Condition Monitoring Expert Tip #2 by Mobius Institute
This tip is sponsored by IMVAC (International Machine Vibration Analysis Conference)
How do you decide how often measurements should be taken?
Regardless of the condition monitoring technology, you must decide how often measurements will be taken. At one extreme, it could be a permanent monitoring system that takes measurements every split second of every day. At the other extreme, it may be infrared analysis that is performed once a year. But how do you make that decision?
The most common answer we receive is that it is based on the criticality of the equipment. More frequent measurements are taken on the more critical equipment. The next most common answer is that it is based on reliability. If you have been monitoring a machine with vibration analysis every 30 days and have not detected a fault for a year you may decide to test it every 60 days, or 90 days. Now, it is true that you have to decide how best to use your precious time. But the one factor often forgotten is the “PF interval”.
The PF interval, also known as the “lead time to failure”, is the time between when you can detect the fault condition and when the equipment will have “functionally failed” – i.e. it can no longer be used. If we use the right technologies with the correct settings and we take frequent measurements, then we will get the earliest warning, and therefore we have the greatest lead time to act. However, if the PF interval is short, then it is possible that if you have extended the measurement period to 90 days, the equipment may develop a fault and fail before you take the next measurement.
There is a lot more that could be said on this topic but suffice to say that it is essential that you understand the PF interval and continue to monitor equipment so that you take at least two measurements between the time the fault is detectable and when the asset will have functionally failed.
Special thanks to Mobius Institute for allowing us to share this condition monitoring expert tip with you!
by Yolanda Lopez
Reposted from EASY-LASER® blog
Are you the type of person who, going by the principle of “We’ve always done it this way, and it’s worked well”, continues to use a ruler or a piece of string to align your sheaves/pulleys? If so, you can definitely save some money, by reading this.
It is a common misconception that it doesn’t matter whether you align your pulleys or not. The belt is flexible, and can handle it, right? And if a belt or sheave becomes worn, it is easy to just replace it. But what you might not be considering is that the cost of energy is greater than the cost of buying new spare parts such as bearings, belts and pulleys. Studies have shown that with correct alignment it is possible to improve the efficiency of your belt drive saving you from 5 to 20% of your energy costs. This can quickly add up to significant amounts, particularly if your enterprise has tens or even hundreds of belt-driven machines.
CONSEQUENCES OF GOOD AND POOR BELT ALIGNMENT
Poor alignment or incorrect installation are the most common causes of abnormal wear of sheaves and pulleys. On the other hand, increased productivity, fewer unplanned operational stoppages and reduced energy consumption are the result of well-aligned machines. In the long run, this is also positive for the environment. By aligning your belt-driven machines, you also reduce vibration that harms the machine and adversely affect the working environment.
One consequence of poorly aligned belt drives that is often overlooked is that incorrectly aligned or improperly tensioned belts can result in abnormal temperatures, caused by the belt’s friction against the pulley. Excessively high temperatures will cause the belts to harden, resulting in cracking. A toothed belt can lose teeth, leading to slipping and efficiency loss. Strong heat sources in the vicinity also affect belts negatively. A thermal camera can help to indicate potential abnormal temperatures.
WHERE DO I START?
Many belt manufacturers advocate preventive maintenance in order to avoid unforeseen stoppages. A scheduled operational stoppage is obviously more efficient and less costly than an emergency repair on a failed drive. However, having a maintenance program for your belt drives can also be efficient. There are a number of factors that determine how often you should perform preventive maintenance. Start by classifying your machines in these ways:
- How critical the machines are for your operation.
- The rotational speed of the machine.
- The drive’s impact on the environment.
- The current status of the drive (i.e., condition/quality of the belts and pulleys.)
When you have done this, you will be in a better position to know how to prioritize your maintenance work.
You should also think about the following:
- First and foremost, it is worth thinking about keeping the area around the machine free of dirt and debris, and ensure that the base is in good condition.
- It is important for the person carrying out the maintenance to have the correct training and equipment to carry out the work satisfactorily. A laser pulley alignment tool is highly recommended.
- Check the machine manufacturer’s specifications regarding how to set up you machine correctly. Write this down so that it is easily accessible the next time maintenance is to be performed. This saves time.
- Check the belt manufacturer’s suggested belt tension values. A spring gauge to measure belt tension is an essential item in the aligner’s toolkit.
- Mixing different belt types or brands is not recommended.
