As Published by Solutions Magazine March/April 2018 issue
by Ana Maria Delgado, CRL and Shon Isenhour, CMRP CAMA CCMP, Founding Partner at Eruditio LLC
During the many root cause analysis (RCA) investigations we facilitate and coach, we notice some themes that continue to manifest themselves in the findings. Often, they are grouped under the heading of precision maintenance or lack thereof. Let’s take a look at some of them and determine if they are also killing your reliability.
The six killers are grouped into three areas: Lubrication, Misalignment and Undiagnosed Wear.
Click here to read the full article.
by Ana Maria Delgado, CRL
It can be argued that lubricants are the lifeblood of equipment. It is extremely difficult to assure equipment reliability when lubrication integrity is not maintained. The key is to keep the lubrication system clean, cool and dry.
According to the Arrhenius Rate Rule, every 18-degree (F) increase in oil temperature in operation reduces oil life by half. Excessive lubrication temperatures can lead to additive depletion, oxidation, varnishing, hazards, corrosion, increased frequency of oil changes and more. All of this leads to reduced equipment reliability and increased costs.
Reduced operating temperature is one of the many benefits associated with proper machinery alignment. This in turn will help you reduce the operational temperature of the lubricants (lifeblood) within your equipment. Best practice equipment reliability includes proper equipment alignment. Your best practice lubrication efforts should include making sure your equipment is operated within proper alignment tolerances. Doing so will help you maintain the “cool” required to ensure that the lifeblood of your equipment is protected.
by Trent Phillips CRL CMRP - Novelis
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
How important is belt alignment?
Misalignment can occur between the driver and driven components no matter what mechanism is used to couple them together. This includes belt driven equipment as well. Unfortunately, proper alignment of belt driven equipment is frequently considered non-critical and often forgotten about by maintenance departments. Belt misalignment is one of the main causes of reduced belt life and other equipment reliability issues that result.
Sheave misalignment and many other belt defect conditions can be detected with proper vibration analysis techniques. Characteristics such as 1×, 2× and other multiples of belt frequency will be evident to the vibration analyst depending upon the specific type of belt defect present. For example, sheave misalignment usually results in high axial vibration at shaft turning speed in both the driver and driven equipment.
How do you prevent belt misalignment and the unwanted reliability issues that result? The best method is to use a laser alignment system designed specifically for this type of application. This technique will provide a very accurate, inexpensive and labor reducing method to ensure the belt driven equipment in your facility is properly aligned. Maintenance employees can be trained very easily and quickly to incorporate proper belt alignment techniques into their everyday maintenance activities. The return on investment is very quick with this type of laser alignment system.
How does a laser alignment system designed specifically for belt applications work? Systems such as the DotLine Laser and SheaveMaster use a special line laser and targets to help you achieve correct belt alignment. Targets are placed on one sheave and the laser tool is placed on the opposite sheave. The laser is projected onto the targets. This permits a quick determination and correction of unwanted angular, offset and twist misalignment conditions that may exist between the sheaves. One employee can easily and quickly determine and correct belt alignment conditions using this type of process.
Belt related defects can have a great impact on your equipment reliability. Don’t ignore best practice belt alignment techniques and induce unwanted reliability conditions in you equipment as a result.
by Trent Phillips
Many people believe that all they need is a good flexible coupling. They believe that flexible couplings will eliminate the need for performing proper machinery alignment. Nothing could be further from the truth! Coupling manufactures provide the allowable misalignment values of the couplings they provide. These tolerances only tell you what the couplings can withstand but do not take into consideration what the coupled machines can withstand. The coupling may be able to tolerate a lot of misalignment, however, components in the machine like bearings and seals may not be able to tolerate the same amounts of misalignment. Even though the coupling is flexible and may be able to withstand a lot misalignment, the stresses of misalignment are still transmitted to the components in the machine causing premature equipment failure. Good equipment health means completing best practice machinery alignment. The reason why some flexible couplings are built to withstand so much more misalignment than what the machines can withstand, is so that machines that experience substantial positional changes from operational load stresses or undergo a lot of thermal growth can be misaligned in the cold and stopped condition to compensate for these anticipated changes.
by Trent Phillips
When rotating hard-to-turn shafts by means of straps, pipe wrenches, chain hoists, or any other means, you could be deflecting the shaft. This can cause significant alignment and repeatability problems to occur, making the task of collecting accurate alignment readings almost impossible. The problem is easy to overcome, though. Simply switch your ROTALIGN ULTRA to Multipoint or Static measurement mode instead of using Continuous Sweep mode. Your readings will be taken while the shafts are stationary and with no external forces applied.
