by Steve Turner

Comparing PMO and RCM Methods of Maintenance Analysis

Methods of Defining Initial Maintenance Requirements

The common methods for defining the initial maintenance requirements for plant and equipment are as follows:

  • RCM;
  • Streamlined RCM;
  • Statistical Methods; or
  • Experience, trial and error.

The origin of the processes is briefly discussed below.

RCM

Nolan and Heap (1978) coined the term Reliability Centred Maintenance (RCM) and developed the original method. RCM was not designed for use for "in service" assets. However, in the absence of better methods since 1978, it has been applied retrospectively in many organisations after the plant has been commissioned. In over 20 year since its derivation, RCM has failed to become a day to day activity performed by most organisations. Few organisations have applied RCM to anything other than their most critical assets which indicates there are serious difficulties associated with applying RCM in organisations with mature plant.

Streamlined RCM

Due to a perception that RCM was a very time consuming and labour intensive activity, a number of shortened versions of RCM have been devised in an attempt to speed up the analysis or increase the overall value of the time committed to analysis. Many of these methods have used the acronym, RCM to describe the process but do not conform to the works of Nolan and Heap (1978) nor the SAE Standard for RCM. These streamlined approaches are known as streamlined RCM techniques.

Statistical Methods

There are three main types of statistical maintenance analysis programs known to the author.

1. One of these is based on MILSTD 2173 and works from the premise that no inspection task is 100% effective. The algorithms adjust the interval of "on condition" tasks to account for less than perfect inspection methods.

2. Another is based on the notion that the more frequent the inspection the higher the cost of maintenance but the lower the chances of failure. The objective of maintenance under this algorithm is to determine the lowest overall cost of maintenance. This algorithm is flawed if inspection is near 100% reliable or is fail safe8 as, providing the inspection is inside the PF interval, more inspections only add to the cost of maintenance but not reduce the chances of failure.

3. The third statistical method has uses to Weibull analysis as a basis. This method suffers mostly from poor data integrity.

The overwhelming problem with statistical methods in the vast majority of industrial plant is that the failure history data is so unreliable and incomplete that any statistical inferences drawn from such data are wildly inaccurate and lack any worthwhile statistical confidence. The algorithms are also reliant on accounting inputs such as the cost of PM, repair and failure. All of these inputs are subject to the vagaries of the accounting systems deployed.

The second large problem is that statistical methods tend to be used by engineers or contractors who are not sufficiently familiar with the equipment an the manner that it is used on site. Often the result is a misguided program which is totally discredited by the tradesmen and operators because of its low quality and secondly because they were not sufficiently involved in its derivation.

Some explanation of the first two methods is contained at Section 3 of this paper.

Experience, Trial and Error

In many cases, capital acquisition programs fail to recognise the need to define the maintenance program prior to the "Operation" stage of the equipment life cycle. Often, the plant is installed and operated without a formal maintenance program. Over time, the operations and maintenance staff begin to conduct inspections and perform various maintenance activities largely at their own initiative. Failures occur and the maintenance program has tasks added to it. In some organisations, the work is formalised by generating electronic or paper based maintenance schedules. In other organisations, the work continues to be done in a completely informal manner. Even though some managers may believe that there is no preventive maintenance done within their plant, this situation is highly unlikely. The confusion is often that the preventive maintenance is not appreciated, as there is no documentation.

Methods of Reviewing Maintenance Requirements

PM Optimisation

Regardless of how a maintenance program has been developed, there is a constant need to review and update the program based on failure history, changing operating circumstances and the advent of new predictive maintenance technologies. The generic process used to perform such analyses is known as PM Optimisation (PMO). PMO has been performed, no doubt, since the world became mechanised and humans realised the benefits of performing preventive maintenance. PMO as a technique has been refined to reflect the RCM decision logic since the formulation of RCM in 1978.

There are a number of methods that have been created under the acronym PMO. One of these has been applied in the US Nuclear power industry for over 8 years and has been recognised as a major benefit by the North American Nuclear Regulatory Commission (Johnson 1995).

