Archive | October, 1997


2:53 am
October 2, 1997
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Building a Solid Foundation for Maintenance Operations

Maintenance strategies, as I suggested in a previous article, should be developed in three stages:

  • Determine the maintenance requirements of each asset in its operating context
  • Decide what resources are needed to fulfill those requirements
  • Decide what systems are needed to manage the resources.

This process was compared to building a house where maintenance requirements are the foundation, the resources needed to fulfill the requirements are the walls, and the systems needed to manage the resources are the roof.

It was also mentioned that if the assessment of maintenance requirements focuses on what each asset does rather than what it is, the way in which the requirements are perceived is completely transformed. In other words, such an assessment changes the size, shape, and location of the foundation upon which the maintenance enterprise is built. If this review is carried out correctly, the foundation is also usually smaller than it would be otherwise. A smaller foundation means that the entire structure (resources and systems) built on that foundation is also smaller.

Of course, as every builder knows, the integrity of any structure depends first and foremost on the integrity of its foundation. So if we want to build a maintenance enterprise that is robust enough to satisfy all the expectations of its customers, we must ensure that its foundation is always the right size and shape, in the right place, and sufficiently solid to bear all the loads placed upon it.

Building a solid foundation means that the building project must be planned properly, the ground must be prepared correctly, the foundation must be properly designed, the right materials must be used, and the foundation must be built by people with appropriate knowledge and skills.

Planning the project means that clear objectives must be established, resources allocated, and a plan prepared.

Preparing the ground means that everyone in the organization served by the maintenance enterprise must clearly understand what maintenance can and cannot achieve, and what he or she must do to help achieve it.

Designing the foundation and selecting the right materials means systematically defining the functions and required performance standards of each asset, deciding what failure modes are reasonably likely to cause it to fail, assessing the effects and consequences of each failure, and selecting a failure management policy that deals appropriately with the consequences of each failure.

Using appropriate people means that the exercise must be performed by groups of people who have a thorough understanding of each asset in its operating context, working under the guidance of someone who profoundly understands the process being used to assess the maintenance requirements and who has a long-term vested interest in the success of the project.

In terms of this structural analogy, it is worth noting that many maintenance enterprises spend immense amounts of time, energy, and money on maintenance management systems (roofs) and on tools such as condition monitoring (part of the walls) but spend little or nothing on clarifying perceptions about what must really be done to cause the assets to continue to do what their users want them to do (the foundation).

The result is elegant roofs and walls built over a foundation that is the wrong shape and size, in the wrong place, and not nearly strong enough to support the loads imposed upon it. The end result is a maintenance enterprise that is not nearly as effective as it should be.

This is not to suggest that we don’t need computerized maintenance management systems or condition monitoring. Of course we do, in the same way that nearly every building needs a roof and walls. However, the roof and walls must fit their foundation, and the foundation must be able to support the rest of the structure.

In essence, the only way to develop a truly viable, long-term maintenance strategy is to invest an appropriate amount of time and energy in every element of the process. In particular, you must avoid the temptation to concentrate too heavily or too soon on maintenance technologies and systems without first ensuring that everyone shares a clear, common, and correct understanding about what must really be done to ensure that every asset continues to do what its users want it to do. MT

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2:36 am
October 2, 1997
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Structuring Reliability Training

Industrial companies are addressing plant capacity improvement in many ways. The cornerstone of these processes is often overall equipment effectiveness, which includes both equipment and process reliability. Several terms are used to describe programs that are structured to improve equipment reliability, including reliability-centered maintenance, reliability-based maintenance, total productive maintenance, and condition-based assessment.

The common thread for successful implementation of all of these initiatives is the applied knowledge and skills of the maintenance craft workers and operations personnel.

As competition drives companies to optimize plant capacity and reduce maintenance costs, some important work force performance issues must be considered:

  • How to boost employee morale by giving employees the skills and knowledge to do the job right the first time
  • How to save energy costs through efficient operations and well-executed maintenance plans
  • How to increase the company’s independence from vendors and their costly services
  • How to decrease the probability of personnel errors
  • How to reduce the number of surprise downtime incidents
  • How to benefit from consistency and accuracy in job activities through the joint participation of maintenance and operations departments

The Integrated Technologies Group of Fluor Daniel addressed these issues as part of its business enterprise optimization services for clients and to prepare its own workforce for contract maintenance activities.

