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Soft Foot has often been noted as the most inexact science portion of Shaft Alignment. Historically, when people think of Soft Foot, they often want to neglect, ignore, or otherwise do everything possible to not deal with it. This is one of the traps that leads down the path of bad habits, bad alignments, and more problems down the line.
Shaft alignment can be thought of as two things: 1) Aligning the couplings and 2) Checking for and correcting Soft Foot. Soft Foot, in fact, plays so much of a role in shaft alignment, that if one were to analyze the 6-Step Alignment Procedure below, one can see that Soft Foot actually appears in 3 out of the 6 steps. Therefore, Soft Foot can be thought of as half the alignment job.
Overall Alignment Procedure
1. Pre-alignment checks
2. Rough alignment to “eyeball clean” (with bolts loose).
3. Rough soft foot: Loosen all bolts and “fill any obvious gaps”.
4. Initial alignment. Get to within 5 to 15 mils at coupling or less than 20 mils at feet.
5. Final soft foot. All feet less than 2.0
6. Final alignment within tolerances.
Note: Step # 1 includes shim inspection and cleaning of machine supports
What is Soft Foot?
Soft Foot is Machine Frame Distortion.
How does it happen?
Soft Foot can happen from a number of things, including:
• Bent Feet
• Bad Bases (warped, uneven, flimsy)
• Dirt, rust, corrosion under feet
• Excessive number of shims
• And many more…
What should be done about it?
A full and extensive diagnosis should be done on every machine foot to determine whether or not the tightening of that particular bolt is causing machine frame distortion, and thereby adding coupling misalignment or machine frame strain.  A few helpful tips to remember are:
• Minimize total number of shims under each machine foot to no more than 4 shims per foot.
• Make sure the area is clean, including machine feet, bases, shim packs, etc.
• Any jacking bolts that may be causing force against the machine frame should be backed off, so as to not interfere with the soft foot check.
• When checking for soft foot, only one machine foot should be loosened at a time, and the deflection or movement at the shaft noted.
With advancements in technology, PRUEFTECHNIK laser alignment tools can help diagnose whether a machine has a soft foot. The newest addition to the PRUEFTECHNIK line of tools, the Rotalign ULTRA, not only diagnoses the soft foot condition of the entire machine, but tells the user exactly how much to shim each foot, in order to correct the soft foot condition.
So the next time someone tries to pass off a bad Soft Foot problem as not being “that bad”, be aware that it is 50% of the alignment.  Your machine’s Soft Foot condition should be taken care of, because if it has not, neither has your Shaft Alignment.

by Ana Maria Delgado, CRL

An accelerometer is often used with a magnet to couple the sensor to the machine. The coupling between the magnet and machine is critical to ensure quality vibration data is acquired.
Placing the magnet onto the machine can create an impact which can shock the sensor for several seconds. Collecting data during this time can skew the results. The magnet should be rolled onto the machine to minimize the impact. Once the magnet is “Rolled” onto the machine the analyst should feel the magnet to see if it has a good contact or is loose. If the magnet feels loose try rotating the magnet either clockwise or counter clockwise to obtain a more secure fit. Additionally, move the top of the sensor to check for a secure fit as well.
These steps will help you check for sensor placement issues that could impact the quality of data collected. By making these checks you have also allowed any impact signals from attaching the magnet to the machine to decay out of the signal.

by Gary James CRL

When wiring an online remote monitoring system or accelerometers into a termination box/switch box, it is a good practice to run the cables in flexible or rigid conduit. After the fact, it is highly recommended to label both ends of each cable with its respective measurement location. If ferrule tags are not available for labeling, colored electrical tape can be used and marked with an indelible marker.
If you have an online monitoring system, it is recommended to send data (overall vibration), alarm values and machine status to your process control system or DCS. The data can be sent using MODBUS TCP/IP or MODBUS RTU. This way, there is no need to run extra wires into your control system.