Each of the PMO methods has differences and there is no accepted standard for PMO. Discussions contained in this paper are therefore, based on the method of PMOknown as PMO2000. Some of the comments and comparisons made between PMO and other methods may not apply to methods of PMO.The PMO2000 process has been developed over a five-year period by OMCS with the assistance of several Australian Companies. There are now 12 users of PMO2000 in the Australia Pacific
Region.

The PMO2000 process is endorsed by SIRF Roundtables Ltd9 and is the global maintenance analysis tool of choice for one of the world's largest mining companies. PMO2000 is the intellectual property of OMCS. The methodology is described in detail at Section 1.

Comparing RCM and PMO

What is RCM

According to the standard SAEJA1011, any RCM program should ensure that all of the following seven questions are answered satisfactorily and are answered in the sequence shown:

1. What are the functions and associated desired standards of performance of the asset in its present operating context (functions)?

2. In what ways can it fail to fulfill its functions (functional failures)?

3. What causes each functional failure (failure modes)?

4. What happens when each failure occurs (failure effects)?

5. In what way dose each failure matter (failure consequences)?

6. What should be done to predict or prevent each failure (proactive tasks and task intervals)?

7. What should be done if a suitable proactive task cannot be found (default actions)?

What is PM Optimisation

The questions answered in completing a PMO2000 analysis are as follows:

1) What maintenance tasks are being undertaken by the operations and maintenance personnel (task compilation)?

2) What are the failure modes associated with the plant being examined (failure mode analysis)?

   a) What is (are) the failure mode(s) that each existing task is meant to prevent or detect

   b) What other failure modes have occurred in the past that have not been listed or have not occurred and could give rise to a hazardous situation.

3) What functions would be lost if each failure were to occur unexpectedly (functions)? [optional question]

4) What happens when each failure occurs (failure effects)?

5) In what way does each failure matter (failure consequences)?

6) What should be done to predict or prevent each failure (proactive tasks and task intervals)?

7) What should be done if a suitable proactive task cannot be found (default actions)? 

The complete PMO2000 methodology has nine steps. The seven questions listed above are a subset of the complete PMO2000 methodology. The additional steps in PMO2000 not listed above are as follows:

  • Grouping and Review
  • Approval and Implementation
  • Living Program

These final three steps are necessary to implement the analysis outputs and ensure that the PMO analysis does not stop once the first review has been completed. These steps are not considered relevant to this paper as it is assumed that RCM analysis must also perform these steps to ensure a successful outcome. RCM and PMO are considered identical in this regard.

Functional Differences between RCM and PMO

RCM and PMO are completely different products with the same aim; to define the maintenance requirements of physical assets. Asset managers should be aware however, they have been designed for use in completely different situations. RCM was designed to develop the initial maintenance program during the design stages of the asset life cycle (Moubray 1997) whereas PMO has been designed for use where the asset is in use.

As a result, PMO is a method of review whereas RCM is a process of establishment. Whilst arriving at the same maintenance program, PMO is far more efficient and flexible in analysis than RCM where there is a reasonably good maintenance program in place and where there is some experience with the plant operation and failure characteristics.

Methodology Differences between RCM and PMO

The central difference between RCM and PMO is the way in which failure modes are generated.

  • RCM generates a list of failure modes from a rigorous assessment of all functions, a consideration of all functional failures and then an assessment of each of the failure modes that relate to each functional failure. RCM seeks to analyse every failure mode on every piece of equipment within the system being analysed.
  • PMO generates a list of failure modes from the current maintenance program, an assessment of known failures and by scrutiny of technical documentation - primarily Piping and Instrumentation Diagrams (P&IDs).

Image 10

The differences in the two approaches mean that PMO deals with significantly less failure modes than RCM and arrives at the failure modes in a far quicker time frame. Experience in the US Nuclear Power Industry was that over a large number of analyses, PMO was on average six times faster than RCM (Johnson, 1995). The methodological differences between RCM and PMO are illustrated at Figure 10.

