Best Practice Maintenance Strategies for Mobile Equipment
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Best Practice Maintenance Strategies for Mobile Equipment
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Best Practice Maintenance Strategies for Mobile EquipmentA Conference Paper presented to the Maintenance in Mining Conference - Bali, Indonesia By Sandy Dunn March 1997 IntroductionThe traditional approach to maintaining mobile equipment - based on fixed interval component replacements and overhauls - is rapidly dying. In its place is a new framework for maintaining this equipment using Condition Based Maintenance approaches, and which focuses strongly on the consequences of failure.At the heart of this new approach lies a strategic tool for determining the most appropriate Maintenance strategy for key items of Mobile Equipment, and their major components - Reliability Centred Maintenance. What is Reliability Centred Maintenance?Reliability Centred Maintenance originated in the Airline industry in the 1960's. By the late 1950's, the cost of Maintenance activities in this industry had become high enough to warrant a special investigation into the effectiveness of those activities. At the same time, the Federal Aviation Agency (FAA) in the US was becoming increasingly frustrated by its experiences showing that it was not possible to control the failure rate of certain types of engines by changing either the frequency or content of scheduled fixed-interval overhauls. Accordingly, in 1960, a task force was formed consisting of representatives of both the airlines and the FAA to investigate the capabilities of preventive maintenance.The establishment of this task force subsequently led to the development of a series of guidelines for airlines and aircraft manufacturers to use, when establishing maintenance schedules for their aircraft. The first set of guidelines was issued in 1967, and was used, amongst other things, to develop the maintenance program for the Boeing 747. A subsequent revision was issued, before, in 1974, the US Department of Defense commissioned United Airlines to write a report on the processes used in the civil aviation industry for the development of maintenance programs for aircraft. This report, written by Stan Nowlan and Howard Heap and published in 1978, was entitled Reliability Centered Maintenance, and has become the report upon which all subsequent Reliability Centred Maintenance approaches have been based. A frequent comment that is heard amongst Mobile Equipment Maintenance professionals is that "Reliability Centred Maintenance is fundamentally sound, but it wouldn't work if it was applied to Mobile Equipment". It is important to realise that RCM has its roots in the most technically sophisticated and maintenance-critical mobile equipment industry of all - the civil aviation industry. It is largely due to the application of RCM principles (together with the enhancements in aircraft design that have flowed from detailed RCM analysis) that the civil aviation industry has been able to improve its safety record from approximately 60 crashes per million take-offs in 1960, to less than 2 crashes per million take-offs today. And this improved performance has come at significantly reduced cost. The original Boeing 747 required 66,000 labour hours on major structural inspections before a major heavy inspection at 20,000 operating hours. In comparison, the DC-8 - a smaller and less sophisticated aircraft using Maintenance programs developed before the advent of RCM - required more than 4 million labour hours before reaching 20,000 operating hours. Furthermore, there are mine sites in Australia and other parts of the world that are effectively using RCM principles, and are reaping the rewards. This paper outlines some of the results that have been achieved, and how they have been achieved. Reliability Centred Maintenance II - The Framework for ImprovementThere are currently a large number of interpretations and variations of the original RCM logic in existence. Some are more rigorous than others, but there are essentially four variations which account for the bulk of the RCM work being performed around the world. The first is that contained in Nowlan and Heap's original 1978 report. The second is the official MSG3 version currently used in the aviation industry. The third, similar to MSG3, is contained in US Military Standard 2173. The fourth is RCM2.RCM2 was developed by John Moubray of Aladon Ltd in the UK over the course of more than fourteen years of experience in applying RCM principles in industrial applications. It does not represent a significant variation from the original RCM principles at a theoretical level - these principles are extraordinarily sound - although it has plugged some small gaps in the logic (notably the failure of the original RCM principles to explicitly consider the potential impact of a failure on the environment, and the logic relating to the effective treatment of "hidden" failures). However, it differs from the other approaches in two key ways:
The process contains training materials and an implementation approach that have been refined through the application of RCM principles at hundreds of sites, in dozens of industry sectors, including mining, over the last decade and more. The RCM2 implementation approach consists of several steps:
Of these steps, Steps 2 and 3 are the most critical to the success of the RCM project. Selecting the Appropriate Equipment for AnalysisFirst, a key consideration in the RCM2 approach, when considering the equipment for analysis, is that the analysis should be able to be completed within a reasonably short period of time (typically within 5 to 15 3-hour meetings). This is important for two reasons:
When dealing with mobile equipment, this generally means that a single piece of equipment is broken down into components or systems for analysis. This permits focus on those systems or components that provide the greatest potential benefits from RCM analysis. For example, at a major Australian coal mine, a haul truck was broken into the following 12 systems:
In assessing which equipment items, and which of their components or systems should be analysed first, the following criteria should be taken into account:
Building the Strategy TeamOne of the strengths of the RCM2 approach, and the reason that it can achieve sustainable improvements in equipment performance in excess of those obtained from other approaches to the implementation of RCM, is its team-based approach.In general, RCM2 recommends that a team of between three and five individuals, under the guidance of a skilled RCM facilitator, meets to perform the analysis. The composition of this team is critical to the benefits that will be obtained from the analysis. In general terms, the team should be made up of those people who know the equipment best. In general, this means having the following people involved in the analysis.