by Alex Nino CRL

Safety in the Workplace

Many accidents can be avoided by simply following a company’s safety procedures. There are many things that might not be considered when thinking about safety. For example, keeping your workplace clean, and free of debris. If objects or spills are left around the work environment, anyone may trip or slip on them. Debris can also end up on or inside machinery and damage equipment. Knowledge of your surroundings can also keep the workplace safe. Know where the nearest fire extinguishers are, and where the emergency kill switch for your machinery is located, as well as emergency exits, and first-aid kits.
Improper attire can also be a safety hazard if not appropriate. Neckties are taboo and long hair should be picked up in a pony tail or tucked in your shirt. Loose long sleeves can get tangled with machinery. Protection for eyes, ears, and head is imperative while in the factory environment.
In intrinsically safe (IS) environments, any electronic components that enter the area must be certified as IS. An item can be deemed as IS when its potential electrical and/or thermal energy is low enough that, within a hazardous atmosphere, ignition will not take place. Cell phones, digital cameras and MP3 players are not intrinsically safe and can be hazardous in explosive atmospheres. If working in an intrinsically safe environment, follow your company’s safety guidelines for a better, safer workplace.
Awareness and communication are also important when it comes to safety. Warning your coworkers when they are violating safety procedures can avoid many accidents. It is good practice to advise those around when a machine is being turned on, or when hazardous materials have been exposed. Always obey all safety regulations. They are in place for our own benefit, not just the company’s.

by Adam Stredel CRL

When performing a Dynamic Balance procedure a few things should be considered:
1.  Inspect the structure/mounts and ensure there no cracks or loose bolts.
2.  If driven via a belt drive make sure that the belt is in good condition and properly tensioned.
• Remember that the second harmonic of a belt frequency can be very close to the rotational speed of the drive.
3.  Inspect the rotating element for build-up and clean as necessary.
• Remember that even slight build-up (i.e., dust) can be the cause of an unbalance.
4.  If the rotating element is a blower, count the number of blades.
• Frequently correction weights will have to be attached to the blades and therefore it may be best to use a fixed location method.
5.  If the equipment is down when you arrive, replace the reflective tape or attach new tape as may be required.
• This will ensure accurate phase data.
6.  When taking your initial phase data turn the averaging function off, if possible.
• Monitor the phase data for a brief time to ensure its stability. Doing this could identify potential problems.
7.  Keep good documentation,keep written notes on what was found:
a.  Phase and amplitude data
b.  Number of blades
c.  Correction locations
d.  When weights were attached or removed
e.  How much weight was attached or removed
f.  Sensor placement
g.  Tachometer placement.
8.  If the equipment is variable speed such as VFD drive or DC drive ensure that the speed is repeatable to within 5% or less run to run.
Learn about our VIBXPERT II Field Balancer.

by Gary James CRL

PERMALIGN is the world’s leading machinery positional change measurement system. Since 1986, it has proven itself as the most accurate and dependable solution for thermal growth measurement. PERMALIGN is a laser based system capable of detecting and accurately measuring both relative or absolute movement, depending on the prisms and setups selected. To this day, it remains unequalled in ease of use and precision of measurement.

