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MS contribution to maintenance management Comment on “Maintenance management decision making”
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European Journal of Operational Research 65 (1993) 140-142 North-Holland
Short Communication
The O R / M S contribution to maintenance management Comment on "Maintenance management decision making" R.J. O r m e r o d OR and Systems Group, School of Industrial and Business Studies, University of Warwick, Coventry, Warwickshire CV4 7AL, UK Received September 1992
Wherever one is concerned with physical assets which support a 'production' process, maintenance is a crucial function. Success in industries as diverse as airline, metal, chemical, oil, electricity, distribution and production line manufacturing depends on maintenance management. I read the invited review by Pintelon and Gelders (1992), "Maintenance management decision making", with great interest and would recommend others to do so. However, I was left feeling uneasy about the implied role of O R / M S in the maintenance field. No doubt the impression I gained was unintended by the authors but as they say, maintenance managment of industrial equipment is important and in my view it is particularly important to O R / M S with its historic roots in the operational domain. I should say at the outset that I make no claim to recent experience in maintenance management nor to knowledge of the present state of theory and practice, hence my interest in reading the paper. The authors state that "Despite the fact that the gap between O R / M S theory and practice is slowly narrowing, it remains very large in mainteCorrespondence to: Prof. R.J. Ormerod, OR and Systems Group, School of Industrial and Business Studies, University of Warwick, Coventry, Warwickshire CV4 7AL, UK.
nance management". This is a perception that is presumably shared by others as references are given. I found this surprising. When I was an operational researcher in the field in the midseventies, maintenance management was one of our mainstays. Our work was a continuation of a long history of involvement in the subject area which is recorded in the history of O R (Tomlinson, 1971) in the UK's National Coal Board (NCB). The work was highly practical, drew on theory and resulted in substantial improvements. One aspect of the work is referenced (Howard, 1984) by the authors of the paper. This concerned the setting up of a service exchange system for sub-assemblies of powered suports. This was part of a wide programme of research into the purchase, use and maintenance of plant conducted for headquarters and many of the coalfield areas. An example of the coalfield work was presented at a Royal Statistical Society conference (Howard and Ormerod, 1977) but I am not sure whether it was published in an accessible journal. These examples were only the tip of an iceberg which contained research into surface plant, underground machinery, stores and repair workshops. This experience was not unique to the NCB. In 1965 the British Iron Steel Research Association published a history of the first 20 years of O R in
0377-2217/93/$06.00 © 1993 - Elsevier Science Publishers B.V. All rights reserved
R.J. Ormerod / The O R / M S contribution to maintenance management
the industry (Collcutt, 1965) a substantial section of which is devoted to maintenance. Again theory was used in a wide variety of situations to improve management practice. More recently Christer (1984) reviewed the contribution of O R to industrial maintenance. He noted that interest in the area had increased and maintenance studies are no longer the exception in a company's portfolio of O R projects. He further states: "It is difficult to conceive of a maintenance organisation of any size without what an operational researcher would identify as a standard problem of a bread and butter nature, where established modelling procedure from elsewhere will readily translate, albeit with some minor modification to account for environmental characteristics". Discussing the reasons for the perceived gap Pintelon and Gelders say "Maintenance problems have many aspects, therefore no general models can be formulated and model assumptions play a crucial role". Quite so, this is why research into the particular operations (i.e. practical OR) has much to offer. They continue, "Essential to making the appropriate model assumptions are: a sound engineering insight, a thorough understanding of the interaction between maintenance and the other business functions and a clear view of the management trade-offs involved. The stochastic character of maintenance activities (unexpected events, uncertainty about processing times) are an additional complication. Lack of appropriate data is another problem". Again quite so, these are all reasons why the well rounded and well grounded O R practitioner, with abilities to cross functional disciplines, to appreciate the wider implications of operational decisions, to understand the implications of stochastic processes and to dig out useful data, is ideally placed to make a wideranging contribution to practice. Both Pintelon and Gelders (1992) and Christer (1984) refer to a survey by Turban (1967) which analysed the low priority of maintenance in the eyes of O R personnel. According to Christer, among the contributory factors identified by Turban were communications problems between the O R analyst and the engineer. Christer asserts bluntly: "Such an observation is thought not applicable within the UK, where it is asssumed an analyst will speak the language of his client".
