Hi all,

In our company we have one lube blower that has high vibration, the spectrum shows several armonics of lube blower (it has 2 lube), i attached some pictures of this. We cleaned the filter yerterday but the vibration keep up.
I would like to hear some comment of your experience about this kind of symtoms

thanks,

Fabian Buzon

GRAFICAS_DE_ESPECTROS_DE_COMPRESOR__P-5331_11-AGOSTO-2006.doc (134 Kb, 29 downloads) GRAPICS

HI Fabian,
Roots compressor usually runs with multiple harmonic of lobe or vane pass frequency. I found that those harmonics may rose a lot either the compressor is loaded or not so you must ensure that you collect data while the compressor is loaded. The compression is adiabatic constant volume compression. The roots opens in the inlet side which create a suction effect to fill the opening space then that space is moved from a low pressure side to a high pressure side instantly. The opening of the pumping vessel in the high-pressure zone creates a shock wave backward or against compressed fluid and compressor’s rotation. I believe that the harmonics comes from that particular shock wave and are dependant to the output rate, pressure differential and probably piping as well. To make things worse those I have seen are mounted on isolators, which do not, damped the vibration very well. My compressor (Atlas copco, GA160) runs between 0.15 ips to 0.5 ips depending on direction and position of the sensor.

Best regard, Marcel

I got a different idea about what type of blower Fabian has. The A-C GA160 is a screw compressor with a 4 and 6 lobe screw arrangement. This sounds to me like a positive displacement blower with two rotors that each have 2 lobes and a timing gear set.

If that is the type of blower, then it is common to find an increase in amplitude at 2 x blower shaft speed and it can be caused by clogged filters (which you have already eliminated), material build-up on the lobes, or looseness in the shaft or bearing fits. Material build-up is fairly likely.

It looks like there are some sidebands around 4 x running speed. I would look at the spacing of those sidebands to see if there is any clue there as to the cause.

The amplitudes are not extremely high for this type of blower. Is this a sudden change? Is this unit higher than other similar ones?

Good Luck,