CRANE CABINS’ SAFETY AND ERGONOMICS CHARACTERISTICS EVALUATION BASED ON DATA COLLECTED IN SWEDEN PORT

This paper presents an evaluation of crane cabins safety and ergonomics characteristics. It is based on previous research data collected for benchmarking analysis for crane cabins operating in one port in Sweden. Six crane cabin types are examined regarding eight characteristic divided in three groups: operator-control devices interaction, safety and anthropometric adjustment according to needs weighting data. Primary analysis of those data was conducted using Pareto analysis. Further analysis are done using developed indexes of characteristics performances while final conclusions were drawn for characteristic of crane cabins using crane index of performance. Taking into account all examined crane cabins only 52.5% of operatorcontrol devices interaction, 75% of safety and 60% of anthropometric adjustment issues are satisfied in current designs.


INTRODUCTION
The study of interaction between man and machine in the system, with regard to the improvements/adjustments in order to improve the efficiency of operations, reduce operator fatigue and protecting the health of operator and ensuring optimum working environment conditions, presents a challenge to engineers as well as many other experts that deal with this issue. Specific biological properties of man in relation to the technical requirements of the machine, which by their nature differ substantially, make this research very difficult. As the biological characteristics in general also have certain changes, research interactions in the man-machine system, aimed at its optimization, are focused primarily on the adjustment of certain characteristics of the machine to man, to use man optimal psycho-physical abilities. Specifically, large number of research is aimed in the direction of the smallest possible expenditure of energy and time by a man while performing work operations on the machine, as well as the preservation of human health when in contact with the machine and work environment. Such investigations require knowledge, in addition to technical, from range of other scientific disciplines, which essentially requires a multidisciplinary approach to problems solving. In this regard, in order to find optimal solutions specific problem is complex linking the necessary aspects of the research on a complex basis towards the achievements of individual scientific disciplines. Till today there is not large extent of research in the field of crane cabins convenience to the operator in aim to use minimal energy and time together with preservation of human health. One of rare research is the ergonomics field is conducted in steel plant in be developed by using the methods of physical, cognitive and organizational ergonomics with the main issue to solve problem of visibility and in that way allow higher productivity due to reduction of physical and psychological stress of the operator, as well as greater safety and security due to the integrated visual system. Authors in [08] even conclude that it could be a project with low economic risk. However, the importance of studying of this problem greatly exceeds the number of published papers. Back and lower limb disorders occur very often to crane operators [10] and almost 30% of them feels extremely uncomfortable [07,11]. One of crane cabins that operates in Serbia is shown in Figure 1. In construction and maintenance sectors cranes contribute to one-third of all fatalities, while large numbers of injuries and deaths is also encountered in transportation, manufacturing and warehousing industry sectors [07,12]. According to evident need this paper describes continuation of research on evaluation of crane cabin char-acteristics that operate in one Sweden port. It is based on benchmarking research data of Nordin (1) the operator must see the cargo, wharf and closest surrounding (2) the operator must understand signals and symbols in cabin (3) the operator has the need to see the display (4) all parts in cabin must be robust and steady due to often careless behavior of operators (5) the placement of indicators and regulators must be logical and ergonomically correct (6) the operator has the need for adjustable work posture and (7) there is a need to have all items fixed in cabin due to risk of theft. As shown in anthropometric adjustment (Table 1, characteristics 6-8).

Measurement of index of performance of characteristics
Purpose of this analysis includes comparison between characteristics, impacts of individual characteristics on types of crane cabins, as well as overall appraisal of characteristics of different crane cabin types and appraisal from group types point of view. In order to compare different types of crane cabins (Table 1), scores obtained by Likert scale were transformed and equalized by introduction of index of performance IP and crane index of performance CIP. Index of performance of characteristics can be defined as: where IP ij is the index of the single characteristic (i=1...6) for individual cranes (j=1...8) from Table  1, g ij is grade for crane characteristics, while cj, is maximum value of Likert scale for observed characteristic. Crane index of performance CIP is the sum of individual values of IP (1) for certain crane, i.e.
where CIPi is one of the cranes i=1,..,6. Those results are presented in Table 2 Table 3 are presented on Figure 2.

Pareto analysis
Influence of observed crane cabin characteristics is further conducted using Pareto analysis. In this case all characteristics are observed equally, regardless on type, starting from the characteristic that is least good. Pareto analysis for crane cabins in Luela port is presented at Figure 3. Analysis of data for Lulea port crane cabins indicates that critical characteristic is symbols understanding with participation of 46.88%. Fixed item in cabin amount 15.63% followed by understandable signals or seeing the cargo, wharf and closest surrounding or placement of indicators with 12.5%. Mentioned characteristics represent 75% of problems in Lulea port crane cabins. Liebherr crane cabin characteristics are expressed by Pareto graph as shown at Figure 4.  display has an influence that amounts 21.74%. Those characteristics cover 73.92% problems in MacGregor type of crane cabin. If see cargo, wharf and closest surrounding is included with 17.39% of influence, than 91.31% of problems are covered. Rest of observed types of crane cabins, i.e. Krupp, Tsuji and MHI are described together since their crane index of performance is significantly lower than above described types (Table 2). For Krupp crane cabin characteristics Pareto graph is shown at Figure 6, for Tsuji at Figure 7 and for MHI at Figure 8. Krupp crane cabins have four influential characteristic, while Tsuji and MHI have 5 influential characteristics with 75% of influence.

Index of unsuitability
Beside Pareto analysis of characteristics, overall comparison was conducted using index of unsuitability of crane types. Let index of unsuitability IU be

CONCLUSION
Conducted analysis of the considered crane cabins and their characteristics according to operators' needs satisfaction given in [1] and according to analysis done in this paper leads to following conclusions: Taking into account all crane cabins only 52.5% of operator-control devices interaction, 75% of safety and 60% of anthropometric adjustment issues are satisfied in current designs. It is evident from Figure 8 that even the best rated Lulea cabins still have a room for 20% improvement, while MHI cabins have unsuitability that amounts 62.5%.
Best characteristics have crane cabins at Lulea port and they are followed by Liebherr and MacGregor producers. Crane cabins at Lulea port and from Liebherr and MacGregor producers have significantly better characteristics than Krupp, Tsuji and MHI crane cabins regarding considered safety and ergonomics characteristics.
Main problems for Lulea port crane cabins are in the fields of interaction between crane operator and controls followed by safety characteristics.
Liebherr and MacGregor crane cabins could be improved by better placement of indicators and regulators and adjustable work posture, followed by the solution of visual problems of operator. It is evident that contemporary crane cabins designs still do not satisfy operator needs in the fields of both safety and ergonomics and according to that future research are expected in those aims. Authors in [13] also propose further research since performance and physical load on the operator should be further optimized by adjusting gain settings to the task, especially in the field of joystick design.