Elsevier

Applied Ergonomics

Volume 36, Issue 3, May 2005, Pages 263-273
Applied Ergonomics

An integrated analysis of ergonomics and time consumption in Swedish ‘craft-type’ car disassembly

https://doi.org/10.1016/j.apergo.2005.01.010Get rights and content

Abstract

Car disassembly is at the edge of extensive rationalisations due to increased legislative demands for recycling. This study focused on (1) assessing current mechanical exposures (physical work loads) for comparison with future rationalised systems, with particular emphasis on time aspects, (2) analysing disassembly work in terms of time consumption and exposures in constituent tasks as defined by a loss analysis technique, and (3) predicting the consequences of car disassembly rationalisation for mechanical exposures. The study showed that disassembly implied pronounced circulatory loads, and that more walking and higher lumbar peak loads were found than in studies of assembly work. Value-adding tasks comprised 30% of the total working time, and implied higher postural exposures for the head, arm, trunk and wrist, as well as less opportunities to recover, as compared to non-value-adding tasks. Organisational-type rationalisations can be expected to increase the time spent in value-adding work, thus increasing local exposures for the average worker, while a concurrent increase in mechanisation level might reduce circulatory exposures, the amount of walking, and peak lumbar loads.

Introduction

Swedish car disassembly companies have recently been investigated in a qualitative explorative study (Kazmierczak et al., 2004). Dismantlers, manufacturers and authority stakeholders described current production systems as ‘craft-type’, facing modest competition and showing good profitability. Work was described to contain a wide variety of tasks and considerable periods of set-up time. The respondents did not report any major musculoskeletal problems in the trade or any particular long-term sick leave. This statement could not, however, be validated due to the lack of specific disorder databases for this occupational group. While ‘craft-type’ production may offer more variation and autonomy to the individual operator than serial mass production (Eklund and Berggren, 2001), it might also imply larger whole-body exposures and higher peak loads due to its low level of mechanisation.

A new EU directive (The European Parliament, 2000/53/EU) now restricts the use of some materials and stipulates minimum reuse and recovery rates for end-of-life vehicles (ELVs, i.e. cars that have reached the end of their useful life). Thus, wastes from ELV must be reduced to 15% of the total car weight by the year 2006 and to 5% by 2015. This implies disassembly of more parts and materials that are not commercially attractive today. For production to stay profitable in spite of increased time spent in non-value adding tasks, comprehensive rationalisations are anticipated. During recent decades, most car assembly plants (‘forward factories’) have adopted lean production strategies (Womack et al., 1990; Docherty and Huzzard, 2003; Metall Report, 2003). A similar rationalisation is now expected in the ‘backtrack factories’ processing large volumes of ELVs (Kazmierczak et al., 2004).

Forward car factories have a long tradition of rationalisations to improve productivity, quality and profitability. Radical rationalisations may lead to excessive job strain and possibly to an increased occurrence of musculoskeletal disorders (Landsbergis et al., 1999). A common major aim in rationalisation is to make more efficient use of time through changes in work organisation. This may be pursued by a work intensification (Brödner and Forslin, 2002), e.g. elimination of rest pauses and a reliance on short-cycle tasks in serial processes. On the other hand, technological rationalisations may reduce whole body exposures and peak loads through increased mechanisation (Attebrant et al., 1995).

The resulting changes in mechanical exposure may be complex, and may be anticipated to cause for example a reduction in rest pauses. Thus, a working day may become less ‘porous’ in the sense that there are fewer opportunities to recover physically and mentally. Changes in ‘porosity’ occur in the time domain of exposure, as opposed to the intensity or level domain. While metrics describing exposure levels are often discussed in the ergonomic literature, there is a paucity of methods and parameters for assessing changes in time aspects of exposure (Wells et al., 1997; Mathiassen and Christmansson, 2004).

This study was a follow-up of our explorative study (Kazmierczak et al., 2004). It aimed at (1) assessing current mechanical exposures (physical work loads) for comparison with future rationalised systems, with particular emphasis on time aspects, (2) analysing disassembly work in terms of time consumption and exposure in constituent tasks as defined by a loss analysis technique, and (3) predicting the consequences of car disassembly rationalisation for mechanical exposures.

Section snippets

Subjects

The 13 car disassembly plants from which chief managers had participated in our previous exploratory interview study (Kazmierczak et al., 2004) were approached again; five of them expressed interest in engaging in the present follow-up study. A total of 10 healthy disassembly male workers (two from each company) participated (median age 39 yr (range 21–57 yr), weight 78 kg (range 73–88 kg), stature 177 cm (range 165–186 cm)). All subjects were right-handed and had a minimum of 1 year of work

Job exposures

In general, an operator was responsible for all dismantling tasks on a particular car. About 25% of the total working time was devoted to old ELV, while newer ‘insurance’ cars, typically crashed in accidents, occupied the remaining time. Based on our video recordings, the mean cycle time while disassembling an ELV car was about half an hour while insurance cars took 3–16 h to dismantle, depending on the number of valuable parts.

Job exposures according to the technical recordings are shown in

Discussion

The main findings of this study were that (1) direct work (value-adding tasks) comprised only 30% of the total working time, (2) value-adding tasks implied higher postural exposures of the head, arm, trunk and wrists compared to non-value-adding tasks, (3) circulatory exposures and walking were substantial and, (4) high low back peak loads occurred.

Conclusions

We documented exposures in the total job as well as in value-adding and non-value adding tasks in car disassembly—an industry on the edge of major rationalisations. The results supported our hypotheses from a prior explorative study that present disassembly can be characterised as ‘craft-type’ work, implying high circulatory exposures, a large number of steps and high peak lumbar loads. However, ‘local’ exposures, estimated as postures and velocities of the trunk, head and upper arm were in

Acknowledgements

This work has been financially supported by National Institute for Working Life in Sweden (Dnr: 1998-0734). The participation of car dismantlers made this project possible and they are gratefully acknowledged. The authors would like to thank Anna Sandell for her assistance in the primary data analyses.

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