Hydrogen Compressor

[FLeroux]

Sorry for my english,

I have on the motor, at the point rear axial, a big peak at 12x RPM and some sidebands.

The compressor is a Garden denver an I think that he can't made this frequency.

Technicals informations:

- motor on babitt
- disk coupling
- pistons compressor (2 stages) (4 pistons)

Do you have a idea ? resonance.....

 

[Crusher]

Mr Fleroux,

The Gardner Denver vibration may be caused by the compressor cycles (3) times the rpm.

 

[ronfrend]

Please give us the amplitudes at each position in each direction. What is the actual speed of the motor and what is the exact frequency of the axial vibration?

I assume that the motor thrust bearing is at the free end - if so the cause of high axial from the thrust bearing can only come from the coupling (misalignment) or from the rotor.

ron.frend@predicon.net

 

[ronfrend]

Frederic,

I received the amplitudes OK but no spectrum. Could you send the spectrum again as a picture file - either BMP or JPG?

From your description it sounds as though you have a J type compressor. In the J type you have 3 LP stages which are mounted at 120' apart with the HP stage at another 120' after the last LP. This will give a frequency of 6x run speed (360/120) for single acting and 12x run speed for double acting. You should almost certainly also see sidebands of run speed around your 6x or 12x due to the asymmetric mounting of the cylinders.

However I would not expect to see very high axial readings. In this sort of setup almost all of the axial thrust is taken by the motor thrust bearing so I think you should look at the alignment between motor and compressor and also check your compressor bearings either by checking the radial clearances or taking an oil sample. My train of thought here is that if the there is a problem with the compressor bearings you may get an axial component of the vibration which would show up at the motor thrust bearing.

I have also had a problem like this once when the motor rotor was out of magnetic centre. This does not happen gradually but usually after a bearing change which causes the rotor to be in a slightly different position axially. Contact your motor vendor for advice on how to correct this if it is the case.

ron.frend@predicon.net

 

[ronfrend]

Frederic,

Received your spectra OK thanks.

Don't bother with the misalignment or rotor magnetic center. I am confident that the vibration is coming from the compressor. But why high in the axial direction? For some reason your crankshaft is pushing out vibration axially. I would suggest looking at the compressor crankshaft and check bearing journal clearances on the main bearings and the crankpin. Also check that the crankshaft itself is not damaged.

Good luck

ron.frend@predicon.net

 

[ronfrend]

Thanks for the email message saying that the problem was caused by a problem with the compressor crankshaft. Glad to be of help.

ron.frend@predicon.net