Vibration issues

A place to exchanges questions and ideas of a technical / procedural nature. Go ahead, try to stomp us !
46Tall
Bilge Dweller
Posts: 9
Joined: Fri Oct 14, 2011 8:32 pm

Vibration issues

Postby 46Tall » Tue Jul 08, 2014 11:07 am

Looking for some help regarding a vibration issue.
We have a 900RPM inline 9 engine driving a 4160V alternator, 3 phase, 2125kVA and are experiencing vibration in the alternator housing. Everything has been checked and re-checked including bolts securing housing to the stator, the stator itself is steady. The drive engine mounts have been checked as well as crankshaft deflections taken, all being acceptable.
Anybody out there have any thoughts suggestions that may help us?

User avatar
Big Pete
Engineering Mentor
Posts: 814
Joined: Fri Apr 24, 2009 11:18 pm
Currently located: Solihull, England

Re: Vibration issues

Postby Big Pete » Tue Jul 08, 2014 11:15 pm

Have you taken power cards/Peak pressures to make sure the engine power output is balanced?
Have you checked the coupling/vibration damper between the engine & the alternator?
Alternator bearings, are they Ball/Roller or plain?
Is there any electrical problem? unbalanced amps between phases? Weird Power Factors?
Did you discover this vibration manually or by taking vibration readings for analysis?
Could the Rotor windings be moving in their slots?
What sort of frequency is the vibration? (Linked to 60Hz/3,600 RPM which would indicate an Electrical problem, or 900 RPM which would indicate a mechanical problem on the engine, or 450 RPM (for a 4 stroke engine) which would indicate imbalanced cylinder power outputs from the engine.
Lots of questions, but we need background information to work on.

Good luck.

B.P.
It is always better to ask a stupid question than to do a stupid thing.

User avatar
D Winsor
Superintendent
Posts: 331
Joined: Thu Nov 22, 2007 8:23 am
Currently located: Dartmouth

Re: Vibration issues

Postby D Winsor » Wed Jul 09, 2014 4:21 am

Has the flexible coupling between the rotor and the engine flywheel been overhauled lately? These couplings do wear out over time and on propulsion engines the flexible couplings are a class item making it a requirement to overhaul the coupling every 5 years
Has the alternator rotor been checked for proper dynamic balance or vibration analysis? It is possible that the rotor could have thrown a balance weight.
Has the alternator overheated lately? If so it is possible that there has been some creep of the copper in rotor windings that would throw the rotor out of balance.
Has the rotor been cleaned? Dust and dirt from the atmosphere collecting in the rotor could also throw the rotor out of balance.
Troubleshooting 101 "Don't over think it - K.I.S.S. it"

User avatar
Big Pete
Engineering Mentor
Posts: 814
Joined: Fri Apr 24, 2009 11:18 pm
Currently located: Solihull, England

Re: Vibration issues

Postby Big Pete » Tue Jul 15, 2014 4:41 am

Hi 46 Tall,

What propgress are you making?

B.P.
It is always better to ask a stupid question than to do a stupid thing.

User avatar
JK
Enduring Contributor
Posts: 2694
Joined: Tue Sep 04, 2007 2:29 am
Currently located: East Coast, Canada

Re: Vibration issues

Postby JK » Wed Jul 16, 2014 5:42 am

What is the machine maker?

I have run into vibration issues caused by the structure under the unit. There was a damaged stiffener under the corner of the engine raft which translated to a vibration in the engine.

rodrigger
Tanktop Cleaner
Posts: 15
Joined: Wed Jul 20, 2011 10:06 am

Re: Vibration issues

Postby rodrigger » Wed Jul 16, 2014 9:48 am

We have a 900RPM inline 9 engine driving a 4160V alternator
. Is it a Bergans coupled to a Siemen's alternator 4160V?. Check out all the above suggestion. If you are located in BC coast and if its Siemens alternator, give JC Controls in Seattle ( Jeff Chia, P.E) a call, he is a expert on those machines

User avatar
JK
Enduring Contributor
Posts: 2694
Joined: Tue Sep 04, 2007 2:29 am
Currently located: East Coast, Canada

Re: Vibration issues

Postby JK » Thu Jul 17, 2014 5:16 am

Siemens generators will not tolerate overspeeds beyond a certain point. If you are aware of that engine overspeeding, you are well advised to get the machine checked out.
Have you taken air gaps?


Return to “The Workshop”

Who is online

Users browsing this forum: No registered users and 3 guests