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Are you running out of time to get your job done? Has your boss or supervisor saddled you with extra responsibilities? Are you not performing your PM tasks on time due to these extra responsibilities? If you answered yes to any of these,  don’t feel alone in this ever-changing industry. We are all being asked to perform more with fewer tools and time. And yes, we must keep our equipment up and running!

I recently ran into this problem at a water treatment facility in the Caribbean. Besides the overwhelming amount of work demanded of the maintenance staff, they also have been unable to maintain their equipment. The plant was going longer than four months without any vibration analysis data collection on their machinery, resulting in preventable equipment failures with the consequently lost revenue and high cost of replacement. Due to the working environment, culture, and qualified staff shortage, the engineering group decided to invest in a wireless vibration monitoring system for their highly critical machinery.

After careful evaluation, they decided to install 8 VIBCONNECT RF sensors on four of their high-pressure pump sets. These pumps are critical in processing seawater into freshwater. Although the process of a desalination plant has several stages, the plant decided to first outfit these (four) 550 HP motors first before proceeding with the rest of the facility.

These critical pump motor sets cannot be ignored and have a good reliability program in place. Nor can they be ignored without end-user (consumer) dissatisfaction from no clean water availability due to equipment reliability issues. The plant made a small investment in the monitoring system in comparison to the cost of replacing the motors which failed.

As the maintenance manager stated:

If we could have prevented that failure and/or known that the asset was headed in that direction, we could have saved thousands of dollars. Not to mention the embarrassment of the bad press that comes from working in a government run institution…“

by Alex Nino CRL

A lot of facilities assign condition monitoring intervals based upon arbitrary schedules such as 30,  90, 180 or 365 days. Often, this is due to a lack of understanding of how equipment fails, misunderstanding of how conditional tasks such as vibration analysis work, available labor, and lack of importance placed upon condition monitoring efforts. These arbitrary collection intervals can actually lead to failures that go undetected and a loss of value from the effort.

To appropriately determine monitoring intervals, a couple of things should be known. First, the point in time (P) that the potential failure becomes detectable must be known (detected with vibration monitoring, for instance.) Second, the time (F) at which the potential failure would degrade to a functional failure must be known. This difference in time (P-F Interval) is the window to take corrective action and avoid the negative consequences of the failure. This difference in time will determine how often conditional tasks such as vibration monitoring must be done to detect potential failures from such things as bearing issues, etc. Typically, the monitoring interval would be set to half of the P-F interval. This allows enough time for the technology to detect the problem and for corrective action to be taken. However, in certain circumstances, it may be necessary to collect data at shorter intervals than half of the P-F interval.image1 -june blog
It is important not to assign monitoring intervals based upon gut feelings, arbitrary calendar intervals, and so forth. Let the equipment tell you how often monitoring must be completed. Not understanding the process above can lead to costly results!

by Trent Phillips CRL CMRP - Novelis

Today’s world-class maintenance departments require data collection on a consistent and periodic basis to guarantee that the assets in a plant operate efficiently and reliably.

Online vibration monitoring actively monitors the health of critical assets for potential failure conditions. This will yield great results by identifying potential failure conditions for repair before unwanted downtime and other costly consequences are experienced.

Typical online condition monitoring can be expensive due to the installation cost for cables, labor, safeguards, etc., and might even be impossible in certain situations due to accessibility issues. Online vibration monitoring systems such as VIBNODE and VIBCONNECT RF were specifically designed to minimize installation costs and provide high measurement quality. These systems offer wireless operation, greatly reducing installation costs and making installation very easy in remote locations, on difficult-to-reach equipment, etc. GPRS (cellular modems) and other options can be utilized to make online monitoring fully remote and provide accurate health condition updates on monitored equipment.

Mario
Condition monitoring data is acquired and wirelessly transferred back to a central location for analysis.
Mario2
Condition monitoring data is acquired and wirelessly transferred back to a central location anywhere in the world for analysis.

by Mario Rostran CRL

The following blog relates to those who field balance using a photo or laser tach and reflective tape.

By far the most common pitfall to field balancing is a problematic tach signal. When one balances a rotor using one’s field balancing unit (VIBXPERT II, VIBXPERT, or VIBSCANNER) the equipment is recording the energy displayed at the frequency of the signal from the tachometer. To help visualize the importance of a clear tachometer signal that is exactly 1 pulse per revolution, look at figure 1.
image4mod
What amplitude will your equipment record if the tach pulses:
1. 1,195 times per minute?
2. 2,002 times per minute?
3. 2,006 times per minute?
4. 2,011 times per minute?
5. 2,013 times per minute?

