Shaft Alignment with 4 Different Measurement Methods

April 24, 2018

Reposted from Easy-Laser®

The latest addition to Generation XT, Easy-Laser® XT660, gives you access to four different measurement methods for shaft alignment. Each with its own advantages. Read more to find out how to use them best!

The four measurement methods are 9-12-3, EasyTurn™, Multipoint and Continuous sweep. Here we describe them individually, so that you know when best to use them.

The rotation of the measurement devices around the shaft is similar to that of a clock; positions 9, 12, 3 and 6.

 

 

 

 

 

 

 

 

 

 

 

Method 1: 9-12-3

The clock method, or 9-12-3 as it is also known, is the origin of all shaft alignment. Anyone who knows how to use analogue dial indicators will recognize this method. A dial gauge is mounted on each shaft, and the measurement values taken at three different points, corresponding to the 9-12-3 positions on a clock, or the angles 0-90-180 of a circle. It is based on geometry (and trigonometry), more specifically circle mathematics. The mathematical assumption is that if we can measure the semicircle, we can then work out what the whole circle will look like, and consequently determine the center of the circle (rotational center) for both shafts. These centers can then be compared to each other and we can thus work out how well-aligned the machines are to each other. And with a laser-based measurement system, also obtain direct feedback from the adjustment of the machine in real time.

Measurement method 9-12-3 – the origin of all shaft alignment.

 

 

 

 

 

 

 

 

 

 

 

 

When should this method be used? One answer is that this method can always be used when you are able to rotate the shafts freely, and there are no other physical obstructions preventing you measuring from the 9-12-3 positions. However, the restriction is that you must position the measurement devices at 9-12-3 as accurately as possible, and that the system does not use the built-in inclinometers to calculate the position (in other words, you must check this yourself).

There is, however, one application when you must use the 9-12-3 method; during shaft alignment on-board sea faring vessels. This is because the inclinometers would move in conjunction with the vessel’s movements on the waves, potentially corrupting the collected measurement values. We therefore recommend using the 9-12-3 method as the inclinometers are switched off.

Method 2: EasyTurn

EasyTurn is a unique further development of the 9-12-3 method, with the freedom to choose at which clock position (which angle) you start collecting measurement values. With the help of some mathematics, we can also restrict the total measurement range to 40 degrees full rotation. From a practical point of view, this means that you can use this method where there is limited possibility of rotating the machines, due to the lack of space around the shafts.

This method is the standard setting in most Easy-Laser shaft alignment systems (except XT660, which uses ”Continuous Sweep” as the standard method, see below).

Measurement method EasyTurn offers down to 20° between measuring points. Great when machine protection or pipes prevent precise positioning according to the clock method.

 

 

 

 

 

 

 

 

 

 

 

 


Method 3: Multipoint

Multipoint is, in turn, a further development of EasyTurn. Multipoint also means that you can start collecting measurement values from any clock position (angle), and complete collection across as small a rotation as 40 degrees. However, as the name suggests, this method means that values are collected from more than three points.

This is advantageous if taking measurements from larger machines where it is difficult to rotate the shafts. Collect the measurement values across a shorter rotation to increase the mathematical probability of obtaining good measurement values. This method also gives a quality evaluation of the measurement series. The evaluation takes into account shifts in temperature, measurement direction and number of measuring points.

With the Multipoint method, several points around the shaft are registered, which allows the measurement quality to be evaluated.

 

 

 

 

 

 

 

 

 

 

 

 

Method 4: Continuous Sweep

Continuous sweep can be described as Multipoint with automatic, continuous measurement value collection. In practice, this means that you can collect measurement values continuously with the measurement devices in motion. I.e. you start measurement value collection (at any clock position/angle) and then rotate the shafts without stopping, in one direction. Continue until you have collected enough measurement values to achieve a good quality calculation (quality evaluation is also performed here just as in Multipoint).

Continuous sweep is best used when it is difficult to stop the machines to register measurement values.

 

 

 

 

 

 

 

 

 

 

 

 

At the end, the shafts’ rotational center is calculated and presented graphically via images and text. This method is very useful in instances where it is difficult to stop the machines to take stationary measuring points, for example, when aligning large turbines.

We hope you now have a clearer picture of the various measurement methods and when best to use them.

The Easy-Laser XT Alignment App can be downloaded free of charge from the App Store and Google Play to try out.

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Easy-Laser® XT11 Alignment Display Unit is Awarded Once Again

April 17, 2018

We at LUDECA proudly share the excitement with our partners at Easy-Laser® for winning the Red Dot Design Award 2018 with their XT11 display unit.

The distinctive Red Dot is established internationally as one of the most sought-after quality marks for good design. Here are some of the things they considered in their evaluation:

• Degree of innovation
• Functionality
• Formal quality
• Ergonomics
• Durability

And yes, this is their second design award with the excellent development and capabilities of the XT11 display unit. They won the iF Design Award in 2017. XT11 has some smart functions, like the screen-lock button which prevents unintentional clicks on the touch screen when you move around the machine you measure. As an option, you can fit your XT11 with a thermal imaging camera, opening up even more possibilities to optimize your machinery for smooth operation.

