Predictive Maintenance (PdM) and Preventive Maintenance (PM)

One of the employee ask me, What is the difference between Preventive Maintenance (PM) and Predictive Maintenance (PdM)?

Here's an straight answer:

"The distinction between preventive maintenance (PM) and predictive maintenance (PdM) is that PdM tracks performance based on conditions while PM is a time-based replacement or service process"

The question now is... what is the best between these two?

Can smart instruments help Predictive Maintenance?

Predictive Maintenance do really needs modern instrument or can smart instruments really help Predictive Maintenance? This question pulls together the entirely unrelated concepts of smart instruments, and predictive maintenance. The smart instruments (sometimes also called “smart sensors”) concept is a hardware-architecture strategy. Predictive maintenance, on the other hand, is a system-level concept.

Smart instruments have been around for a decade or more. The technology falls under the general heading of “embedded systems,” which includes any device containing a microcomputer, but no fully developed user interface. Examples include automotive engine control modules (ECMs); microprocessor controls for major appliances, such as dishwashers, microwave ovens, etc.; and mobile systems, such as cellphones and digital cameras. Smart instruments include one or more sensors to make physical measurements, a microprocessor to partially analyze sensor data, on-board memory to hold parameters and intermediate results, and I/O capabilities to report results to the next level of automation. Components for such devices are packaged together and mounted as close as possible to the point of measurement.

Predictive maintenance strategies monitor selected variables that engineers believe have maintenance-predictive power. For example, a rise in a bearing’s temperature may warn of impending need for additional or replacement lubricant. Automatically monitoring such variables makes it possible for the system to tailor the maintenance program to the machinery’s actual needs, saving time, supplies, and replacement parts, and avoiding unplanned work stoppages. The alternative is scheduled maintenance, which generally provides more maintenance than necessary on average, but may miss extraordinary events.

For example, a system described by engineers at SKF provides automatic bearing lubrication based on predictive maintenance principles. Traditional scheduled-maintenance calls for a technician to apply a certain amount of oil at set intervals. The schedule is (theoretically) based on historical data about how rapidly that type of bearing uses lubricant under the prevailing use conditions. Being statistical in nature, that data may over- or under-predict the needs of a particular bearing. In addition, even experienced technicians tend to apply more lubricant than necessary, which can actually harm the equipment. Failures can occur when the particular bearing uses lubricant at a rate significantly slower or faster than average. In the first case, too much lubricant would be applied. In the second, too little.

Physical phenomena associated with impending requirements for bearing lubrication are temperature rise and increased bearing noise (vibration). A smart instrument monitoring bearing temperature and noise can tailor the maintenance program to the particular bearing. It can automatically report a pattern of increasing operating temperature coupled with increased bearing noise appears. Maintenance personnel can then use this information to predict when lack of lubrication will begin damaging the bearing, and schedule a technician to apply lubricant just ahead of the danger point. This manual system reduces lubricant requirements, protects equipment more effectively, and reduces unscheduled downtime. Because maintenance operations still occur infrequently (typically at longer intervals than with scheduled maintenance because safety margins can be reduced), however, more lubricant than necessary is typically added at each maintenance, leading to some waste.
Smart-instrument-based predictive maintenance
Smart sensors can help make an automated system for bearing lubrication.

In SKF’s automated system, maintenance personnel do not schedule the lubrication visit, but the condition-monitoring computer automatically controls a microvolume pump to add oil in small quantities until the temperature and noise begin to trend down. When these parameters drop within specifications, the pump stops adding lubricant. This strategy applies just the needed lubrication when it’s needed, independent of the bearing’s peculiarities. By adding lubricant frequently in very small quantities, it is possible to keep the lubricant level very close to optimum. This reduces waste to a minimum by virtually eliminating overlubrication, and eliminates downtime for lubrication entirely.

The automated bearing lubrication system is just one example of a well-developed automated system based on predictive maintenance principles. Predictive maintenance systems based on monitoring physical parameters are actually quite common today. As embedded system techniques and smart sensors become more common in control applications, look for more instances of automated maintenance systems.

Source: www.controleng.com/blog | August 18, 2008

Successful Predictive Maintenance (PdM) Programs Depend on Consistency

The following is an except from the article entitled "Choose Your PdM Partners Wisely Or Discover Another Reason Why PdM Programs Can Fail" by Alan Friedman, appeared on reliabilityweb.com

One reason many in-house programs fail is a lack of consistency on many levels. A successful Predictive Maintenance (PdM) program relies on long-term consistency on the technical level in terms of collecting repeatable data for trending. This means that assets must be tested the same way time after time, year after year, in terms of test speeds, loads, test positions, test types etc. Consistent testing ensures accurate trending of machine condition, the development of meaningful baselines and alarm criteria and, therefore, accurate fault diagnosis and repair recommendations. This is very different from the process of using the technology to troubleshoot an asset. Troubleshooting is a valid use of these technologies, but does not result in a change in maintenance philosophy, nor does it provide the large ROI’s such a change in philosophy should produce.

On a higher level, such technical consistency also depends on the reliability of management and personnel. Oftentimes, due to lack of financial justification, PdM programs are stopped and personnel are reassigned to different tasks. New maintenance managers may not understand the technology and may recommend a new approach to using – or not using – it which disrupts the consistency of a program. In-house “experts,” in seeking to keep their jobs secure, may not document or follow fixed procedures for monitoring equipment or share information with others, causing programs to fail when they leave for greener pastures.

There are many reasons why programs bloom and then decay. People who have different ideas about how Predictive Maintenance (PdM) should be done come and go, priorities change, technology changes, expertise changes and approaches change. The one sure thing is that all of these starts and stops and changes in direction ensure a program will never be successful. This is another reason why an external partner is a good option to keep the program running steadily regardless of what is happening within the maintenance department of your facility.

In general, it can be said that a good Predictive Maintenance program requires a consistent approach, with a clear set of objectives that can be measured to monitor the success or failure of the program. The program must continue to remain consistent through good times and bad, regardless of who in the facility (or outside the facility) is running the program, collecting data, analyzing it or writing reports. This sort of consistency is often difficult to maintain within a facility, and is an example of where a good partnership with a Predictive Maintenance service provider can be a huge asset. Especially if this partner has a long track record of managing successful PdM programs and has a well-defined approach to managing such programs. This is different from hiring a vibration expert to come on-site at times to troubleshoot machines or structures.