The material presented here outlines our approach. It can be used as a basis for assessing your training needs and developing a program, or as a basis for developing specifications for a training program or materials to be supplied by others.

The primary objective of this initiative was to create a cost-effective method of delivering specialized skills for a selected group of employees to enable them to mitigate equipment failures.

Knowledge and skills transfer for maintenance personnel
The scope and content of the reliability training component of our program is based on an analysis of the classical reliability-centered maintenance (RCM) analysis process model.

Instructional Model For Maintenance

Fig. 1. Instructional model for maintenance personnel covers the main elements of reliability-centered maintenance.

Our analysis was accomplished by a team of reliability engineers and training specialists. The team focused on the definition of the knowledge and skills that facilitate maintenance craft worker participation in the corrective engineering and maintenance task implementation activities. Five topics, as well as the prerequisite knowledge for learning these topics, were identified, Fig. 1.

The basic building blocks, or prerequisites, for technical skills development can be found in existing craft training materials, vendor programs, or instructional materials designed for site or equipment-specific applications. However, the materials developed for equipment-specific training should reflect the results and recommendations of the RCM process, because these recommendations form the basis of maintenance.

A crucial step in the maintenance task implementation component of RCM is to determine the training and the special tools required to carry out the tasks. Procedures must be developed or revised to document the steps involved in performing difficult tasks. The documentation should be amply detailed to identify proper training requirements. Measurements must be used to gauge the results of the programs.

In addition, because the workforce also must be educated in the fundamentals of RCM and their roles in supporting the process, we developed a series of print-based and interactive media programs (computer-based training) to support this need. Topics covered to support the instructional model for maintenance personnel include the following:

  • Introduction to reliability
  • Selecting and performing preventive and predictive techniques
  • Identifying and explaining approaches to root cause failure analysis
  • Implementing root cause failure analysis
  • Identifying and explaining failure modes and effects analysis
  • Identifying and explaining wear and failure points
  • Identifying and explaining prevention or mitigation tasks

Knowledge and skills transfer for operations personnel
As companies move toward the elimination of traditional organizational lines between the production and maintenance departments, they often use elements of total productive maintenance (TPM). The five pillars of TPM call for

  • Maximizing equipment effectiveness
  • Involving operators in daily maintenance
  • Improving maintenance efficiency
  • Training to improve skill levels
  • Emphasizing maintenance prevention.

Operators in many companies are assuming responsibility for cleaning, routine inspection, and selected fundamental maintenance tasks. In addition, operators can provide valuable predictive or diagnostic support because of their familiarity with the equipment and their awareness of changes in the condition of a machine or a process. Operator feedback can provide valuable information for the root cause failure analysis process.

Instructional Model For Operations

Fig. 2. Instructional model for operators begins by introducing personnel to basic maintenance concepts.

Our skills enhancement program for operations personnel is outlined in Fig. 2. The building blocks necessary for advanced knowledge and skills development include a working knowledge of plant systems and equipment, safety and regulatory parameters, and equipment-specific skills. These training requirements are typically provided by equipment vendors, consultants, and inhouse subject matter experts.


We found there is a void relative to training products that are used to provide operators with the fundamentals of predictive technologies and preventive strategies and that also support the development of core maintenance skills at a technical level appropriate for operations personnel. Routine maintenance skills for operators was the first area we addressed in the development of the operator-performed maintenance (OPM) section of our program.

We developed 21 training modules covering mechanical, electrical, instrumentation and electronics, and general maintenance topics (for example, Introduction to Walk-Down and Inspection Programs).

The OPM modules were developed at an introductory level of maintenance technology appropriate for operators and nonskilled maintenance personnel. We also provided recommendations on how personnel can use their senses to determine equipment performance deviations and problems. Information about what an operator should look, feel, smell, or listen for is provided in module activity sheets.

The OPM modules were followed by a series covering the principles of RCM. Whereas the routine maintenance skills training facilitates the expansion of operator roles, the reliability-related modules enable production personnel to participate in equipment diagnostics and fault resolution. Each course should include an effective blend of classroom knowledge transfer and structured on-the-job training.

Because most companies have reliability programs that are specific to their industry and facility design, their training needs vary accordingly. Training programs and materials designed to support a broad range of equipment maintenance requirements can usually be tailored to support site-specific needs.

