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Complementary Technology – Misalignment

Visualise, Measure, Troubleshoot and Correct machinery misalignment with Motion Amplification® and Easy Laser® Reliability Products from GVS.

 

Motion Amplification® and Easy-Laser® are fantastic complementary tools for visualising misalignment, measuring thermal growth, and correcting misalignment making Proactive (Precision) Reliability Maintenance even more achievable.

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Easier than ever to measure flatness and straightness

Now presenting Easy-Laser® XT20 and XT22, the most user-friendly precision laser transmitters ever designed! 
 

One of the most important things during a machine installation is to ensure the flatness of the base. With the new XT20 and XT22 we have facilitated handling, which makes for faster measurements and fewer fault sources. More reliable machine installation, put simply. 

Both transmitters can be used for flatness and straightness measurement. In addition, the XT22 can direct the laser beam at 90 degrees to the laser plane, which means you can solve virtually all types of geometric measurement jobs. The area of use therefore does not stop at measuring the flatness of bases. The XT22 also has a higher technical specification for straightness thanks to fiber laser technology, and can take measurements at distances up to 40 m. The XT20 can take measurements at distances up to 20 m, but is also IP55 rated water and dust proof.    

New technology improves reliability  

We have installed electronic precision levels in the XT transmitters. This gives the advantage of faster feedback when levelling and less risk of errors during calibration, because all users see the same angular value (compared with reading spirit levels).   

The laser transmitters are wirelessly connected to the XT Alignment app. In this way, the user can be guided during calibration and the measurement procedure. In the event of temperature changes, vibrations or impacts that can affect the measurement result negatively, the app gives a warning during measurement. Data about the transmitter and measurement environment can be downloaded together with the report. This all provides greater reliability and traceability for your measurement jobs.  

Functions for easier use  

The rotating head is completely stable and retains its position during measurement. At the same time, with the new fine turning mechanism it is easy to set the pointing direction of the laser beam to hit the detector, even at distances up to 40 m. We guarantee that this will be very much appreciated by users out in the field. All operation is also managed without the need to lock/unlock rotation, which facilitates use considerably.    

Just like Easy-Laser’s previous laser transmitter, the new XT20/XT22 can be installed and positioned in many different ways: with integrated super magnets, on rods to be height adjustable, on stands and magnetic feet etc. We know that this is an important factor in practice to combat all those situations the user faces in reality.   

A rechargeable Li-Ion battery gives long operating times, up to 30 hours. If necessary, the transmitter can also be run directly off the mains.  

Developed for use with the XT Alignment app  

The XT20 and XT22 are used with the programs Values, Basic flatness and Straightness (new) in the XT Alignment app.   

The laser transmitters can be purchased separately (as a kit with charger and fixture) but are also included in complete systems, such as the XT770 GEO. The XT70-M unit can be used as a detector. They can also be used with E series detectors. Note, however, that the XT Alignment app is required to calibrate the electronic levels, and other things in the design of the XT transmitters differ from previous products. Therefore, always ask us first if you plan to replace an older transmitter.   

Easy-Laser have been known for their reliable geometry measurement systems for decades. With the new Generation XT laser transmitters we are taking a step into the future, to a whole new level of reliability, precision and user-friendliness. The XT20 and XT22 are the laser transmitters of the future, in every way.   

Take a look for yourself or visit the XT20/XT22 product page to learn more.

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The way you install your rotating machinery is the way it will perform!

Because of my many years of experience in the field of installation and maintenance of rotating equipment I can say that installation is a fundamental thing. But why is this phase so important?

Well, because the installation has direct impact on the machinery, and it will determine operating conditions, performance, and life cycle cost. Basically, the way you install your rotating equipment is the way it will perform. And personally, I always ask myself why companies buy million-dollar pieces of equipment and let inexperienced installers do the installation. Then, they spend another million dollars in condition monitoring watching them fail.

Don’t get me wrong; condition monitoring is extremely important to understand what is happening to the machines and detect an early failure. But the fact is that most of the failures occur due to poor installation and design. Here, let’s focus on the installation phase of rotating machinery.