But why choose your Predictive Maintenance (PdM) partners wisely? Here's his conclusion:

Whether you are considering starting a new program, revamping a dead one, outsourcing or looking for someone to become a long term partner to step in when needed and step back when not needed, make sure you pick the correct partner. The company should have a good track record of managing successful programs, should use good equipment for the job, and should make necessary equipment available to you as part of a sale or service or as a lease as needed. Make sure your partner can train staff at all levels, from using the products to analyzing graphs, but, more importantly, is capable of managing your particular program and answering specific questions related to auditing your program. The importance of helping you calculate the economic impacts of these technology and maintenance practices to your bottom line can not be underestimated.

More than anything, consider that choosing the right partner may make the difference between a consistent and effective program that runs smoothly over the next ten or twenty years and an endless series of false starts and investments in misused equipment. One thing is for sure, successful programs, more often than not, involve good partners.

To read the full article click here: Choose Your PdM Partners Wisely

Reliability Centered Maintenance Advantage and Disadvantages

Reliability centered maintenance (RCM) is the maintenance approach used when following a process that assesses equipment condition and determines the maintenance requirements of any physical asset in its operating context.

Basically, the RCM methodology addresses key issues not dealt with by other maintenance programs. This approach recognizes that all equipment in a facility is not of equal importance—to either the process or to facility needs and safety. Focusing on reliability of equipment means recognizing that equipment design and operations differ, and that each piece of equipment will have a different probability of undergoing failure from degradation than will another. A reliability-focused approach will mean structuring a maintenance program based upon the understanding of equipment needs and priorities, as well as limited financial and personnel resources, to plan activities such that equipment maintenance is prioritized while operations are optimized.

Simply put, RCM is a systematic approach of evaluating a facility's equipment and resources to best match the two needs. This results in a high degree of facility reliability and cost-effectiveness, and is highly reliant on predictive maintenance. However, it also recognizes that maintenance activities on equipment that is inexpensive and less important to overall facility reliability may be best left to a reactive maintenance approach, focusing both labor and financial resources on higher priority and more costly equipment. The following maintenance program breakdowns of continually top-performing facilities echo the RCM approach, which utilizes all available maintenance tactics. As is shown, all maintenance approaches are used, but the predominant strategy used is predictive.

• <10%>
• 25% to 35% Preventive
• 45% to 55% Predictive

Because RCM is so heavily weighted on utilization of predictive maintenance strategies, its program advantages and disadvantages mirror those of predictive maintenance. In addition to these advantages, RCM will allow a facility to more closely match its resources to operational needs and at the same time improve both reliability and also reduce associated maintenance costs.

Advantages

• Can be the most efficient maintenance program
• Lowers costs by eliminating unnecessary equipment maintenance or system overhauls
• Minimizes the frequency of overhauls
• Reduces probability of sudden equipment failures
• Focuses maintenance activities on critical system components
• Increases component reliability
• Incorporates root cause analysis

Disadvantages

• Can have significant startup costs associated with staff training and equipment needs
• Savings potential is not readily seen by management

Predictive Maintenance Implementation: Advantages and Disadvantages

A predictive maintenance approach strives to detect the onset of equipment degradation and to address the problems as they are identified. This allows casual stressors to be eliminated or controlled, prior to any significant deterioration in the physical state of the component or equipment. This leads to both current and future functional capabilities.

Basically, predictive maintenance differs from preventive maintenance by basing maintenance needs on the actual condition of the equipment, rather than on some predetermined schedule. Recall that preventive maintenance is time-based. Activities such as changing lubricant are based on time, like calendar time or equipment run time. For example, most people change the oil in their vehicles every 3,000 to 5,000 miles traveled. This is effectively basing the oil change needs on equipment run time. No concern is given to the actual condition and performance capability of the oil. It is changed because it is time.

This methodology would be analogous to a preventive maintenance task. If, on the other hand, the operator of the car discounted the vehicle run time and had the oil analyzed at some periodicity to determine its actual condition and lubrication properties, he or she may be able to extend the oil change until the vehicle had traveled 10,000 miles. This is the fundamental difference between predictive maintenance and preventive maintenance, whereby predictive maintenance is used to define needed maintenance tasks based on quantified material and equipment condition.

Advantages

• Provides increased component operational life and availability
• Allows for preemptive corrective actions
• Results in decrease in equipment and/or process downtime
• Lowers costs for parts and labor
• Provides better product quality
• Improves worker and environmental safety
• Raises worker morale
• Increases energy savings
• Results in an estimated 8% to 12% cost savings over which might result from a predictive maintenance program

Disadvantages

• Increases investment in diagnostic equipment
• Increases investment in staff training
• Savings potential is readily seen by management

There are many advantages of using a predictive maintenance program. A well-orchestrated predictive maintenance program will all but eliminate catastrophic equipment failures. Staff will then be able to schedule maintenance activities to minimize or eliminate overtime costs. And, inventory can be minimized, as parts or equipment will not need to be ordered ahead of time to support anticipated maintenance needs. Equipment will be operated at an optimal level, which will also save energy costs and increase plant reliability.

Past studies have estimated that a properly functioning predictive maintenance program can provide a savings of 8% to 12% over a program utilizing preventive maintenance strategies alone. Depending on a facility's reliance on a reactive maintenance approach and material condition, savings opportunities of 30% to 40% could easily be realized. In fact, independent surveys indicate the following industrial average savings resulted from initiation of a functional predictive maintenance program:

• Return on investment: 10 times
• Reduction in maintenance costs: 25% to 30%
• Elimination of breakdowns: 70% to 75%
• Reduction in downtime: 35% to 45%
• Increase in production: 20% to 25%

The down side of using a predictive maintenance approach are its initial costs. The up-front costs of starting this type of program can be expensive. Much of the equipment requires expenditures in excess of $50,000. And, training of in-plant personnel to effectively utilize predictive maintenance technologies and practices will require substantial additional funding. And, beginning a predictive maintenance program requires an understanding of the facility's predictive maintenance needs and the approaches which need to be undertaken. It is also essential to have a firm commitment, by management and all facility staff and organizations, to make it work.

Predictive Maintenance Program

A Quality Rotating Machinery Predictive Maintenance (PdM) Program for your facility will return your investment many times over. This type of PdM Program is based on periodic vibration measurements of your Rotating Machinery. In many cases, a Return On Investment (ROI) of less than one year (six months typical) is quite common. A Contract PdM Program eliminates the initial capital investment required to conduct your own PdM Program.