- If the transmission has several belts abreast, all the belts should be replaced together, even if only one is found to be defective.
- Measuring energy consumption before and after alignment is a simple way of verifying that you are now saving money.
- Listen to and look at the machine. If you suspect that anything is abnormal, you should investigate this. You should look out for unusual and abnormal wear or damage.
- Inspections should be performed frequently, perhaps as often as once a month.
- In addition, preventive maintenance should be performed at 6 to 12 month intervals.
- Follow the belt manufacturer’s instructions when replacing belts. Make sure that you also store belts correctly: don’t hang them, coil them flat! (Belts are a perishable product!)
Click here for examples of how much you can save by having your belt drives correctly aligned.
If you are ready to start improving the efficiency of your belts and sheaves, find the tool that best fits your needs.
by Yolanda Lopez
As Published by Uptime Magazine December/ January 2017 issue
Do No Harm: The Hippocratic Oath Applied to Reliability
The Greek physician Hippocrates (c.460 BC – c.370 BC) is credited with an oath that was meant to provide certain ethical standards a physician was to uphold. While maintenance is not of the magnitude as being a doctor, organizations would do well to apply portions of the Hippocratic oath to their maintenance practices. Two such examples are: “…to teach them this Art, if they shall wish to learn it, without fee or stipulation; and that by precept, lecture, and every other mode of instruction, I will impart a knowledge of the Art to my own sons, and those of my teachers, and to disciples…” and “I will follow that system of regimen which, according to my ability and judgment … and abstain from whatever is deleterious and mischievous.” This article focuses on the latter, “and abstain from whatever is deleterious and mischievous,” or in 21st century vernacular: Do no harm.”
Maintenance reliability professionals have a responsibility to their superiors to deliver results that improve the bottom line via increased uptime and productivity. But they also have a responsibility to those technicians who are expected to assist them in the process of increasing asset uptime and improving reliability. Regardless of your certification or the acronym attached to your signature block, without the technician’s solid understanding and performance of the basics, you will not achieve either goal. Two key ingredients of any reliability effort are precision installation and maintenance practices. Without them, you will find yourself replacing the same motors, pumps, etc., repeatedly.
From the reliability-centered maintenance (RCM) teachings of Stanley Nowlan and Howard F. Heap, both engineers at United Airlines, and John Moubray, the originator of RCM2, it is learned that there are six distinct failure curves. Furthermore, as many as 68 percent of failures can be attributed to infant mortality or failure induced at start-up/installation.
Read the full article to learn how precision installation and maintenance practices are two key ingredients of any reliability effort.
by Ana Maria Delgado, CRL
As Published by Maintenance Technology Magazine August 2016 issue
Clinging to a single approach that made economic sense for your plant ‘back in the day’ could be an expensive strategy.”
Overall values are the most common measurements and calculations used in vibration analysis. What’s more, some reliability and maintenance programs rely solely on them. The goal is to remove monitored equipment from service once the overall vibration level exceeds a certain threshold. Although this approach would appear to be quite cost effective, in reality it frequently isn’t. In fact, overall vibration monitoring can become extremely costly for a facility.
If you are asking yourself questions such as: What should you do once an overall vibration level exceeds your target amplitude and the equipment is removed from service?, Who should collect routine vibration data?, What other valuable condition-monitoring data might be missing? Or how do you motivate others to take corrective actions?, then this article is definitely a must-read.
by Trent Phillips CRL CMRP - Novelis
As Published by BIC Magazine December 2015 issue
A world-class reliability program is not achieved overnight, yet you must start somewhere. Your first step is to vest your entire human capital in its success. Reliability is a culture, not a goal, and it flows from the top down. Therefore, executive sponsorship with integrity and enforcement is a must. Obtain buy-in to the culture of reliability from everybody in your organization, or the effort is doomed to fail. Start with this realization, and your reliability effort will ultimately succeed, and you and your stakeholders will reap its rewards.
The reliability workflow must be well organized and underpinned by a Computerized Maintenance Management System (CMMS). Let’s look at how it works in a world-class program.
Ultrasound analysis detects a bearing fault in a critical motor early in the P-F curve. The analyst enters this data in the CMMS and trends it. The analyst decides to request a work order with recommendations. This is Stage 1 in the work order process.