How and Why PMO Is Faster than RCM

Overview

The main reasons why PMO is faster than RCM are summarised below. The points are discussed in detail later in the paper.

1. Insignificant failure modes are not analysed by PMO whereas RCM analyses all likely failure modes.
2. Using PMO, many failure modes can be rolled up and analysed together whereas with RCM, failure modes are analysed separately.
3. With PMO, a detailed functional analysis is an optional step. The function of the equipment is completed as part of Consequence Evaluation because a consequence of any failure is a loss of function by definition.

How and Why Failure Mode Analysis of insignificant Failures Is Avoided by PMO

The equipment design and the way it is operated determine the type and likelihood of failure modes. In the context of maintenance analysis, failure modes can be broken into categories based on the following:

  • their likelihood,
  • their consequences, and
  • the practicality and feasibility of preventing or predicting them. This point is illustrated in Figure 11.

Image 11

Figure 11

The focus of good equipment design is to ensure high levels of reliability, maintainability and operability. This means eliminating high likelihood and high consequence failures.

It is therefore, not surprising that when reviewing the complete set of likely failure modes using RCM analysis, that by far the greatest number of outcomes, or recommendations, are No Scheduled Maintenance. This is to say that for the failure modes left in the design in question, either:

  • Their likelihood is very low,
  • There is no technically feasible predictive or preventive maintenance task known to manage them, or
  • The task that is known costs more to do than the cost of the cost of unexpected failure. The less critical the equipment is to productive capacity, the more likely that the cost of the maintenance outweighs the costs of the failure over a given life cycle.

In the author's experience, full RCM analysis of equipment shows that, on average, about 80% of failure modes result with the policy of No Scheduled Maintenance. This information is presented in Figure 12. This number rises with electronic equipment such as a PLC and falls with equipment that has a high number of moving parts such as a conveyor.

It therefore follows that, if the objective of a maintenance analysis workshop is to define the maintenance program, and all the likely failure modes are analysed, around 80% of the analysis will be low value adding (or a complete waste of time). This is because the analysis finds that there is no maintenance solution for 80% of the failure modes. Those failure modes could have been culled at the start with no loss of analysis quality.

With this same objective in mind it is therefore logical to seek a process which limits the analysis to those 20% of failure modes that are likely to yield a maintenance solution and no more. In practice this is not completely feasible, as that pool of failure modes that receive PM is not defined until the analysis is performed.

If the failure modes are low consequence and infrequent, then there is unlikely to be any cost effective modifications either.

Figure 12

The missing element here is failure modes that have hazardous consequences but have not happened before. It is accepted that the downside of this approach is that failure modes that could result in a hazard may be omitted so therefore it is wise to obtain the technical documentation and perform a "desk top"10 FMECA to trap these hazards if they exist. PMO2000 therefore errs on the side of caution and lists the failure modes that have the following attributes:

  • Are currently the subject of Preventive Maintenance;
  • Have happened before; or
  • Are likely to happen and may cause a hazard.

How and Why Using PMO, Many Failure Modes Can Be Rolled up and Analysed Together

RCM treats each failure mode independently resulting in the same analysis and tasks being written many times. PMO starts from the maintenance task and therefore many failure modes can be listed against the one task. This significantly reduces the analysis time by reducing the records that need to be dealt with. The concept can be best described by reference to the following example.

Using PMO

Image 15

Providing vibration analysis was a technically feasible task to prevent all these failure modes from occurring unexpectedly, PMO would consider the failure modes as a group and set the task interval to the lowest common interval of inspection.

Image 15

The above tables show how, right from the outset, RCM has created a lengthy analysis process compared to PMO. The resulting maintenance program will be the same with vibration analysis being selected as the best form of maintenance to manage all the failure modes. The only difference is that RCM has analysed five independent failure modes where as PMO has analysed them together.

