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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
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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
Bending Greaterthan 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) Evaluation and Risk Factors
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)
Use a scissor lift with pallet Use a vacuum lifting system Solution
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
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
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