What do we expect from our machinery?
  • Reliable operation – We expect our rotating equipment to deliver its intended purpose or service without failure.
  • High performance – We expect our equipment to perform as per design.
  • Long service life – If our equipment has been designed for 20 or 30 years of operation, that is what we want to achieve.
  • Low maintenance cost – We expect not to spend any additional money after the investment has been made.
Responsibilities towards the installation

Communication, Procedures, and Integrity. These are responsibilities which are so important in the installation phase. Let me explain:

Communication
It is a must to assure proper communication among the Design, Engineering, and Installation teams. We know there are constant challenges to keep the installation work to be on time and within specifications. The teams must have constant communication to be able to solve any difficulties or changes. In the real world not everything fits as it fits on the drawings. I think many of you have experienced this, right?

Procedures
Installation procedures must be created according to design specifications and every member of the team must be familiar with them. Depending on which industry, the procedures will differ from each other. It is not the same thing to perform installation on the nuclear plant compared to pharmaceutical industry. There should always be a reference to which specific standard belong to the site where the installation is taking place. API Recommended Practices for Machinery Installation and Installation Design (API 686) are the perfect foundation to start with.

Integrity
Integrity is an important part of the installation phase and it starts with Safety. Everyone who participates in the installation must go through safety training. Specific trainings must be performed such as working in heights, confined spaces, fire protection or chemicals handling. Breaking the safety rules will put the project behind the schedule therefore it is very important to follow them.

Always do things in the right order

The installation of rotating equipment must follow a certain order. The order of the installation procedure is designed to always start from the base. Foundations are the cornerstone of the entire installation. They are designed to hold rotating machinery and transfer and dissipate stresses and dynamic forces produced by pulsations and processes. Therefore, special attention must be paid to the foundations. They must be flat, coplanar, and levelled. If we skip the order of the installation procedures, we will not be able to complete further steps and not achieve reliable operation of our rotating equipment.

Finally, all the work must be properly documented during the process by creating digital reports to be able to review and compare the values and data. This is important for the references because further work will depend on the results.

Author

Roman Megela
Senior Reliability Engineer
Easy-Laser AB  

This article was originally published in MaintWorld Magazine

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The 4 different types of soft foot

Soft foot is a term we often use when we talk about shaft alignment. In fact, you must always perform a soft foot check before the actual alignment work can start; it is an essential part of securing a reliable installation. Let’s go through the different types of soft foot and why they occur.
 

By soft foot, we mean that the machine is not resting evenly on all feet. Another expression you may have heard is machine frame distortion.

Why do we need to check and correct soft foot? Can it be that big a problem if there is a tiny gap underneath one machine foot or a little pile of dirt under another? Well, yes. Because if the machine is not standing perfectly flat on the machine base, you can (and most likely will) run into problems such as shaft deflection, increased vibrations, bearing failure – and, in the end, machine breakdown. And that will be a lot more expensive than fixing the soft foot problem in the first place! Luckily, all Easy-Laser shaft alignment systems come with a program for soft foot check that tells you which feet you need to adjust and how much.

There are four types of soft foot which all have one thing in common: one or more feet are not resting firmly on the machine base. And there are different reasons for that. So, let’s take a look.

1.    Parallel soft foot

Parallel soft foot (sometimes also referred to as rocking soft foot) means that not all four feet are on the same plane. Think of a wobbly table at a restaurant, where you can rock it back and forth. In this case, the laser system software will show high readings (>0,05 mm) for soft foot at opposite corners. With a feeler gauge, you can determine which foot or feet you need to shim and how much. 

There are three possible reasons for parallel soft foot:

  • The leg is too short.
  • The base plate or mounting pads are not coplanar.
  • Missing shims under one or more feet.

To correct parallel soft foot, you add enough shims to remove the rocking effect (use as few as possible, and no more than four shims!).

2.    Bent foot / outside angled soft foot:

This is a common type of soft foot that occurs when the foot’s bottom is at an angle relative to the base. In this case, the laser system will show a high soft foot reading at three or four feet. The foot with the highest soft foot reading will show a tapered air gap from one corner of the foot to another. 

There can be several reasons for this condition, for example:

  • The machinery has been dropped or roughly handled.
  • The base plates are bent or poorly machined.
  • There’s a severe vertical angular misalignment.
  • The feet are welded.
  • Foundation settling has occurred.

The best way to correct this problem is to re-machine the feet, the base, or both. If this is not possible, step-shimming is an option (although you should try to avoid it).