There are three classifications of machinery maintenance methods: Breakdown, Preventative, and Predictive Maintenance. Each method has its own associated costs and benefits.

Breakdown Maintenance, by its own nature, is the most expensive method of plant maintenance. This method has no scheduled maintenance until a machine destroys itself, and it must be replaced at great cost. The machine breakdown often brings the production process to an immediate halt. Breakdown Maintenance has high costs in manpower, replacement parts, and lost production.

Preventive Maintenance, the next logical method, relies on a periodic inspection the machines. During the inspection, machine damage is found and corrected. This method requires a large inventory of replacement parts prior to the machine's inspection. Preventative Maintenance has a lower associated cost because manpower can be planned in advance.

Predictive Maintenance involves monitoring the machine's vibration characteristics or symptoms to diagnose its condition. This method relies on the machine's condition to accurately schedule the repair interval. The machine's condition also determines the required replacement parts. Predictive Maintenance has the lowest cost of the three methods with the highest possible savings.

A Machinery PdM Program is beneficial to all industries that have rotating machinery on their site such as:

• Petroleum
• Chemical
• Power Generation
• Co-Generation
• Pulp and Paper
• Water Treatment
• Building Services
• HVAC
• Mining
• Food Processing

Typical Rotating Machinery commonly included in a Machinery PdM Program include but are not limited to the following:

• Electric Motors
• Pumps
• Fans
• Gear Boxes
• Turbines
• Compressors
• Paper Machines
• Reciprocating Machines
• Blowers
• Machine Tools
• Chillers
• Conveyors

Predictive and Preventive Maintenance in a Declining Economy

In a declining economy saving operating expenses has become a priority for most firms. Predictive and preventive maintenance although similar, are two different tools used by facilities managers in order to save precious dollars. Both maintenance systems help keep earnings (the bottom line) stable by avoiding costly repairs and maximizing equipment up-time. Normally cutting expenses for operations means fewer support staff, hiring freezes, and a repair versus replacement strategy on equipment. But what happens when the forecast for low or declining sales does not improve or is mired in a deep recession?

A recent survey conducted by Facilities Planners and Architects, Inc. of facility managers and business owners revealed intended reactions to the current economic situation. The survey highlights are:

• Limiting capital expenditures to sustainability initiatives such as more efficient lighting systems
• More plans to reduce square footage
• Outsourcing non-core services such as janitorial services
• Assessing the condition of the facilities and better strategic planning of their use
• Initiating predictive maintenance programs

Obviously, it is always a good idea to watch your expenses. The results echoes this and indicates a long overdue desire to become more energy efficient, a focus on core responsibilities by outsourcing non-core functions, a strategic look at assets and the initiation of efficiency and savings programs. The survey mentions predictive maintenance as one of the most popular choices for cost saving solutions. It should be noted that predictive maintenance is not the same as preventive maintenance. Successful predictive maintenance starts with preventive maintenance. To better understand let us take a look at both.

Predictive vs. Preventive Maintenance:

Preventive maintenance occurs on a pre-determined schedule and is intended to increase efficiencies by reducing the amount of reactive work and increasing the ability of management to manage work. Most importantly, it allows for the early identification of problems and significantly increases the life cycle of equipment, lowers capital expenditure requirements and allows for better planning of capital budgets. In addition, when integrated with handheld technologies and a combination of asset management, work order management and inspections, work flow efficiencies are increased to maximum levels. The data collected through this method becomes the building block for predictive maintenance.

Predictive maintenance does have its benefits in a difficult economy particularly because it can be less labor intensive than preventive maintenance. Predictive maintenance programs are based upon the actual condition of the equipment and a determination of when maintenance should be performed to minimize costs. New technology techniques such as ultrasound, infrared and vibration online testing make predictive maintenance a viable alternative in certain circumstances. However, for most equipment the complex metrics for making educated guesses is provided by preventive programs.

The goal of a facility manager or business owner is to make sure equipment has the highest possible uptime and to extend the life cycle of the equipment as long as possible at the most reasonable economical cost. Some predictive maintenance plans will require a capital investment in higher technology sensing equipment but most will be built upon the foundation and metrics provided by an existing preventive maintenance program. Facility managers should not rely on just a predictive maintenance solution to save expenses especially if dealing with high value equipment or if safety is at stake.

Tough times call for tough decisions as both maintenance programs have their place. The solution may be a combination of the two maintenance programs or it may be dependent on your industry, type of equipment and survival strategy. What is your company going to do?

Source: Mintek | http://EzineArticles.com/?expert=S_W_Smith

Predictive Maintenance (PdM) Definition to the Next Level

Predictive maintenance (PdM) techniques help determine the condition of in-service equipment in order to predict when maintenance should be performed. This approach offers cost savings over routine or time-based preventive maintenance, because tasks are performed only when warranted.

PdM, or condition-based maintenance, attempts to evaluate the condition of equipment by performing periodic or continuous (online) equipment condition monitoring. The ultimate goal of PdM is to perform maintenance at a scheduled point in time when the maintenance activity is most cost-effective and before the equipment loses optimum performance. This is in contrast to time- and/or operation count-based maintenance, where a piece of equipment gets maintained whether it needs it or not. Time-based maintenance is labor intensive, ineffective in identifying problems that develop between scheduled inspections, and is not cost-effective.

The "predictive" component of predictive maintenance stems from the goal of predicting the future trend of the equipment's condition. This approach uses principles of statistical process control to determine at what point in the future maintenance activities will be appropriate.

Most PdM inspections are performed while equipment is in service, thereby minimizing disruption of normal system operations. Adoption of PdM can result in substantial cost savings and higher system reliability.

Reliability-centered maintenance, or RCM, emphasizes the use of predictive maintenance (PdM) techniques in addition to traditional preventive measures. When properly implemented, RCM provides companies with a tool for achieving lowest asset Net Present Costs (NPC) for a given level of performance and risk.

Predictive Maintenance: A Short Introduction to Thermography

To gain the maximum benefits from your investment in infrared systems, use it on critical systems that generate capacity in the plant

Thermography is a predictive maintenance (PdM) technique for monitoring the condition of plant machinery, structures and systems — not just electrical equipment. It uses instrumentation to read infrared energy emissions (surface temperature) to determine operating conditions. By detecting thermal anomalies (areas hotter or colder than they should be), an experienced technician can locate and define a multitude of incipient problems within the plant. Infrared technology works on the principle that objects having a temperature above absolute zero emit energy or radiation.

