Ergonomic Assessment

Josh Prince

Keith Heerdegen

Mary Cook

Stacking

We measured 3 types of boxes that are most common it the warehouse.

We recorded the dimensions and more importantly the force the box exerts.

Box1

Height-15 in Length-24 in Width-14 ½ in Weight-18 kg Force- 50 lbs/sq. in

Box2

Height- 20 ½ Length-25 ½ Width-17 ½ Weight-14 kg Force-24 lbs/sq. in

Box3

Height-22 Length-20 ½ Width-9 ½ Weight-12 kg Force-22 lbs/sq. in

Job description

NIOSH recommended weight is 23 kg (225 N).

Employees commonly are either stacking these boxes off pallets or back on them.

Can stack anywhere from 5 boxes to hundreds of boxes in a given job.

Lift boxes overhead

Evaluation and Risk Factors

Bending– Greater than 15°

Twisting– Greater than 15° in some

incidences

Head and Neck– Ideal

Energy consumption increases 50% when working bent over

Can cause over-exertion (account for ¼ of all reported occupational injuries)

Will cause increase stress on discs in back (up to 225%)

Evaluation and Risk Factors

Arms– Reaching overhead – Over extending

Elbows– Out of position– Not at 90° angle

Wrists– In and out of neutral

position– Extended greater than 10°

Back and disc problems

Shoulder pain

Tendinitis in elbow or shoulder

Arthrosis (joint degeneration)

Evaluation and Risk Factors

Standing– Knees are straight and not

locked Repetition

– Lifting can occur more than 20 times in an hour

Force– Boxes can weigh over

25lbs. Grip

– Moderate pinch grip– Awkward handle

Muscle strain

Arthritis

Fatigue

Muscular- lactic acid build up and shortage of oxygen

General (weariness)

Solution

Lift with legs, not with back Keep arms at sides and elbows at 90 degrees (less

strenuous) Wrists should be in neutral position at all times. Keep the boxes on pallets to avoid extra stacking Take breaks to avoid fatigue Be as efficient as possible (human body only

converts 30% to energy)

Solution

Use a scissor lift with pallet

Use a vacuum lifting system

Pallet Jacks

Dimensions of a stacked pallet:

– Height- 82 ½ inches

– Width- 43 ½ inches

– Length- 49 inches

– Weight- 789lbs

Using Pallet Jacks

Employees use pallet jacks to move pallets that can range from 300 lbs to 1400 lbs.

Use both push and pull forces.

Distances vary but can end up pushing for an extended period of time (up to 1 minute without stopping)

Using Pallet Jacks

Pull Force- 26 lbs/sq. in

Push Force- 58 lbs/sq. in

Evaluation and Risk Factors

Back and Neck– Straight and upright– No bending involves

Twisting– Minor twisting when

turning the pallet jack

Standing– Knees are straight and

not locked

Injuries will most likely occur at the shoulder, arm, or upper back.

Causes a lot of muscle strain especially in the legs. Pulled muscles Muscle strains

Evaluation and Risk Factors

Arms– Extended in front of body

when pulling– In good position when

pushing

Elbows– In front of body and not

at 90° when pulling– At sides and close to 90°

when pushing

Tendinitis

Arthrosis (joint degeneration

Fatigue

Possible CTS

Evaluation and Risk Factors

Wrist– In neutral position when

pulling– Extended greater than

10° when pushing Repetition

– Can be exerting force for up to a minute without rest

– Usually frequent stops (times for rest)

Evaluation and Risk Factors

Grip– Slight pinch grip

Evaluation and Risk Factors

Static effort in the arms (prolonged state of contraction of the muscles). This causes:

– Less oxygen to the muscle Lactic acid builds up Muscle can’t recover

– Fatigue– Higher heart rate– Higher energy consumption– Longer rest periods needed– Less efficient

Solutions

Pull the pallet jack instead of push since it creates less of a force.– It keeps the wrists in neutral position.

Keep the elbows at sides and at 90° while pulling.– More efficient.– Less stress on the arms and shoulders.

Solutions

Take frequent rest break to avoid fatigue.– Will also help limit the static effort.

Avoid twisting the body when turning. – Turn with the arms

Try to install a more adequate handle on the jack.

Use a automatic power jack

References

Kroemer, K. H. E. and E. Grandjean. “Fitting the Task to the Human: Fifth Edition.” Taylor and Francis. 1997