direct coupling alignment

[petronila]

Dear Friends

We are going to couple a 1500 HP -4 Pole- sleeve bearing electric motor with one Hellicoidal gear box, is direct coupling, the problem is the process start with in no load for 30 minutes and later take total load so is not a continuos duty.

Wich considerations we have to take account for a good alignment including termal expand and all this? The shaft diameter is 4.5 inches.

Thanks and regards

Carlos

 

[rbulsara]

1500 HP motor and drive? All the precautions you can think of and know. There are professionals who do alignment and vibration analysis for living. Hire them. Follow manufacturers' recommendations, that includes mfrs of the coupling, the motor and the gearbox.

Continuous duty or not has no bearing on the alignment. Type of coupling and gear box may be.

Rafiq Bulsara

http://www.srengineersct.com

 

[rbulsara]

In short leave this to mechanical engineers or post in a mechanical forum.

Rafiq Bulsara

http://www.srengineersct.com

 

[electricpete]

It seems like you have 2 choices:
1 – compromise alignment – midway between target corresponding to no-load temperature and target for continuous run temperuatre.
2 – ignore startup and focus on continuous run conditions.

I am inclined toward #2 because I’m guessing the time spend running at load is a lot longer than the 30 minute no-load.


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

 

[electricpete]

Actually it can take most machinery more than 30 minutes to reach equilibrium anyway. So again that argues for #2.

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

 

[MikeHalloran]

At that power level, with a sleeve bearing device involved, direct coupling is just stupid.

How long will it take for the replacements to arrive?



Mike Halloran
Pembroke Pines, FL, USA

 

[electricpete]

I'm not sure where you're coming from with that comment Mike. To me "direct coupled" means that a flexible (or rigid) coupling is used instead of a belt. That seems pretty common to me in sleeve bearing applications. Using a belt on the other hand would seem stupid to me.

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

 

[electricpete]

What I meant to say was not “stupid”.
But it is not common to use belts with sleeve bearings.
On the other hand direct coupled is very common with sleeve bearings.
And a great many of those direct-coupled sleeve bearings machines endure brief periods with less than optimal alignment on the way to thermal equilibrium. It is not ideal, but we have many that operate that way reliably. The question can be a matter of degrees (how misaligned)...none of us can answer that without knowing more.


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

 

[MikeHalloran]

Pete, I read the OP's use of 'direct coupling' to mean 'rigid coupling'.

If a proper flexible coupling is used, then there should be no particular concern about alignment changing with warmup, etc.



Mike Halloran
Pembroke Pines, FL, USA

 

[petronila]

Thanks for the answers Pete, the problem goes more far of the good alignment, we was made a vibration analisys and we found strange vibration level in the gear box (2X) so we think maybe the problem could be wrong alignment.
I will attach the analisys later to know your comments.

Regards

Carlos

 

[petronila]

Hello Pete and Friends

The vibration analisys is attached all report is wrotte in Spanish but all data was collected with SKF instrument and the keys are the followings:

Figura 4.1 Global vibration levels in NDE Motor
Figura 4.2 Vibration Spectrum NDE Motor
Figura 4.3 Global Vibration levels DE Motor
Figura 4.4 Vibration Spectrum D.E Motor
Figura 4.5 Global Vibration Level in Gearbox
Figura 4.6 Vibration Spectrum in Gearbox

NOTE: Gearbox is double helicall, reducer.

Thanks for the inputs

Carlos

 

[petronila]

The vibration analisys is attached all report is wrotte in Spanish but all data was collected with SKF instrument and the keys are the followings:

Figura 4.1 Global vibration levels in NDE Motor
Figura 4.2 Vibration Spectrum NDE Motor
Figura 4.3 Global Vibration levels DE Motor
Figura 4.4 Vibration Spectrum D.E Motor
Figura 4.5 Global Vibration Level in Gearbox
Figura 4.6 Vibration Spectrum in Gearbox

NOTE: Gearbox is double helicall, reducer.

Thanks for the inputs

Carlos

 

[edison123]

With all those 1X and 2X, it looks to me like a misalignment. How was the motor aligned ? Laser, dial gauges ?

Muthu

http://www.edison.co.in