The work order is now reviewed by both maintenance and operations, thereby ensuring buy-in from operations as well. This is Stage 2. This review process ensures only truly needed or valuable work is approved. Also, older open work orders can be combined with this one to further streamline planned activity on the asset. For instance, an earlier work order was created to align the machine, but the work was never carried out, resulting in the bearing damage the ultrasound analyst has now detected. The review process would catch the older open order and add it to the present order. This would prevent the millwright from going out to align the machine tomorrow only to have a repair technician go out the following week and repair the motor but do no alignment on it. This review process tries to eliminate inefficiency, duplication and detrimental work sequences.
Stage 3 assigns the work order to the maintenance planner for action. Only approved and truly necessary work enters the planner’s backlog. The planner ensures work is properly prioritized. Two things are needed: The criticality ranking of the asset (ascertained from systems’ criticality analysis) and its operational criticality. Both of these factors can be multiplied together to create a more accurate prioritization of the workflow. The planner creates a new work plan if needed and should consult with maintenance supervisors and technicians; valuable insights may be gained into what parts, tools and equipment should be specified in the work plan. Next, the planner orders the maintenance, repair and operating materials (MRO) spares and tooling required to complete the job and verifies the parts are available and kitted (best practice). The planner should not concern himself with scheduling.
Now on to Stage 4: assignment to the scheduler. The scheduler allocates the HR and necessary time to accomplish the task, with a cushion for unforeseen complications. He too should consult with the maintenance supervisor and technicians to obtain cooperation and buy-in to the schedule. Coordination with operations is crucial. Operations “owns” the equipment and must sign off on the schedule to bring the asset down.
Stage 5 assigns the order to the appropriate maintenance and electrical supervisors, who in turn assign specific tasks in the work plan to their respective repair technicians, electricians and millwrights, and verify MRO spares has delivered the parts kit to the proper location.
Now the work order enters Stage 6: the work execution phase. Once the technicians have completed the work, they report to their supervisors, who return the asset to active duty status in the system. Operations is notified the asset is ready for service, and MRO spares is notified of any unused parts and supplies that should be returned and reintegrated into the MRO spares inventory. Technicians and supervisors should feed their observations and data into the CMMS system.
Stage 7 sees the ultrasound analyst performing follow-up data collection on the asset to ensure all is well. The work now goes back to the planner to be formally closed. This ensures all important data has been accumulated and distributed within the system, enabling key performance indicators to be updated.
As good data accumulates, reliability engineering will use it to improve the entire reliability and maintenance process, discover frequent failure patterns, identify training needs, drive out defects, streamline production and help to improve the design process. As the plant becomes more efficient and productive, greater resources can be allocated to defect elimination and strengthening condition-based maintenance technologies, further impelling the transition to a proactive, reliability-centered culture. Reliability is a never-ending journey of continuous improvement.
by Alan Luedeking CRL CMRP
I recently spoke to a reliability engineer who was rolling out our alignment and vibration equipment to 15 plants across the U.S. This customer got us involved early on in the process. They didn’t just set aside budget money for the equipment purchase, but also enough to properly train their field service personnel on the proper use of the new technologies. We didn’t just address the use of the alignment tools, but also issues like proper equipment installation, lubrication, etc.
One of the topics of discussion was alignment tolerances. Since this customer has high speed ammonia compressors, they wanted to ensure their equipment was properly aligned and therefore adopted our alignment tolerances as their corporate standard. Since these tolerances are built into the alignment tool, it was not only easy for the user to determine if the equipment met their established corporate alignment standards, but also for management to review the work to ensure it was correctly completed. This oversight is easily accomplished via software we provide that allows complete storage of all alignment results on your network and allows easy report generation of the field results for review.
I was told that their vibration analysis program still identified equipment that was out of their alignment tolerances. How could this happen? It turned out that contractors were performing work without being held to the standards as plant personnel, including alignment tolerances or requiring the use of specific equipment to perform the work. In addition, the contractor was not required to provide a copy of the results for review and digital storage.
How could this happen? Unfortunately, it is not so uncommon. Many facilities or corporations do not require that maintenance activities be performed to standards or use equipment they can trust for the results. Additionally, they do not clearly write job plans that are issued to internal maintenance employees or contractors specifying how the acceptable results are to be achieved (what steps are required, what tools are required, what documentation of results is required, etc.) In addition, the Maintenance Scheduler does not review the results of the completed work to confirm that it was satisfactorily completed within acceptable specifications. Oversight failures as well as failure to include these items in your job plans and work orders can easily result in continued maintenance issues and repeated or wasted efforts to keep your equipment running.
by Frank Seidenthal CRL