Most materials can be supplemented with more detailed equipment-specific courses or seminars that are consistent with the technical knowledge and skills of the incumbent work force and promote overall program objectives. MT

Michael E. McGrey is senior director at Facility and Plant Services, Inc., a Fluor Daniel Co., 100 Fluor Daniel Dr., Greenville, SC 29607-2762; (864) 281-4400.


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1:28 am
October 2, 1997
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Advanced Maintenance Technologies Help Solve Robotics Problem

Infrared thermography and waveform analysis identify mechanical failure and highlight increased duty cycle concerns in robotic work cell.

Root cause investigation of a single fault on a piece of critical production equipment at Accuride’s Henderson, KY, plant uncovered multiple hidden problems. Solving those problems resulted in increased productivity.

The investigation began shortly after an operator noticed a hunting and surfing motion in the work station’s Motoman K150 robot as it loaded a press. When excess following error increased and caused the machine to fault regularly, the staff decided to replace the reduction gear assembly on the affected axis.

The manufacturer was asked to send a technician to assist in the assembly replacement. Repairs were made, the axis was exercised with no load, and it showed no apparent faults, noises, or unusual vibration.

The reduction gear was disassembled to locate the cause of the failure, and a badly deteriorated bearing was found.

When the unit was placed in production the next day, setup personnel commented on the extreme heat of the repaired axis servo motor. This open dialogue between the plant’s maintenance and production teams allows flexibility in problem solving, which greatly facilitates the company’s maintenance objective.

How hot is hot?
When the motor encoder assembly was scanned with a Cincinnati Electronics infrared camera, it showed a temperature 20 deg F above the temperature of the same axis on another K150, Fig. 1. The reduction gear on the hot axis was found to be extremely worn.

The installation of a new unit appeared to correct the extra play or looseness in the system. The motor, which had logged 24,000 hours of production, also was replaced to eliminate concern that it might deserve a rebuild. The robot is in use 24 hours a day, 7 days a week, so testing, troubleshooting, and replacement are done at the expense of production.

Was this a poor repair?
Was the new $8000 reduction gear defective? Was something overlooked, or were there multiple problems? The plant’s experience in motion control indicated that the most obvious causes of overheating in pulse-width modulated servo systems are oscillation due to tuning or noise, overload, and phase unbalance.

Duty cycle and load are primary considerations. Because they are typically addressed at the design stage, they were assumed to be satisfactory at this stage of the investigation.

A balanced load on all three phases was quickly verified using a digital multimeter that measured true rms current. Oscillation and following error were stable and there were no major or minor faults. Testing of the cable harness and brake circuit proved inconclusive.

Waveform analysis
The staff continued the investigation of the problem by checking speed and torque curves with a dual trace Fluke 105 Scopemeter. They found that the torque curve was roughly parallel to the speed curve. Ordinarily, torque decays as speed levels off because maintaining speed requires less effort than acceleration or deceleration. Testing before disassembly showed a fairly normal torque curve with no load and abrupt changes to the unusual parallel pattern when a working load was applied.

Two weeks passed before production schedules would allow the time to disassemble any major components. The Motoman technical support technician returned to assist in identifying the cause of excess heat. Oscillation and unbalanced loads were eliminated before he arrived, so it became a matter of disassembling minor mechanical components. One tapered roller bearing out of four on the cantilever arm had disintegrated and parts were wedged between frame members.

After repairs were completed, additional tests showed a very clean speed waveform and rapidly decaying torque curve. This repair appeared to be a resounding success, but new infrared images showed only a small overall decrease in radiant heat. At this point the waveforms were again checked and found to compare favorably to those of another robot doing a similar task.

Further investigation revealed a rapid sequence of torque spikes related to programming procedures. There were more start-stop sequences than needed in cycle programming. Removing three stop-start cycles, and merging two positions, reduced the demand on the robot by 32 full-torque moves per minute and reduced radiated heat 15 deg F.

Because inrush current during startup is 200 percent or more of running current of the axis motor, it is likely that the more efficient program will result in significant reduction in stress to the unit. An unexpected benefit was a 2 second cycle time increase.