How and Why Using PMO, Rigorous Functional Analysis Is Optional

RCM begins with a complete functional analysis of the equipment whereas with PMO200011 the effort expended on functional analysis is variable or discretionary. The reasons why PMO2000 allows this are as follows:

  • Consequence evaluation is performed at Question 5 of PMO2000. As consequence evaluation implicitly involves understanding what loss of function is incurred, a functional assessment is performed at this stage as part of consequence evaluation. To perform a separate functional analysis is a duplication12 of effort.
  • In some cases, the precise functionality of equipment is almost impossible to determine and / or practically meaningless. A case in point is the function of a fan in a cooling system. Its function is likely to be to supply a certain cooling capacity of air measured in BTU's per hour or equivalent dimension. This becomes an equation based on ambient temperature and flow rates. To source this information would normally be very time consuming. The practical value or usefulness would be very low as there is not likely to be a gauge on the fan that measures BTU/hr to assess whether the fan is serviceable or not according to the precise function. To the operators, the performance standard written in BTU/hr would be a completely foreign concept.
  • Functions neither influence the task interval selection nor the task type selection whatsoever.

To apply RCM in accordance with the standard, a functional analysis can consume 30% of the total analysis time. If the objective of a maintenance analysis workshop is to define the appropriate maintenance policy for the equipment, then a full functional analysis consumes a lot of time, but adds little value.

Strengths and Benefits of PMO Compared with RCM

PMO Is a Method with Enormous Flexibility

RCM analysis can not regulate or filter which failure modes are analysed at which time therefore RCM analysis requires the presence of all trades simultaneously as the failure modes come out in a rather random manner. With PMO it is possible to review the activities of a particular trade on a particular piece of equipment or site because PMO begins with maintenance tasks which can be filtered on the field, trade. This is particularly useful when it is considered that the activities of one trade are ineffective or inefficient.

There have been highly successful PMO analyses performed exclusively on either operator rounds, on instrumentation rounds, on lubrication rounds, on vibration analysis rounds etc. This type of focus is not possible using RCM.

PMO is Self-Regulating in Terms of Investment and Return

PMO is highly effective where equipment has numerous failure modes but where the vast majority of these are either random, instantaneous or not of high consequence. A simple example would be a mobile telephone. Mobile phones have hundreds of functions. To define the functions of a mobile phone would take at least one day depending on how rigorous the group was in defining performance standards.

The other point here is that RCM would require the input of specialist electronics engineers to define the failure modes properly whereas PMO would require only the operators. PMO on the other hand, would take no more that 20 minutes to complete the analysis in total and realise that the only maintenance that is required is to do with managing the consequences of battery deterioration.

PMO Is Six Times Faster than RCM

The positive effect of deploying a process of maintenance analysis that is six times faster than RCM for the same given outcome can not be overstated. The benefits are listed below:

  • Resources to perform analysis are generally the most scarce on the site. PMO will allow the analysis team to cover six times the area with the same given resource thus having a much lesser impact on the normal operation of the plant. PMO also allows the organisation to be implementation intensive rather than analysis intensive.
  • Maintenance analysis like many other investments is subject to diminishing returns. Using a costly and resource intensive program such as RCM reduces the scope and ability of maintenance analysis to those areas of plant that are in the bottlenecks. Because PMO is far less costly to do than RCM, it can be done economically on considerably more assets within the plant; typically where the gains from analysis will be less, but not insignificant.
  • Where the maintenance of failure modes that have safety or environmental consequences is considered suspect, the use of PMO will allow these issues to be dealt with much faster than by using RCM.13

Weaknesses of PMO

The only valid weakness of PMO compared to RCM for plants that have been in operation for some time, is that PMO does not list the complete set of failure modes. This may be important from a spares assessing perspective. However, if the motivation for performing maintenance analysis is to generate a focussed and effective PM program, then this weakness is irrelevant.