Infrared radiation is one form of emitted energy. Infrared emissions are invisible without special instrumentation. The intensity of infrared radiation from an object is a function of its surface temperature. However, measuring temperature with infrared methods is complicated, because three sources of thermal energy can be detected from any object: energy emitted from the object itself; energy reflected from the object; and energy transmitted by the object. Only emitted energy is important in a PdM program. Reflected and transmitted energies distort raw infrared data. Therefore, they must be filtered out of acquired data before meaningful analysis can be performed.

Variations in surface condition, such as paint or other protective coatings, can affect the actual emissivity factor for plant equipment. They may change, sometimes radically, both the surface temperatures and heat distribution recorded by the infrared scanner. If the technician fails to compensate this, it will be difficult, if not impossible to accurately diagnose the incipient problems. In too many cases, they will be missed and serious damage or catastrophic failure will occur.

In addition to reflected and transmitted energy, the user of thermographic techniques must consider the atmosphere between the object and the measurement instrument. Water vapor and other gases absorb infrared radiation. Airborne dust, some lighting and other variables can distort infrared radiation measurements. Because the atmospheric environment is constantly changing, using thermographic techniques requires extreme care each time data is acquired.

Most infrared monitoring systems or instruments use filters to eliminate the negative effects of atmospheric attenuation. However, the user must recognize the specific factors that will affect infrared data accuracy and apply the correct filters or other signal conditioning methods.

Collecting optics and radiation detectors are basic elements of an industrial infrared instrument. Optical systems collect radiant energy and focuses it upon a detector, which converts it into an electrical signal. The instrument’s electronics amplifies the output signal and process it into a form that can be displayed. Three general types of instruments are used for PdM: infrared thermometers or spot radiometers, line scanners and imaging systems.

Infrared thermometers

Infrared thermometers or spot radiometers provide the actual surface temperature at a single, relatively small point on a machine or surface. Point-of-use infrared thermometers are commercially available and relatively inexpensive. Their typical cost is less than $1,000.

Within a PdM program, the point-of-use infrared thermometer can be used in conjunction with many microprocessor-based vibration instruments to monitor the temperature at critical points on plant machinery or equipment. This technique is typically used to monitor bearing cap temperatures, motor winding temperatures, spot checks of process piping temperatures and similar applications. It is limited in that the temperature represents a single point on the machine or structure. However, when used in conjunction with vibration data, point-of-use infrared data can be a valuable tool.

Line scanners

Line scanners provide a single dimensional scan or line of comparative radiation. While this type of instrument provides a somewhat larger field of view (the area of machine surface), its use in PdM applications is limited.

Infrared imaging

Unlike other infrared techniques, thermal or infrared imaging provides the means to scan the infrared emissions of complete machines, processes or equipment in a very short time. Most imaging systems function much like a video camera. The user can view the thermal emission profile of a wide area simply by looking through the instrument’s optics.

Infrared imaging systems cost between $8,000 for a black and white scanner without storage capability to more than $60,000 for a microprocessor-based, color-imaging system. However, the lower-price units, which only operate in a scanner mode, are not very useful for a long-term PdM program.

Training and applications

Training is critical with the use an imaging system. The variables that can destroy thermal data accuracy and repeatability must be compensated for each time data is acquired. In addition, infrared data interpretation requires extensive training and experience.

Inclusion of thermography into a PdM program will enable you to monitor the thermal efficiency of critical process systems that rely on heat transfer or retention; electrical equipment; and other parameters that will improve both the reliability and efficiency of plant systems. It can also be used to detect problems in a variety of plant systems and equipment, including electrical switchgear, gearboxes, electrical substations, transmissions, circuit breaker panels, motors, building envelopes, bearings, steam lines and process systems that rely on heat retention or transfer.

Safety considerations

Equipment used in infrared thermography inspection is usually energized. For this reason, attention must be given to safety. These safety rules should be followed when performing infrared inspections.

• Plant safety rules must be followed.
• Because proper use of infrared imaging systems requires the technician to use a viewfinder similar to a video camera to view the machinery to be scanned, he or she is blind to the surrounding environment. Therefore, in addition to the technician, a second safety person is required to ensure safe completion.
• Notify area personnel before scanning.
• A qualified electrician should be assigned to open and close electrical panels.
• When safe and possible, equipment to be scanned should be on line and under normal load with a clear line of sight.
• Equipment having interlocked covers without an interlock defect mechanism should be shut down when allowable. If safe, the control covers should be opened and equipment restarted.

When used correctly, thermography is a valuable predictive maintenance and reliability tool. However, benefits derived are directly proportional to how widely it’s used. If it’s limited to annual surveys of roofs or quarterly inspections of electrical systems, the resultant benefits will be limited. When used to monitor critical processes or production systems regularly where surface temperature or temperature distribution indicates reliability or operating conditions, thermography can yield substantial benefits. To gain the maximum benefits from your investment in infrared systems, use it on critical systems that generate capacity in the plant.

Source: R. Keith Mobley, Contributing Editor | Plantservices.com

Predictive Maintenance New Tools

Learn about condition monitoring beyond oil analysis, temperature and vibration in Sheila Kennedy's monthly Technology Toolbox column.

Getting the most out of installed assets will become more difficult as baby boomers retire. Their unique skillsets and hands-on experience will be hard to replace. One way to minimize this organizational strain is by monitoring the mechanical stress on your machines.

New ultrasonic techniques for condition monitoring make it possible to “hear” friction and stress in rotating machinery, which can predict deterioration earlier than conventional techniques. Condition monitoring, coupled with strategic data integration, help to automate critical processes that influence total plant health.

Ultrasonic condition monitoring: Ultrasonic technology is sensitive to high-frequency sounds that are inaudible to the human ear, and distinguishes them from lower-frequency sounds and mechanical vibration. Machine friction and stress waves produce distinctive sounds in the upper ultrasonic range.
Changes in these friction and stress waves can suggest deteriorating conditions much earlier than technologies such as vibration or oil analysis. With proper ultrasonic measurement and analysis, it’s possible to differentiate normal wear from abnormal wear, physical damage, imbalance conditions and lubrication problems based on a direct relationship between asset and operating conditions.

Among the machine process measurements that can be gauged are speed/rpm, head pressure, weight, and a valve’s position. Ultrasonic sensors that are integrated with condition monitoring software can produce alarms or e-mail notifications when thresholds are exceeded, and trigger maintenance activity.