Project results
As bottlenecks inhibiting production were resolved, the duty cycle of the machine increased. Continuous improvement of the process and equipment have pushed this unit, one of the more reliable production cells, to the limit. Engineering had recently increased the working speed and position of this material handler; this increase probably precipitated the problem.

What had been the quickest part of the process has now become a concern of reliability and capacity. Yes, the robot can maintain this level of production, and there are still gains to be made. However, programming practices have become more critical, along with the need for more diligence in monitoring the condition of every system. A new opportunity exists to utilize the time gained, increasing productivity with minimum expense.

This investigation illustrates the value of thorough fault analysis. A single fault without clear resolution led to the identification of a series of problems whose resolution produced gains. These gains then may stress other parts of the machine train. Their resolution may then spotlight another opportunity. Continuous improvement resembles a cat chasing its tail: the target keeps moving but the goal remains the same. Collected data may be difficult to interpret without previous experience, but each effort will generate a record for future reference. MT

Bill Cunningham is a senior maintenance planner at Accuride Corp., Henderson, KY, a division of Phelps Dodge Industries. He has over 20 years’ maintenance management and hydraulics expertise and was instrumental in establishing predictive technologies at this facility. Kevin Harrison is an industrial electrician with 16 years’ experience at the plant. He is a licensed master electrician and a certified infrared thermographer. Continue Reading →


12:01 am
October 2, 1997
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Back In The Good Old Days, Part II

bob_baldwinLast month when I discussed two massive monuments to a bygone industrial era, the Cornish pumping engine and the Quincy mine steam hoist, I noted that the romantic good old days were not all that good. But people still wish for simpler times when the industrial scene was less complicated.

Not so long ago, machinery reacted reasonably well to the application of an acetylene torch or a sledge hammer. Today, the torch and hammer approach will destroy precision components such as antifriction bearings. Similar change has taken place in the electrical area where there is concern about harmonics and waveforms.

But these changes are only differences in parts, tools, and techniques. What people really miss, I think, is the protection of the old mass production mentality which was simple and straight forward. Technology was applied to allow workers to work harder and faster. Today, we are being asked not only to work harder and faster, but also smarter and to tighter tolerances. The tools and technology are up to the new challenge but I’m not sure about some business management practices.

In the good old days, inventory was your friend–a buffer that could accommodate the inevitable breakdowns.

Today, inventory is the enemy–a drag on investment, and there is no longer such a buffer to cover mistakes.

In the good old days, maintenance personnel could just focus on fixing things when they broke.

Today, maintenance personnel must manage the equipment and attend to it before it breaks. If it does break, they must find out what happened and reduce the risk of it happening again.

In the good old days, maintenance managers worked on improving repair efficiency. They were measured on how fast they could get the equipment back on line.

Today, maintenance managers must also focus on reliability and work on improving maintenance effectiveness. Mean time between failure is now a part of the matrix for measuring performance.

In the good old days, management furnished maintenance with torches and hammers.

Today, management is still making sure maintenance has a good supply of torches and hammers. But what about advanced technology and training? On the other hand, maybe this is as good as it gets. Perhaps maintenance managers back in the good old days had to go to the mat and fight for every torch and hammer they got.

Thanks for stopping by,


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8:13 pm
October 1, 1997
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Using a CMMS To Support RCM

A modern computerized maintenance management system should have the functionality to support a reliability-centered maintenance effort. Here is how they can work together.

Asset optimization at minimum cost is a fundamental principle of modern business management. It translates into getting the maximum uptime and hence the value from any asset or equipment. Most plants have a preventive maintenance (PM) program in place. Usually, equipment condition is assessed each time PM is performed. After a number of PM actions have been performed and recorded on the same equipment, sufficient data can be available to determine whether the equipment needs more or less frequent PM work and how PM frequency should be adjusted.

Reliability-centered maintenance (RCM) is the method that best addresses the requirement for maximum reliability at minimum cost, or more pragmatically, doing the right maintenance at the right time. RCM results in a maintenance program that focuses PM on specific probable failure modes only. It has a strong bias toward condition monitoring and trend analysis of equipment performance.

Nonintrusive condition monitoring, such as vibration monitoring and oil analysis, can reveal deterioration in performance and warn of impending loss of equipment functionality or failure. When sufficient data are available, trending can be used and maintenance can be performed when measurements stray out of a predetermined safe operating range.

