Rcm 4 hour overview for rcm teams
13 likes2,430 views
The document provides an overview of reliability centered maintenance (RCM) concepts and process. It discusses the history and principles of RCM, failure patterns, and the RCM process steps. The process involves understanding the operating context and functions of equipment, identifying potential failures and their effects, and determining the most effective maintenance tasks. Understanding failure patterns is important for developing the proper maintenance strategy, such as on-condition tasks, restoration tasks, or redesign tasks. The document uses examples to illustrate RCM concepts.
Rcm 4 hour overview for rcm teams
- 2. 2 RCM Overview for RCM Teams Reliability Centered Maintenance x
- 3. 3 • Based on Reliability Centered Maintenance Concepts • Proven Technology • Provides a structured approach to establish a Maintenance strategy x
- 4. 4 • Provides a strategy for stocking spare parts • Provides an easy way to track implementation of an RCM analysis x
- 5. 5 Course Outline I. RCM History II. Principles of RCM III. Maintenance Tasks IV. Understanding Failure •Failure Patterns •Effective Maintenance Tasks for each pattern x
- 6. 6 V. RCM process steps •Operating Context •Primary and Secondary Functions •Functional Failures •Failure Modes •Probability Rating •Failure Effects •Consequence Rating VI. Case study x
- 7. 7 Reliability Centered Maintenance History • 1974 - United States Department of Defense commissioned United Airlines to report on the maintenance process used in the aviation industry • Conducted by • Stanley Nowlan • Howard Heap x
- 8. 8 Reliability Centered Maintenance History • At this time the airline industry was using a high amount of redundant systems combined with scheduled discard and scheduled restoration tasks to ensure safety • Records showed that the maintenance tasks had little or no effect on the reliability of the aircraft. In fact some of the maintenance was shown to be intrusive, and could cause failures. • Today RCM remains the process used to develop and refine aircraft maintenance x
- 9. 9 x Principles of RCM •What Function does this machine serve? •What is the Functional Failure? •How does the Failure occur? •What are its Consequences? •What can be done to PREVENT the Failure? •What can be done to reduce the Consequences of a failure?
- 10. 10 MAINTENANCE: Focus on equipment performance ensure physical assets continue to fulfill their intended function improve equipment performance to meet business needs performed in a cost effective manner x
- 11. 11 •The objective of RCM is to use existing process knowledge to develop a maintenance program that will maximize equipment up time. (Reliability) • RCM looks to accomplish this by applying a series of questions to a modified FMECA (Failure Mode Effect and Criticality Analysis). x
- 12. 12 • Maintenance tasks tend to fit in one of five categories •On Condition Tasks - or Condition Monitoring •Restoration Tasks - restore equipment to its original state •Discard Tasks - complete replacement of a component •Failure Identification Tasks - operating check of hidden functions to ensure they work when needed •Redesign Tasks x
- 13. 13 Understanding Failures • In order to set up the proper maintenance for a piece of equipment or component you must first understand how it fails. • RCM requires an understanding of six failure patterns and designs a maintenance program using techniques best suited for each pattern x
- 15. 15 A Pattern A •Commonly referred to as a bath tub curve •For many years this was thought to be the only failure pattern for equipment. •We now know it is really a combination of separate failure patterns x
- 16. 16 A • This failure pattern shows early life failure followed, by a period of random failure, until it reaches an age where it becomes rapidly more prone to failure. • 4% of the failures in the Nowlan and Heap study fit this failure pattern • On-Condition monitoring is the preferred maintenance strategy.