A great majority of the PERMALIGN applications involve installing two roof prisms and two laser monitors on the inboard bearing housing of each machine.  By measuring the bearing housing movement, the alignment change can be determined from the relative movement of the machines.  The preferred method of installation is to drill and tap a 10-32 × ½” deep hole into some part of the machine that is directly connected to the bearing housing as shown below.
Permalign Monitoring Setup
Sometimes, this is not possible. The next solution is to construct a strong bracket (usually of 5/8″ thick steel plate) that can be physically attached to the bearing housing.  This usually involves temporarily replacing a housing bolt with a longer bolt that allows the bracket to be “sandwiched” to the machine as shown below.
Angle Bracket
Sometimes, the presence of obstructions (proximity probes, electrical conduit, piping) can interfere with the positioning of the brackets and the PERMALIGN components.  When designing brackets for these situations, the fastest and easiest method is to take advantage of CAD.  I am not referring to “Computer Aided Design”, but something far more effective in the field – “Cardboard Aided Design”!
Get a piece of cardboard, a pair of scissors and cut out a template for the bracket that you will need.  You can bend it in any shape you wish and mark your mounting points with a marker.  Need to make a design change?  Just cut it to change the dimension!  As shown below, this precision engineered template was crafted with a pocket knife.CAD Template
Below is the template next to the fabricated piece.  The template provides an easy to follow map for building the bracket.  PERMALIGN brackets are usually torch cut in the field, ground and welded together.  The design emphasis is for it to be STRONG, not pretty!
Angle Bracket - CADTemplate
Below is the final result.  The cardboard template allows the design to be checked prior to fabrication and installation.
Final Setup
 

by Daus Studenberg CRL

Vibration Alarms Save Time!

Do you use accurate alarm values for your vibration analysis program or other CM technologies?   Setting accurate alarm values will help you identify equipment defects occurring in your equipment.  However, the benefits go beyond this.   Missing alarms or inaccurate alarms may force your analyst to review every machine each time data is collected.  This wastes a lot of time reviewing data that could be used more productively for other reliability efforts.  Setting accurate vibration alarms means that data for each machine does not have to be reviewed each time it is collected.  The vibration analysis software, vibration data collector or other CM technology can alert your analyst of those machines that actually need review.  This will increase the analysis accuracy and save you time and money.

by Trent Phillips

Many of you watch or at least are familiar with the various Crime Scene Investigation (CSI ) television series where advanced forensic techniques are utilized to catch the criminals or “bad actors”.  When it comes to your “bad actors” from an equipment perspective, where is your CSI unit? What is your forensic approach to equipment failure?
Rather than simply accepting equipment failures, they should be literally treated like crimes against your organization.  These failures rob the organization of equipment availability and capacity, divert your Maintenance resources, consume spare parts, and steal profit. While you may not be able to prevent failures from occurring, at a minimum you need to understand why they occurred from a root cause perspective.
To do this, perform an autopsy on the failed equipment. Cut apart failed bearings or open gearboxes as examples. Inspect the components. Ideally, the Maintenance Engineering group should become your CSI Unit and investigate to understand the root cause.  In the event that organization does not have the Maintenance Engineering function, you can to develop a “champion” who is detail oriented with strong mechanical skills. I don’t advocate rotating the champion function among many people as it takes time to develop the necessary skills. Another resource for consideration is that many quality vendors provide a service of analyzing the failures so that you can both understand how the component failed, and often at no cost. In addition to vendors, there are a number of other resources available to you such as the Maintenance Engineering Handbook, and searching Google images on the Internet. 
In the end, the goal is to understand the possible root cause(s) so that you can modify your practices to ensure the elimination of those potential failures from robbing your organization. If doing autopsies, what are some of the root causes and outcomes that your organization has identified? What other steps or ideas would you recommend regarding autopsies?
This was a guest post from Jeff Shiver, CMRP, CPMM of People and Processes, Inc.

by Ana Maria Delgado, CRL

When experiencing lack of repeatability using a laser system, check the components for looseness:

  • Brackets: Make sure that they are rigidly attached to the shafts (or solid coupling hubs). The surface imperfection where the brackets are mounted plays no role provided the shafts are rotated and the bracket is firmly attached to the surface.
  • Risers: Most brackets systems will have risers (support posts) attached to them to mount components. Make sure they are firmly attached to the brackets.
  • Lasers, Receivers, Prism: Also make sure they are firmly attached to the risers.
  • Brackets rubbing: the brackets and everything they support must not touch or rub on any stationary part during rotation.