We often start a balance job by haphazardly placing our tach and tape. Because both the tach and tape are well-engineered, we may go on without a problem. But just a little attention to some of the common tach signal problems is usually all it takes to avoid having to restart a botched attempt at field balancing. What should be avoided when setting up a tachometer?

1. Don’t place your tach too close to the rotor. Most tachometers are used in the fieldwork sending some type of light out and bouncing it back, so they have a sending function and a receiving function. The wavelength of the light is such that not just any light will be accepted by the receiver, but only that wavelength of light sent out by the sending unit. So the receiver counts a pulse every time that wavelength of light appears (or disappears, depending on whether you are triggering by leading or trailing edge). The receiver is no smarter than that, we must supply the rest of the intelligence. When we put the receiver too close to the rotor, even a poor reflector may be able to bounce back enough of the light signal to create a pulse. The balancing technician should determine the distance from the rotor to set up their tach with the understanding that they want a good signal bounced back from their chosen reflector AND ONLY THEIR CHOSEN REFLECTOR! Most often, a 6-inch space is sufficient.

2. Don’t place your tach pointing perpendicular to the rotor. Earlier we stated that “both the tach and tape are well-engineered”. One thing most of us field balancers take for granted is the reflective tape. This tape is actually a well-engineered tool. Reflective tape is faceted in such a way that light can strike it at an acute angle, and still be reflected right back along the axis from which it came. This allows the tach to be staged at such an angle that light will strike the rotor, even a rotor that is itself a good reflector, and be reflected off and away from the receiver UNTIL the tape comes into the line of the light, and then with its special faceting, it will bounce the light back to the receiver. This gives one clean pulse every time the tape comes around, and only when the tape comes around.

3. Don’t use old reflective tape that may not be in proper working condition. Make sure the tape is clean and in good shape. Reflective tape works very well when it is clean and in like-new condition, but can get dirty or even deteriorate if conditions are right. Replacing a small piece of tape is most often very quick, easy, and cheap compared to extra balancing runs or possibly even worse.

4. Don’t use a tach with dirty lenses. Make sure the tach lenses are clean and in good shape. When your lens is dirty, it forces you to do things (in order to get a strong enough signal to go through the dirty lens) that aren’t conducive to a clean, clear, once per revolution pulse; like move the tach too close to the rotor, or place it at a 90° angle to the rotor.

Doing everything we have suggested here could take all of 5 minutes (if you work slowly) at the beginning of a field balance job, but it could save a lot!

by Mike Fitch CRL

Recently, while assisting a customer in setting up a vibration database, the subject of creating the best trending template for a boiler feed water gearbox came up. This particular application requires trending templates to monitor a complex machine train consisting of four separate machines. For the purpose of this discussion, we’ll concentrate only on the gearbox in the machine train. The gearbox is a speed increaser. It is a little unusual in that a hydraulic torque converter allows the speed of the main boiler feedwater pump to be varied. This gearbox is designed with three individual shafts (an input shaft, intermediate shaft and output shaft), all enclosed within a single gearbox housing.

The speed of the input shaft is constant at 29.93 Hz (1796 rpm) and attached to this input shaft is a pinion gear with 88 teeth. The pinion gear runs in mesh with another gear mounted on the intermediate shaft with 27 teeth. This results in a gear mesh frequency of 2,633.84 Hz. We must determine the required frequency range (Fmax) by multiplying our calculated gear mesh frequency by 3.25 resulting in a Fmax of 8559.98 Hz. In the software, we can’t select 8559 Hz so we’ll need to select the next higher value, 10kHz.
The next step in the process is to determine the speed of the intermediate shaft by using the following formula:
Intermediate shaft speed = 29.93 Hz × 88 teeth = 2,633.84 Hz / 27 teeth = 97.54 Hz or 5,852.4 rpm.

We must now determine the required lines of resolution (LOR) since we have two fairly closely spaced running speeds. We have the intermediate shaft speed, running at a constant speed of 97.54 Hz and the output shaft speed which is variable.