- 17. 17 •An age limit may be an effective maintenance strategy, provided a large percentage of units survive to the age at which wear-out begins. • Simple electromechanical systems fit this failure pattern. A
- 18. 18 B Pattern B •Shows age related failures where a component has a low level of random failures, until it reaches an age where it becomes rapidly more prone to failure. x
- 19. B • 2% of the failures in the Nowlan and Heap study fit this pattern • On-Conditioning monitoring is the preferred Maintenance strategy. • Scheduled Discard or Restoration may also be an effective maintenance strategy. • Aircraft reciprocating engines fit this failure pattern - belts, sheaves, chains, sprockets, and impellers are other examples 19
- 20. 20 CPattern C •Shows a steadily increasing probability of failure but no one point where we can say it reaches an age where it becomes rapidly more prone to failure. • 5% of the failures in the Nowlan and Heap study fit this failure pattern x
- 21. C • On-Condition monitoring is the preferred maintenance strategy. • Scheduled Discard or Restoration may also be an effective maintenance strategy. It depends on the cost of downtime in comparison to the cost of component replacement. • Aircraft turbine engines fit this pattern. Other examples of Pattern C components are Pipes, Tires and Clutches. 21
- 22. 22 D Pattern D • This failure pattern shows that the equipment starts up and runs for a short time with no failures, increasing quickly over a short period of time, to a consistent level of random failures. x
- 23. 23 D • 7% of of the failures in the Nowlan and Heap study fit this pattern. • On-Condition monitoring is the preferred maintenance strategy. • Hydraulics and pneumatic components fit this failure pattern.
- 24. 24 E Pattern E • Random failure pattern, the probability an item will fail is the same at any given point. • Ball bearings are an example of a failure pattern E component x
- 25. 25 E • 14% of the failures in the Nowlan and Heap study fit this failure pattern. ( Exponential Survival Distribution ) • More recent studies indicate failure rates between 42% and 72%. • On-Condition monitoring is the preferred maintenance strategy. • Time based maintenance is not effective in reducing these failures.
- 26. 26 F Pattern F • Early life failure pattern, the probability of failure declines with age. The highest probability of failure occurs when the equipment is new. • Electronic components are an example of this failure pattern x
- 27. 27 F • 68% of the failures in the Nowlan and Heap study fit this pattern. • More recent studies indicate failure rates between 16% and 29%. • Look to solve early life failures by using “burn-in” techniques. • If failure rates are too high, explore redesign possibilities.
- 28. A B C D E F x 28 4% On-Condition Task 2% On-Condition Task Scheduled Discard Task Scheduled Restoration Task 7% On-Condition Task 65% On-Condition Task 17% On-Condition Task Redesign Task Industry today 5% On-Condition Task Scheduled Discard Task Scheduled Restoration Task
- 29. 29 The RCM Process The RCM process is structured and interactive, it takes the combined effort of a cross functional team to complete the RCM process. The remainder of this course will use a case study to simulate how the RCM process flows and demonstrates the outputs of an RCM analysis.
- 30. 30 The RCM Process We begin the RCM process by writing a formal Operating Context for the machine we are analyzing.
- 31. 31 The RCM Process The Operating Context will clearly describe: • Why the asset exists • When it was purchased and installed • What the expectations are of this process • The consequences of unscheduled downtime • The present condition and performance of this process
- 32. 32 The RCM Process Describing Primary and Secondary functions With an Operating Context and process drawings, the RCM team can now begin to describe the machine functions. The first function of any machine is the Primary Function The remaining machine functions are know as Secondary Functions.
- 33. The RCM Process Describing Primary and Secondary functions The Primary Function is the major reason why an asset exists. A primary function should include the following: • Performance Standards • Quality Standards • HSE Standards “Think about - What you have when the process starts, and what you want when the process is finished.” 33
- 34. Describing Primary and Secondary functions The RCM Process While the primary function is the reason an asset exists, it is important to list the remaining Secondary Functions. Secondary functions are often less obvious, but should be considered just as crucial as the primary function. Secondary functions can be active, such as to be “To be able to pump”, or passive as in “To be capable of relieving an over pressure condition”. 34
- 35. 35 The RCM Process Describing Primary and Secondary functions Examples of Secondary Functions: • To be able to contain fluid in a gear box. • To be capable of shutting down the machine in the event of and emergency. • To be able to support the mixer • To be able to provide visual indication • To be capable of protecting personnel from rotating equipment.
- 36. 36 Class Exercise •Read the Operating Context for the Methanol Unload System •List the primary function and three secondary functions.