Between the two measurement modes, multipoint will be the measurement mode of choice. The jerky, starting/stopping motion you will most likely be experiencing will make it very difficult to stop at the specific angles needed for static mode.
by Tyler Wulterkens CRL
When taking individual soft foot readings on a four-footed machine, one foot at a time, always with the other three feet tight, if the two highest values appear diagonally opposed to each other, you have “rocking” soft foot situation. There are three potentially correct shimming solutions to this problem, but only one best solution.
Here’s how to find it: Loosen both diagonally opposed soft feet, leaving the two not soft feet tight. Feel the shim packs. If one is loose and one is snug, mike the air gap that appears under the loose one and shim that one by the amount of the air gap. If both shim packs are loose, shim both feet, by roughly half the soft foot value you got for each of them individually, or mike the airgaps with both of them loose and shim those amounts individually at each soft foot respectively. There are subtleties involved with this procedure that are best learned in an in-depth training course, but this will already go a long way toward solving these problems. Note If your two largest soft foot values do not appear diagonally opposed, you do not have a rocking problem, and other causes and solutions must be explored, again best learned through specialized training.
Have you heard about our Soft Foot Wizard?
by Pedro Casanova CRL
We recently ran a poll to find out what the Top Machine Faults are for the attendees of the IMC-2012 International Maintenance Conference. Here are the results, which came from maintenance and reliability professionals who attended our Learning Lab:
Bearing Failure: 31%
The good news is that all our lab participants were acquainted with our Condition-based Maintenance tools which can help them detect, prevent and correct all these problems.
It is essential to understand how equipment performs in a facility and to be able to identify these common machine reliability issues before they result in functional failures in your equipment. Payback technologies like vibration analysis, alignment and balancing when part of a comprehensive condition monitoring program can improve your equipment performance, reduce equipment downtime and minimize risk.
by Ana Maria Delgado, CRL
Vibration analysis is the best all-around technology for diagnosing and predicting problems in rotating machinery. Over the years I have seen time and time again where adopters of this technology have saved themselves and their companies countless man hours and thousands of dollars by getting to the root cause of a problem early on. By analyzing the data, they are able to schedule their valuable time on the right problem on the right machine long before the problem escalates into a major outage or emergency. But too many companies have not adopted vibration analysis. While it is true that one could spend many years learning the skills of the multiple levels of the vibration analysis disciplines, it is also true that even a basic understanding of the relationship of the time waveform and the spectrum can yield huge benefits and savings to a new user.
For example, the root cause of most roller bearing/seal failures is either shaft misalignment or rotor imbalance, which can take months to develop. It is also the most common problem analyzed within most facilities in the first two years of vibration analysis implementation. The good news is that misalignment and rotor imbalance are the easiest problems to diagnose by observing a high amplitude 1× running speed frequency in the spectrum. After that, a phase analysis with your analyzer can easily differentiate between misalignment or an imbalance problem, and quickly completed without shutting down the machine.
We all know that Rome wasn’t built in a day but we all must start somewhere and just a few days in an analysis class could yield major benefits to new companies.
Thanks to Jay Gensheimer with Solute LLC for this valuable post.
by Ana Maria Delgado, CRL
Often, seal failures are not the cause of an incorrect installation or the wrong seal type for the product being pumped, but a symptom of misalignment. If a seal starts dripping or misting product within days after installation, or suffers a “catastrophic” failure within weeks of being placed in service, the first suspect should not be the seal vendor or the technician installing the seal; misalignment should be considered as a good candidate for the cause of failure. Visualize a typical pump-motor system of bearings, shafts, seal and coupling. The weakest link in the chain is usually the mechanical seal. In the last ten years, seal technology has progressed substantially in both material composition and design (most notably cartridge seals), in compensating for shaft vibration. However, significant misalignment can still overwhelm the ability of a seal to keep both seal faces pressed firmly together or to withstand seal face cracking.
So remember, the next seal failure you encounter, quickly check misalignment with a good laser alignment system to see if the weakest link has failed due to misalignment.
by Ana Maria Delgado, CRL
Being bolt-bound means you have to move the machine sideways to get it aligned and you can’t: you’ve run out of room. The anchor bolt is up against the side of the hole in the foot.
Being base-bound means you need to bring the machine down to get it aligned, but you can’t: the machine feet are down against the base and there are no more shims left to remove from under them.
