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Maintenance strategy
- 2. Why is this important? Technology / Solution Maintenance Strategy Improved Business Performance Customer Business Objectives Business objectives drive the maintenance strategy, which in turn drives the technologies and solutions applied. Maintenance strategy definition and development is a critical success factor in the customer’s value chain.
- 3. Terminology The four main maintenance strategies are: • Reactive Maintenance (RM) • Preventive Maintenance (PM) • Predictive Maintenance (PdM) • Proactive Centered Maintenance (PCM)
- 4. Terminology Reactive maintenance (RM): • Maintenance performed after a failure or after an obvious, unforeseen threat of immediate failure. In reactive maintenance, machines are operated in a run-to-failure (RTF) mode, and daily maintenance activities are driven by unforeseen problems from assets breaking down without detection of the impending failure.
- 5. Terminology Preventive Maintenance (PM): • Maintenance tasks conducted at regular, scheduled intervals based on average statistical/anticipated lifetime to avoid failure— including inspection, service and/or replacement. Intervals may be calendar or operating time.
- 6. Terminology Predictive Maintenance (PdM): • Maintenance based on the actual asset condition (objective evidence of need) obtained from in-situ, non-invasive tests and operating and condition measurements. Also referred to as Condition Based Maintenance (CBM).
- 7. Terminology Proactive-Centered Maintenance (PCM): • A program of continuous maintenance optimization based on feedback from Root Cause Failure Analysis (RCFA) repairs, quantitative PM’s, PdM routines, CM systems, and operations.
- 8. Terminology Condition Monitoring (CM): • The process of recording measurements that define condition without disrupting operation (e.g., vibration, fluid and electrical characteristics, and thermal gradients) and comparing each to limits.
- 9. Terminology Reliability Centered Maintenance (RCM): • A systematic, disciplined process to ensure safety and mission compliance that defines system boundaries and identifies system functions, functional failures, and likely failure modes for equipment and structures in a specific operating context. •RCM develops a logical identification of the causes and effects (consequences) of system and functional failures to arrive at an efficient and effective asset management strategy to reduce the probability of failure.
- 10. Terminology Functional Failure: • The System is no longer capable of performing the intended function. •For example, a pump that is designed to produce 100 gpm at 200 psi is considered to have functionally failed if it can only produce 90 gpm at 200 psi.
- 11. Terminology Failure Modes & Effects Analysis (FMEA): • A methodology for identifying the functions of an asset, ways it can fail to perform those functions, the causes of those failures, and the methods for detecting or mitigating those failures. •FMECA:Failure Modes, Effects, and Criticality Analyses: An integral part of RCM directed to determining type, probability, cause and consequences of potential failures.
- 12. Terminology Root Cause Failure Analysis (RCFA): • A methodology used to identify the fundamental cause(s) that, if corrected, will prevent recurrence of an event or adverse condition.
- 13. Terminology Computerized Maintenance Management System(CMMS): • A computer system for measuring, managing, and analyzing the maintenance process. Includes MRO task planning and scheduling, inventory control and management, labor and material cost accounting, and asset historical data.
- 14. The P-F Interval – Mechanical Asset Example (Centrifugal Pump) Quantitative PM P-F Interval 5-8 weeks The P-F interval is the interval between the occurrence of a potential failure and the decay into a functional failure Time can be measured in seconds, minutes, days, months or years. P1-Px indicate detectability intervals by various techniques or technologies. Vibration P-F interval 1-9 months Wear Debris in oil P-F interval 1-6 months Audible noise P-F interval 1-4 weeks Heat by touch P-F interval 1-5 days P1 P2 P5 P6 F IR Thermography P-F interval 3-12 weeks P3 P = Potential Failure Is an identifiable condition which indicates that a functional failure is either about to occur or is in the process of occurring F = Functional Failure The point at which the asset fails to deliver to it’s intended purpose P4 P7 Process Performance Data (highly dependent on tuning of system / instruments) ~1 week – 6 months Condition Time P Relays Terminology
- 15. Comparative Total Maintenance spend formature maintenance programs $10 $15 PdM PCMPMRM $20 MaintenanceCost$/hp/yr $5 From EPRI Power Generation Study Maintenance Strategies No te : This chart re pre se nts e stablishe d pro g ram s
- 16. Selecting the Right Maintenance Strategy The maintenance strategy is unique to each asset, and should address the specific root-cause failure modes of the asset. A mix of strategies can be applied to any one asset – for example, PdM may be used for detectable fault types, but PM or RM may apply for other failure modes. The purpose of this section is to introduce the main steps in selecting the right strategy: 1. Identify the Asset Base 2. Criticality Analysis 3. Develop the Strategy 4. Assign Technology & Tools 5. PM Task Optimization
- 17. 1. Identify the Asset Base The Master Equipment List (MEL) A complete and accurate equipment library is required for effective: - PM/PdM work planning and execution - Spare parts inventory management - Cost accounting - Reliability management - Lifecycle cost management It is important to note that many existing MELs are in poor condition, with ambiguous naming conventions and inaccurate hierarchy structure. These may need significant re-work to be applicable for Maintenance Management
- 18. 2. Asset Criticality Ranking Asset Criticality ranking helps determine the right level of asset management resources (technology, parts, and people) for each asset. This enables the business risk of each asset to be managed in an appropriate manner. The Primary criticality ranking criteria are: • Safety, • Environment & Regulatory Compliance, • Production, • Maintenance & Operating Costs • Product quality Plus other criteria if relevant The criticality ranking process produces a balanced ranking of All Assets in the plant – each with a 4-digit numerical criticality number. A cross-functional team is usually assembled to agree on criteria weighting and asset evaluation. Typical Asset Criticality Ranking Tool
- 19. 2. Asset Criticality Ranking On the Asset Criticality Pareto Chart, natural “break points” appear to segregate the assets into identifiable criticality classifications For the most critical assets (typically 1 0 -1 5% o f asse ts), a Reliability Centered Maintenance (RCM) approach is used to determine the appropriate maintenance strategy. Critical assets are assessed using Failure Modes & Effects Analysis (FMEA) process. Less Critical assets are assigned a strategy using standard Templates Non-Critical assets Run-to- failure Distribution of Assets 15% CriticalityRanking 30% (typical) 50% (typical) 5%
- 20. Course Review • The four maintenance strategies are: i. RM – Reactive Maintenance ii. PM – Preventive Maintenance iii. PdM – Predictive Maintenance iv. PCM – Proactive Centered Maintenance • A single asset or system may have several maintenance strategies deployed to address its various failure modes. • It is important for us to understand our Customer’s maintenance strategy so we can build credibility and trust, and advocate appropriate technology or services solutions to help them meet their business objectives.