- 37. 37 Methanol Unload System Operation Performance Statement The methanol unload system is located at building Z Kodak Park. The pumping system was designed to unload methanol from a tractor trailer tanker to a holding tank. It was purchased and installed in 1995. The unload system was designed and installed for off loading full and partial loads of methanol. The holding tank is a 20,000 gallon stainless steel tank mounted inside a sealed concrete vault and surrounded by pea -gravel. The holding tank has a level float that provides continuous level readings and a high level shutdown at 18,000 gallons. Level alarms warn the operator in the control room with a light on the control panel, an audible bell and a message on the CRT. A high level condition will shut down the pump, it will be able to restart when the level drops below 13,000 gallons. The emergency high level device is a high level probe set at 19,000 gallons. The emergency high level probe will alarm and shutdown the entire system, it will not be able to restart without operator intervention. The concrete vault is designed for environmental protection should the tank overflow, or leak. There is a Solvent Vapor Detector located inside the vault, it is capable of detecting minute amounts of vapor. Approximately a one quart spill will trigger the detector, the entire system will be shut down. The trailer unload pump is a stainless steel centrifugal pump. The designed flow and pressure of the pump are 120 GPM at 70 PSI. The pump is isolated by hand valves on either side and protected by a minimum flow indicator and a pressure tap. The minimum flow indicator must see a liquid flow of greater that 100 GPM or the pump will shutdown after one minute of low flow condition. The pressure tap will shutdown the pump if the discharge pressure falls below 50 PSI for more than one minute. Piping between the pump and holding tank is 2” stainless steel and has drain valve taps before and after the pump. Trailer wagons average 5,000 gallons and the cost of methanol is $9.00 per gallon. Chemical spills are not tolerated at Kodak Park, leaks of more than 1 quart are reported to loss control at a minimum cost of $20,000 per incident. If a spill of more than one quart reaches the soil outside of the concrete vault it requires a total shutdown and clean up of the spill area resulting in at least 3 days of lost production. Tank trucks are scheduled in at two hour intervals, starting at 7 am each day with the last deliver at 3 pm, the average cycle time to unload is 40 minutes. If a truck is not unloaded when the next one arrives on site, the driver calls dispatch and cancels the next delivery. We are charged for the undelivered load at the regular rate. Any time the tank runs dry there are consequences of catastrophic proportions.
- 38. Methanol Case Study P&ID Drawing SV3 LS3 LS2 PS1 LS1 SV2 TV1 SV1 FS1 SVD1 Hose Pump DV1 DV2 38
- 39. 39 The RCM Process Functional Failures The next step in the RCM process is to list out the Functional Failures for the primary and secondary functions.
- 40. 40 The RCM Process Functional Failures Functional Failure - Is the point in time when a process or component can no longer perform its function at all or is unable to meet its desired performance standard. A Functional Failure statement includes: • An exact performance level that defines the point of failure. • Is normally stated as either a total loss of functional capability or a reduced functional capacity.
- 41. 41 Class Exercise List out the functional failures for the primary function and three secondary functions of the Methanol Unload System.
- 42. 42 The RCM Process Failure Modes Once the Functions and Functional Failures have been listed, we look to identify the Failure Modes. The Failure Mode is the specific manner or cause of a process or component failure.
- 43. 43 The RCM Process Failure Modes Failure Mode statements should include: • The specific component that has failed • The specific cause of the failure For example - Pump bearing fails due to lack of lubrication. The bearing is the specific component, and lack of lubrication is the specific cause.
- 44. 44 Failure Modes The RCM Process When listing failure modes you should: • List all failure modes that have occurred • List failure modes that may not have occurred but are likely to at some point in time.
- 45. 45 The RCM Process Probability Rating Once a failure mode has been identified and listed, we then look to assign a probability rating to the failure mode. The probability rating combined with the consequence rating is used to help us determine the criticality of a failure mode.
- 46. 46 The RCM Process Probability Rating Probability -The likelihood that an event will happen. If there is no maintenance history for your process, we use the experience of the mechanics and operators to access the probability of failure. High - The failure has happened often enough to be considered a dominant failure mode. Medium - The failure has happened often enough to remember and probably will happen again. Low - The failure has never happened or has happened so infrequently that I can’t remember last time it did.
- 47. 47 The RCM Process Failure Effects After listing a Failure mode and defining its probability of failure, we now can describe the Failure Effect. The Failure Effect is the physical effects of a failure mode on the functional capability of the equipment.
- 48. 48 The RCM Process Failure Effects Failure Effect statements include: • The first sign of evidence the failure has occurred to the operating crew. • Describe as much as possible the chain of events that precede the failure. • Describe the chain of events that happen after the failure occurs
- 49. 49 Failure Effects The RCM Process Failure Effect statements include: • The consequences resulting from the failure • Any secondary damaged caused by the failure • Downtime that resulted from the failure • How often the failure occurs.