Are you in a quandary with either of these situations? No problem! You have five possible solutions:
- Open up the holes in the feet.
- Turn down the anchor bolts.
- Redrill and tap new holes in the base.
- Make an “Optimal Move”.
- Make a “Rolling Move”.
Let’s take the last one first. Making a rolling move of a bolt-bound machine simply means shimming up one side of the machine but not the other (or lowering one side but not the other.) This displaces the horizontal centerline of rotation of the shaft. But this is a big no-no! Do not do this! It will create angled soft feet and distort the machine frame when you tighten them because the feet are no longer evenly supported. Moreover, with gearboxes you may change the gear mesh pattern and destroy the machine. Many machines must be carefully leveled in addition to being aligned, so rolling moves are out!
Download entire article including making an “Optimal Move” with ROTALIGN ULTRA.
by Alan Luedeking CRL CMRP
Thank you for joining us for our Webinar Detecting Misalignment through Vibration Analysis. We hope you found the presentation to be valuable and very informative. If you missed our Webinar, you can view the recorded version at any time. Watch now!
Here are the answers to your questions:
Q: How do you account for thermal growth when installing new or repaired equipment?
A: If you already know that the machines will move as you run them, you must misalignment them ‘cold’ to compensate, so they grow into alignment as you run them. The trick, of course, is to know exactly how much! There are various methods to ascertain this precisely, the best being to perform a live monitoring job with PERMALIGN or ROTALIGN ULTRA Live Trend. To fully answer your question, I’d suggest that you take a peek at our Webinar “Thermal Growth and Machinery Alignment”
Q: If using dual channel phase without tacho, do you recommend orientating accels axially for angular misalignment detection and orientating accels radially for parallel misalignment? Is this relative to using 2 channel cross channel phase to determine angular or parallel phase?
A: Both types of phase measurements are easy to take. Relative phase is the most convenient way to measure phase on a machine because the machine does not need to be stopped to install reflective tape on the shaft. Phase can be measured at any frequency. Most single-channel vibration analyzers can measure absolute phase. Multi-channel vibration analyzers like the VIBXPERT have standard functions for measuring both absolute and relative phase. See below section “When to use Phase Analysis”
Q: Can’t you only find imbalance from phase?
A: Phase data can be used to verify a lot of vibration issues including imbalance, but it is not only for imbalance itself. I have included a few examples of what issues can be detected below by using phase. Both types of phase measurements are easy to take. Relative phase is the most convenient way to measure phase on a machine because the machine does not need to be stopped to install reflective tape on the shaft. Phase can be measured at any frequency. Most single-channel vibration analyzers can measure absolute phase. Multi-channel vibration analyzers like the VIBXPERT have standard functions for measuring both absolute and relative phase. See below section “When to use Phase Analysis”
When to use Phase Analysis
Everyone needs phase analysis. A phase study should be made on problem machines when the source of the vibration is not clear or when it is necessary to confirm suspected sources of vibration. A phase study might include points measured only on the machine bearings or it can include points over the entire machine from the foundation up to the bearings. The following are examples of how phase can help analyze vibration.
- Soft Foot
The term soft foot is used to describe machine frame distortion. It can be caused by a condition where the foot of a motor, pump or other component is not flat, square and tight to its mounting, or many other things, such as machining errors, bent or twisted feet and non-flat mounting surfaces. Soft foot increases vibration and puts undue stress on bearings, seals and couplings. Soft foot on a motor distorts the stator housing creating a non-uniform rotor to stator air gap resulting in vibration at two times line frequency. A good laser shaft alignment system should be used to verify soft foot by loosening the machine feet one at a time. I’d suggest that you take a peek at our Webinar “Soft Foot”
Phase can be used to identify soft foot while the machine is in operation. Measure vertical phase between the foot and its mounting surface. If the joint is tight, the phase angle is the same between surfaces. If the phase angle is different by more than 20 degrees, the foot is loose or the machine frame is cracked or flimsy.
- Cocked Bearings and Bent Shafts
Phase is used to detect cocked bearings and bent shafts. Measure phase at four axial locations around the bearing housing. If the bearing is cocked or the shaft is bent through the bearing, the phase will be different at each location. If the shaft is straight and the bearing is not twisting, the phase will be the same at each location.
- Confirm Imbalance
A once-per-revolution radial vibration usually means rotor unbalance. Use phase to prove imbalance is the problem. To confirm imbalance, measure the horizontal and vertical phase on a shaft or bearing housing. If the difference between the phase values is approximately 90 degrees, the problem is rotor unbalance. If the phase difference is closer to zero or 180 degrees, the vibration is caused by a reaction force. An eccentric pulley and shaft misalignment are examples of reaction forces.