141
Presumably this assumption is still correct for the UK; it would seem to remain a problem in Europe as a whole. The root of the problem seems to lie in the way that O R / M S is perceived as theory, techniques and science rather than technology and practice grounded in the workplace (i.e. for maintenance, the world of the engineer). Pintelon and Gelders proceed to list quantitative techniques (optimisation, Markov, Queuing, Simulation, etc.) that may be applied to maintenance management, leaving the impression that the application of techniques is the O R / M S contribution to maintenance management. This view of O R / M S , the reasons for its development and its dangers have been addressed before (see, e.g. Haley, 1984) and the arguments do not need repeating here. Early in the paper the authors state: "Operations (sic) R e s e a r c h / M a n a g e m e n t Science techniques are among the tools which can help maintenance decision making. They allow subjective decisions to be replaced by objective decisions, taking into account accurately formulated functions and a complex set of constraints". They then go on to describe the slow growth in the adoption of the techniques in the field. This again encourages a narrow and overly restricted view of O R / M S . Far from striving to replace subjective decisions, the operational researcher could attempt to understand and reconcile contrasting subjective views, or help the decision makers reach their subjective view quicker, or capture the subjective views of experts for wider use, or try to design information flows to support better informed subjective decisions. Christer (1984) recognises the importance of subjective views in his section on problem definition where he discusses methods for collecting and using both objective and subjective information. There is a role for the inventor of better, quicker, richer algorithms but if "no general models can be formulated", other directions may be more productive. Pintelon and Gelders seem to be accepting a model of O R as science informing the practitioners of maintenance management, presumably engineers. What is missing is a recognition of the model of O R practitioners as technologists (Keys, 1989) striving to improve maintenance manage-
142
R.J. Ormerod / The OR/MS contribution to maintenance management
ment in particular organisations, drawing on the techniques of OR, engineering, statistics, psychology or whatever. The acid test for O R / M S is not simply whether the techniques and tools are taken up by management but whether OR practitioners are succeeding in helping maintenance management organisations improve their performance.
References Christer, A.H. (1984), "Operational Research applied to industrial maintenance and replacement", in: R.W. Eglise and G.K. Rand (eds.), Developments in Operational Research, Pergamon, Oxford. Collcutt, R.J. (1965), The First Twenty Years Operational Research, British Iron and Steel Research Association (BISRA), London.
Haley, K.B. (1984), "Techniques maketh OR", Journal of the Operational Research Society 35/3, 191-194. Howard, J.V. (1984), "Service exchange systems - the stock control of reparable items", Journal of the Operational Research Society 35, 235-246. Howard, J.V., and Ormerod, R.J. (1977), "Models of colliery organisational systems", Royal Statistical Society Industrial Applications Section and Research Section Conference, UMIST, Manchester. Keys, P. (1989), "OR as technology: Some issues and implications", Journal of the Operational Research Society 40, 753-759. Pintelon, J.M., and Gelders, E.F. (1992), "Maintenance management decision making", European Journal of Operational Research 58, 301-317. Tomlinson, R.C. (1971), OR Comes of Age, Tavistock, London. Turban, E. (1967), "The use of mathematical models in plant maintenance decision making", Management Science 13 , 342-358.
European Journal of Operational Research 65 (1993) 140-142 North-Holland
Short Communication
The O R / M S contribution to maintenance management Comment on "Maintenance management decision making" R.J. O r m e r o d OR and Systems Group, School of Industrial and Business Studies, University of Warwick, Coventry, Warwickshire CV4 7AL, UK Received September 1992
Wherever one is concerned with physical assets which support a 'production' process, maintenance is a crucial function. Success in industries as diverse as airline, metal, chemical, oil, electricity, distribution and production line manufacturing depends on maintenance management. I read the invited review by Pintelon and Gelders (1992), "Maintenance management decision making", with great interest and would recommend others to do so. However, I was left feeling uneasy about the implied role of O R / M S in the maintenance field. No doubt the impression I gained was unintended by the authors but as they say, maintenance managment of industrial equipment is important and in my view it is particularly important to O R / M S with its historic roots in the operational domain. I should say at the outset that I make no claim to recent experience in maintenance management nor to knowledge of the present state of theory and practice, hence my interest in reading the paper. The authors state that "Despite the fact that the gap between O R / M S theory and practice is slowly narrowing, it remains very large in mainteCorrespondence to: Prof. R.J. Ormerod, OR and Systems Group, School of Industrial and Business Studies, University of Warwick, Coventry, Warwickshire CV4 7AL, UK.
