

      Boxes, totes, and containers should have handles.

Handles or hand cutouts provide the best coupling between the handler and the
object. According to the 1991 Revised NIOSH Lifting Equation, the ideal handle
design is 0.75"1.5" in diameter, at least 4.5" long, and features a 2.0" hand
clearance. Handlers should be of a cylindrical shape with a smooth, nonslip
surface. The optimal handhold cutout has a 1.5" or greater height, a length of at
least 4.5", a semioval shape, and a 2.0" hand clearance, a smooth nonslip
surface, and at least a 0.25" wall thickness. Handholds near the bottom of the
container allow the handler to carry the load near knuckle height and minimize
static muscle loading of the upper extremities. The edges of the container should
be rounded, not sharp. Sharp edges create
opportunities for contact stress between the box and the hand, arm and body.



Analyzing manual materials handling tasks

Prioritize task analysis

Once we understand material flow, it is time to evaluate tasks. This should be
done on a priority basis, first examining the worst and most strenuous tasks. The
safety and health department should review accident statistics to determine
priorities. The employees who perform the tasks being evaluated are a vital
source of information. Ask employees for their views on where the most
strenuous, demanding and dangerous materials handling tasks exist. Likewise,
poll supervisors and other management personnel. This also is the time to
examine the accident-investigation procedure to see if it is effective.

Analyze the job -- tasks

Once priorities have been set, break the tasks down into elements, which are the
simplest single actions needed to define the process at a particular stage of an
operation. Among the considerations are:

      Recognize manual materials handling is more than just lifting. It also
       includes lowering, pushing, pulling, holding, carrying and transferring
       activities.
      Measure the frequency and duration of the task. Determine the frequency
       of the task in activities-per-minute. Be sure to note how the activity varies.
       Be careful in estimating an average frequency which may be cyclical; that
       is, very fast then very slow. Note the average duration of the task.

Be aware of the tradeoff between frequency and weight. As loads become lighter
and are lifted more frequently, fatigue becomes a factor. As loads become
heavier and are lifted less frequently, considerations regarding the structure and
strength of the back are important. Allow the employee as much time as possible
to complete the task, considering the needs of production. Determine the type of
pacing. Make additional allowances for forced pacing.

Minimize reach requirements. Design the operation to accommodate the smallest
person's reach. Avoid unnecessary material stacking, storing or placement for
work-in-process material (such as neatly orienting parts in containers when they
will be dumped out in the next operation). Structure equipment to use gravity to
move materials wherever feasible. Simplify tasks by combining operations and
steps.

Analyze the job -- load

The load consists of the item or collection of items handled, many of which are
stored in containers.
Adjust all containers for the required volumes. Use large containers for high-flow
volume and small containers for low volume. Avoid using large containers for
low-volume materials to reduce the need for workers to reach.

Remove handling uncertainties. Remove an employee's doubt about whether he
or she should manually or mechanically handle an object by using obviously
small and large containers or parts.

Plan for incoming materials to arrive in suitable containers to minimize product
handling.

Ask customers how you can best design product-needs packaging to meet their
materials handling needs.

Reduce deadweight ratio of containers. Consider the weight of the container
which must be repeatedly handled and transferred vs. the parts inside. The
weight of the container should be minimal compared to the weight of the product.
Keep manually handled loads as small as possible, paying attention to the width
and length. To prevent obstructed vision, load height should be 30 inches or less
when manually handled.

The load center of gravity (or balancing point) should be as close as possible to
the person handling it. Stress on the back increases as the distance from your
center of gravity increases. For example, a 10-pound dictionary held 30 inches
away from the body's center of gravity would be the equivalent of a compact 50-
pound load held close to the body.

Ensure that the load will be easy to grip. This can be accomplished by ordering
cardboard boxes with handle cutouts; using containers with handles, lift straps or
textured containers; and avoiding awkwardly designed items.

Stabilize contents in boxes and containers to reduce surprises. Insert vertical
baffles or dividers, balancing the weight in a box or using packing materials to
avoid shifting parts. Minimize the potential for injury by protecting the employee
from loads with sharp edges or projections. Potential for injury also exists with
reactive loads, such as metal shavings.

Equipment
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