With mobile equipment, our experience has been that greatest value is obtained by having the Technical Specialist role filled by one or more representatives of the equipment manufacturer. This allows the organisation performing the analysis to benefit from the collective experience of others using the same equipment. The field service representative is often the most likely candidate for this position, however, we have found that, on occasions during an RCM analysis, there is information required relating to the more technical design aspects of the equipment that the service representative often is unable to answer. On these occasions, access to a more senior engineering representative of the manufacturer is required. It is often worthwhile having this person involved throughout the analysis, as well as the field service representative. This leads to another question frequently asked by mobile equipment maintainers - "Equipment manufacturers know more about the equipment than we will ever do. Their maintenance schedules are based on the collective experience of their entire fleet, so what benefit could there possibly be in us performing RCM analysis on this equipment". Equipment vendors and manufacturers cannot, and do not, know exactly what it is that you require from your equipment. Nor will they know, in detail, the conditions under which you operate your equipment. Your requirements and operating conditions will be different from other users of the same equipment, and will require different maintenance strategies. Manufacturers' generic Maintenance programs do not take these differences into account. For example, the failure modes and failure frequencies for a haul truck working at an iron ore mine in Western Australia's Pilbara, where haul trucks run uphill unloaded and downhill in a loaded state, where the average summertime ambient temperature is around 40 degrees Celsius, and where the humidity is generally less than 20%, would be quite different from those at a diamond mine in Canada, where the trucks run uphill loaded and downhill empty, where the average ambient temperature is below zero degrees Celsius, and humidities may be close to 100%. Yet a generic manufacturer's maintenance program would be the same for both applications. Furthermore, the source of most manufacturers' profits is from the sales of service and spare parts. There is, therefore, a potential conflict of interest for manufacturers between developing a maintenance program that is best for you, the client, and one that is best for them. Given this conflict of interest, is there difficulty in involving manufacturers in RCM analysis projects? Perhaps surprisingly, given that the project has the potential to reduce their income stream, our experience has been that most manufacturers are more than willing to participate in these projects. The professional manufacturers see it as being another opportunity for them to enhance the quality and level of service that they provide to their clients. A limited few have declined participation. All team members should be selected primarily because of their high level of skill and experience in dealing with the equipment being analysed. However, it is also important to realise that in the early RCM analyses, these individuals also play a vital role as Change Agents for the RCM process, as well as providing technical input to the decision making process. An important consideration in the selection of team members, therefore, is that they should all
It is worth noting that, in the Airline industry, RCM analyses are also performed using teams. These teams do include representatives from the aircraft manufacturers, but do not include shopfloor or flight crew representation. The teams are made up, primarily, of professional engineering staff. This perhaps reflects the greater maturity of this industry in applying the RCM principles, but it certainly is a reflection on the highly regulated and disciplined shopfloor culture of the airline industry which has been built up over decades of regulatory intervention. In short, flight crew and maintenance tradesmen follow highly detailed operating and maintenance procedures. If they fail to follow those procedures, then the regulatory authorities prosecute the airline and the individuals involved. For serious or repeated breaches, this generally leads to termination of employment within the industry. This same discipline does not exist within the mining industry. It is an interesting to consider whether it should exist. However, in the meantime, the differences in industry culture suggest that a different approach should be taken, if the benefits of RCM analysis are to be obtained in the mining industry. Overcoming the ChallengesIn applying RCM2 to mobile equipment there are a number of challenges to be overcome.Building the Case for ChangeBefore embarking on an RCM2 project (or any project which involves introducing significant change), it is important to establish the need for change. Some major RCM implementations have "run out of steam" very early on, often after only one or two analyses have been completed, and occasionally before even one has been completed. The reason for