“The time [remaining] before potential failure can be relatively short,” says Wil Chin, director of field systems for ARC Advisory Group. “With ultrasonics, you can pick up very minute problems manifested by changes in friction, giving maintenance and operations more time to deal with an issue before it shuts down a line or plant.”

Ultrasonic technology also can be used to establish optimal operating parameters, thereby extending asset life. For example, when stress levels are correlated with operating load, it’s possible to identify the rotational speed that generates the least amount of stress on an engine. In a centrifugal pump application, ultrasonic technology can identify cavitation and allow operators to adjust the pump speed and process parameters to reduce detrimental effects on the pump and surrounding equipment.

An additional benefit of ultrasonic technology is the ability to better manage just in time (JIT) inventory. One steel company saved almost $3 million in inventory using a solution from Swantech that provided significant advance warning of possible deterioration within their assets.

Stress wave analysis: “Friction is always present in any machine,” explains Ralph Genesi, president and CEO of Swantech. “Our ultrasonic Stress Wave Analysis (SWAN) technology quantifies this friction and then tracks it as it changes over time with variable loading conditions.”

For example, Swantech’s condition monitoring solution detects minor damage in its earliest stage, and helps to isolate the specific components and location of the components involved. The system calculates the extent of the damage and rate of progression so that maintenance can be scheduled accordingly.

“Swantech is the first to combine ultrasonic sensor technology into a condition monitoring software package,” Chin adds. “The data doesn’t have to be analyzed by a reliability engineer to determine the problem, because the software’s analysis engine recommends the potential cause.”

Integration with maintenance: Condition monitoring systems and smart sensors are becoming increasingly sophisticated, less expensive and more prevalent in the plant environment. User-friendly alternatives are replacing tools that once required specialized skills to operate. Data can now be gathered, analyzed and presented in an actionable format in real time. However, the diversity of condition monitoring methods and devices can impose its own burden.

“Automation suppliers are in the catbird seat, central to all plant information, but without touchpoints to the rest of the equipment or the solution itself,” says Chin. To overcome this issue, automation companies like Invensys and Rockwell Automation are developing or acquiring condition-monitoring technology. “The objective is to compile all data for the operator to view from a single interface – one screen for asset health and another for control.”

To expedite predictive maintenance tasks, condition monitoring suppliers are developing interfaces to enterprise asset management systems so that work orders, inventory requests and associated processes can be activated automatically.

Swantech’s condition monitoring technology is being incorporated into the Invensys Asset Performance Management (APM) solutions under the Invensys name. Integration with Invensys’ Avantis maintenance management software will be available. Swantech is also being integrated with the Indus Asset Suite.

Source: Sheila Kennedy | Plantservices.com

PdM News: R&M Offers HoistMonitor To Improve Efficiency

R&M Material Handling is now offering HoistMonitor as part of the option list for its RX and QX quick delivery programmes, to improve end-user efficiency.

HoistMonitor is built into a hoist’s electrical panel and supervises and records key data from the hoist. This allows for more efficient planning and scheduling of predictive maintenance, inspections and repairs, R&M said. The data can be accessed directly from the HoistMonitor or from a keypad display in the pendant station when equipped with HoistMonitor Plus.

“Predictive maintenance is a reality for efficient operations on the shop floor,” said a spokesperson for R&M. “Knowing when important maintenance milestones will occur allows you to schedule service during non-working hours.

“Planning hoist repairs and inspections decreases downtime while increasing performance.”

Source: hoistmagazine.com | 16 November 2009

Predictive Maintenance Finally Gets Wide Adoption

With the need to push costs down, plants are implementing condition-monitoring systems.

At the LyondellBasell Industries oil refinery in Houston, a condition-monitoring program has changed the way the company manages maintenance. Now, instead of gathering readings on paper reports that never get reviewed, plant operators collect data on handheld electronic devices, aggregate the data and track trends that can indicate a problem.

A faulty seal or broken pump can lead to a costly production interruption. “Now, operators have an actual reading from devices,” says Mark Fisher, operations reliability supervisor at LyondellBasell. “If the reading is above a certain limit, they’re prompted to tell their maintenance folks so they can prevent a catastrophic shutdown. The readings allow us to fix things before they break.”

Before implementing a Wonderware IntelaTrac system, the plant took temperature and vibration readings on paper. “You can’t trend on a piece of paper,” says Fisher. “The supervisor would set up a big pile of run sheets in a three-ring binder. By the time anyone got around to looking at them, it was too late to take any action in a timely manner.”

He notes that the paper reporting didn’t include specific data ranges to indicate problems. “With the paper system, one operator would look at the reading and see something wrong, while another operator would see it as OK.” With the handheld data readings, a note will pop up on the screen when the range is exceeded, prompting a call for maintenance. “We lose the inconsistency,” says Fisher.

Big brother?

Fisher notes that there was resistance to the new system initially. “At first, operators were skeptical. They thought it was Big Brother.” That changed when operators started to detect fans that weren’t working and seals that were plugged—problems that had gone undetected with the paper system.

Plants are turning to condition monitoring to reduce costs and replace the knowledge of baby-boomer engineers who are about to retire. Some are implementing predictive tools in-house, while others outsource it to software companies or original equipment manufacturers (OEMs). Many plant operators are just now getting around to implementing condition-monitoring technology that’s existed in their control systems for years. Ease-of-use portals and dashboards are helping resistant workers switch to monitoring technology. Condition monitoring includes a number of analytical tools, including vibration monitoring, oil analysis, temperature monitoring and infrared imaging. They share one thing in common—collecting data on plant equipment and analyzing the data to see when things are out of whack. Sophisticated condition monitoring can also catch subtle aspects of equipment performance. “It may not be the temperature that’s the issue, but that it’s rising quickly,” says Colin Shearer, senior vice president of strategic analytics at SBSS Inc., an analytic software company in Chicago.

For some companies, predictive maintenance has become a boardroom issue. “There are companies that consider condition monitoring a strategic advantage,” says Tom Alford, product manager, integrated condition monitoring at vendor Rockwell Automation Inc, in Milwaukee. “One power-generation company called out condition monitoring in its annual report as part of the company’s strategic vision.”

The recession has encouraged the use of predictive maintenance tools. The tools are becoming more popular as plants struggle to extend the life of their equipment and optimize equipment operation in the midst of a severe downturn. Plants can no longer afford scheduled maintenance—which often means replacing something that’s not broken—or the costly fix-it-when-it-breaks maintenance strategies.

