Download - Royal Australian Navy

More documents

Recommendations

Info

NAVY ENGINEERING BULLETIN MARCH 2003 39 cases (11%), whereas Patterns D, E and F were not age related and constituted the vast majority of failures (89%). In the case of Pattern F, scheduled overhaul activities associated with the traditional Pattern B introduced infant mortality and contributed to early life failures and the appalling accident rate at the time of 60 crashes per million take-offs (approximately 40 of these being due to equipment failure). The low percentage of age-related failures (Patterns A, B and C) and the preponderance of failure patterns D, E and F in automated systems shifted the aviation world towards an emphasis on condition-based maintenance with a corresponding move away from scheduled overhaul activity as the primary means of asset care. This shift in maintenance focus has been at the root of a 120-fold improvement in aircraft safety due to equipment failure since the mid 1960s. The history and development of RCM Recognition of the complex nature of aviation equipment failure culminated in a new approach to the development of aircraft maintenance programmes which was first trialed on the Boeing 747 in the late 1960s. This methodology, known as MSG-1 recognised that: • scheduled overhaul had little effect on overall reliability of a complex item unless there was a dominant age related failure mode; • the intrusive nature of the overhaul activity itself was the cause of unreliability; and • there are many items and failures for which there is no effective form of scheduled preventive and/or predictive maintenance. Over the subsequent decade, the rudimentary MSG-1 approach was further developed and towards the end of the 1970s, both commercial airline and defence aviation safety and reliability had been transformed. In 1974, the US Department of Defense commissioned United Airlines to prepare a report on the processes used by the civil aviation industry to prepare maintenance programmes for aircraft. The resulting document, entitled ‘Reliability-centred Maintenance’ by its’ authors, Stan Nowlan and Howard Heap, heralded the birth of a new era in maintenance programme development. Reliability-centred Maintenance is therefore the specific maintenance development process described in this report. In the early 1980s, RCM was first applied to non-aviation assets, primarily in the South African mining industry through John Moubray. Through this pioneering work, Moubray discovered that the original Nowlan and Heap FIGURE 3: RCM DEVELOPMENT SINCE 1965 concept, though sound, needed further development for nonaviation use and also required a comprehensive training process to underpin it. In 1990, Moubray developed the industrial version of RCM known as RCM II which over the past decade or so has become the standard approach adopted throughout the world. The principal developments of RCM over a thirty year period are shown above (Figure 3). In the mid 1990’s, the Royal Navy developed a naval version of Moubray’s RCM II known originally as Naval Engineering Standard 45, since issued as Defence Standard 02-45. Both RCM II and Def Stan 02-45 approaches are fully compliant with a new SAE Standard SAE JA 1011 (Evaluation Criteria for Reliabilitycentred Maintenance processes). So what is RCM? RCM is a process used to determine the maintenance requirements of any physical asset so that it fulfils its intended functions over the life cycle and in its’ operating context. The RCM process must therefore start by defining user requirements or ‘functions’. This in itself is usually something of a challenge for most organisations. Unless this user requirement is understood, it is hardly surprising that operators and maintainers have difficulty agreeing and communicating on when equipment failure has occurred. SAE JA 1011 compliant RCM asks the following seven questions from which a comprehensive approach to failure for the asset can be developed: • What are the functions of the asset in its present operating context? • How can the asset fail to fulfil each function? • What would cause each functional failure?
40 NAVY ENGINEERING BULLETIN MARCH 2003 • What happens when each failure occurs? • In what way does each failure matter? • What can be done to predict or prevent each failure? • What should be done if no suitable proactive task can be found? The first four questions develop a functional Failure Modes and Effects Analysis (FMEA) and the last two define the appropriate failure management policy. The vitally important fifth question determines how we should react to the failure in relation to whether the failure is ‘Hidden’ or ‘Evident’ and whether Safety, the Environment or Operations (Mission in the naval sense) are FIGURE 4: TYPICAL RCM REVIEW GROUP affected. These seven questions can only sensibly be answered by people who know the asset best; this includes maintainers and operators, supplemented by representatives from OEMs The group (a typical example of which is shown in Figure 4) is guided through the RCM process by a competent ‘Facilitator’ who is an expert in the RCM process and its application rather than the system expert. RCM is an integral part of the Integrated Logistic Support (ILS) process as defined in Def Stan 00-60 (and highlighted in Def Stan 02-45). The process falls squarely within the Logistic Support Analysis (LSA) process and provides inputs which are needed for a rational approach to spares, tools and skills determination. Application of RCM produces a ‘safe minimum’ maintenance programme which includes: • A comprehensive range of failure management tasks for maintenance and operations staff (incorporating predictive, preventive, detective maintenance as well as the foundation for the development of all likely corrective tasks); • Mandated and recommended redesigns of either the asset or the way it is operated or maintained; and • Recommendations for ‘no scheduled maintenance’ or runto-failure which require the development of strategies to deal with such failures as they occur. The process has been applied widely to mechanical, electrical and electronic systems as well as to platform structures. John Moubray’s book ‘Reliabilitycentred Maintenance’ and Def Stan 02-45 both provide comprehensive details of how this is achieved. The RN RCM Programme Following a Strategic Defence Review in the early 1990s, a decision was made by the Royal Navy to use RCM to address excessive maintenance manpower and resource costs and to develop a rational approach to risk management and extension of upkeep cycles. Since RCM was a ‘new’ technology for naval platforms and systems, although well established in many other applications, full implementation was to be dependent of the success of a trial to be conducted on the Hunt Class HUNT CLASS MCMV MCMVs. If successful, application would proceed across the fleet to include frigates, auxiliaries and submarines. At the outset, the decision was made to apply a ‘Whole of Platform’ approach, using the RCM process as a means of not only reviewing maintenance on specific systems, but also providing a solid foundation for optimising upkeep cycles. Hunt Class Trial The Hunt Class trial began in 1996 and used four vessels as a control group for comparison with non-RCM maintained vessels. Selection was based on: • Hunt possessing the majority of the significant functions of larger vessels (Float-Move-Fight); • Systems being sufficiently complex to test the RCM process comprehensively; and • Low risk to fleet operations if the trial was not successful. The RCM analysis took place in 1996 and 1997 following a period developing Naval
Page 2 and 3: NAVY ENGINEERING BULLETIN MARCH 200

Download - Royal Australian Navy

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?