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RustyCas

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Reply with quote  #1 
Below is a spectrum taken on a small(ish) diesel engine, horizontal position, on the engine mount above the rubber isolator.  I've rarely ever done a diesel engine, so don't know what is considered normal.  In this case there is no reason to suspect a problem.  Does this look normal?

Maerz Kiln Emergency Fan Engine.png


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Walt Strong

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Spectrum looks typical and a little high amplitude, but more information is needed. The 1/2 order indicates probably 4-cycle engine. Diesel/gas engines are not like an electric motor or centrifugal pump!

With Diesels it is important to note whether 2 or 4-cycle and number of cylinders. Speed and load can have a significant effect on vibration levels. I keep the vibration measurement points at shaft elevation, unless doing an ODS test. The CAT engine folks have vibration criteria based on displacement and velocity. ISO also covers diesel engines.

I have found torsional vibration measurements to be very effective for diagnosis of engines with high vibrations. Ultrasound is good for detecting faults with fuel injectors and fuel pumps. Exhaust temperature with IR meter can detect fuel and valve issues. A tach-synchronous (reference TDC) vibration waveform can also detect cylinder and bearing issues. There are special-purpose diesel engine analyzers that primarily measure performance with dynamic pressure, but they include vibration and ultrasound for multi-channel measurements.

Walt
John from PA

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Reply with quote  #3 
Quote:
Originally Posted by Walt Strong
With Diesels it is important to note whether 2 or 4-cycle and number of cylinders.

Walt


I’d add firing order; usually it can be found on the nameplate.  Needed if it becomes necessary to get involved with a torsional study.
Walt Strong

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Firing Order; another essential detail to understand engine dynamics when a "problem" is present! Might as well add shaft coupling type and auxiliary driven components.

Walt
fburgos

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looks normal to me, 1/2x and harmonics.... my knowledge on ICE is overall trending, zero diagnosis
OLi

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I have done balancing in the flywheel on beasts like that, you can see alignment problems as usual and on occasion I use standard bearing condition measurements on the injectors to verify that they all are the same or not. Once a serious camshaft drive train failure, confirmed by major visible iron flake content in the oil.....
From time to time we have discussions here if the generator would be following 10816-3 or the specific standard 8528-9 it depends on if you are selling or buying I guess.

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