Easy-Laser XT11 runs the XT Alignment app, which can also be run on iOS and Android phones and tablets. This is a unique feature in the alignment industry – the user can combine display units and different types of measuring units to suit their needs and budget – but will only have to learn one alignment program!

Congratulations to our partners at Easy-Laser for winning this great award on this excellent product!

Contact us if you would like to see the Easy-Laser XT11 display unit in action or watch the XT11 video.

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Is Your Vibration Analysis Pointed in the Right Direction?

April 10, 2018

With the proliferation of online monitoring systems utilizing permanently mounted sensors, users will need to beware of “direction sensitive” vibration and possible sudden unexpected failure due to insufficient data. The thought of insufficient data may seem incredible when thinking of constantly monitored equipment, but consider the all too common (imho) practice of uni-directional (one direction) monitoring of machine trains.

Many installations, due to initial cost, are mounting a single vibration sensor at each bearing. While this may be sufficient for most equipment trains, most of the time, it will certainly not be sufficient for all equipment trains all of the time. Although I don’t have hard data available, if I were to make a statement based on personal experience, and anecdotal evidence from other practitioners, my statement would be something like this: “80% of horizontal equipment could be pretty well monitored by sensors mounted at the horizontal radial position on each bearing.” I say pretty well monitored because I just can’t bring myself (as an analyst) to be completely satisfied without the vertical and axial data.

This setup would catch virtually all unbalance and roller bearing faults (excluding thrust bearings), some to most misalignment faults and a sprinkling of others. I use the word “catch”, to mean it would give an indication of a developing problem. Accurate diagnosis of unbalance, misalignment, bent shaft, and even looseness in many cases (as well as a host of other possible faults) would require more data.

If the online vibration program manager takes these facts into account and governs the program accordingly, they should be pretty successful. If they add to the online program a “full battery” vibration survey, maybe semi-annually, just to catch the less common, but possibly very destructive defects that could develop undetected by the uni-directional monitoring, they would most likely be very successful.

What could be so destructive and yet be completely undetected by the uni-directional sensors? The Big R for one, Resonance. Resonance is often extremely directional. Consider a case history LUDECA co-published with one of our customers in the December 2012 Wastewater Processing magazine:

In the table below (Figure 1), the 1× amplitudes are displayed. I have hidden all but the vertical data, as though it were monitored only by vertical sensors.

Figure 1 – Initial vibration amplitudes on pump and motor

Everything is wonderful right? Look at the motor outboard vertical, only 0.00384 inches per second—very impressive. Of course, at this point you are thinking “he is setting me up for something” and you are correct. Even though most anyone would love to have these amplitudes on virtually any machine, this particular machine was tearing itself apart with vibration!

We will give the reader a little more data, just to help add emphasis to the directional nature of a resonance. We will add the axial data to our table in Figure 2:

Figure 2 – Initial vibration amplitudes on pump and motor

 

 

 

Still very, very good… so far. Now look at Figure 3, with the addition of the horizontal data.

Figure 3 -Initial vibration amplitudes on pump and motor

 

 

 

The motor outboard horizontal amplitude is 162 times the amplitude of the motor outboard vertical! What if the user had only vertically mounted sensors? What about vertical with the added information of axial? You may be thinking “if I had only horizontal sensors, I would have been ok”, and for sure you would have been better off than having only vertical. You would at least have known you had a problem, but you would not have known what that problem actually was. You would likely have assumed the vertical and axial are probably vibrating badly too. Hopefully you would have verified the vibration in the other directions. As it was, the user had data from all directions and a simple glance told the analyst with a high degree of confidence what the problem was. Resonance is almost alone in creating that kind of directional disparity.

To reiterate, the online vibration program manager should be successful if they take into account the fact of limited data and supplement the online program with a “full battery” vibration survey at a cost effective interval, just to catch the less common, but possibly very destructive defects that could be developing undetected by uni-directional monitoring.

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All About Arc-Seconds

April 3, 2018

An arc-second is a measurement unit for angle. It is often used in describing level and plumb.

1 arc second = 1/3600 degree = 0.000278 degree =0.0000048 inches/inch =0.0048 mils/inch = 0.0048 mm/m

1 degree = 17.347 mils/inch

1 mil/inch = 1 thou/inch = 1 mm/m (The metric-imperial relationship is purely a coincidence!)

A high accuracy machinist bubble level, a commonly used tool to check level of baseplates and foundations, is typically 0.24 mils/foot (often mentioned as a “quarter of a thou per foot” in the field) = 0.02 mils/inch = 4.15 arc seconds.

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Don’t Let your Equipment/Machinery Get a High

March 27, 2018

While the person in charge of collecting vibration data is actually collecting the data, they should watch the data “live” for unusually high amplitudes or discontinuities in the data. This will not increase the data collection time, and if any of these issues are detected, the person can evaluate whether or not the data is “good” or not; if not, the data can be recollected, or if it is “good” then additional data may need to be collected to ensure that proper analysis can be performed on the equipment. Field notes can be made about the machine condition and its status. If the machine condition is determined to require attention, the analyst might need to contact someone at the facility. Remember that sudden increases or decreases are usually a sign of machine problems. Looking at or analyzing the data in the field can give the analyst a good idea of what issues need to be analyzed, thereby reducing the time analyzing data in the office. If not analyzing the data on the spot, one can at least make notes to aid in later analysis.

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