With the pressure to drive down costs, many manufacturers turn to technology they already have on hand but haven’t implemented. “Since we’re having a slowdown in capital projects, they’re starting to use the products that they bought in the past,” says Rich Chmielewski, manager for PCS7 at Siemens Industry Inc., in Alpharetta, Ga. “We’re getting questions about reporting and diagnostics. Our customers are starting to use technology they’ve had but haven’t been using.”

Making Connections

Much of the infrastructure of predictive maintenance systems has been in play for years. Plants already use smart devices that can sense temperature and vibration. They’re also using a fieldbus network that transmits the device data. “You take the data from smart devices and smart control valves, and you send it along the Hart and fieldbus communication and networking systems,” says Stuart Harris, general manager of the Plant Asset Management business at Emerson Process Management, an Austin, Texas, automation supplier. “You take all that data and apply reliability analytics to see the efficiency of the equipment. Then you combine predictive diagnostics with decision support to make the connection with performance.”

One of the biggest hurdles to adopting condition monitoring is getting people to change long-held maintenance practices. “How do you get away from fix-it-when-it’s-broke? A lot of people are stuck in that type of maintenance,” says Emerson’s Harris. “You stop doing some things in routine maintenance that don’t add a lot of value. Then you identify opportunities for bringing in technology that avoids things getting broke.”

The best transition from old-style maintenance to condition monitoring is gradual. “Maintenance is cultural. In many organizations, the effectiveness of maintenance is measured by how quickly they fix machines when they break rather than measuring the overall cost of maintenance,” says Jonathan Hakim, president of Azima DLI, a
condition-monitoring company in Woburn, Mass. “Either that, or it’s measured on ‘Do I perform all my planned maintenance on time?’ To be effective, condition monitoring has to be combined with a move away from planned maintenance.”

Some plants implement monitoring one piece of equipment at a time, so the data collection and analysis in a broad changeover doesn’t stymie the change. “The idea is to give people the right information to collect,” says Jim Frider, manager of mobile solutions at Invensys Operations Management (Wonderware) in Lake Forest, Calif. “You have to know what’s too much data and what’s too little. That helps to get operators on board, which is always challenging.”

Portals, dashboards and benchmarking have helped ease the switchover to predictive maintenance and condition monitoring tools. “Advances in predictive maintenance have less to do with new technology than with new ways to bring the data to the user,” says Bill Polk, research director at AMR Research Inc., in Boston. “It’s how you see the preventive maintenance data that’s important. It’s now aggregated and put into portals.”

Outsourced Monitoring

Some plants turn to equipment OEMs, control vendors or software companies to run their condition monitoring programs. These maintenance monitoring contracts can make predictive maintenance affordable for mid-size to small manufacturers. Some control vendors contract with plants to run their maintenance remotely. A program designed and run by Houston-based vendor ABB Inc. came in handy for Vale Inco’s Voisey’s Bay nickel mine in Labrador, Canada, a site that is more than 150 miles from the nearest road. The Toronto-based company needed to know in advance when a part might fail, because turnaround on spare parts shipments is counted in days, not hours.

To make things more difficult, the mine was a greenfield site, so there was no historical data to indicate acceptable data ranges on the equipment. ABB also had to teach the condition-monitoring program to plant engineers. “That was relatively easy, since it was greenfield,” says Jeff Vasel, global asset optimization manager at ABB. “Change management is easier when you start with people who are new to maintenance.”

ABB monitors the site’s equipment remotely. “I can access their site right now. We monitor heat exchangers, control loops, even the electric flow. We also track vibration and ultrasonics,” says Vasel. “We are able to predict when a pump or motor will fail within 40 hours. Since we can’t get equipment up there quickly, we have to know when the parts will fail so we can have them at the site when it happens.”

The outsourced model has delivered tangible benefits to small and mid-size companies that can’t afford pricy in-house monitoring and analytical systems. “The small manufacturers are getting the same benefits the large end-users are getting,” says Shaun Kneller, account manager at vendor B&R Industrial Automation Corp., in Roswell, Ga. “So the small guys are able to avoid scheduled maintenance. Instead of replacing a bearing every month, they’re replacing it every six months.”

Brain Mapping

The brain drain has also prompted adoption of condition monitoring. The most knowledgeable plant engineers are retiring over the next few years. One way to capture their expertise is to program it into plant technology. “The gray hair brigade is reaching maturity and it’s tough to get new blood in because plants aren’t as sexy as high tech,” says Barry Lynch, a manager with the Proficy Maintenance Gateway at GE Fanuc Intelligent Systems, a Charlottesville, Va., automation supplier. “We’re basically taking the knowledge of the mature workers and pouring it into the IT (information technology) rules. You capture their intellectual property and digitize it.”

As well as digitizing the expertise to keep an individual plant’s equipment running efficiently, the best practices derived from knowledgeable workers can be converted into benchmarks or best practices. “The expertise on how to solve equipment problems lives with a field force of people nearing retirement,” says Brian Anderson, vice president of marketing at Axeda Corp., Foxboro, Mass., which provides remote monitoring services. “You can capture their knowledge and turn it into rules. Then you can use that expertise on a global basis.”

Whether it’s on the control dashboard or outsourced to a vendor, predictive maintenance and control monitoring is seeing widespread adoption in the last couple of years. The economic downturn has prompted tough cost-cutting measures, which means the end of the old and costly “fix-it-when-it-breaks” maintenance mentality. Those who produce predictive maintenance tools have overcome resistance to adoption with easy-to-use dashboards or by taking on the chore themselves.

Source: Rob Spiegel, Contributing Editor | November 2009

Predictive Maintenance Technology Using Fluke Ti25 IR Infrared Thermal Imaging Camera

The Fluke Ti25 is an industry leading infrared camera system. The Ti 25 is the ultimate tool for troubleshooting, preventive maintenance and predictive maintenance. This thermal Imager is the perfect tool to add to your problem solving arsenal. Built for tough work environments, this high performance, fully radiometric infrared camera is ideal for troubleshooting electrical installations, electro mechanical equipment, process equipment, HVAC/R equipment and others.

Companies use infrared for both predictive maintenance programs and diagnostics tools. Processing manufacturing has many pieces of equipment that can literally cost thousands of dollars every hour of downtime. With infrared companies can predict well in advance any problems that may be on the horizon. The return on investment for an infrared program is usually meet after only a few detections of potential problems.