Discussion of Common Misconceptions about PMO

In recent times, there have been a series of attacks launched against any process that does not conform to SAEJ1011. The most prominent being written by Moubray (Moubray, 2001). These issues are discussed in the following paragraphs of this Section.

   Because as standard has been set for RCM, asset managers must use that process across their whole plant to be safe from prosecution.

False

In August 1999, SAE JA1011 entitled "Evaluation Criteria for Reliability-Centered Maintenance (RCM) Processes" was issued. The sole purpose of this standard was to provide criteria for people to be able to determine what is RCM and what is not. This is evidenced on the front page of the Standard by the following passage:

"This document describes the minimum criteria that any process must comply with to be called "RCM." It does not attempt to define a specific process" 

The first point is that many of the attacks on PMO have been based on misconceptions on how the process works and are based on unsubstantiated and incorrect data and assumptions. These false statements are corrected in the questions that are part of this section of the paper.

The second point is that the logic used does not pass careful scrutiny. For example the logic used by Moubray (Moubray 2001) goes this way.

  1. Society has reacted to equipment failure and accidents producing serious consequences by enacting laws seeking to call individuals and corporations to account. [No Objection]
  2. Everyone involved in the management of physical assets needs to take greater care than ever before. [No Objection]
  3. RCM is the most rigorous method of defining the maintenance requirements of physical assets. [No Objection] 
  4. Any method that streamlines the RCM method is by definition missing something and therefore exposing the user to excessive risk. [Incorrect and no evidence to support this premise]
  5. There has been a standard written to allow purchasers of equipment to write contracts that specify the use of RCM, to be sure that what they are purchasing conforms to a known standard. [Irrelevant]
  6. Now that there is a standard for RCM, all asset managers must use the standard across every asset in their plant if they want to be immune from prosecution in court should an industrial accident occur in the plant. [Based either on an irrelevant point or argument or an incorrect and unsupported premise]

   PMO is unsafe to use, as it does not adequately investigate failure modes that may lead to hazards in the plant.

False

There are several important points that deal with the issue of safety and environmental consequences of failure and the use of RCM or PMO to treat these concerns. The most important point being that neither PMO nor RCM offer adequate protection from the causes of multiple evident failures. Asset managers should therefore, consider using HAZOP or similar techniques as their primary hazard management process. The three main points are discussed below.

Point 1
Except for hidden functions, the RCM analysis technique considers only the first order effects of failure. This is evidenced by the fact RCM treats all failure modes "on their own". It does not consider the consequences of two or more evident failures occurring simultaneously. As catastrophes are generally the result of several compounding failures, RCM can not, of itself, be regarded as a comprehensive defence against prosecution when plant failure contributes to a disaster. Managers should not undertake RCM in the belief that they will be immune from prosecution by doing so. It can be said that due to these omissions, RCM is a streamlined version of a comprehensive safety analysis program and therefore fails the same tests that its supporters claim to be its virtues.

Point 2
Anecdotal evidence regarding the causes of recent disasters raises some observations. Firstly, the greater the disaster it seems, the more numerous were the contributing factors. Secondly, few if any of the disasters of recent times have been caused by a lack of a preventive maintenance program. Where plant failure has contributed to the disaster, the failures had been known to the company, but the company chose not to rectify them. This is a most uncomfortable but common scenario found in today's industrial maintenance climate. This was a case in point in the recent Esso disaster at the Longford Plant where what would normally be considered abnormal became normalised over time (Hopkins, 2000). There were numerous items of equipment known to be in an unserviceable condition but no action was taken to repair them. Managers find it acceptable to live with a high level of broken or badly performing equipment, and more disturbingly, find it acceptable to treat preventive maintenance as an optional activity. PM is frequently skipped without any real assessment of the risks being exposed. The greatest threat to industrial safety therefore, is not the lack of a PM program, but the lack of resources required to complete the program and perform the corrective maintenance to bring the plant to an acceptable operating condition. In this predicament, responsible managers will not pour their valuable resources into a long-winded RCM program that will deliver them a better PM program over a long period. Rather they will take on a shorter program that delivers the same analytical results, but allows significant productivity gains to be made thereby allowing the backlog of corrective maintenance to be recovered and the PM program to be achieved.

