Work Identification Methodologies
Work Identification is by far the foundation of any maintenance process. Identifying the right work at the right time (i.e. an assets base program) will mobilize organizations to achieve the desired performance of their assets and their facilities.
Different strategies are available to define or refine the maintenance program for equipment. These typically include the application of Reliability-centred Maintenance (RCM2), the application of predictive maintenance needs assessments, the use of preventive maintenance optimization techniques, failure analysis techniques and the application of Maintenance Task Analyses (MTA). Each of these approaches use RCM ‘thinking' but is much less rigorous in approach, therefore exposing your organization to an increased risk of equipment failure when applied. Maintenance Managers and Facilitators need to be educated on the appropriate selection of these maintenance program development approaches.
There are many other similar approaches available in the market place that combine elements of the above that can be applied in pursuit of maintenance program development efficiency. Organizations ultimately employ the solution with the lowest resource intensity capable of delivering the highest equipment reliability performance.
Unfortunately, lack of business focus combined with improper target asset selection leads companies to select the inappropriate application and consequently spend money and resources unnecessarily.
The Right Work Identification Methodology.
There are two camps when it comes to embarking on a work identification initiative. One camp would apply the same methodology across all assets using the same application or methodology, the other camp typically uses one application for the critical assets only. The fact of the matter is they are both correct, conceptually speaking. All assets that contribute to the business goals and effectively have "business" consequences should be proactively reviewed for the purpose of reliability. However, based on a combination of Risk Prioritization Asset Prioritization and current operating context, a custom selection of your process from fundamentally similar methodologies will yield the optimum results. As the adage goes - You need not kill a fly with a sledge hammer.
Asset Risk Prioritization
Before your organization decides what assets are candidates for review or refinement via a work identification methodology, STOP and ask yourself - Which asset impact my business the most and in what order?
Asset Prioritization is an essential part of the up-front strategic planning required to ensure the success of reliability improvement projects. It is the key to expediting the return on investment of a reliability focused maintenance solution such as an RCM analysis on an asset.
An Asset Prioritization process ensures that your reliability improvement projects are always focused on the assets of highest risk. The definition of high-risk assets, if not formalized, may vary across the organization since the people involved may have used a non-technical basis to assess risk. Often we hear people say, "All of our assets are critical to our business". However, those opinions are often raised without consensus, and confuse "criticality" with "risk." The goal is first to achieve consensus on the degree of risk for assets and to create the momentum required to advance the implementation of a reliability improvement strategies such as work identification. The objective of a Asset Prioritization process is to identify those assets that are most likely to negatively impact business performance because they both matter most when they fail and/or they are because they failing too often. Potential consequences of asset functional failure are assessed based on criteria such as safety, environmental integrity, quality, output, customer service and operating costs. Frequency of failure and therefore corrective maintenance work order frequency is multiplied by the consequence score to determine a Relative Risk number.
The resulting Relative Risk rating is used to identify and prioritize candidates for work identification strategies such as RCM.
This process ensures Production and Maintenance Managers continuously focus on achieving business results rather than reacting to asset failure.
Before we discuss choosing a work identification application, let's first look at what is fundamentally available to companies embarking on proactive maintenance methods.
Reliability-centred Maintenance (RCM) is a highly structured work identification methodology. RCM can go beyond maintenance program development by including failure modes addressing causes of human error and design deficiencies. When these are included RCM produces the following outcomes:
- Maintenance programs evaluated on technical feasibility and economic worthiness.
- Recommendations addressing changes to standard operating practices.
- Operational and maintenance training/procedural recommendations.
- Physical redesign recommendations.
- Consolidated and validated information for use in training programs.
The RCM process requires answers to the following seven questions:
1. What are the functions of the asset in its present operating context?
2. In what ways can it fail?
3. What causes it to fail?
4. What happens when it fails?
5. Does it matter if it fails?
6. What can be done to predict or prevent the failure?
7. What can be done if you can't predict or prevent the failure?
What Will RCM Do For You?
An Asset Maintenance Program is designed by selecting maintenance tasks directed to mitigate failure causes or failure modes. Tasks are defined to detect, predict or prevent failure and provide a proactive management policy to take action to minimize or eliminate the failure consequence.
In defining the maintenance program, each task needs to be rationalized against the cause of failure it is meant to address. If a task does not address a known cause of failure, it should be excluded from the maintenance program.
