Sign up Calendar Latest Topics Donate
 
 
 


Reply
  Author   Comment   Page 2 of 2      Prev   1   2
javaboy522

Member
Registered:
Posts: 5
Reply with quote  #16 
Hello Experts;
Good day. Here i attached some FFT signature of the Centaur 4702 Two shaft gas turbine from Solar Inc. 

In the spectrum you see the 2X peak is going high in a specifiq band of the GP (Gas producer speed) that is 88% to 91% of 15015 RPM. Before that and after that speed the 2X peak is well within limit. 

Please guide me what are the possible causes of that? Then we discus in detail on this thread.

The spectrum capture at the FWD end of the diffuser.

Regards

Attached Images
jpeg 2979357.jpg (119.83 KB, 16 views)
jpeg 2979358.jpg (120.53 KB, 16 views)
jpeg 2979359.jpg (120.67 KB, 14 views)
jpeg 2979360.jpg (120.67 KB, 13 views)

John from PA

Sr. Member
Registered:
Posts: 963
Reply with quote  #17 
Quote:
Originally Posted by javaboy522
Hello Experts;
Good day. Here i attached some FFT signature of the Centaur 4702 Two shaft gas turbine from Solar Inc. 

In the spectrum you see the 2X peak is going high in a specific band of the GP (Gas producer speed) that is 88% to 91% of 15015 RPM. Before that and after that speed the 2X peak is well within limit. 

Please guide me what are the possible causes of that? Then we discus in detail on this thread.

The spectrum capture at the FWD end of the diffuser.

Regards



Often this type of behavior indicates some form of resonance.
Ralph Stewart

Avatar / Picture

Sr. Member
Registered:
Posts: 235
Reply with quote  #18 
Quote:
Quote from javaboy522
In the spectrum you see the 2X peak is going high in a specifiq band of the GP (Gas producer speed) that is 88% to 91% of 15015 RPM. Before that and after that speed the 2X peak is well within limit.


Javaboy522,

I am unsure of what you are calling "2X" in your spectrums.

Are the ones which I marked in a copy of your spectrum shown below, marked correctly?

Thanks and Have a Great Day,
Ralph

1x and 2x.JPG


__________________
Ralph Stewart
AlertAnalytical.com
javaboy522

Member
Registered:
Posts: 5
Reply with quote  #19 
Ralph;

Yes u marked correctly. It is not a resonance behavior because it is not directional The 2X peak rise simultaneously on vertical and horizontal in the same time.

Regards 
Ralph Stewart

Avatar / Picture

Sr. Member
Registered:
Posts: 235
Reply with quote  #20 
Quote:
Ralph;

Yes u marked correctly. It is not a resonance behavior because it is not directional The 2X peak rise simultaneously on vertical and horizontal in the same time.

Regards


Javaboy522,

Thanks for the info. [smile]


My question now is concerning the "2x".
The "2x" does not appear to be a harmonic of "1x".
Have you confirmed 2x is, in reality, a "2x"?

If I measure from the "red" left hand border line to the "1x" position, the distance from the "1x" to the marked "2x"  does not appear to be the same distance. The "2x" appears to be a higher frequency than a "real" 2x.

Can you confirm this with your software cursors?

Thanks and Have a Great Day,
Ralph

__________________
Ralph Stewart
AlertAnalytical.com
John from PA

Sr. Member
Registered:
Posts: 963
Reply with quote  #21 
Quote:
Originally Posted by javaboy522
Ralph;

It is not a resonance behavior because it is not directional. Regards 


...and where did that concept come from?  
Vibe-Rater

Avatar / Picture

Sr. Member / Moderator / Supporter
Registered:
Posts: 1,398
Reply with quote  #22 
And all this mention of 1x and 2x and spectral plots are displayed in Hz not orders........ ? rgds

I know that's not particularly helpful.   Just sayin........
John from PA

Sr. Member
Registered:
Posts: 963
Reply with quote  #23 
Quote:
Originally Posted by Vibe-Rater
And all this mention of 1x and 2x and spectral plots are displayed in Hz not orders........ ? rgds

I know that's not particularly helpful.   Just sayin........


Hz, cpm, orders, that of course is another topic, and as best I recall it has been discussed.  Personally I prefer my frequency axis in Hz or CPM because in my own mind I can then determine severity.  For example, 2 mils pp at 1000 Hz will likely kill a machine, whereas 2 mils at 10 Hz will not.  The problem with orders is you need to know at least the fundamental speed of the machine, something that some people posting their problems here don't provide.

There is however, a time and place for everything.   
Batman

Avatar / Picture

Sr. Member
Registered:
Posts: 100
Reply with quote  #24 
I know this is not much relevant but out of curiosity, what software is being used by Javaboy please?
John from PA

Sr. Member
Registered:
Posts: 963
Reply with quote  #25 
Quote:
Originally Posted by Batman
I know this is not much relevant but out of curiosity, what software is being used by Javaboy please?


It's been several years since I've seen it, but the screen dumps resemble the Oros/NavGate software package. 
Ralph Stewart

Avatar / Picture

Sr. Member
Registered:
Posts: 235
Reply with quote  #26 
Quote:
Originally Posted By John from PA:

Hz, cpm, orders, that of course is another topic, and as best I recall it has been discussed.  Personally I prefer my frequency axis in Hz or CPM because in my own mind I can then determine severity.  For example, 2 mils pp at 1000 Hz will likely kill a machine, whereas 2 mils at 10 Hz will not.  The problem with orders is you need to know at least the fundamental speed of the machine, something that some people posting their problems here don't provide.


John,

My thoughts also. [smile]

I have used Hz since the early 1980's and will forever, I guess. [cool]

And John, you are correct, There was a discussion on this a while back.

The way I see "choices"  is, "To each his own.".

It is a possibility that no matter how much others "criticizes" another for not using the "Criticizer's"  frequency units of choice, be it ORDERS, Hz, or CPM, they are going to use what they want or feel comfortable with using.

Only my opinion and I could be totally wrong, but probably not. [smile]

Now, back to the current case. [confused]

Thanks and Have a Great Day,
Ralph

__________________
Ralph Stewart
AlertAnalytical.com
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.