When the boiler feedwater pump is operated at 100% the output shaft running speed of the gearbox is 94.33 Hz or 5660 rpm. There are only 3.21 Hz or 192.6 CPM between the two shaft speeds within the gearbox. Therefore, our lines of resolution setting will need to be high enough to provide separation while performing analysis. With a Fmax setting of 10kHz, we will need a minimum of 3200 lines of resolution to distinguish between the two shaft speeds. 10kHz Fmax / 3200 LOR = 3.125 Hz bin width, but to be on the safe side I would recommend selecting the next higher resolution setting (6400 LOR). This will provide a 1.56 Hz (96.3 CPM) resolution to easily see the two different shaft running speeds for accurate analysis.

Below is an example of improper resolution for accurate analysis:

Improper resolution settings resulting in a flat top 1× for the output shaft speed. Proper resolution settings:
Correct resolution settings allowing clear distinction of the output shaft speed.
The lesson here is that proper vibration analysis requires understanding the machine design. Additionally, it is critical that the proper maximum frequency (Fmax) and lines of resolution (LOR) be determined. Improper Fmax settings will result in data being missed. Inadequate lines of resolution (LOR) can cause closely spaced peaks to merge together making it impossible to distinguish between them. These errors will result in poor vibration analysis results. Pay close attention to the details when setting up the equipment in your vibration database.

by Dave Leach CRL CMRT CMRP

Purchasing a condition monitoring tool is one step in your journey to implementing a reliability program. Proper training on how to use the new technology,  planning the work correctly,  ensuring the work is completed on schedule and done so correctly is critical to success. Just as important is understanding the risks associated with your equipment, especially when it fails. A criticality assessment along with failure modes and effects analysis will help you understand those risks and determine where to focus your maintenance activities.

I recently spoke to a plant engineer that had purchased alignment and vibration equipment from LUDECA. He had performed several alignments and collected baseline vibration data. The decision was made to start aligning machines that required maintenance and this was a wise choice to ensure failure modes were not inserted into equipment during routine maintenance activities. Unfortunately, this facility had not performed a criticality assessment on their machinery! It turns out that the plant had a catastrophic failure on a piece of equipment that was vital to the overall production processes of the plant. The first comment made was “why did we have this failure when we recently invested in alignment and vibration equipment?”

You must fully understand the risks to safety, production, environment, and profits that your equipment imposes on your facility. As you can see from the example above, not understanding these factors may lead to continued equipment failures and their undesired consequences. To ensure that you do not continue to experience maintenance failures requires that you fully comprehend the risks that each piece of equipment entails. Had this facility understood the failure modes and the (criticality/risk) impact each machine posed, they would have been able to focus their maintenance efforts where they were most needed to keep the plant efficiently operational.

As part of this endeavor, it is important to apply condition monitoring (vibration analysis and properly targeted alignment, among other things) on the equipment within your plant, because it is extremely difficult to be reliable without doing so. However, you must understand how and where to direct those efforts to ensure that unwanted risks are reduced. Understanding how your equipment can fail (FMEA), the consequences of those failures (RCM or risk assessment), what equipment is most important to keep your plant operational (criticality assessment) are all important to ensure that your maintenance efforts are properly focused. These efforts may avoid the experience this facility had and prevent your plant from experiencing the same unwanted effects.

by Frank Seidenthal CRL

You should regularly back up any active database to guard against data loss and to protect the investment made in your database design. A backup allows you to easily restore an entire database without the hassle of rebuilding everything from scratch. Backups help protect a database from system failures and help protect against mistakes.

As the size of your database grows,  you should consider archiving the older data. Archiving is the process by which you periodically move older records from one database to an archive database. If you want to automate creating backups of database files,  consider using a product that performs automated backups of a file system, such as file server backup software or a USB external backup device. To decide how often to make backups, consider how often your database changes: • If your database is an archive, or if it is used only for reference and rarely changes, you should make a backup every time that your data changes. • If your database is active and your data frequently changes, you should back up your database on a schedule. The more active the database or greater the number of changes, the more often you should schedule the backups. The easiest way to back up an OMNITREND database is to use the copy and paste function within Windows Explorer. Locate your Access database within Windows Explorer and left-click on the file to highlight it; next right-click on the file and select copy. While in Windows Explorer navigate to the location where you would like to copy the database and right-click on the location and select paste. You have now created a backup of your database. If you are uncertain as to where the database file is located; open OMNITREND and the top bar will inform you of the location and name of your database. OMT imageIt is recommended that the backup database be stored on a different computer than the original. If that computer crashes it will result in the loss of both the original and the backup database. A few suggestions as to where to store a backup database would be a CDROM/DVD, USB stick, network drive, the cloud, or another computer.