The RCM process includes a detailed failure mode and effect analysis. All failure modes, considered reasonably likely to occur, are identified. This ensures the failure management strategy is comprehensive, addressing all reasonably likely causes of failure. Recommendations must be made to deal with each cause of failure. Failure effect descriptions provide sufficient information to evaluate the consequences of failure. The RCM decision logic provides criteria for determining if a task can technically manage the failure consequence and also provide criteria for establishing whether the task is economically feasible.
Sometimes, the default decision in RCM could be a conscious decision to allow the equipment to run-to-failure because the failure consequences are tolerable and preventing the failure may not be technically feasible or worth doing. Also, human error causes and design deficiencies can account for a surprisingly high number of failure modes in an RCM analyses. Other default decisions covered by question 7 provide the ability to define recommendations to modify operating procedures, train maintainers and operators, and to redesign the equipment. The technical basis for each recommendation is provided. All reasonably likely failure modes are addressed by recommending the best failure management strategy whether it is proactive maintenance or not.
In RCM, failure is defined as the inability to meet a performance standard. Functional failures are defined for each performance standard that can be breached.
Physical assets exist in the first place because we want them to perform specific ‘functions' at or above a minimum level of performance. Most assets have more than one function with related performance standards. To ensure that all ‘functional failures' are considered and all failure causes are identified the maintenance program development strategy must start by considering all the functions and performance levels required by the owner/user.
Each step in the RCM process is logical and necessary. A properly applied RCM analysis minimizes the risk that significant causes of failure are overlooked. All reasonably likely causes of failure are considered and addressed by recommending the optimum failure management strategy. One of these outcomes is a technically based Asset Maintenance Program designed to deliver the targeted performance requirements of the owner/user. This is by definition, the base work for the asset being analyzed. Existing routine tasks not validated by RCM are the non-value added component of work and should be eliminated. The complete identification of the base work will also result in the minimum deviation work.
Predictive Maintenance Needs Assessment
In recent years, tremendous advances have been made in the area of condition monitoring and predictive maintenance. When properly applied this form of maintenance is highly desirable allowing the user to leave the equipment on-line until its condition deteriorates to the point that failure is imminent. The useful life of equipment is maximized. Personnel conversant with these technologies are able to quickly identify opportunities to apply their trade with other equipment and systems. Predictive Maintenance Needs Assessment combines predictive maintenance expertise and process expertise to make recommendations for the application of condition monitoring techniques. This includes, but is not limited to, the application of vibration monitoring, thermography, lubrication serviceability and wear and contamination testing, traditional non-destructive testing techniques and electrical equipment monitoring techniques. The objective is to realize the benefits of applying predictive maintenance technology in the shortest time with minimum resource intensity.
The Predictive Maintenance Needs Assessment attempts to define the predictive maintenance component of base work. This could include displacing some intrusive maintenance tasks.
Maintenance Task Analysis
Maintenance Task Analysis is an extremely cost effective and practical way to develop a maintenance program for equipment. It implements the obvious proactive tasks recommended by various reliable sources of knowledge about the equipment -- the input of skilled trade personnel and specialists. Over time, equipment templates summarizing MTAs are developed to speed up the review process. In all cases, these templates need to be carefully reviewed to ensure that the recommended tasks are applicable and effective in the context of the equipment being reviewed.
Maintenance Task Analyses or reviews are intended to define base work. In the absence of a proactive maintenance program, this approach is effective in reducing preventable failures or managing the consequences of the failure.
However, they are not conducted following a rigorous process. The potential exists to miss required tasks, specify tasks that are not required, and incorrectly specify task intervals. This can result in the creation of non-value added work or deviation work resulting when unnecessary intrusive maintenance interferes with an otherwise stable system.
Failure Analysis Methods
Different approaches are available to investigate the cause of failures and identify what should be done to prevent them from re-occurring. Like RCM, failure analysis methodologies seek to identify the failure modes responsible for equipment failure. Failure analysis is conducted in reaction to a specific failure (i.e. after the fact). It seeks to identify the cause of that failure and what should be done to prevent the specific failure cause in the future. Often the focus of failure analysis is on the component(s) that have failed and, depending on the methodology, may not identify the root cause.
One possible way of conducting a failure analysis review is to conduct a partial RCM analysis. When a failure occurs, identify the functional failure that has been breached, not just the component failure. Complete the RCM process for the single functional failure. Identify all reasonably likely causes of failure including the (root) cause of the failure this time. Apply the RCM decision logic to define the appropriate failure management strategies for all the causes of the functional failure.
