Electricpete
I share hereby some figures that can illustrate the difference in stiffness or rigidity between Motor and compressor bearing
On the left side the NDE end which vibrates. string reduction by a tapered section, followed by a long distance to the bearing
not shown: details of...
Maybe final update after some work on site and evaluation
After presentation of results to involved parties it seems to be mutually agreed that
existing vibration levels are acceptable without further hardware changes
I share hereby some excerpts of the report and some facts about the...
Update:
measurement campaign finished
Report is created
no specially high excitations are found coming from compressor side as torsional or bending load with high frequencies
only raised noise floor detected
Problem identified as a resonating bearing housing
a fix will be tried out...
The compressor type is recently installed in similar cases and run without problems, but with other motors. I can't tell if the now used motor type Has references under same operation conditions. I will check if we can share additional info
Electricpete thank for your Input
we're still waiting for measured date form the field, before we can start with further Actions.
I'm lacking still a good and sound hypthesis able to explain our peaks in spectrumn.
So asymmetric stiffness looks like such an explanation term.
you mean you...
was you said is true
we checked also for possible failures in model data or model of calculation.
inertias and masses are somewhat easy to check, the most unreliable part is the stiffness of the complex system.
what we can not explain the high peaks around 120 and 225Hz.
the sheer height of the...
thank for the Input. the mentioned points are right
But maybe you get me wrong, we havent replaced old motors, we're faced with the problem form the begin on.
new motor should tell only we can exclude wear phenoma.
for your curiosity: the torque oscillations were calculated by simulation program (not measured in the field yet).
The spectrum is more or less normal for a 4 crank machine.
Depending on the different masses and compression curves for each stage one can expect also 3rd and 5th order.
3 can we...
the recip load comes from a reciprocating compressor which typically generates a series
of frequencies acc. FFT
Mto= 120.155 kN Mt=Mt0+SUM[Mt(j)*COS[j*ABS(w)*t-phi(j)]]
ord. j Freq [Hz] Mt(j) [kNm] Mtj/Mto [%] phi(j) [deg]
1 7.5 33.727 28.07% 235.6
2 15 5.754 4.79% 62.5
3 22.5...
We will start a measurement campaign in the field to analyse more closely the origin of the higher frequencies around 120 and 240Hz
For us it's still not clear if the harmonics point more to an mechanical or an electrical issue (if such an differentiation is meaningful).
That's why we placed...
During operation we experienced high vibration on the pedestal at nde side on new installed 6MW Motor, single bearing type, running speed 450RPM.
Harmonic spectrum showed peeks at 7.5 and 22.5Hz that can be explained by bending exciatation 1st and 3rd Order.
The calculated bending frequency of...