Benefits of RCM
RCM is an engineered approach for determining the right proactive maintenance to achieve design reliability at minimal direct maintenance cost. The process recognizes that some failure modes are preventable, some are predictable, and some are entirely random. RCM targets all these failure modes with proactive maintenance activities that prevent, predict, or watch for signs of incipient failures.

Traditional maintenance approaches rely on the recommendations of equipment suppliers or on historic precedence. Although well intentioned, both of these approaches have serious drawbacks. Suppliers usually write only one maintenance manual for their equipment and provide it to all users. Equipment failure can produce widely different environmental, safety, production, or maintenance consequences, depending on equipment location and application, and yet, maintenance recommendations from the equipment manual will be the same for all.

The traditional “we’ve always done it this way” approach is similarly flawed for its lack of focus on failure mechanisms, causes, and effects. It also fails to eliminate historic maintenance activities that may be unsuited to the nature of the failure modes.

Failure of equipment such as a pump has both causes and failure mechanisms. The failure mechanisms are “how” the failure progresses to the point at which equipment function has stopped. These chains of events have an unfortunate and usually predictable conclusion, such as “stopped pumping.” If each component in the equipment is examined closely, it becomes apparent that it has a finite, and often small, number of failure mechanisms unique to the component or to its operating environment. RCM seeks to identify these mechanisms and then addresses either their cause through preventive maintenance or the conclusion of the failure mechanism by predicting when it will happen and taking appropriate steps to prevent the failure of the equipment function.

Performing the appropriate maintenance just in time can produce significant cost savings, in addition to increased equipment uptime. RCM is a powerful tool for optimizing just-in-time maintenance actions. RCM targets only preventable failure causes with actions intended to prevent them, predictable failure mechanisms with actions that take advantage of the predictability of the mechanism, or the tell-tale signs that show the failure mechanism is in its early stages so that steps can be taken to prevent the functional failure. RCM does not result in over maintaining the equipment with actions that do not address specific failure modes.

RCM programs produce the greatest return when applied during the design stages for equipment additions, plant modifications, and new plants. Once a PM program has been established, there is often a great deal of reluctance to change it. In all fairness, RCM will result in a number of maintenance tasks that are identical to those traditionally performed. Nevertheless, many plants are over maintained and many are under maintained. If breakdowns account for more than 20 to 25 percent of the total maintenance workload, a plant can benefit from RCM. A plant that experiences very few breakdowns but suffers from what may be excessive downtime for maintenance or excessive maintenance costs is likely being over maintained.

RCM can result in significant reductions in direct maintenance costs. In one recent application of RCM, the number and frequency of maintenance tasks were reduced by almost 50 percent while availability increased 10 percent. In the aircraft industry, where RCM had its genesis, heavy inspection and overhaul workloads have been reduced by orders of magnitude while aircraft availability and safety performance have increased. In both cases, before RCM was applied, over maintaining was the result of doing things the traditional way.

Achieving optimized maintenance
RCM combines a thorough evaluation of critical equipment to identify failure modes and their effects with a logical process of determining the right maintenance actions focused on the least intrusive methods first. RCM first focuses on determining what is most critical to an operation, assuring that the most benefits are realized as soon as possible. After equipment or systems have been identified and ranked by criticality, the rigorous failure modes and effects analysis process is applied to identify the failures, failure modes, and effects of those failures. Then the analyst has sufficient knowledge of each failure to apply RCM task identification logic and derive applicable and effective maintenance tasks and frequencies.

A rigorous RCM program can take considerable time and effort to put in place. Methods have been developed that guide the user through the steps to determine which equipment needs to be monitored or “registered” in the RCM program. Required data include the operating function and performance specifications. After the types of failures and failure modes that can occur have been determined and the effect of these failures has been evaluated, maintenance procedures to reduce the incidence of failure can be recommended.

The discussion that follows outlines the RCM approach and reviews the type of information support a properly configured computerized maintenance management system (CMMS) can bring to the process. It is based on the authors’ experience with the RCM process and CMMS software supplied by their respective companies.

1. Select equipment and locations to be reviewed
The CMMS database should be three dimensional, with information on the physical asset (or equipment or component), the equipment type, and the location of the asset.