Editor's Notes
- Welcome to the TITLE computer-based training (CBT). Please note that this course is narrated. Use the Audio button and volume control in the lower-right corner of this screen to adjust the audio volume. Click the Play button or the Next button to begin.
- The four maintenance strategies are: Reactive Maintenance (RM) Preventive Maintenance (PM) Predictive Maintenance (PdM) Proactive Centered Maintenance (PCM) These will be defined in more detail on the next pages
- Page through this slide to see definitions of the four main maintenance strategies.
- Page through this slide to see definitions of the four main maintenance strategies.
- Page through this slide to see definitions of the four main maintenance strategies.
- Page through this slide to see definitions of the four main maintenance strategies.
- The P-F Curve shows us that the application of Predictive and Quantitative Preventive Maintenance provides us sufficient lead time to plan and schedule prior to failure.
- Typically Predictive Maintenance has half the net cost as Run-to-Failure, and PCM may be half as much again. This illustration shows the potential outcomes from investing in a specific Maintenance Strategy type. There is always some investment hurdle to overcome in changing strategy, however such costs are typically fully recovered within 2 to 3 years.
- In the last section we examined the Four common maintenance strategies: PCM, PdM, PM, RM This section will discuss the steps involved in selecting which strategy to apply to each asset. It is important to note that there is not one correct strategy to apply, the selection of ideal maintenance strategy is made according to a defined procedure described here. In some cases, it can be appropriate for the machine to run-to-failure. In other cases Predictive Maintenance may be determined to be the right approach. Condition Monitoring is not a maintenance strategy. It is a technique to apply technology effectively in a PdM strategy. If Condition Monitoring is being performed, it does not mean an effective PdM strategy is in place. However, if there is a PdM strategy in place, there will certainly be Condition Monitoring activities occurring. RCM is also not a maintenance strategy. It is a toll that may be used to help analyze a system or asset to select the best maintenance strategy to suit the application.
- The equipment data library is a database of equipment and their attributes that is loaded into the Computerized Maintenance Management System (CMMS), built using logical conventions and taxonomy. The first step is to develop a complete and accurate equipment data library in the CMMS, along with corresponding ID tags on equipment in the field. The extra effort required to develop this equipment data library will pay for itself many times over. For example, value from the equipment data library is delivered every time a repair work order is issued, a piece of equipment needs to be identified in the field, a reliability or cost history is needed, and when spare parts need to be identified and purchased. The equipment library starts with development of a logical equipment hierarchy, tagging convention, description, equipment class and subclass identification, and nameplate data. This information is compiled in a database that is uploaded into the CMMS. Corresponding field tags are also physically placed on the equipment.
- After the equipment data library has been developed, the relative criticality of all equipment must be ranked in terms of safety, the environment, production, maintenance costs, and product quality. Weightings for each ranking criteria are determined based on input from team members representing key plant functions, and then the ranking of each asset is determined using consistent and balanced criteria. The criticality ranking data is then uploaded to the CMMS so that each equipment record in the CMMS has a corresponding criticality value. The criticality value should be a numerical value of at least 4 digits to enable accurate ranking of all plant assets. A granular Criticality Ranking of the equipment allows you to focus more attention on the that has the largest financial impact on your overall operation. Criticality is used to direct the efforts for Maintenance Strategy Development Criticality is used by maintenance planners to prioritize corrective work based on the risk the asset poses to the business. Criticality may also be used to help determine the optimum level of spare parts that should be carried in inventory.
- After the Criticality assessment in done on all plant assets, we can rank the assets on a Pareto Chart as shown. Normally, natural groupings will appear, segregating the assets into several criticality classifications. Each classification uses a different analysis technique to determine the appropriate asset management strategies. The highest criticality assets represent the greatest operating risk to the business, and therefore receive the most intensive and expensive assessment. These assets have Reliability Centered Maintenance (RCM) analysis applied and typically account for only 10 to 15% of all assets on the site. The next classification (typically 30% of assets) are analyzed using Failure Mode Effects Analysis (FMEA), which is faster to implement than RCM, but well suited to standard machine types. Around 50% of assets typically fall into a “Less Critical” category and have a Maintenance Strategy assigned from standard templates, based on a recognized “good practices” approach for equivalent machine types. Possibly 5% of equipment may be left off a maintenance program altogether and simply repaired or replaced when it fails. This would only be if it meets certain criteria.. (Cheap, Redundant, short lead time to replace, short Mean time to repair…)