The Fluke Ti25 features Fluke's patented IR fusion capabilities. IR fusion allows the user to blend both the infrared and visual light image. IR fusion ability allows the user to diagnose problems more effectively and efficiently. Other features include; a thermal sensitivity of just 100mk, 160x120 resolution, instant high low spot meters, sixty second voice annotation, seven different color palettes, a six hundred and ninety two degree temperature range, an industry leading two year warranty, and Smart View 2.1 software with all future upgrades of the software for free. This is all backed by Fluke's award winning customer service and un matched product durability.

Recently the Fluke Ti25 recently won an award from Plant Engineering magazine for product of the year. Different manufactures entered several different models, and the Ti25 took the award.

Develop Good Strategies For Effective Preventive Maintenance (2/2)

A second and more dominant area of confusion occurs when a scheduled task reveals unacceptable equipment deterioration (like the problem above in the MO situation, except it was not unexpected since a PM task discovered its presence). So actions are taken to repair/restore the full functionality before an unexpected operational impact can occur. Is the repair/restore action preventive or corrective?

If you will recall that the purpose of the PM task is to perform actions that will retain functional capabilities, then the answer is essentially self evident — the repair/restore action is preventive. Why? Because a proper structuring of the PM task will always include not only the search for equipment condition, but also the requirement to do something about it if the search uncovers a problem.

This search includes PM tasks that require inspection, monitoring parameters that detect failure onset, discovery of hidden failures and even restoration of equipment that was deliberately allowed to run to failure. Unfortunately, though, many CMMS programs will not allow the user to create or code a new work order to cover the emergent work as PM. This additional PM work can only be coded as CM. This inflates the cost of CM, and can lead management to question why CM costs are increasing even when their PM program had been recently improved.

As a general rule, corrective maintenance is more costly than preventive maintenance. If anyone should doubt this, then just compare two similar plants or systems where one has a proactive maintenance program and the other a reactive maintenance program. Which one do you think has the lower overall maintenance cost and higher availability?
Why do preventive maintenance?

For the past 15 years, as part of our seminars and client training programs, we frequently ask the question "Why do preventive maintenance?" The answers that we consistently hear reflect the popular belief that PM is done for a rather narrowly defined reason and this, as such, leads to the exclusion of a number of golden opportunities for PM enhancement.

So why do you do preventive maintenance? The overwhelming majority of maintenance and plant engineering personnel will respond "To prevent equipment failures." Would that have been your response? If so, you are correct — but not complete in your viewpoint. Unfortunately, we are not yet smart enough to prevent all equipment failures. But that does not mean that our ability to perform meaningful preventive maintenance tasks must end there.

In fact, there are three additional and important options to consider. First, while we may not know how to prevent a failure, frequently we do know how to detect the onset of failure. And our knowledge of how to do this is increasing every day, and is creating a whole new discipline called predictive maintenance. Second, even though we may not be able to prevent or detect the onset of failure, we often can check to see if a failure has occurred before equipment is called into service. Various standby and special purpose equipments (whose operational state is often hidden from the operator's view until it is too late) are candidates for this area. Thus, discovery of hidden failures is yet another PM option available to us.

There are also situations in a well planned PM program where economics and/or technical limitations can dictate a decision to do nothing — he appropriately labeled Run-To-Failure (RTF) option. This RTF option is not to be confused with the more general situation of missing potentially useful PM actions due to oversight or lack of attention to PM planning.

To summarize, there are four basic factors behind the decisions to define and choose preventive maintenance actions:
1. Prevent (or mitigate) failure occurrence.
2. Detect onset of failure.
3. Discover a hidden failure.
4. Do nothing, because of valid limitations.

Source: Anthony M. Smith and Glenn R. Hinchcliffe (Plant Engineering - November 1, 2005)

Preventive and Predictive Maintenance

by Ken Staller, Senior Maintenance Consultant

If you ask ten people what their definition of Preventive Maintenance is, you will get ten different answers. The tasks range from very simple to fairly complex. What's more, the manner in which they are performed and the depths to which they are carried out vary considerably. For the purpose of this guide to Preventive Maintenance (PM) and Predictive Maintenance (PDM), I will use the following definition: PM and PDM are a series of tasks and company policies that, if followed, improve and keep business profits as high as possible. This is achieved by adhering to three general guidelines.

• Maintain the production equipment and plant utility systems equipment as close to brand new condition as possible and have all equipment ready to start up and run with no unplanned shutdowns.
• Maintain the production equipment and plant utility systems equipment in the best possible operating condition for the purpose of producing quality manufactured goods while the machines are in service.
• Complete all PM and PDM work on a regularly scheduled basis without exceeding the "Point of Diminishing Returns on Investment" for the labor, tools and materials required to perform the work.

The difference between Preventive and Predictive Maintenance is that Preventive Maintenance tasks are completed when the machines are shut down and Predictive Maintenance activities are carried out as the machines are running in their normal production modes.

With PM and PDM systems – as in all systems and processes of work – there are the Who, What, When, Where and Why questions to answer before any actual work begins. With the above three guidelines we have already defined the "Why" question.

The "Who" question relates to several different types of members of the PM and PDM team.

• Someone who has an abundance of maintenance and plant engineering experience should write the individual tasks. To receive the expected results from the investments made in the PM and PDM protocol, the person writing the details of what needs to be done must have a deep understanding of the many aspects of machines. Aging, wear, component material fatigue patterns, effects of dirt and other contaminants, heat/cold, humidity, effects of chemical contact, vibration, lubrication practices, measurement processes, maximum safety methods, work efficiency standards, work scheduling, people skills, and plant processes are all factors that must be carefully considered.
• The mechanics and electricians that perform the PM and PDM work must be of high caliber and possess the skill levels of a maintenance department. On average, 85% to 90% of PM and PDM work orders call for machine inspection work and only 10% to15% lubrication work. The people performing these tasks must fully understand machine and machine component operations before they can effectively inspect for specific problems and negative operating trends.
• The management person directly responsible for the people performing the PM and PDM work must understand the work to be accomplished and set the performance standards, goals and expectations. They must be able to monitor the quality and quantity of work completed as well as measure the results. Also, they should be able to make on going changes and improvements to the individual PM tasks as part of an overall continuous improvement effort. These changes are dictated by the results of measurements and changes in the plant processes and equipment. Finally, the management person should also be able to complete component failure analyses. Determining why and how a component failed is the first step in determining how to prevent subsequent failure.
• The plant upper management must view the PM and PDM work system as required constant work practices that are just as important to the production process as any other function. This will require a minimal planned downtime of equipment to accomplish all PM and PDM work.
• Production employees also are a significant part of PM systems. They can be, and many times are, the first to see changes in the equipment they operate. Total Productive Maintenance (TPM) represents the active participation of all production employees in various machine set-ups, inspections and, in some cases, the lubrications of machinery. The amount of participation in TPM varies with the complexity of the equipment, the types of processes involved and the overall skill levels of the work force. Training the work force and the setting its expectations varies with the philosophies of the plant management of each facility.
• Contractors should be included in some PM work, especially the PDM work involved. Many contractors can supply cost effective services in some of the more specialized inspections and tests required. For example, many plants do not have trained refrigeration mechanics and they hire contractors to do the scheduled PM on Heating Ventilation and Air Conditioning (HVAC) units for the plant systems. Other contractor applications may be for air compressor and air dryer PM. In addition, vibration and ultra sonic analyzing is highly specialized aspect of PDM and requires extensive training and high test equipment purchase and upkeep costs.