Looking out for these simple little things can save you many headaches during your alignment job.

by Pedro Casanova CRL

Fault frequencies are very important in vibration analysis, because they allow the analyst to correlate vibration data to specific components in the equipment that may be in some stage of failure (equipment faults). Fault frequencies change with any adjustment in the speed of the equipment being monitored. Most modern vibration data collectors and software will automatically re-calculate the displayed fault frequency information as the rotational speed of the equipment changes. Component information (bearing information, gear information, etc.) is required to calculate and display the fault frequencies of specific components in machinery. 
It is important to create fault frequency setups at the beginning of a vibration analysis program. Not doing so will affect the overall success of the vibration analysis program.

by Ana Maria Delgado, CRL

When aligning a vertical flange-mounted machine, it can be helpful to tweak the flange configuration in your laser alignment system to take advantage of different shimming alternatives. For instance, if the OD of the flange is larger than the diameter of the mounting bolt circle, a good laser system will compensate for this by taking into consideration that when shimming your pivot point is not the bolt circle but the flange OD. Thus, all shimming corrections will be positive.
However, if you already have shims at all the bolt positions, you could take advantage of the opportunity to minimize the required shimming corrections by forcing the smallest correction position to be zero. Do this by entering a distance for flange OD as being equal to your bolt circle. Of course the best laser systems already allow for all the different shimming alternatives (positive, negative and zero sum options) right in the software, so you don’t have to use this trick.

by Ana Maria Delgado, CRL

Unbalance occurs when the rotor’s mass is no longer at the center of rotation.  Unbalance can be caused by many factors:

  • Assembly error
  • Machine tolerances
  • Eccentric components
  • Wear
  • Corrosion
  • Thermal distortion
  • Mechanical distortion
  • Material buildup
  • Bent components
  • Broken components

Many things can prevent the successful correction of unbalance.  Equipment resonance, bearing issues, product buildup and many more equipment problems can prevent a successful balancing  job from being completed.  All Equipment defects should be corrected before attempting to balance equipment.

by Trent Phillips

The following tips are presented for consideration for when “the going gets tough”, meaning that problems like residual soft foot or “bad geometry” or becoming bolt-bound impede your ability to easily obtain an excellent alignment. First, a few definitions:

  • Residual Soft Foot present: A bit more soft foot than you are comfortable with, but that you can’t do anything about, perhaps from slightly angled feet or a bit of pipe strain. Learn about our Rotalign ULTRA Soft Foot Wizard.
  • Bad geometry: Equipment whose distance from – coupling center to front foot- is equal to or greater than the distance from front foot to back foot.
  • Becoming bolt-bound or base-bound: You must still move a little but have run out of room in the anchor bolt holes in the feet, or must still come down a bit but have no shims left under the feet to remove. Learn about our Rotalign ULTRA Move Simulator.

Final Vertical Misalignment Correction (Horizontal Misalignment already “close”)
1. Get front feet position close to offset tolerance. Finish the alignment by correcting the rear feet only.
2. Final feet position should make offset at the coupling center decrease. To achieve this:
Front feet position 
Positive 
Negative 
Examples: 

-2
Back feet position
More Positive
More Negative
Examples: 
4
-3 etc.
3. It is bad to leave feet positions with opposite signs, even if the values are very small.
Examples:
Front feet position


-2 
Back feet position
-1
-2
1 etc.
4. It is bad to leave the value of the front feet position higher than the backfeet position even if they have the same sign.
  
