We have a unit cnsist of 3 stage compressor LP,IP&HP. the high vibration reading was on the HP Drive End (DE) bearing only. This bearing was connected to the Non Drive End (NDE) of the increaser gear box the domenant frequncy was 1x. So, we dicide to do site balancing for this unit.
My Q is : where should the angle of the correction wiaght? is it with the rotation? or opposit the rotation?

if there is any Q please feel free to ask

reagrds

..............rotor.........................

The collector I use goes opposite rotation as has every post or topic I've read. I think thats common practice.

The Entek 1500 can be set to do either way. I use with rotation. Don't know why, just that's the way I have always done it.

Dave

Dave, I guess I'm a little confused. Since a TTL tach measures phase opposite rotation, how can we use "with rotation"?? Does it just not matter when the program does the calculation? (Something else to experiment with I guess)

I also use a DataPac 1500 and use with rotation. When you select with rotation or against rotation it will calculate for you You just got to make sure you put the weight at the right degree.
Gary

Gents,
as per Bently Nevada i think most of you heard about it, they are telling that you should go againset the rotation.
we tried our self in the rotor kit(simulator)and we put the CW opposit the rotation and it was done sucssfuly.
if anyone has got any information please shoooot it up.
regards ............rotor............

People have used all the conventions for balancing. The balance program takes into account some convention; some programs have allowed for various conventions. Most people use against rotation for adding the weights.

Bently has used against rotation in their programs. Just to be sure that you have the correct idea, make sure that you haven't just balance a rotor with a 0 or 180 degree phase for the balance weight, because 0 and 180 are the same for against or with rotation. CW and CCW can lead to trouble; stick with ˜against rotation' or ˜with rotation' as the software requires. Remember, the same rotor rotates both CW and CCW depending upon where you stand.

By the way the trigger has nothing (little if any) to do with whether one applies the balance weight with or against rotation or whether the vibration is measured in lag or lead angles. The instrumentation package determines the lead lag convention.

If one measures in lag angles (lag as a positive lag – over the years some have put a negative sign for lag, including Bently in an old software package, which in my mind converts the lag angle to a the angle a lead angle.). Using against rotation for the balance weights, gives a consistent angular convention. The balance weight angle convention is associated with the force input coordinate system for the balance problem.

I've use RTA's to do a lot of balancing and they typically measure 0-180 + or -. On a polar graph with zero on top and CW rot minus is to the right.

If you only have one point indicating imbalance in a gearbox; what leads you to conclude that you need to balance 'a spot'?

Are you sure you are dealing with unbalance?

Sam brings up the essential point. Is this a balance job? At least do a coastdown analysis. What has changed?