Dynamic measurement – are you missing a checkbox?
19 August 2020

Dynamic measurement – are you missing a checkbox?

I want to start by making you think about car manufacturing. You can pick any car manufacturer you want.

The way they build cars is based on their procedures which comply with international standards. Once the vehicle is built it goes for quality inspection. There the individual systems are checked making sure they are working as intended. Is then the car ready for delivery? No, of course it is not. The individual vehicles are going for testing and the car runs on the test bench for a certain amount of time. That means the quality inspection will assure that the whole system works perfectly together and is fully integrated.

How about rotating machinery?

So, what do we do when it comes to the maintenance and installation of rotating equipment? Do we test the machines before they come into the operation? We know some of the manufacturers of rotating equipment are individually testing and certifying their machines before they leave the facilities. But that does not necessarily mean that whole systems will be integrated together and work properly. In that scenario, it is like you buy your new car without it being tested. Get it, drive it, and find out for yourself if it works. Sounds safe and reliable?

What are dynamic forces?

In the assembly and installation phase, the rotating equipment is being installed. Only that. Then it is handed over to pre-commissioning and commissioning teams where the equipment is going to be tested. The commissioners will run the process and check vibration, temperature, and pressure. Here is where dynamic measurement comes in place.

Dynamic measurement is on-site laser measurement which is performed to measure and show movements of the machinery when in operation. Thermal growth, pipe strain, nozzle load or any other dynamic forces which affect our equipment. For example, how does pipe strain affect our asset? Pipe strain is the misalignment between the suction flange of the asset and corresponding pipe flange connection. This misalignment makes deformation of the body of the asset and as consequence stress the bearings which leads into an increase of vibration. The similar thing happens with thermal growth, the machine condition where the increased temperature of the asset will change its physical condition making it grow in vertical and horizontal direction compared to its shaft centreline.
 


 

This will lead to misalignment which produce shaft deflections. And again, this will stress the bearings and produce vibration. When the shafts are deflected, the bearings get to carry different loads than for what they were designed. We expect our equipment to be stable and solid. In the case there is unexpected movement, dynamic measurement will show us how much and in which direction the movement occur. This is a final test prior to enter into full operation and certify proper installation.

How does it work?

When the machinery is installed in place and final laser alignment has been done, the lasers will be mounted on the machinery using special dynamic measurement brackets. Now you will have two choices, to start measure offline to running or running to offline. That means you will start measuring from the ambient temperature and run your asset until it reaches full operating conditions, or vice versa you will start measuring at full operating capacity and let the machine run to stop and cool down to ambient temperature. That will provide you with the full picture of how your equipment behaves under the load. Then you have your data so you can have a plan for necessary corrections. This is one very important part of reliable machinery installation.    

Roman Megela Gazdova
Reliability Engineer

 

This article was originally published in Maintworld magazine.

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