- Looseness, Bending or Twisting
Phase is used to detect loose joints on structures and bending or twisting due to weakness or resonance. To check for looseness, measure the vertical phase at each mechanical joint. When joints are loose, there will be a phase shift of approximately 180 degrees. The phase angle will not change across a tight joint.
- Shaft Misalignment
Shaft misalignment is easily verified with phase. Measure each bearing in the horizontal, vertical and axial directions. Record the values in a table or bubble. Compare the horizontal phase from bearing to bearing on each component and across the coupling. Repeat the comparison using vertical then axial data. Good alignment will show no substantial phase shift between bearings or across the coupling.
- Operational Deflection Shapes
Instead of comparing the phase and magnitude numbers from a table or bubble diagram, operational deflection shape software (ODS) can be used to animate a machine drawing. An ODS is a measurement technique used to analyze the motion of rotating equipment and structures during normal operation. An ODS is an extension of phase analysis where a computer-generated model of the machine is animated with phase and magnitude data or simultaneously measured time waveforms. The animation is visually analyzed to diagnose problems. ODS testing is able to identify a wide variety of mechanical faults and resonance issues such as looseness, soft foot, broken welds, misalignment, unbalance, bending or twisting from resonance, structural weakness and foundation problems.
Phase and magnitude were measured from permanently mounted X and Y displacement probes on a turbine generator. The values listed in the table were used in ODS software to animate a stick figure drawing of the high- and low-pressure turbine shafts and the generator shaft. The picture to the right of the table is a capture from the ODS animation showing the vibration pattern of each shaft and the relative motion between shafts at 3,600 cycles per minute (turning speed).
Many machines vibrate due to deteriorated foundations, looseness, resonance of the support structure and other problems that occur below the machine bearings. A phase study might include hundreds of test points measured all over the machine and foundation. Good ODS software can make it easier to analyze phase and magnitude data from a large number of test points. Analysis of an ODS involves observation and interpretation of the machine in motion.
Q: Will coupled drive and belt drive systems show up the same on the spectra?
A: Yes, vibration data on a belt drive system will look different from a coupled drive but not when looking at the common defects of a machine. For example the vibration data on a belt drive motor will show additional vibration below turning speed due to the belts. The common defects such as imbalance, looseness, and misalignment (to name a few) will show up the same on a belt drive system or a coupled drive system.
Q: In the below spectrum we see a looseness, do we need to correct first the looseness before the misalignment?
A: When looking at vibration data there is always more than one issue showing within the vibration data. I suggest that correcting the highest amplitude vibration issue first and the secondary issue will usually decrease in amplitude. For example on this vibration spectra I would suggest correcting the misalignment issue first. The misalignment is the root cause affect of the looseness. Once the misalignment issue is corrected the looseness issue will not be seen on the spectra data.
Q: Will this show up in both horizontal and vertical or is it predominately just one or the other?
A: The answer is that an alignment issue will show up both the horizontal and vertical orientation when collecting vibration data. Of course depending on the type of misalignment the horizontal or vertical orientation could be higher. Once a single orientation has a high amplitude level of misalignment it will cross over into the other orientation as well. Of course if the alignment issue has a small amplitude level it might only be noticed in a certain orientation and again that depending on the type of misalignment that is present.
Q: How can vibration analysis instrumentation be integrated into a building’s BAS computer system?
A: There are generally two different vibration programs that exist in a plant. One would be walk around data collection. This is where a person goes out and places a sensor on a machine to collect the vibration data and then transfers that vibration data in a database. The second would be continuous monitoring where sensors are permanently mounted to a machine. Vibration data is collected every minute or less depending on the need. The walk around vibration database does have a SAP export feature that would allow you to export certain data from the database over into your system.
Most cases the continuous monitoring is best to feed data into another system. We have customers that use our continuous monitoring devices (online systems) to feed into their SCADA systems. This allows for an overall value of 4-20 MA signal to be sent across into another system. Now the other system, like the SCADA, can now alert if certain levels have been reached.
Q: What vibration is typically associated with a damaged impeller or damaged fan blade?
A: The vibration associated with a damaged impeller or fan blades is called vane pass frequency. When looking at the spectra vibration data you would be interested in the number of vanes or impellers that are on the machine. For example if you had six vanes the vibration data would show a peak in the spectra data at 6 times turning speed, 12 times turning speed, 18 times turning speed, 24 times turning speed, 30 times turning speed. Depending on the frequency maximum for your spectra would determine how far out the vane pass frequency would occur or be seen.