- 50. 50 The RCM Process Consequence Rating Once the failure effect has been clearly described, the team can now assign a Consequence Rating to the Failure Mode. The Consequence of the failure mode is the impact the failure has on your business - • HSE • Cost • Secondary Damage • Downtime
- 51. The RCM Process Consequence Rating The impact on your business, safety, environment or cost of repair if failure occurs High - The failure causes a loss in capacity that will adversely impact production schedules. This failure has a direct adverse effect on HSE. High repair cost or waste. Medium - This failure will cause the operating department to shift schedules, crews may have to work overtime or additional costs will be incurred to manufacture product. This failure does not effect HSE issues. Low - The failure has no impact on the end user customer, there is a lot of unused machine capacity or a large amount of stored product. There is no secondary damage resulting from this failure and no impact to HSE. 51
- 52. 52 Class Exercise List out five Failure Modes that would cause you to be unable to unload methanol at all. - Assign a probability rating for the failure mode - Clearly describe the effects of the failure - Assign a consequence rating to the failure
- 53. 53 Methanol Tank Farm Failure History Component # of failures Repair Time Work around SOP's TV1 1 0 Pump from top of trailer Hose connector 4 0 Pump from top of trailer SV1 failed closed 2 6 hrs SV1 leaks by Leaking now DV1 left open 1 72 hrs DV2 left open 0 DV1 or 2 failed closed 0 FS1 failed closed 2 0 Rely on Pressure reading, extra operator FS1 failed open 0 Pump seal leaking 8 6 hrs Pump impeller 1 10 hrs Pump motor 0 Pump motor coupling 8 30 mins LS1 failed open 1 4 hrs LS2 failed open 1 4 hrs LS3 failed 0 PS1 failed low 1 30 mins Rely on Flow reading, extra operator PS1 failed high 0 Pump bearing 1 6 hrs Pump pipe flange seal 2 2 hrs SVD1 failed 1 4 hrs Substitute a portable sniffer Component Cost Lead time P/N FS1 $4,000 6 hrs SW123 Hose coupling $150 2 hrs HC-99 Impeller $10,000 3 months IMP-345 LS1, LS2, LS3 $75 2 hrs LS-239 PS1 $350 2 hrs PS-124 Pump seal $500 2 days SEV-789 Pump bearing $400 2 hrs TMP-41 Flange seal $25 2 hrs FS-Y2K SVD1 $5,000 75 days SVF-UALL SV1 $35 4 hrs STV-1000 DV1 $35 4 hrs STV-1000 Pump motor coupling $35 4 hrs COUP-1
- 54. 54 The next step of the RCM analysis is the decision process. It is where we determine the type of failure consequence and the proper maintenance strategy. There are four types of failure consequences. • Hidden • Health, Safety, and Environmental • Economic • Non-Economic The RCM Process RCM Decisions
- 55. 55 Hidden Failures • Have no direct consequences • Require multiple failures to be evident to the operating crew Examples: • Safety devices • Redundant systems
- 56. 56 Health, Safety and Environmental Failures •Have a direct effect on the health & safety of individuals or the environment Examples: •Leaks •Spills •Emissions •Pinch points
- 57. 57 Economic Failures •Direct adverse effect on Production costs Examples: •Non-Conforming Product •Yield losses •Maintenance cost •Operating Costs •Parts costs
- 58. 58 The RCM Process Determining the correct Maintenance Strategy In working our way through the decision process, the final step is to determine the correct maintenance strategy and interval. • Predict the failure is about to occur • Prevent the failure from occurring • Reduce the consequences should the failure occur. • Redesign to eliminate the failure This requires an understanding of the different types of maintenance.
