reason of the vibration on the motor

[ngrs1967]

Dear All,

I have 2 electrical motor for the double hammer crusher.During test run we have meausured high vibration. I believe we made realy good alignment on the coupling but we could not solve the problem. I published the graphic which show the status and I need some advice for the graphic.

Thanks in advance

ngrs

 

[drawoh]

ngrs1967,

Your problem is not clear to me. I would be very surprised if something called a double hammer crusher did not vibrate. Are you concerned that vibration is being transmitted back to your motors?

JHG

 

[TPL]

Define high vibration? What criteria are you using to judge the severity? Is the vibration measured in peak or rms terms?

Taking your data at face value, your vibration is predominantly 1X with 3.4mmsec@354 deg (H) and 1.7 mm/sec@245 deg (V) - looks like residual unbalance - but the foundation/mounting method will be contributing to the vibration seen.

Why have you assumed alignment is an issue? What is the history of this unit? What are your concerns? Have you just acquired a vibration data collector and are seeing things that have been there for a long time? Have you had failures?

 

[electricpete]

The vibration is up to 7 mm/sec rms.
The phase relationships shown would be quite unusual for motor unbalance. (H are in-phase IB/OB, while V are 180-out IB/OB).
Are the axial phases corrected for sensor orientation?
Has vibration been measured on the driven equipment and base?

=====================================
(2B)+(2B)' ?

 

[electricpete]

Another way to describe the phase relationships is that the direction of rotation of the 1x vibration orbit is opposite on the two ends of the motor.

=====================================
(2B)+(2B)' ?

 

[ngrs1967]

Dear all

at first thank you for interest. I have just install the electrical motors with crusher. It means, these are the new equipments.At first the vibration was 17 mm/sc. I have put addtional concrete on the frame and it is reduce a little bit.

 

[TPL]

EPete:

I only got the first couple of pages downloaded - how do you know vibration is in rms terms? Do you use similar equipment?

Are the phase angle readings relative or absolute? The phase angle difference between V and H suggests that a single balance would work if you could get access.

Additional concrete on the frame caused vibration to reduce - are these units mounted on springs/inertia bases?

 

[electricpete]

how do you know vibration is in rms terms?

Most people who report vibration in mm/sec are giving rms values in the same way that most people who report vibration in ips are giving peak values. Probably moreso, because ISO specifies vibration in mm/sec rms.

Are the phase angle readings relative or absolute?”

I consider them relative. Even if a keyway was used as a reference and phase sensing biases are known, what possible use could this be to your remote analysis?

? The phase angle difference between V and H suggests that a single balance would work if you could get access.

One end of the motor has H phase 90 degrees more than V.
The other end of the motor has H phase 90 degrees less than V.
As noted above, that gives orbit with opposite direction of rotation on each end.
In theory this might represent a balance forcing function combined with a complicated modal response, such as horizontal rocking (parallel to axis) combined with vertical pitching (pivoting about a point in center of motor), but that’s not likely imo… and I don’t think it would be corrected by a single-plane / static balance solution if pitching type response is excited by unbalance. Just my opinion based on my own experiences fwiw … but machines have fooled me before.

Nqrs1967 – to confirm/disprove misalignment, you might try uncoupled run.
There are several questions asked but not yet answered above.


=====================================
(2B)+(2B)' ?

 

[drawoh]

ngrs1967,

So what has actually happened? You have a double hammer crusher. Your motors are vibrating. The vibration goes down when you add concrete to your base.

The activity of hammering and crushing ought to cause vibration. You can prevent your machine from shaking your motors by mounting them on a separate, isolated platform. Vibration will be transmitted through the floor, and through your driveshaft. Axial and radial vibration can be isolated by a splned, double U-joint. Non-constant torque will be transmitted through your shaft, and will be an awkward problem to solve.

If your double hammer crusher is shock mounted, you are creating a degree of freedom that allows vibration. I have solved vibration problems by mounting equipment solidly to the floor, although it was not heavy duty industrial equipment.

Adding concrete may have increased your mass, changing your harmonic frequency. If you moved your harmonic frequency away from what your machine is doing, the vibration would go down. There are lots of possibilities here.

If you disconnect your motors from your machine, do they still vibrate?

JHG