Alicia Piedrabuena Cuesta; Carlos García Molina; Magda Liliana Cáceres; Alfonso Oltra Pastor*; Fernando Gómez Sendra*; Álvaro Page del Pozo*; Carlos Chirivella Moreno; Alberto Ferreras Remesal; Raquel Ruiz Folgado

Instituto de Biomecánica (IBV)
Universitat Politècnica de València
Camino de Vera s/n. Edificio 9C
46022 Valencia, España

* The IBV Health Technology Group, Bio-engineering, Biomaterials and Nanomedicine CIBER (CIBER-BBN)

The manual material handling is considered one of the main risk factors in the appearance of back injury.To perform the analysis of the level of risk, different more or less complex procedures are applied according to the type of task.

 

The main objective of this article is to provide information that will allow prevention technicians to choose the appropriate procedure for the assessment of ergonomic risks inherent in the manual material handling, one that will enable a more agile analysis without sacrificing reliability in the results.

 

In order to achieve this goal, we formulated ten case studies in which we varied both the handling conditions and their level of complexity. For each one of them we made a comparison between the result of applying the recommended procedure from the technical point of view and the simplified procedure. Thereafter, prevention technicians and experts in ergonomics assessed their usefulness. We chose the application Ergo/IBV as our computer tool.

 

The simplification proposals were found to be very useful in cases 6 (palletizing up to 8 layers), 7 (variability in weight) and 10 (different tasks that the same worker performs during the course of the day) and quite useful in case number 8 (important variability in terms of weight and frequency). "

INTRODUCTION

The manual material handling is considered one of the main risk factors in the appearance of back injury, primarily in the lumbar region. This type of musculoskeletal disorder (MSD) is usually very painful and debilitating and causes numerous complications. It is one of the main causes of absenteeism and there is a need therefore to evaluate the risk to whichworkers handling heavy loads are subjected and, depending on the results, to take the relevant measures for improvement.

To perform the analysis of the level of risk, different more or less complex procedures are applied according to the type of task(Table 1). Tasks involving the manual lifting of loads are defined according to the characteristics of the work being performed. Thus, “simple manual lifting” is one in which the handling conditions (the weight of the load, the horizontal distance and the vertical distance among other factors) do not change. However, if any of the factors involved in the lifting varies, then this is referred to as a “multiple task”. When the work involves performing more than ten subtasks, it is considered to be of a “variable nature”, and finally, if the worker rotates between two or more different lifting tasks, this is defined as a “sequential task”.

The prevention technician selects and applies the procedure that he or she considers most suitable according to the type of work being carried out in the workplace. However, in certain cases there is very little time to make such an assessment and therefore, despite the existence of specific ergonomic evaluation methodologies, it is extremely useful to provide him or her with simplification criteria.

The main objective of this article is to provide information that will allow prevention technicians to choose the appropriate procedure for the assessment of ergonomic risks inherent in the manual material handling, one that will enable a more agile analysis without sacrificing reliability in the results. With this purpose, the IBV has developed a guide to choosing and applying risk assessment procedures in tasks involving the manual material handling based on criteria of ease of use and precision in the calculation of the risk, within the framework of the funds made available by the Prevent Foundation through the 8th I+D Scholarship in Occupational Risk Prevention (2013-2014).

METHODOLOGY USED

In order to carry out the project, ten case studies (Table 2) were formulated in which we varied both the conditions of handling and their level of complexity. We chose the Ergo/IBV application as our computer tool as it permits the evaluation of occupational ergonomic and psychosocial risks and one of its modules features valuation methodologies of tasks involving themanual material handling of a simple, multiple, variable and sequential nature. These modules are based on the risk assessment procedures that are outlined in Table 1.

In each of the ten cases, we carried out an analysis using the procedure that was recommended from the technical point of view and, also, the proposed simplified procedure. We then made a comparative analysis of the risk indexes (RI) obtained for each one. Finally, in order to assess the simplifications that we made in the different case studies that we formulated, from the point of view of their complexity/simplicity, their usefulness as far as the prevention technician is concerned and even the time "savings" achieved during evaluation, we drew up an assessment questionnaire that was distributed to prevention technicians and experts in ergonomics.

RESULTS

The results obtained are summarized inTable 3. For each of the case studies we obtained an index of risk using the assessment method that was deemed most appropriate from the technical point of view and using the proposed simplified procedure. In case study 7 we obtained an index of equal risk between the two procedures. In case studies 2, 3, 4, 5, 6, 8 and 10 the risk level obtained from the two analyses was very similar. In relation to the scores obtained in the evaluation questionnaire as far as an improvement in the ease of use was concerned, the simplified procedures for tasks 6, 7 and 10 were considered very useful and quite useful in the case of procedure number 8.

CONCLUSIONS

After analyzing the case studies with the two proposed procedures, we found that their usefulness and accuracy varied according to the type of task and its level of complexity. The following is a summary of the main conclusions obtained for each of the different cases that we analyzed and of the comments provided by the technicians and experts in ergonomic methodologies.

♦ As case study 1 involved the simple manual material handling, no alternative procedure is required.

♦ In case studies 2, 3, 4 and 5 (case studies involving two weights or two heights) the simplified version provides a good approximation to the risk levels that are obtained using the most appropriate methodology from the technical point of view. However, and given the simplicity of the tasks analyzed, the time saved by using the simplified version is not very significant.

♦ Case studies 6 (palletizing to eight heights) and 7 (variability in weight) are clear examples of how a simple simplification, without the need for costly and complicated calculations, can significantly help the technician as far as agility and time-saving in the analysis is concerned.

♦  In case study 8 (important variability in parts in terms of weight and frequencies), the calculations that have to be made in order to make a multiple task more simple are not complex but do not represent a saving of time with respect to the basic procedure, especially whenever we have a file with the orders that we can export directly. However, from the technical point of view it is important to know how a variable task can be simplified to a multiple one, without having to limit oneself to the restrictions imposed in the procedure presented in the analysis of variable tasks.

♦  In reality, case study 9 (important variability in the frequency and weight of the parts) does not imply a simplification in the analysis, but it is very interesting to take into account the importance that a few references of very high weights can have at the level of the overall risk of the task, in relation to the total weight handled during the task.

♦ The simplification noted in case study 10 (different tasks performed by the same worker during the course of a day) is very interesting, both from the point of view of addressing the assessment, and from that of the simplicity of the simplification (the calculations that are required). Furthermore, from the technical point of view it is important to know how a sequential task can be simplified to a multiple one, without having to limit oneself to the restrictions imposed in the procedure presented in the analysis of sequential tasks.

The data obtained provide information of interest for prevention technicians when it comes to selecting a simplified risk assessment procedure for the manual material handling, that allows them to make an analysis in less time without losing accuracy in the results.

ACKNOWLEDGEMENTS

Project financed by the Prevent Foundation’s 8th I+D Scholarship in Occupational Risk Prevention (2013-2014).