The physical assets database should contain detailed equipment specification data that includes not only nameplate data but also any other physical attributes that the user requires. It could have a critical parts list as well as a list of standard PM tasks and other applicable jobs. A history of costs incurred, symptoms, cause codes, failure modes, and corrective action codes can be accumulated by the CMMS together with a description of the actual work performed, and parts and materials required to complete that maintenance. These data are then available to the planner, the craftsperson, and the manager.

The location database describes the plant’s facilities and physical process locations. Specifications, including operating conditions, can then be maintained for any location. All history data are stored by location as well as by equipment. Costs can then be rolled up the location hierarchy as required. In addition, downtime can be tracked for each location.

The equipment type database contains key data such as parts lists, specifications, and standard maintenance procedures to be stored only once for many pieces of equipment of that type.

It is not necessary and it is often too expensive to set up an RCM program for all equipment and locations in the plant. An analysis of criticality of the equipment is necessary to determine which equipment need not be analyzed or can be deferred to later in the program.

The equipment and locations to be first registered in the program are those that are critical to safety, the environment, and the operation of the process or plant, and that contribute significantly to lost production. Also included are equipment with high maintenance cost, high repair frequency, or low mean time between failures, and equipment that has the most downtime. A modern CMMS should identify equipment or locations that meet any of these criteria and produce reports showing the top 20 items for review.

Once equipment or locations are selected, they can be registered in the reliability program and the database. Registration can then trigger the display of typical symptoms associated with that location or equipment when a work request is created. Additional reliability information can be entered when work orders for registered equipment or locations are completed.

2. Define equipment functions and performance standards
RCM requires definition of primary, secondary, and protective functions of registered equipment. A versatile CMMS should include a facility for defining specifications for equipment and locations. These specifications will typically include operating characteristics and performance standards such as temperatures and pressures, as well as other measurements. The combination of specifications and measurements defines the performance standards for the equipment.

Defining equipment functions requires a thorough review of equipment purpose, both in the process or primary function (such as to pump fluid at a specific range of flows, pressures, and temperatures under specified suction conditions) and in the secondary and protective functions (such as to contain fluid, to prevent reverse flow of fluid from discharge to suction, and to provide visual indication of seal failure). The definition of equipment functions should be specific and detailed and include limits on operating parameters for satisfactory equipment function in its intended role.

3. Determine functional failures
The reliability team evaluates all possible failure modes for each piece of equipment in the RCM program and the failure types for each failure mode. Once determined, these failure types can be entered in a CMMS data table as descriptive information along with an appropriate failure code. This procedure serves the dual function of moving the RCM analysis forward as well as providing valuable information for the ongoing reliability analysis. The failure codes are captured by the equipment and location history function in the CMMS, thus enabling statistical analysis.

Detailed operating parameters were specified when equipment functions were defined. Functional failures occur when equipment performs outside these operating parameters. These off-specification operations, often seen by equipment operators and used as complaints about the equipment or descriptions of equipment failure, are failure types.

Determining all possible symptoms associated with each equipment type provides a further benefit. After the values are entered, they can be displayed when a work request is created for equipment or locations registered for reliability. Selecting these failure descriptions gives the work request description more meaningful information than simply “Fix pump P-101.” RCM will result in the identification of failure types that can be used as failure codes.

4. Identify failure modes and root causes
The failure mode and root cause of any failure is often identified only after a multidisciplinary approach to reviewing failure data. The root cause could be poor maintenance, unstable operating conditions on startup, operation outside the design standards, incorrectly specified equipment, poor engineering design, etc.

The root cause determination is a key step in the RCM analysis for preventable failure modes. Knowledge of the failure modes enables the analyst to identify failure effects that may be detectable with condition assessment technologies such as vibration analysis, oil analysis, and infrared thermography.

In addition to the root cause, there may be contributory causes. Most failures are caused by a combination of events that trigger a specific failure mechanism. For example, a noncontact oil seal combined with the use of a water hose to clean process equipment will result in oil contaminated with water and eventual failure of the bearings. Contributing causes are often reviewed as part of the root cause determination.

A CMMS data table can store a number of “cause codes” for each equipment type. Although contributing causes are not necessarily root causes, they do allow the operator or mechanic to enter any number of known con~tributing causes for a work order. This information is then stored as part of the equipment and location history.