by Mickey Harp CRL

Being a successful condition monitoring (CM) analyst requires qualities such as intelligence,  dedication, a thick skin, willingness to help others, ability to focus, and more. Success in this profession is not easy. In fact, it can be argued that success is a constant struggle. The most successful CM analysts will have certain traits that are keys to their success; however, possibly the most important is the drive to “know” – to know what is causing that anomaly, defect, or early failure.

Read my entire article at PLANT SERVICES: Keys to Condition Monitoring Success

by Trent Phillips CRL CMRP - Novelis

A hidden failure is not obvious under normal circumstances. Hidden failures can expose your facility to increased risks that may have serious consequences. The sources within your facility for hidden failures may be many. A good reliability program will give special consideration to these types of potential failures and their associated risks.

Have you considered that the software used within your facility may lead to hidden failures in a sense? Your software may lack documentation,  reporting, and analytical capabilities. Data may be hidden,  improper diagnostics made, or corrective action not taken based upon the information, etc., all of which can lead to equipment failures. Intentional misuse of the information may be possible as well without the ability to apply proper oversight.

Make sure the software you use properly collects, stores and reports information of value that can be used to drive your maintenance and reliability efforts. Make sure that the information is correctly analyzed and appropriate action is taken. Otherwise, your software tools may give you indications of problems that go unmitigated until costly failures occur.

by Trent Phillips CRL CMRP - Novelis

Centrifugal pumps come in a variety of shapes and sizes and are used in diverse ways to fulfill many different applications. These pumps deliver a life-sustaining liquid directly to our homes that is required for our very survival. For example,  during emergencies, these pumps provide fire departments with the water needed to extinguish fires. Their value is critical,  but their importance is often taken for granted.

Centrifugal pumps are designed to deliver a specific flow and pressure as dictated by the application. Centrifugal pump curves typically show the design-rated flow (usually expressed in gallons per minute or GPM) across the X-axis of the curve and the pump’s total pressure (total head) along the Y-axis. Different size impellers can be installed on these pumps depending upon the design requirements. The engineer must accurately calculate the required operational parameters because once installed the pump will operate at the point where the system head intersects the pump curve.

Based on the pump curve below, several different impeller diameters can be utilized for this specific pump ranging from 7½ to 9½ inches. In our hypothetical system, we have calculated a total system head of 100 ft. and we need 50 GPM for sufficient cooling in our manufacturing process. Based on our calculations an 8½ inch diameter impeller would result in the pump meeting our design point of 50 GPM @ 100 ft. head @ 73 % efficiency.
Pump Selection
So far everything is working out perfectly for our project, but if the system head is not calculated correctly or the pump is ordered with the wrong diameter impeller we will have process and reliability problems.

If the correct diameter impeller (8½ inches) isn’t specified, then the pump manufacturer may simply supply the pump with the maximum diameter impeller (9½ inches). If we installed our new pump with the wrong size impeller it would operate well to the right of the required operating point of 50 GPM @ 100 ft. head. This would result in excessive vibration levels, motor overload, reduced bearing life, seal problems, and cavitation problems.

As a result, we would experience higher maintenance costs, higher operational costs, reduced MTBF, and reduced pump efficiency.

The chart below shows that centrifugal pumps are usually most reliable when operated from 80% to 110% of their best efficiency point (BEP). Outside of this range, unwelcome reliability problems will occur.
Pump Reliability Curve
The scenario above occurs more often than realized! Many pumps are operated outside of their best efficiency range and unwanted consequences are experienced. A good reliability program will always seek to determine the root causes of failures. Simply replacing failed components such as worn impellers, damaged bearings, etc., does little to address the root cause of the problem. Not understanding why a component failure will doom you to replace it again in the future and true reliability gains are not made. Proper equipment specifications and design are critical in ensuring long-term reliability. It is very difficult or impossible for maintenance to overcome poor design or specification. Centrifugal pumps that are specified properly for the application, correctly installed, aligned, and balanced will increase your pumping system reliability. This will lead to reduced maintenance costs, improved uptime, and other valuable results.

by Dave Leach CRL CMRT CMRP

Today’s manufacturing facilities increasingly depend on Computer-Aided Machines (CAM) and robotics in their many processes. This highly technologically advanced machinery is designed with many failsafes and protection systems capable of shutting down the machine to maintain the integrity of the part being machined and the equipment itself.