3.    Squishy foot:

Squishy foot is sometimes also known as spring foot. With squishy foot, the feeler gauge won’t detect any gap underneath the foot. Instead, the problem is usually that the space between foot and base is filled with too many shims from a previous attempt to fix soft foot. There may also be a build-up of other unwanted material such as dirt or rust under the foot.  

Reasons for squishy soft foot may be:

  • Dirt, grease, paint, or rust between the foot and the base.
  • Too many shims (remember, you should not use more than four shims per foot).
  • Bent shims.
  • Shims with burrs or thread marks.

To get rid of this problem you need to thoroughly clean the area around and underneath the foot, and replace old shims with new, crush-resistant ones.

Here you can read more about shimming best practices.

4.    Induced soft foot:

Induced soft foot is caused by external forces that affect the machine frame, and it can be hard to detect. The laser system will indicate more than one soft foot, usually on the same side or the same end of the machine. The feeler gauge will find a gap, usually parallel or nearly parallel.

Some possible causes of induced soft foot are:

  • Coupling or pipe stress.
  • Overhung machines.
  • Belts or chain loads on pulleys and gears.
  • The flex conduit is excessively rigid.
  • Structural bracing is attached to the machine.
  • The jacking bolts are inadvertently left tight.

To correct induced soft foot, you need to remove the external forces that cause the problem. This may require more than one soft foot check since these forces can occur anytime during the shaft alignment process.

One step closer to trouble-free operation

Like we said in the beginning of this article: to correct soft foot is essential. No machine is designed to work under stress or with a high level of vibration, which are consequences of soft foot. So, make sure all feet are placed firmly on the ground (or base, in this case) and you have created the best possible conditions for perfect shaft alignment and trouble-free operation!

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How to deal with Thermal Growth

All rotating machinery is subjected to thermal exposure. The machines will react differently depending on temperature and material, either by expanding or shrinking. And that is a fact. Thermal growth is a serious thing when you think about it.

All rotating machinery is installed in trains. Trains mean there is a driver, the motor, and driven, which can be a pump, blower, compressor, or any other type of process machine. During the installation of rotating machinery, precision shaft alignment is performed. The shaft alignment will ensure that both shafts (driver and driven) are collinear. Collinear means that both rotational centerlines are positioned as if they were one.

The effect of heat on driver vs. driven

When the machines are started, the driver and driven heat up in very different ways. A compressor in a hot environment will quickly increase in temperature due to friction of its internal rotating parts, and compression of the media will generate and add more heat. Comparing to the driver, which can be an electrical motor, the situation is very different. The temperature will increase to a certain level and then remain the same — two machines with two different behaviors. 

So, what happens when one of them increases its temperature relative to the other? It’s simple; the machine will start expanding. And when the machine expands, it will grow in all directions, move its rotational center out of collinearity and cause misalignment. But not only misalignment. Since there is a change in the machine geometry, pipe strain might also add more stress to the housing

 

Take thermal growth into account from the start

There are so many consequences of thermal growth in rotating equipment. Misalignment will, for example, also result in a bent shaft. Bent shaft will result in improper distribution of forces in the bearing, which will lead to failure of the lubrication. Therefore, we must be able to anticipate thermal growth by using available information from the OEM, or by performing the calculation by ourselves. So how do we do that? 

The key is to identify how much growth to expect. This number must be used when performing the shaft alignment to “intentionally misalign” the machines prior to start. Let us use the compressor as an example again. If we assume that the compressor will operate at a higher temperature than the motor, when aligning, we must place the compressor below the rotational centerline of the motor. How much below will be determined by the expected thermal expansion growth of the material.

Final test run

When the machine is aligned with the thermal growth considered, it must run and operate until it reaches its full operating condition. Then it must be stopped, and the shaft alignment verified. This is our test run of the machine, to confirm a proper and reliable installation, and to achieve full operational life. We want to test before we go to full production to ensure our thermal expansion calculation was correct. 

Think about aircraft maintenance. When there is an aircraft engine replacement, the pilots perform test flights until it can be confirmed that everything is operating as it should. And you don’t want to be on the plane knowing nobody performed the test run, do you?

Roman Megela Gazdova
Senior Reliability Engineer, Easy-Laser AB

 

So now you know the importance of thermal growth, how are you going to factor this in? 

No problem with Easy-Laser’s XT app.

Simply enter in the offset & angle values and the program will automatically calculate thermal expansion of the machine.

Contact GVS to learn more.