An Italian meat-processing company produces sausages and typical Italian cotechino from the mix of different types of pork meat. Raw meat arrives from the supplier on metal trays of 35 – 45 kg. Trays are arranged on stacks about 170 cm tall (10 full trays/stack) and stored into the refrigerating room (Figure 1). Stack retrieval from the refrigerating room to the blending area is performed by means of a forklift truck. The meat blending process starts with the preparation of a meat mixture into a blending machine.
Figure 1. Preparation of the meat mixture for the blending machine.
Figure 2. Workers unloading full trays into the carts.
Two manual workers unload raw meat from the full stack of trays into special cart to feed the blending machine (Figures 1 and 2). The weight of each full tray is between 35 and 45 kg, while full carts weigh 200 kg. The height of the full stack is about 250 cm (15 empty trays/stack). After unloading, empty trays (10.5 kg) are manually stacked on piles of similar height (Figures 1 and 2). Unloading job is performed for 2 – 3 hours per day, in the morning.
The risk assessment for the unloading task has highlighted the presence of biomechanical overload of back and upper limb due to manual handling of loads over 3 kg. Such work conditions suggest the adoption of an engineering control to improve the ergonomics of the analyzed task. The following is the implementation of the proposed procedure for the application of the engineering control.
Application of the Proposed Procedure
1. Problem Identification
Employer, occupational health specialist, safety coordinator and workers representative perform the ergonomic analysis of the unloading task. The ergonomic risk assessment reveals high risk of biomechanical overload of back, upper limb and shoulders.
The risk of repetitive movements of the upper limb is analyzed with the OCRA checklist method (ISO 11228-3 2007). The OCRA checklist value for the left arm is 23 (high risk), while the value for the right hand is 20 (medium risk). Such values invert when the worker switches the arms to perform the same activity.
The risk assessment of the lifting tasks is performed through the Revised Niosh Lifting Equation (Waters 1993). The results reveal a VLI of 3.14, which confirms the high-risk due to the trays unloading activity. In particular, the presence of two operators to halve the handled weight is not a measure for the risk reduction. The lifted weight reduces from 45, 35 and 10.5 kg to 26.5, 20.5 and 6 kg. In particular, the EN 1005-2 provides directions to evaluate the actual lifted weight for two people handling the same load. Such standard applies a corrective factor (0.85) amplifying the average handled weight (e.g., 45 kg / 2 / 0.85 = 26.5 kg).
2. Nominee of the TC
Employer, production manager and safety coordinator nominate the TC. The following employees compose the team: safety coordinator, workers representative, external consultant expert on ergonomics, blending area supervisor.
3. Reunion of the TC
3.1. Screening of the Alternatives and Choice of the Control
The TC alternates two meetings with several surveys on the field. The surveys highlight evident disergonomics and reduced clearance due to the presence of fixed machines and plants. Given the characteristics of the task and the work environment, the TC chooses to install the customized semi-automatic manipulator in Figures 3 and 4.
Figure 3. Semi-automatic manipulator in the blending area.
The engineering control in Figure 3 assists the worker while reducing the ergonomic risk for the back and the disergonomics for the upper limb. The particular gripping system with multiple control of the manipulator improves the posture of the shoulder. Such system allows the operator to perform a wide range of movements with the arms. Furthermore, the retrieval of the full trays and the deposit of the empty trays on high stacks are performed assuming a comfortable posture (Figure 4). Consequently, the ergonomic risk is significantly reduced, despite the manual operation is not eliminated.
Figure 4. Tray unloading with the semi-automatic manipulator.
3.2. Plan of the Intervention
The TC contacts the supplier or the manufacturer of the solution to define the plan of the intervention. The design of the manipulator, the realization of the customized parts and the installation in the plant requires four months.
3.3. Definition of the Formation and Training Programs
The TC plans a training day for the personnel involved. The program of the training day includes a theory session of two hours, followed by a two-hours practical session. The four workers performing the unloading task are involved in the program. The safety coordinator and the occupational health specialist deliver the formation program to the workers, while the workers representative is responsible for the training session. The program ends with a post-training test that verifies the knowledge and the abilities of the personnel involved.
4. Intervention and Adoption of the Solution
The intervention is performed as planned in Step 3.2. The manipulator works at full speed following the pre-defined time schedule. The personnel involved are provided with a dedicated practical guideline addressing the proper utilization of the solution.
5. Actuation of the Formation and Training Programs
The formation and training programs are performed as planed in Step 3.3. After the post-training tests, the supervisor certifies the positive results and closes the intervention. The four workers adopt the solution, following the directions of the practical guideline.
6. Check and Analysis of the Results
Safety coordinator, first-line supervisor and workers verify the ergonomic impact of the solution, identifying the contribute to reduce the risk for biomechanical overload.
The application of the risk assessment methods in the ISO/TR 12295 reveals an acceptable risk for both the back and the upper limb. Finally, the supervisor of the blending area monitors the proper utilization of the solution, ensuring the respect of the directions in the practical guideline.
6.1. If the Check Is Ok, Then Perform a Task Analysis after 6/12 Months
The safety coordinator, the external consultant and the workers representative perform an initial check two months after the conclusion of the intervention. Further periodic checks are scheduled every 6 months. The occupational health specialist certifies the workers’ fitness to work every year, assessing the improvements in their safety and health.