this very often can be attributed to a poorly defined and communicated need for change. There will always be many within the organisation who feel that there is little scope to improve the way things are done at present.It is important, therefore, that all the key decision makers, and especially those who will be being asked to contribute resources (people or financial) to the project be fully trained and familiar with RCM principles, the RCM2 implementation approach, and the potential benefits to be gained from that approach before the project is commenced. Their commitment to the project must be beyond question. Managing the Manufacturer's InputWhile, as mentioned earlier, manufacturers are generally willing to participate in RCM analyses, despite a potential conflict in interest with their desire to sell additional spare parts and service, situations often arise during the course of the analyses where this conflict of interest comes to the fore. It is often, in addition, difficult to argue with the "expert" from the manufacturer, given his assumed greater technical knowledge of the equipment being analysed.It requires a the RCM facilitator to be extremely strong, both in terms of his technical knowledge of the RCM process, and in personality, to manage this situation effectively. For example, in one RCM2 implementation at a large Iron Ore mine in Western Australia, there was considerable debate about the most appropriate maintenance strategy for maintaining Haul truck brakes. The manufacturer's representative insisted strongly that the manufacturer's original PM tasks and frequencies were optimal, and should not be adjusted. It took considerable debate and discussion over a reasonably lengthy period before the manufacturer's representative would accept that the Mining company's standard of performance required for Haul truck brakes was justifiably different from the standard set by the manufacturer, and that this indicated that a change was required to the maintenance schedules from those recommended by the manufacturer. Implementing the New Maintenance SchedulesThere is a temptation to think that the hard work is over once the RCM analysis is complete. In fact, the job is probably only about 50% complete once the RCM analysis is concluded. It remains to ensure that management is satisfied that the proposed routine maintenance tasks will ensure the desired long-term equipment performance, to compile the individual RCM decisions that have been made on a failure mode by failure mode basis into aggregated maintenance schedules, and then to implement those schedules.The first task is taken care of through a technical audit by another experienced RCM facilitator, followed by a review and formal sign-off by management. This requires management to dedicate some time to conduct the review, and management time is a resource in scarce supply! We have noted RCM projects that have stalled at the management review stage, simply because management do not have sufficient time (or did not consider the task to be sufficiently important - see the need to build a case for change discussed above) to complete this task within a reasonable timeframe. The second task requires the services of a maintenance planner - and these resources are also hard to obtain. However, the most difficult step in the process is often proved to be the final one - actually implementing the new maintenance schedules. Anecdotal evidence suggests up to 40% of scheduled maintenance inspections do not get marked off as having been completed, and up to 50% of those that do get marked off as having been completed are not actually done - the infamous "crib room checks". Old habits die hard, and if it was a simple matter of issuing new job cards, there would be no guarantee that the new maintenance schedules would be done any more effectively than the old ones they replace. Involving as many maintenance tradesmen as possible in the RCM analyses goes a long way to building their commitment to effectively performing the new scheduled inspections. By learning and applying the RCM principles, they become aware of the reasons why the changes have been made. They also, more importantly, become aware of why these inspections are required in the first place, and the potential consequences if they are not performed effectively. Similarly, involving production management in the RCM analyses also builds their commitment to releasing equipment for scheduled maintenance. Involving Production operators increases their commitment to performing their routine inspections more effectively, and also increases their commitment to the early reporting of defects and potential maintenance problems. However, not everyone can be involved in every analysis. Some may not participate at all - especially early in the program. We have found it vital that any RCM implementation program be accompanied by a communication and training program to inform all those not directly involved in the analyses, and build their commitment to change. This generally takes the form of a one-day training seminar. This seminar teaches the basics of RCM principles, and also guides the participants through a completed RCM