Examples:
Front feet position

-2 
Back feet position
1
-1 etc.
Final Horizontal Misalignment Correction (After vertical is within tolerance)
The above rules apply for the Horizontal corrections also.  For small equipment remember to torque in steps.

by Pedro Casanova CRL

Knowing the exact bearing information for your equipment can make bearing defect analysis much easier.  However, it may not always be possible to acquire the bearing information for your equipment.  This can make it difficult to determine the bearing fault frequencies for correct analysis.
It is possible to remember easy formulas to calculate the approximate bearing fault frequencies for rolling element bearings.  The following formulas are easy to remember and can help you when the bearing information is not known:
FTF = 0.43 × RPM
BPFO = 0.43 × N × RPM
BPFI = 0.57 × N × RPM
Where:
FTF = Fundamental Train Frequency
RPM = Revolutions per minute
BPFO = Bearing Pass Frequency Outer Race
N = The number of rollers
BPFI = Bearing Pass Frequency Inner Race
The values derived from these formulas should be within 10% – 15% percent of the actual bearing fault frequencies.
Other formulas are available that will more accurately estimate bearing fault frequencies than the ones listed above.  LUDECA will be happy to provide those to you upon request.

by Trent Phillips

About Lines of Resolution

Lines of resolution (LOR) describes the number of lines of information that appear in the spectrum (FFT) acquired by the vibration data collector.  LOR can be calculated by dividing the overall frequency range collected (Fmax) by the number of lines selected.   
LOR represent the amount of detail in the collected data.  Without sufficient detail in the collected data, multiple peaks may merge together.  This may prevent the correct identification of machinery faults and lead to false conclusions.  It is very important that the correct LOR and sensors (accelerometers) be selected for the specific equipment being monitored

by Trent Phillips

When trouble-shooting alignment problems encountered when using a laser system it is imperative to distinguish between lack of ‘Repeatability’ and lack of ‘Response to Corrections’.
Repeatability: The consistency of alignment condition results between two or more consecutive sets of readings, without any intervening adjustments or changes in field conditions.
Response to Corrections: How accurately the machines respond to corrections made (shimming or moves).
On well-built machinery, a good laser system should be able repeat readings within 0.5 to 3 mils Offset and 0.5 to 3 mils/10 inches Angularity depending on the magnitude of the misalignment. There is little sense in proceeding with the alignment until repeatability is established. If repeatability is poor, seek for and correct the underlying reasons for it first, before attempting to correct the misalignment. Some of these reasons may include mechanical looseness (worn bearings allowing the shafts to rotate inconsistently within them, loose brackets, loose support posts, loose anchor bolts, mounting to a coupling hub that is not solid to the shafts, brushing against obstructions as you rotate, external forces acting on the machinery while readings are being taken (welding going on, pipe strain), changing field conditions (external vibration, machines cooling off or heating up), significant torsional play (coupling backlash), etc.

by Pedro Casanova CRL

Standard vs. Vector Tolerance Evaluation

If you are aligning very critical machines and your laser system does not offer you the ability to apply vector tolerances, you can still do so manually, by keeping these criteria in mind:
The standard industry norms of 2 mils offset and 0.3 mils per inch of angularity at 1800 rpm equate roughly to vectors of 1.4 mils of offset and 0.17 mils per inch of angularity. Therefore, you can apply a sliding scale when you look at your misalignment results: If you have misalignment only in one plane (either vertical or horizontal), apply the full value of the standard tolerance; if you have roughly equal misalignment in both planes apply the more conservative values shown above to both. This way you will not exceed your vector limits in any direction. To find the vector limits for any RPM, simply take the square root of the standard limits.
Of course, none of this would be necessary if you have one of the better laser systems that features vector tolerances and calculates them for you automatically.

Download our paper about Alignment Tolerances.
 