5. Assess failure effects and consequences
It is important to recognize the consequences of potential failures, and recognition implies an understanding of the criticality or significance of the failure.

When the failure mechanisms are analyzed, some of the failure effects become evident. Local or equipment effects are usually obvious. The analysis then progresses up the equipment hierarchy to determine effects at the system and plant levels.

For example, a failed relay contact in a cooling tower fan starter may prevent the fan from starting, which in turn prevents the cooling tower from providing sufficient process cooling, which in turn results in the shutdown of part of the plant because of overheating of the process at certain critical heat exchangers. In this case, in which cooling is critical, failure of a seemingly insignificant relay can have significant operating consequences. Knowledge of the relay’s condition is now recognized as being important, and monitoring relay condition through infrared thermography or regular cleaning of the contacts becomes a worthwhile task. Now assume that the relay in this example results in the shutdown of only one of two fans, each of which can supply sufficient tower capacity for the process. The relay is now far less important, and it may be appropriate to simply wait until it fails and then fix it. Knowledge of the effects of the failures can therefore be important in making decisions on appropriate proactive steps.

6. Define maintenance strategies
Maintenance strategies to avert the probability of failure are determined on the basis of the foregoing analysis. These strategies have two components: what maintenance will be performed and when it will be performed. RCM provides a series of questions in a logical progression using the knowledge of the failure effects as an input to determining appropriate maintenance actions.

The question sequence first looks for hidden failures, failures with no obvious signs or effects that alert operators to the presence of the failure. If hidden failures have safety consequences, a failure finding task is appropriate if the failure cannot be prevented or predicted. If failures are not hidden, those having safety, environmental, production loss, or maintenance cost impacts are defined, in descending order of importance. It is important to determine whether it is possible to

Monitor for the presence of the failure before it has progressed to a total loss of functional performance
Prevent the failure through a time or usage-based action such as an oil change
Prevent failure consequences by replacing the failing item at some predetermined time or usage-based interval
Take default action

Default actions are based on the consequences of failures. A failure mode having unacceptable safety or environmental consequences should be designed out of the system or equipment, or it will be necessary to take contingency action to avert the consequences of the failure when it eventually occurs. Similarly, if the impact on production is severe, redesign may be warranted, but if the impact is minor, run to failure may be acceptable.

Through its focus on specific failure modes, RCM avoids the use of maintenance tactics that do not address the failure modes the equipment experiences. Rarely will an overhaul result from RCM because up to 65 percent of all failure modes are random in nature and do not respond to time-based overhaul actions.

Overhauls are typically appropriate only when equipment has a large number of time or usage-sensitive failure modes such as component wear caused by frequent start and stop cycles. In such cases, an overhaul is appropriate to collect component replacement actions into a single combination task. Overhauls that include much inspection work can usually be replaced with condition monitoring. Most overhaul work is followed by a series of smaller problems immediately after startup. These problems can be avoided.

7. Implement and refine the maintenance tactics
No maintenance system is effective without ongoing feedback and reviews. As work orders are completed, additional data can be collected. This practice enables capture of any failures that occurred, and codifies the corrective or preventive actions taken. Up to four codes are captured for all work orders on any equipment or location: failure code, symptom code, cause code, and action code. Useful statistical information can be calculated from these codes and their distribution over time.

RCM increases equipment and plant uptime while reducing costs through the performance of the right maintenance at the right time. It avoids the unnecessary and unwarranted use of well intentioned but misplaced maintenance activities that do not improve reliability, or worse, that result in increased failures.

A modern CMMS can be the foundation for effective RCM. It also can be the foundation for managing equipment reliability as part of normal maintenance management.

RCM is a one-time project that defines maintenance strategies that lead to maximum uptime of equipment at minimum cost. Management of equipment reliability is an ongoing strategy that requires the use of a CMMS with broad functionality that can analyze vast amounts of data collected as part of the maintenance management program. MT

Jim Picknell is a manager at Coopers & Lybrand Consulting, 145 King St., W., Toronto, ON M5H 1V8; (416) 869-1130. His company can facilitate the installation of a reliability-centered maintenance program. Keith A. Steel is senior industry consultant at Revere Inc., 3500 Blue Lake Dr., Suite 400, Birmingham, AL 35243; (800) 411-6614; Internet His company supplies the Immpower computerized maintenance information and asset management system.

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