analysis so that they can see the principles at work, and get a feel for the changes in the maintenance program that may result. Making the Resources availableA major challenge is making all the team members available for all the team meetings.In the ideal situation, team meetings would be held at the rate of one or two per week. This allows time for team members to continue in their normal jobs, without adversely impacting on their job performance. It also allows them time to find out important information that they need for the analysis, but which may not be immediately available. However, for mobile equipment analyses in the mining industry, we have found that the most successful way of making sure that team meetings are held, with all members present, is to temporarily remove the team from the workforce for the time required to complete the analysis - normally up to one week. This is generally easier to administer, given the difficulty of co-ordinating different shift rosters. It also means that the manufacturer's representative can attend all meetings, which is more difficult in remote mine sites, when meetings are held less frequently. The downside of this intensive approach, however, is that the analysis can be very wearing on the participants, particularly those used to more manual labour. This intensive, full-time approach also requires management to make a deliberate decision to release the team members from their normal duties for the analysis. For them to agree to do this, they must be convinced of the benefits that could be gained from the analysis - which is altogether appropriate and worthwhile (see building the case for change, discussed above). Obtaining Step Change in Equipment Performance LevelsTo date, RCM2 has been successfully applied to large mobile plant in at least four large Australian minesites in the Iron Ore and Coal industries. The items of plant covered includes Production Drills, Haul Trucks and large Electric Shovels.Example 1 - Haul TruckIn one case study at a large coal mine, RCM2 was applied to a large haul truck from one of the major manufacturers. At the time that the study was undertaken, the engine in the truck was subject to a routine major overhaul every 12,000 operating hours.Detailed RCM analysis, which included consideration of almost 500 failure modes for the engine, found that there was no failure mode for which the most appropriate preventive task was a routine overhaul, at 12,000 hours or at any other frequency. Condition Monitoring, including oil analysis and visual inspections and adjustments, was to be used instead to predict when the engine required major overhaul. Incidentally, a similar move to Condition-Based Maintenance by the Barrick Goldstrike Mine in Nevada extended the average time between major overhauls for Caterpillar 16G Grader Engines from the "required" 12,000 hours to almost 18,000 operating hours. Example 2 - Production DrillRCM2 was applied to a production drill at a large Iron Ore mine. At the second team meeting, the team determined that the main air compressor on the drill had three levels of protection built in - an exhaust air over-temperature trip, a high cooling water temperature trip, and a low cooling water level trip. The mine was based in North Western Australia, where ambient air temperatures were generally very high. According to the team members, the exhaust air temperature was almost always within 2 or 3 degrees of its trip point. However, the cooling water temperature was always well below its trip point. The group determined that the normal sequence for an over-temperature trip was that the compressor would always trip on the high exhaust temperature trip. Only if this trip was not working, would the compressor trip on high cooling water temperature. Only if both of these trips were not working, would the compressor trip on low cooling water level, however this was seen to be a very unlikely event.While performing this investigation, the compressor tripped on the low cooling water level trip. Visual inspection showed the cooling water system to be full of coolant - the trip had been a spurious one. An inspection of the log books showed that this spurious trip was a frequent cause of machine unreliability. The group came to the conclusion that the low cooling water level trip was unnecessary, and should be removed, but before doing so, checked with the equipment manufacturer to make sure they had not missed some vital fact. The manufacturer informed them that the low cooling water level trip had originally been installed for their machines that operated in sub-zero temperature conditions, where the coolant could, potentially, freeze, causing the radiators and hoses to burst. Under these conditions, the low cooling water level trip would be the first to activate. But the manufacturer's view was that this trip was totally redundant and unnecessary for equipment operating at high ambient temperatures. The low cooling water level trips were removed from the production drills, and significant improvements in equipment reliability were obtained, together with some reduction in maintenance costs.
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