The "What" and "Where" of PM consists of what equipment is to be inspected and lubricated and to what extent and detail the work is to be performed. Typically detailed PM and PDM procedures are written for all production equipment to insure that all machine components are inspected and lubed for maximum sustained operation. This process should also be applied to other plant equipment systems, such as machines that supply the plant utilities including air compressors, air dryers, boilers, electrical sub-stations, motor control centers, and wastewater treatment. Plant safety systems also should be included, including natural and propane gas systems, tanks, fire alarms and suppression systems, emergency lighting, overhead cranes and hoists, and ceiling mounted items such as lights, fans, and piping. Many plants also choose to include PM work on HVAC systems, overhead door and dock plates, forklifts, company vehicles, truck fleets, roof leak detection, air emissions and other systems usually not considered until there is a problem.

The detail and extent of the PM and PDM work varies with the type of equipment involved. The written PM procedure is the document that tell workers what needs to be done. This document needs to contain all of the tasks that will provide the most thorough inspections and lubrications of machines in planned down time, without exceeding the point of diminishing ROI. Generally, the PM inspections of most machines are one of two types. The first is for any thing that moves or causes some other machine part to move. This needs to be inspected for damage, wear, loose and missing fasteners, etc., and proper lubrications performed. The second is the inspection of static, non-moving machine components such as wiring, plumbing lines and hoses, structural support members, etc., for damage, cracked welds, loose and missing fasteners, etc. These procedures may be lengthy or simple, depending on the type of machines involved. The main concern is that the person writing the procedures is very experienced in plant maintenance and plant engineering. This person must understand and be experienced in all phases of static and dynamic machine principals and actual machine degradation analysis.

"When" PM should be performed depends on several factors. Some machines are simple in design and function and some are not. Typically, there are items to be inspected and lubricated on a daily basis. Other inspections and lubes are progressively more detailed and regularly performed on a bi-weekly, monthly, quarterly, semi-annual and/or annual basis, depending on what is required.

In addition to the machine design and basic function, several other factors help in determining the best time interval between PM tasks. One is the amount of time the machine runs between regularly scheduled shutdowns and/or how much time is available for PM. Does the machine run 24 hours per day, seven days per week, or eight hours per day five days per week? Another factor is the environment in which the machine runs. Is it humid and damp, or extremely hot and dry? Does the machine receive shock loads or run with moderate to high vibration levels? Is the machine subject to chemical spillage or leakage, ultra violet light, etc? Good operating and cleaning practices, or the lack of them, have a significant impact on PM scheduling. In addition, planned shutdowns for plant expansions, machine rebuilds, inventories, vacations, etc., also dictate when some of the more involved PM work can be accomplished.

Predictive Maintenance 101

Most of the above information relates to Preventive Maintenance procedures that are completed on machines while shut down. There are other tasks that are considered Predictive Maintenance (PDM) practices. One of these, usually done while the equipment is shut down, is oil sampling and analysis. Oil samples are taken and sent out to laboratories that specializing in analyzing industrial oils. The cost is relatively inexpensive and provides much valuable information. This process identifies the lubricating ability of the oil; its stability; contents of water, wear metal particles, and dirt; among other aspects.

Another extremely important PDM procedure is vibration analysis. Using a portable vibration analyzer, readings are taken from many points on machines. These readings are direct and extremely accurate measurements of the vibration amounts and frequencies produced by the moving parts of the machine. These vibration amounts and frequencies are used to tell if any parts need replacing or adjustment, and exactly what internal parts are causing problems. Bad bearings, excessively worn gears, and poor coupling alignment can cause excessive vibration, weakened mounting fasteners and many other mechanical problems. Vibration analysis also can tell you if pumps have loose impellers, air cavitation, faulty valves, or mounting problems. In addition, it reveals trending information. When vibration readings are taken, they provide a base number to use as a gauge to determine if and how much internal machine changes are taking place between inspections. This is the very best tool for detecting the correct health of machines and for trending the internal activities inside motors, gearboxes, pumps, large fans, compressors, and many other machine components. There is no better way to detect machine problems before they cause an unplanned shutdown due to a component failure. What's more, the fact that vibration analysis is done while the machines are running in their production modes allows the testing to be done at any time and is especially important for any plant that runs 24 hours per day, seven days per week.

A Comprehensive View of Preventive & Predictive Maintenance

There are many aspects of maintenance and other plant functions that have an effect on the number of machine breakdowns and the length of downtime. Some of these considerations are not normally associated with the term Preventive Maintenance, but nonetheless contribute to equipment failure. Therefore, they should be considered as a part of comprehensive approach to Preventive & Predictive Maintenance.

• Proper start-up protocols. Start-up operations; changeover and set-up; and shutdown procedures should be carefully planned and consistently implemented on all machines.
• Procedures lists for unplanned shutdowns. Outline what is to be done when an unplanned power outage occurs and what to do before the power comes back on.
• Emergency management plans for floods, fire, etc.
• Machine component rebuild programs to insure quality and consistency.
• Machine cleaning practices and procedures.
• Available informational equipment manuals for maintenance personnel.
• Solid troubleshooting skills by all maintenance personnel

The above information provides an outline of a comprehensive PM and PDM system. This approach is unassuming and leaves little, if nothing, to chance. While there are many variables to take into consideration, if properly designed, instituted and operated, the PM and PDM system will help to ensure dependable and predictable performance from all serviced equipment, machines, and related processes.