1)  Lifting from the Mono.

2)  Stacking parcels too high.

3)  Pushing the whole line.

i) Lifting more than 23kg (50)lbs from the mono by one worker.  This increases the strain on the lower back to above recommended levels particularly when it is near the bottom of the mono.

ii) Picking parcels from the mono without using the forklift to raise the mono and/or not lowering the side of the mono to it’s lowest point contributes to excessive reaching and stooping for parcels.  This places unnecessary and unacceptable stress on the shoulders and lower back.

iii) Workers may experience excessive manual material handling demands as a result of the job rotation schedule.  When back to back heavy lifting rotations occur. 

This assessment included various ergonomic tools such as a biomechanical model, WSH MMH checklist, NIOSH 1991 Lifting Equation, Moment of Force calculations as well as kinesiology principles.

Note:  Respondents to the discomfort survey identified the Feeder and Lane 4 positions as the 2 main tasks that contribute to work related discomfort.

Stacking parcels above chest level.

The conveyor is 84.5cm high with parcels adding an additional 50-69cm.  This can be 21cm above shoulder height for the average female worker.  This reach and the weight of the item can increase the risk of injury to the shoulder area.

Pushing the whole line down the conveyor.

The force to push random parcels was measured to be15-25kg.  This task is acceptable if the workers do not push across the body and they keep their ‘elbows in’ when pushing.

All workers should use the forklift and drop the sides of the mono cage. 

Before proper job procedures and training is implemented, investigate whether all monos are functioning properly and invite worker input to determine why the forklift or the drop sides of the mono are sometimes not used.

Heavy items (>23kg) should be lifted by 2 workers.  Note: the capabilities of the worker should be taken into account as most ergonomic guidelines are based on young and healthy workers.

Review the job rotation schedules to determine if the feeder position is followed immediately by another heavy lifting task, eg Lane 4. Investigate a shorter duration at this task if the previous recommendations cannot be met.

Keep stack heights to below 132.5cm or 52 ¼”.

Reference – Body Space: Anthropometry, Ergonomics and the Design of Work, 2^nd Ed., Taylor and Francis.

Develop proper job procedure and training.

A slight negative slope on the conveyor has helped in other similar workplaces.

1)  Fit, Reach and See

2)  Resting the palm of the hand on the key pad.

3)  Pushing parcels onto the conveyor.

i) Work should be designed so that the worker can FIT into their workstation, REACH regular items with ease and SEE their tasks in a clear field of vision.

ii) The Coding task when performed in a sitting position does not allow the workers to fit, reach or see well.  Most respondents to the discomfort survey use this as a ‘sit’ workstation.

iii) If the worker sits low in the chair so that their knees do not hit the side of the conveyor then pushing parcels onto the main conveyor becomes strenuous on the shoulder joint.

iv) If workers sit up in the chair then their legs do not ‘fit’ and upper body twisting occurs to place parcels onto the conveyor.

v) Reaching for the keypad while reading the code on the parcel is outside the proper ‘work reach envelope’.  This increases the strain on the shoulders and twisting on the spine.

The placement of the bar coder is also a little outside the proper reach envelope.

vi) The monitor and keyboard are too low for proper viewing.  This results in neck and eye strain while looking at/for information.

i) Resting the palm of the hand on the keypad is an ergonomic risk factor known as ‘direct pressure’.  This pressure can build up in the hand and cause fatigue and other nerve related discomfort.

i) Parcels are usually pushed straight out onto the conveyor.  When the worker is facing the workstation (monitor) this places the shoulder in an awkward position.  There may be some reaching behind the body, pushing with the elbow behind the midline of the body or extended reaching.

ii) Also, the frequent piling of parcels leads to tossing parcels over each other in order to be placed on the conveyor.  This is not a smooth motion for the shoulder to do and places some mechanical strain on the shoulder joint. 

iii) There is also an incline between the two conveyors.  This adds to the shoulder strain to push the parcels.  The force to push a parcel at this location was 18.2kg.  The same parcel was measured at the end on the conveyor.  That measurement was 13.6kg

This workstation is the only sitting position in this area.  Therefore, it should be designed as a comfortable ‘sit workstation’.

The conveyor needs to be redesigned to allow adequate leg clearance and allow the worker to get as close as possible to their work.

See figure 2.1

The working envelope should be a 45° angle with the workers facing the centre of the angle between the conveyor and workstation table.  Their feet should be in a ‘V’ position and supported with adjustable footrests.  The chair should provide back support, be height adjustable and should swivel easily.  A sit-stand stool may also be a good choice for those that prefer to stand and those with arm lengths less than 50%ile average. See figure 2.1.

The most frequent objects reached for (keypad, parcels and bar code) should be located in the 10 o’clock and 2 o’clock position and oriented towards the worker.  See figure 2.2.

The best place for the monitor is where most workers prefer it to be.  This means that depending on lighting conditions, eye-monitor distance, monitor angle and software font size and colour. There are guidelines but worker consultation and asking their input is the best practise in this situation.

The current key pad has many angle adjustments.  Workers should be trained to avoid ‘direct pressure’, and why it is important to keep a good wrist position while using the equipment.

The placement of parcels onto the conveyor would be improved if the workstation is designed as suggested in figure 2.1.  Reaching behind the body and extending the arm should be minimized.

Consult with the engineering department to determine the most feasible options for reducing the build up of parcels. 

Can a buffer system be introduced so that parcels do not have to be thrown over another parcel?  Can a new orientation of coders and the conveyor system be developed to eliminate this problem?  See figure 2.3 for an example.  Is there adequate space at this location and others?  Can the pushing onto the second conveyor be eliminated?  Can the worker control their section of the conveyor belt with the use of foot pedals? 

1)  Reaching too far to push parcels.

2)  Pushing certain parcels over the roller ball table.

The reach distance for pushing the parcels to the conveyor is usually 44-80cm depending on the size of the parcel.  The parcel needs to be pushed far enough for the conveyor to ‘catch it’.  The reach distance for this task should be limited to 45cm.  Otherwise extended reaching stresses the shoulders and the lower back.

The distance between the roller balls (5.5cm) makes some heavier boxes more difficult to push and may allow for the strapping to get caught.  This increases the force required to push the parcels. These unexpected and forceful ‘jerky’ motions can lead to shoulder strain.

Reduce the distance that workers have to push parcels to ~45cm. 

This may be accomplished by improving the layout of the current system, semi-automating the process or by providing a mechanical assisting device.  There are a number of options that are in use in the food processing and millwork industries that solve this problem.

References - Body Space: Anthropometry, Ergonomics and the Design of Work, 2^nd Ed, Taylor and Francis.

Develop a roller ball table that has a smaller diameter between the balls.