As these machines typically run at very high speeds,  it is of great importance to perform condition monitoring on their bearings, motors, and gearboxes. Large amounts of debris and fluids can accumulate inside these machines during normal operation. This can complicate the use of a regular sensor and cable assembly to collect vibration data.

Consider using a small sensor with an integral cable and an armored jacket along with a vibration analyzer like the VIBXPERT or an online condition monitoring system such as VIBNODE. This combination of technology, sensor(s), and cable will allow your facility to reliably monitor the health of your CAM machines and maintain both performance and reliability.

Sensor-with-integrated-cable
Sensor with integrated cable

by Mario Rostran CRL

It is critical (pun intended) that you have a criticality ranking for your equipment.  This will help you properly direct maintenance and reliability efforts.  It is difficult to have granularity on the actual role equipment plays if the criticality scale is small (1-10).  It is best to use a higher scale with categories that comprise the overall ranking.  For example use a 100-scale with 10 categories and each one being 0-10.

by Trent Phillips CRL CMRP - Novelis

Make sure that these P’s are part of your Condition Monitoring program in 2015:

  1. Proper understanding
  2. Proper employee training
  3. Proper implementation (applying the technology to the correct equipment)
  4. Proper setups (correct monitoring parameters)
  5. Proper monitoring intervals
  6. Proper standards
  7. Proper analysis
  8. Proper reporting
  9. Proper equipment follow-up (after-repair inspections, start-up inspections, etc.)
  10. Proper execution of the results (ensuring that the recommendations of the CM effort are implemented and completed

We look forward to serving your maintenance and reliability needs. Cheers to a Successful Year!

by Trent Phillips

Equipment vibration levels and bearing life are directly correlated. Many studies have established this link. Increased vibration levels due to misalignment,  unbalance,  looseness and other factors will greatly reduce the life span of bearings and other critical components within your equipment. It is not the amount of vibration that affects bearing life, but the forces that cause this vibration. These dynamic forces are propagated into components like bearings, reducing their life span. Reducing vibration levels means that the forcing functions are reduced/eliminated and bearing life is improved as a result.

Reducing vibration levels in your equipment will decrease the maintenance efforts required to keep it running, improve uptime and save your company money. These savings can be used to help justify your condition monitoring and reliability efforts as well.

Eliminate vibration before it kills your equipment, production, and profits.

by Trent Phillips

Can you answer a simple question? Is your equipment basically sound? It’s not a trick question. There are some things that the more studious maintenance practitioners among us have discovered through dedicated equipment failure data logging followed by mining that data. In his article “Examining the Processes of RCM and TPM” Ross Kennedy of the Center for TPM points out that studies have been undertaken to determine the main causes of premature equipment failure,  as they relate to statistical lifetime rates. Mr. Kennedy states “Studies conducted by the Japanese Institute of Plant Maintenance and companies like DuPont and Tennessee Eastman Chemical Company have shown that three major physical conditions make up some 80% of the variation.”

In other words, 80% of the equipment tracked in these studies that didn’t achieve its projected lifetime was all affected (or perhaps we should say “afflicted”) by one or more of three physical conditions causing the accelerated failure rate:

  1. Lubrication problems
  2. Looseness problems
  3. Contamination problems

Based on these findings, TPM (Total Productive Maintenance) strives to maintain equipment in what it has termed “Basic Equipment Condition”, or Clean, Tight, and Lubed. Many companies promote their activities by giving their equipment a little TLC (Tight, Lubed, and Cleaned). However, you put it, if your equipment isn’t clean, tight, and lubed properly, expecting reliability is illogical because your equipment is not “basically sound”.