nance management". This is a perception that is presumably shared by others as references are given. I found this surprising. When I was an operational researcher in the field in the midseventies, maintenance management was one of our mainstays. Our work was a continuation of a long history of involvement in the subject area which is recorded in the history of O R (Tomlinson, 1971) in the UK's National Coal Board (NCB). The work was highly practical, drew on theory and resulted in substantial improvements. One aspect of the work is referenced (Howard, 1984) by the authors of the paper. This concerned the setting up of a service exchange system for sub-assemblies of powered suports. This was part of a wide programme of research into the purchase, use and maintenance of plant conducted for headquarters and many of the coalfield areas. An example of the coalfield work was presented at a Royal Statistical Society conference (Howard and Ormerod, 1977) but I am not sure whether it was published in an accessible journal. These examples were only the tip of an iceberg which contained research into surface plant, underground machinery, stores and repair workshops. This experience was not unique to the NCB. In 1965 the British Iron Steel Research Association published a history of the first 20 years of O R in
0377-2217/93/$06.00 © 1993 - Elsevier Science Publishers B.V. All rights reserved
R.J. Ormerod / The O R / M S contribution to maintenance management
the industry (Collcutt, 1965) a substantial section of which is devoted to maintenance. Again theory was used in a wide variety of situations to improve management practice. More recently Christer (1984) reviewed the contribution of O R to industrial maintenance. He noted that interest in the area had increased and maintenance studies are no longer the exception in a company's portfolio of O R projects. He further states: "It is difficult to conceive of a maintenance organisation of any size without what an operational researcher would identify as a standard problem of a bread and butter nature, where established modelling procedure from elsewhere will readily translate, albeit with some minor modification to account for environmental characteristics". Discussing the reasons for the perceived gap Pintelon and Gelders say "Maintenance problems have many aspects, therefore no general models can be formulated and model assumptions play a crucial role". Quite so, this is why research into the particular operations (i.e. practical OR) has much to offer. They continue, "Essential to making the appropriate model assumptions are: a sound engineering insight, a thorough understanding of the interaction between maintenance and the other business functions and a clear view of the management trade-offs involved. The stochastic character of maintenance activities (unexpected events, uncertainty about processing times) are an additional complication. Lack of appropriate data is another problem". Again quite so, these are all reasons why the well rounded and well grounded O R practitioner, with abilities to cross functional disciplines, to appreciate the wider implications of operational decisions, to understand the implications of stochastic processes and to dig out useful data, is ideally placed to make a wideranging contribution to practice. Both Pintelon and Gelders (1992) and Christer (1984) refer to a survey by Turban (1967) which analysed the low priority of maintenance in the eyes of O R personnel. According to Christer, among the contributory factors identified by Turban were communications problems between the O R analyst and the engineer. Christer asserts bluntly: "Such an observation is thought not applicable within the UK, where it is asssumed an analyst will speak the language of his client".
141
Presumably this assumption is still correct for the UK; it would seem to remain a problem in Europe as a whole. The root of the problem seems to lie in the way that O R / M S is perceived as theory, techniques and science rather than technology and practice grounded in the workplace (i.e. for maintenance, the world of the engineer). Pintelon and Gelders proceed to list quantitative techniques (optimisation, Markov, Queuing, Simulation, etc.) that may be applied to maintenance management, leaving the impression that the application of techniques is the O R / M S contribution to maintenance management. This view of O R / M S , the reasons for its development and its dangers have been addressed before (see, e.g. Haley, 1984) and the arguments do not need repeating here. Early in the paper the authors state: "Operations (sic) R e s e a r c h / M a n a g e m e n t Science techniques are among the tools which can help maintenance decision making. They allow subjective decisions to be replaced by objective decisions, taking into account accurately formulated functions and a complex set of constraints". They then go on to describe the slow growth in the adoption of the techniques in the field. This again encourages a narrow and overly restricted view of O R / M S . Far from striving to replace subjective decisions, the operational researcher could attempt to understand and reconcile contrasting subjective views, or help the decision makers reach their subjective view quicker, or capture the subjective views of experts for wider use, or try to design information flows to support better informed subjective decisions. Christer (1984) recognises the importance of subjective views in his section on problem definition where he discusses methods for collecting and using both objective and subjective information. There is a role for the inventor of better, quicker, richer algorithms but if "no general models can be formulated", other directions may be more productive. Pintelon and Gelders seem to be accepting a model of O R as science informing the practitioners of maintenance management, presumably engineers. What is missing is a recognition of the model of O R practitioners as technologists (Keys, 1989) striving to improve maintenance manage-
142
R.J. Ormerod / The OR/MS contribution to maintenance management
ment in particular organisations, drawing on the techniques of OR, engineering, statistics, psychology or whatever. The acid test for O R / M S is not simply whether the techniques and tools are taken up by management but whether OR practitioners are succeeding in helping maintenance management organisations improve their performance.
References Christer, A.H. (1984), "Operational Research applied to industrial maintenance and replacement", in: R.W. Eglise and G.K. Rand (eds.), Developments in Operational Research, Pergamon, Oxford. Collcutt, R.J. (1965), The First Twenty Years Operational Research, British Iron and Steel Research Association (BISRA), London.
Haley, K.B. (1984), "Techniques maketh OR", Journal of the Operational Research Society 35/3, 191-194. Howard, J.V. (1984), "Service exchange systems - the stock control of reparable items", Journal of the Operational Research Society 35, 235-246. Howard, J.V., and Ormerod, R.J. (1977), "Models of colliery organisational systems", Royal Statistical Society Industrial Applications Section and Research Section Conference, UMIST, Manchester. Keys, P. (1989), "OR as technology: Some issues and implications", Journal of the Operational Research Society 40, 753-759. Pintelon, J.M., and Gelders, E.F. (1992), "Maintenance management decision making", European Journal of Operational Research 58, 301-317. Tomlinson, R.C. (1971), OR Comes of Age, Tavistock, London. Turban, E. (1967), "The use of mathematical models in plant maintenance decision making", Management Science 13 , 342-358.