- 59. 59 Types of Maintenance •On Condition - Inspection, measurement observation, non-destructive task for parts prone to failure. (Predictive) •Restoration -Once the end of useful life is reached, you restore the component to “like new” condition (Preventive)
- 60. 60 •Discard - Once the end of Useful Life is reached, you remove and replace the component. (Preventive) •Failure Identification - Inspection for undetected failure of components not used during normal operation (Consequence reduction) Types of Maintenance
- 61. 61 On-Condition Monitoring Traditional methods • Vibration analysis • Lubrication analysis • Thermography • Motor Circuit Evaluation • MCEmax testing • Ultrasonic testing
- 62. 62 Contemporary methods Process Monitoring • Temperature • Pressure • Electrical Current Statistical Techniques • Trend Charts • Control Charts On-Condition Monitoring
- 63. 63 Informal methods •People’s senses • Daily walk around • Cleaning • Listening • Visual observations • Smell • Touch On-Condition Monitoring
- 64. 64 RCM Maintenance Intervals • For scheduled discard and restoration tasks • Are determined by knowing the “Useful life” of the component
- 66. 66 RCM Maintenance Intervals For On-Condition Tasks • When setting up tasks for On-Condition maintenance, use the P-F interval of the failure.
- 67. 67 Typical Failure Curve P F P-F Interval P - The point in time when failure begins F - The point in time when equipment can no longer deliver it’s primary function x
- 70. 70 P F 1 2 3 4 5 6 7 Time PerformanceLevel Reaction Time Inspection Interval 1/2 Ball Bearing PF Curve
- 71. 71 MTBF (Mean Time Between Failure) is not valid or useful in determining Maintenance task intervals. x
- 72. 72 • When determining maintenance task intervals, the team should be conservative, when data for failure history is not available. • Tasks should be cost effective.
- 73. 73 Class Exercise •Run each of your failure modes through the RCM decision and Spare Part Flow Charts •Determine the correct task and interval •Determine the correct spare part strategy
- 74. Will failure be detected while the operator is performing their normal duties? Will this failure on its own effect HSE? Will this failure have operational (economic) consequences? Is there a failure finding task that would detect the failure? NO START YES NO No scheduled maintenance required NO Establish a failure finding task YES Is there any early warning the failure is going to occur? YES Is there an on-condition task that is applicable and cost effective? YES Is there a scheduled rework or discard task that would reduce the failure rate? NO Is this task applicable and cost effective? YES NO YES Redesign of the 1. Equipment or 2. Procedures or 3. Process is REQUIRED NO NO Implement a preventive maintenance task (Scheduled rework or discard) YES Does this failure effect HSE? Consider Redesign of the 1. Equipment or 2. Procedures or 3. Process to reduce consequences to an acceptable level NO NO YES YES YES NO YES NO Implement predictive (on-condition) maintenance task YES NO NO YES Implement a preventive maintenance task (Scheduled rework or discard) Is there a business case for a redesign? Redesign No scheduled maintenance required (Consequence reduction strategy ) YES NO Implement predictive (on-condition) maintenance task Reliability Centered Maintenance Decision Flow Chart Is there a scheduled rework or discard task that would reduce the failure rate? Is there any early warning the failure is going to occur? Is there an on-condition task that is applicable and cost effective? Is this task applicable and cost effective?
- 75. Risk Consequence High Negligible Negligible Low Medium High Extensive Spare Parts Risk Matrix Do Not Stock Part Stock The Part Risk CONSEQUENCE Negligible - *No impact on production *No HSE risk *No impact on process Low * No impact on production * No HSE risk * Some impact on process Medium * Some impact on product * Some impact on process * No HSE risk High * Unacceptable product * Failed process * HSE risk Extensive * Defective product to Customer * Loss of this machine shuts down a customers process * Someone will be injured Formula : Part Stocking Cost = Purchase price + (.30 X Purchase price X yrs of no use) W aiting For Parts Cost = Out of pocket cost per hr X Lead time in Hrs waiting for part PROBABILITY Negligible - can not imagine this ever happening Low - can not remember the last time it happened Medium - happens occasionally High - happens often DO NOT STOCK THE PART - The risk of not stocking the part is low RISK - The risk factor varies based on many local decision points. If your business has a high risk tolerance, do not stock the part. If your business has a low risk tolerance, stock the part STOCK THE PART - The part can be stocked as an LMSC, minus one, Stock 1, Sub-stock room, or KSC stock. Pick the option that suits your needs. Spare Parts Risk/Cost Decision Model START Is there any early warning the failure is going to occur? Can a replacement part be acquired before the failure occurs? Is there a known age at which the part fails? Does waiting for part to be delivered cost more than Stocking Part ? Do not Stock Part Yes No Yes Is part already stocked? Look for a replacement part or redesign Continue to Stock Part Yes No No No Yes No Yes Yes Is part Obsolete? NO