Q: When we laser align our mechanics say they can’t keep their coupling gap correct. What is a good method to laser align and maintain coupling gap at the same time?
A: There are two kinds of coupling gap we have to keep in mind when aligning a machine. The first is the simple gap difference between the coupling faces arising out of any angular misalignment between the shafts, and the second is the axial installation gap specification and tolerance that is demanded by manufacturer of the coupling.
Typically, you rough align the machines and then set the installation gap of the coupling before you completely tighten it down. If the hubs are shrunk fit, then you guide yourself by the position of the hub on the shaft ends and hope your holes in the base are drilled in the right place when your machines are set down. The correction of any misalignment (angular and offset) typically will never affect the installation gap by enough to make any difference, since we are talking about changes to angularity in thousandths of an inch, whereas the installation gap may have a tolerance of as much as a quarter inch in or out. So I’m not exactly sure what your mechanics are concerned about. With a good laser alignment system, you perform both angular and offset corrections simultaneously, and the axial gap between the couplings is not a concern.
I hope these answers were beneficial to all of you. If you have any additional questions, please feel free to contact me.
by Mickey Harp CRL
PLANT SERVICES • JULY 2011
Misaligned pumps can affect energy efficiency
Align pumps with laser accuracy.
By Heinz P. Bloch, P.E., Process Machinery Consulting
- Intern approaches pump alignment with laser accuracy.
- Tips to compare the energy wasted by a hot coupling to the energy loss.
- Misalignment affects bearing load and excessive bearing load causes exponential decreases in bearing life.
In the summer of 1994, Jack Lambley, an intern at Imperial Chemical Industries’ (ICI) Rocksavage site in the United Kingdom, was quantifying the effect of misaligned process pumps on power consumption. He arranged to have a surplus pump overhauled and fitted with new bearings. He then had the pump installed in a suitably instrumented closed-loop arrangement operating on water. Prüftechnik loaned Lambley a laser-optic alignment instrument.
As an undergraduate student, Lambley had learned that misalignment affects bearing load and that excessive bearing load causes exponential decreases in bearing life. His supervisor, Steve Moore, had asked Lambley to read the engineering sections of SKF’s general catalog, which stated that a 25% increase in bearing load cut its rated life in half.
Continue reading “Misaligned pumps can affect energy efficiency”
by Ana Maria Delgado, CRL
by Adam Stredel CRL
In a sense, this post is about one, and only one topic: MONEY. If alignment can be improved, machinery failure rate drops dramatically. Equipment failures are a major maintenance expense and have numerous incidental or associated costs. In fact, the cost of parts and labor to repair the machine can be one of the smaller costs. Lost production, contractual penalties, consequential damages, and liability for injury can all be much more expensive than the repair itself.If half of the alignments in your plant are done with a straight edge and the other half with dial indicators, our experience tells us that the average misalignment in the plant will be about 15 mils (offset and angular misalignment, where the angular misalignment is expressed in mils/10″). This misalignment will create an average power loss of 0.842% (please note that this is a very conservative figure: there is a high likelihood of this value being significantly higher.)
For machines operating 365 days a year, 24 hours a day, at an average cost of energy of $0.06 per Kilowatt hour, the Total Cost of Lost Power (TCLP) for a small industrial plant running up to 150 small to medium-sized machines (average of 35 HP) can be determined to be:
TCLP = 150 machines × 35 HP/machine × 0.7457 Kw/HP × 365 days/year × 24 hours/day × 0.00842 × $0.06/KwHour = $17,325.70 per year.
With precision alignment it is possible to achieve an average misalignment of just 2 mils. This misalignment creates an average power loss of 0.041%. Thus, the new TCLP will be:
TCLP = 150 machines × 35 HP/machine × 0.7457 Kw/HP × 365 days/year × 24 hours/day × 0.00041 × $0.06/KwHour = $843.65 per year.
Therefore, the reduction in Cost of Power is: $17,325.70 – 843.65 = $16,482.04.
These savings easily pay for a new laser alignment system in one year, without taking into consideration all the other attendant benefits from the reduction in misalignment, such as reduced vibration resulting in improved product quality, greater manufacturing output efficiency, and reduced wear and tear on the machines with the consequential reduction in labor, repair and spare parts expenses. Add to this the reduction in unscheduled downtime and the savings become almost incalculable.
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by Ana Maria Delgado, CRL