Point 3
Failure modes that are listed as having a hazardous consequence occur approximately14 once in every two hundred. In facilitating analysis of over 15,000 failure modes over a period of eight years, I have only once found a failure mode with potentially hazardous consequences that was not already the subject of PM. In all likelihood this failure mode would have been detected through PMO during the technical documentation review. This means that PMO provides close to the same defence against equipment failure, as does RCM.

The other issue here is the time it may take to detect the rare failure modes that may be the difference between using RCM and PMO. Finding that one in 15,000 failure mode carries a cost of 15,000 man hours15 or 8.5 man years. Few managers would consider that to be a good return for a program aimed at improving safety.

   PMO assumes that all the failure modes associated with equipment are covered by the existing maintenance program.

False 

PMO recognises that there are many failure modes that are not covered by the maintenance program and therefore includes a step to add to the list generated by the PM analysis, those failure that have occurred in the past and those that may occur and potentially result in a hazard. It is usual during a PMO workshop to add 10% to 30% to the total program because of preventable failure that have been managed as unplanned occurrences in the past. 

   PMO is a method that analyses 20% of the failures and gets 80% of the results that RCM achieves.

False 

PMO2000 analyses around 40% of the failure modes that RCM would however the resulting maintenance program is the same regardless of whether RCM or PMO2000 is used. The objective of PMO2000 is to provide a comprehensive maintenance program covering all the failure modes for which there is a technically feasible, cost-effective maintenance solution. 

   When applying PMO, it is often very difficult to identify exactly what failure cause motivated the selection of a particular task, so much so that either inordinate amounts of time are wasted trying to establish the real connection, or sweeping assumptions are made that very often prove to be wrong. 

False

This misconception is most easily dealt with by example. Consider the following tasks and assess for yourself the difficulty in identifying the correct failure mode. Then open the maintenance schedule for your motor car and try some others for yourself.

Listed Task - Failure Mode Analysed

  • Inspect the fan belt for signs of wear - Fan belt wears
  • Inspect the brake pads for wear - Brake pads wear
  • Replace the spark plugs - Spark plugs wear
  • Change the oil in the sump - Sump oil deteriorates due to wear or aging

  In reassessing the consequences of each failure mode, it is still necessary to ask whether "the loss of function caused by the failure mode will become evident to the operating crew under normal circumstances." This question can only be answered by establishing what function is actually lost when the failure occurs. This in turn means that the people doing the analysis have to start identifying functions anyway, but they are now trying to do so on an ad hoc basis halfway through the analysis.

True but unimportant
This is correct but it in no way makes the analysis neither onerous nor difficult or time consuming. The point here is that 30% of the analysis time is not spent defining functions when this is not required.

PMO is weak on specifying appropriate maintenance for protective devices. This is because in many existing maintenance programs only one third of protective devices are currently receiving any form of
maintenance, one third are known but do not receive any form of maintenance and the final one third are not known as protective devices. 

False

Point 1
PMO2000 is no weaker than RCM in this regard. Using PMO2000, protective devices that are receiving no PM are found during the review of the technical documentation in exactly the same way as RCM would find them. The most common means is to trace piping and instrumentation diagrams looking for hidden failures. 

Point 2
The statistics presented to support this claim are dramatically opposed to the author's experience. It is true that some maintenance departments do not know of some protective devices and some are known but do not receive any testing. However my observation is this. Firstly the number of unmaintained protective devices is more likely to be about 10% rather than 66% and secondly of the 10%, the likelihood and consequence of multiple failure do not warrant frequent testing.

   PMO focuses on maintenance workload reduction rather than plant performance improvement. Since the returns generated by using RCM purely as a tool to reduce maintenance costs are usually lower than the returns generated by using it to improve reliability, the use of PMO becomes self defeating on economic grounds, in that it virtually guarantees much lower returns than RCM.