by Alan Luedeking CRL CMRP

Your vibration software should have the capability to automatically import and export data from and to your CMMS system. Vibration programs like the OMNITREND software can provide you with the means to address this issue.
Having the ability to automatically share information between your CMMS system and vibration software can be of great value. This capability can allow you to automatically build your vibration database with the same equipment names, equipment ID’s and hierarchy locations that are contained in your CMMS system. This can potentially save your company critical time and expense when starting a new vibration program or updating your current program.
Alarm condition information and much more can easily be shared between your CMMS software and vibration software. This provides the ability to alert your Maintenance Manager, planning and scheduling resources and other team players about the important equipment conditions found by your vibration program.
Most CMMS and vibration software do not directly share information. Direct storage of data into another program greatly increases the risk of information corruption. Of course, this is never a good thing when it occurs and the risk should be minimized as much as possible. Most CMMS and vibration programs have the ability to map specific information for import and export via a file transfer process. A template is created that determines what information should be exported and in what format it should be stored. The template is stored and automatically executed on a scheduled basis determined by the user. Both the CMMS system and vibration software will create temporary files to share the required information with each other. Each system will automatically import this information and store it in their specific databases(s) from the temporary files. This type of process minimizes your efforts and provides routine and scheduled data sharing between both systems.
This type of data exchange will provide continuity in your reliability efforts and removes confusion when creating work orders based upon the defect findings from your vibration program. The result will better integrate your reliability program with your maintenance process.

by Ana Maria Delgado, CRL

Measuring machinery misalignment with today’s tools, particularly computerized laser alignment systems and well-designed bracketing, is no longer as difficult a task as it once was, when all you had were a straight edge, feeler gauges and maybe a set of dial indicators with some make-shift hardware.
Why then, is it that aligning the machinery to given target values is so often still so cumbersome and time-consuming? There may be several reasons, among them unnecessarily tight tolerances specified by the machinery vendor, or problems with worn-out bearings, or inadequate bases, lack of jackscrews, etc. But by far the greatest obstacle to expeditiously reaching your alignment goal is soft foot. ‘Soft foot’, or machine frame distortion can be measured by various means, and indeed it must be measured and corrected before proceeding with the alignment. Why? Simply because an uncorrected soft foot condition will make alignment a trial-and-error procedure where indicated corrective shimming and lateral moves no longer bring you to the expected results. Severe soft foot may also be quite harmful to the machinery itself.

Laser alignment with Soft Foot Wizard
Soft Foot Wizard

Correcting soft foot may not be easy, but it is worth every minute you spend on it, because once done, the alignment of the machines becomes a much easier task. Many alignment systems available today have soft foot measuring programs, and the most advanced system even features a soft foot ‘wizard’ which analyzes the type of soft foot measured (there are a number of different soft foot conditions) and suggests how to correct it.
Conclusion: If you want to make aligning your machinery easier, quicker and more accurate, start by correcting soft foot.
 

by Ana Maria Delgado, CRL

Frequency can be defined as how often an event occurs per unit of time.  A vibration spectrum is displayed as a horizontal and vertical plot (X and Y).  The horizontal (X) axis is the frequency axis and shows a representation of how often an event occurs.  Typically, the vibration analyst may use multiple units of reference for the frequency axis when doing vibration analysis.  The most common units used for the spectrum (FFT) are cycles per minute (CPM) and Hertz.  The least known unit for the spectrum frequency axis is “Orders” or multiples of shaft turning speed.  It is critical to understand the differences in the frequency units (Hz, CPM and Orders).  It can be advantageous to view data in different units depending upon the machine and problem being analyzed.
 
Orders are ratios of frequencies to multiples of a shafts turning speed.  For example, a 60 Hz motor turning 1780 RPM would also have a rotational speed of 29.66 Hz.  The rotational speed would be referenced as one (1) order. Two (2) orders would be twice the shaft turning speed (59.33 Hz) and so on.
 
Certain equipment defects occur based upon some multiple of turning speed.  Looking at data based upon order references can make it easier to remember the specific defect frequencies and identify them during routine analysis.
 
Order-based analysis is a good way to set up and ensure that the correct frequency range is being monitored for variable speed machines, etc.  You can define your analysis setups in orders and be ensured that the correct frequency ranges will be measured by your vibration data collector as the speed of the machine changes over time.
 
Most modern vibration analysis software and vibration data collectors support order-based data collection and analysis.  If you are unsure, then you should consult the provider of your vibration software and hardware and find out.

by Ana Maria Delgado, CRL

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