Selecting a Work Identification Application
Should an organization not be achieving the desired performance for prioritized assets, it is advantageous to consider its operating context to determine the next best course of action and the appropriate selection of a work identification application.
Asset distinction can be summarized by a four quadrant philosophy as seen in Figure 1 below.
In Quadrant 1, performance is deemed poor and there is little to no formalized maintenance program in place. The program may also be deemed invalid or has not been reviewed or updated in response to physical changes to the asset or changes in the expected levels of performance. The asset experiences frequent functional failure and maintenance is therefore reactive in nature and cost in-effective.
In this case Maintenance Task Analysis and/or a Predictive Needs Analysis is suggested to optimally develop a maintenance program
Figure SEQ Figure \* ARABIC 1: Operating Context Quadrants
Focus should be placed on efficiency and speed of implementation to keep cost and resource pressure minimal.
Be aware that this process may lead to non-value-added maintenance tasks and/or frequency intervals that are technically invalid.
In Quadrant 2, which is common with organizations with a mature work force, asset performance is good but a formal and documented maintenance program is not present. In this case, organizations are dependent on the people maintaining or operating the equipment and in most cases suffer when employees are on vacation or retire.
It is very important in this instance to document the maintenance tasks being performed using Maintenance Task Analysis ensuring the equipment experts are utilized correctly. Management should also focus on transferring this knowledge to new hires and expand the training documentation to account for lessons learned during these analyses.
The cautions remains that Maintenance Task Analyses may overshoot the minimum maintenance program and create non-value added work and/or tasks with incorrect frequencies. Or, Maintenance Task Analyses may not consider all failure modes that could occur, but have not thus far, resulting in future functional failures.
In Quadrant 3, the selected asset has a high level of maintenance program definition but asset performance generally unacceptable. The high level of maintenance program definition indicates that the poor performance is not due to lack of attention but rather ineffective content. The solution to this problem is not that obvious and a more rigorous approach is required. It is therefore recommendable to apply a rigorous, structured approach like Reliability-centred Maintenance. By applying RCM, the base work will be defined; non-value added work eliminated and deviation work minimized. Management should review and/or modify the RCM analysis if and when a failure occurs or whenever there is a change in the operating context for the asset.
RCM objectives and business related goals should be established at management level and communicated to all parties concerned prior to commencing the RCM analysis or review process.
In Quadrant 4, the asset in question has a high level of maintenance program definition and asset is performing well. This indicates that the maintenance program is effective at managing failure. If the maintenance program wasn't created using an approach like RCM, chances are there is a fair amount of non-valued added work being done and improvement here rests with work task optimization.
In quadrant 4, RCM is an option if the current program was not developed using this application in the first place. RCM will aid organizations minimize or eliminate the non-value added work. Failure Analysis (i.e. post failure) can be used to focus on failures that occur and in turn refine the existing maintenance program.
Operational performance indicators and the total number of failures associated with an asset may be acceptable when first reviewed. However, the risk of a failure with severe safety, environmental or economic impact may be many orders of magnitude higher than desirable and not recognized. The implication of this is that statistically the organization will experience a catastrophic failure in the future and more probably the near future.
In Pursuit of Rapid Results
Prioritizing your assets by risk, in conjunction with the asset distinction process described above, provides a means for deciding the initial mind set required in addressing an asset maintenance program. Within most organizations assets will be found at various levels of performance with varying degrees of maintenance program definition.
It follows that no one strategy for maintenance program development will satisfy all situations. The plan addressing the maintenance programs in an organization could include multiple yet parallel strategies. Low performing assets in the company, where minimal proactive maintenance has been applied, become candidates for the rapid deployment of Maintenance Task Analysis incorporating Predictive Maintenance Needs assessments.
Other equipment may initially warrant a combination of Predictive Maintenance Needs Assessment and maintenance program optimization. Still other equipment may require that current programs simply be documented to sustain them.
In theory, non-rigorous strategies should be applied quickly, with low resource intensity quickly covering the entire asset base. Once all the ‘low hanging fruit' is eliminated, all that would remain would be problems requiring a more rigorous approach to find a solution. As the organization progresses more of the effort expended on the work identification function will be directed to applying rigorous approaches. Eventually, RCM will become the primary application to perfect the maintenance program, minimize risk and maximize results.
Article submitted by Andrew Boushy and Roger Zavagnin, Certified RCM Practitioners, IVARA
- Ron Thomas - Reliability Practices, Dofasco Inc
- Reliability-centred Maintenance. Industrial Press, New York. 1997. - John Moubra