True and False

PMO2000 focuses on many measures. One is machine reliability and one is human productivity. It is our experience that one of the greatest threats to industrial disaster is the considerable backlog of corrective 16 and preventive maintenance work that many maintenance departments carry. Indeed many of the recent catastrophes have been caused, or were compounded, by equipment failures that were known but not rectified.

The second point is that many organisations are caught in a vicious cycle of reactive maintenance. This is where PM is missed resulting in breakdown that consumes more labour resources than the failure would have if it had been repaired earlier and in a planned manner. This then reduces the labour available to perform PM and thus the cycle continues. For this reason it is strategically sound to focus on the elimination of unnecessary work and redirect these resources to work that adds value. This strategy has a compounding effect that in the long run far outweighs the reliability improvement that tends to be fixed return in perpetuity rather than a compounding one.

The final point is that maintenance analysis consumes valuable resources, those being the people that know the equipment best. The supervisors who release these people are often caught in a dilemma. Releasing those people for workshops means that the backlog is going to get worse in the short tem. Unless those supervisors feel confident that the investment in the program will recover the manhours invested quickly, the supervisory level becomes uncooperative and this has a wide ranging destabilising effect on the program as a whole. Corrective maintenance is defined as a fault that is known and reported and rectified in a planned rather than reactive manner. 

In short, a focus on human productivity is an essential ingredient in implementing a successful maintenance analysis program. With this in mind it is imperative that the analysis time is not wasted on low value adding activities such as the analysis of failure modes that result in no scheduled maintenance and the exhaustive activity of functional analysis.

8 Any incorrect sample will suggest there is a failure when in fact there is not. Oil analysis or vibration analysis are examples where most of the problems are fail-safe.

9 SIRF Roundtables Ltd was formed on 1 July 2000 out of the Strategic Industry Research Foundation Ltd as a result of the foundation's withdrawal from its industry shared learning networks (including the IMRt) and related support activities.

10 Review the technical documentation assessing if consequences of any failure would lead to a hazardous situation.

11 Not a feature of most other PMO processes.

12 This point is also relevant where functions are hidden, as the loss of hidden functions will result in consequences that are conditional on some other failure occurring.

13 It should be noted that neither PMO nor RCM provide adequate protection against the consequences of equipment failure where two evident failures occur simultaneously. This is an occurrence that has been a significant factor in a large number of the world's recent disasters particularly when a combination of in appropriate human action and plant failures coincide.

14 Source is the author's experience.

15 Assuming three team members and a facilitator working at 1 failure mode every 15 minutes.

---

About the Author

The author, Mr Steve Turner, is a professional engineer who has been extensively trained in RCM methods and has deployed them over a 20 year period in various roles as an airworthiness engineer, a maintenance manager, as part of a design team and as a consultant. Over the past five years, Mr Turner has developed a process of PM Optimisation known as PMO2000. This method is currently in use at 12 major industrial sites in Australia and the Asia Pacific Region.

Upcoming Events

August 9 - August 11 2022

MaximoWorld 2022

View all Events
banner
80% of Reliabilityweb.com newsletter subscribers report finding something used to improve their jobs on a regular basis.
Subscribers get exclusive content. Just released...MRO Best Practices Special Report - a $399 value!
DOWNLOAD NOW
The Three Laws of Preventive Maintenance

The Three Laws of Preventive Maintenance

Each preventive maintenance task in an Uptime Elements developed Reliability Strategy is generated for an identifiable and explicit reason

Digital Built America: Smarter, More Sustainable and Resilient

Digital Built America: Smarter, More Sustainable and Resilient

Building back better means transitioning the current infrastructure to smarter, more sustainable forms of development to safeguard the country’s future.

DIPF Curve and RCM Failure Patterns

Predictive Maintenance Deja Vu All Over Again

Compared to total asset failures, what percentage of asset failures can be "reliably predicted" with predictive maintenance?