You’ll notice that the companies Mr. Kennedy cites as participants in such studies are well known for their reliability programs. Most would see them as well ahead of the pack so to speak, but they too found some low-hanging fruit through this study. Now that the studies have been done, we can all benefit from them. It doesn’t take a lot of hi-tech equipment to work on these areas, but many still overlook them because they seem too simple. Don’t get caught in the trap of looking for exotic means of reliability improvement before you’ve gotten good at the basics.
As a part of a corporate reliability group for a Fortune 500 Company (in my distant past), we added a 4th element to what should constitute “Basic” equipment condition for assets, and that element was shaft alignment.
Only when your equipment is:

  1. Precision aligned
  2. Properly lubricated
  3. Properly fastened and mounted
  4. Free from excessive foreign material contamination

Should you feel comfortable answering a “yes” to the simple question: “Is your equipment basically sound?”
It is important to always remember one additional best practice activity that is critical to equipment reliability.  Keep your equipment balanced where applicable as well.  Unbalance is another common problem resulting in costly reliability issues within a facility.

by Mike Fitch CRL

MAINTENANCE TECHNOLOGY • September 2014

The roles and responsibilities of today’s equipment-health-focused professionals go beyond collecting and analyzing data.
MT asked a condition-monitoring expert to tell us what the job descriptions don’t.

Many colleges and universities require their students to take a basic psychology course. Most students wonder why. But according to Trent Phillips of LUDECA,  Inc.,  a condition-monitoring (CM) analyst would be very likely to know why.

As the study of mental processes and behavior, psychology teaches the use of behavior and scientific methods to investigate questions and arrive at appropriate conclusions. Such tactics, says Phillips, are critical to anyone who aspires to be a successful analyst—including those in the field of equipment condition monitoring.

Read the entire article/interview “Are You A Psychologist, A Condition-Monitoring Analyst, Or Both?”

by Trent Phillips

Tips for visually identifying loose components on a machine:

  • Make sure that the machine has reached normal operational temperature,  because loose components may not appear until this temperature has been reached.
  • Squirt water or soapy water on components. This may create small bubbles and allow identification of the loose component.
  • Use a strobe light
  • Utilize technologies such as vibration and phase analysis.

by Trent Phillips

Education and responsibility go hand in hand. Leaders of reliability programs should expect their employees to return from a training course with a better idea of how Condition Monitoring can effectively increase equipment reliability and be willing to provide the support to take full advantage of the education gained.
Indeed,  there is a narrow window of opportunity to maximize this enthusiasm. Even the most passionate reliability professional eventually will fall captive to the stagnant grind of doing the same tasks over and over, especially when he or she has realized that the status quo is not changing.

Leaders must continuously provide their team with the necessary tools and support to improve their program, while those who are performing the tasks must use what they have learned to effectively increase equipment reliability.

Is the window of enthusiasm closing on your Condition Monitoring program? Have you maximized your staff’s education and opportunities? Reliability Excellence can be achieved when your team collectively contributes and applies the knowledge that has been obtained.

Learn about The Reliability Leader Certification

by Pete Oviedo Jr

A US manufacturer of chemical products and food supplements has recently experienced an increase in demand for the products they manufacture. To maintain and supply that increased demand,  they have increased their reliability efforts. They have done so by re-evaluating their current vibration analysis program and the negative impact recently experienced with unplanned downtime.

After careful analysis of the risk factors preventing their overall business goals from being achieved, the company reached out to LUDECA for a viable solution to their current problems. We installed a VIBCONNECT RF wireless condition monitoring solution. The installation was quite challenging because the units to be monitored were located three stories high and the control center is about 600 feet in length with hurricane-proof walls. The VIBCONNECT wireless system not only monitored overall data, spectral and waveform data continuously every 30 minutes, but also enabled the facility to identify two bearing failures on an important motor-blower set.
Vibconnect RF install
Is your company faced with the same challenges?  Is your vibration program catching the failures on all your equipment?  Are processes being stopped and demand not being met?  A proper condition monitoring and reliability-centered effort will always provide a positive return on investment.

by Alex Nino CRL

Planning to succeed

Most facilities have a planning and scheduling process for maintenance work activities. The goal of the planning process should be to determine and prepare the parts,  tools, permits, steps, etc. that are required to perform the maintenance activities at the scheduled times. The planning process could fail if the total number of equipment issues overwhelms the planning system. The planning process should include proactive activities to identify failure conditions on equipment. Tasks such as Condition Monitoring activities should be one of the driving influences for planning and scheduling activities. Substantial focus should be given to activities that prevent or identify equipment defects.
 
 

by Trent Phillips

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