Dear all,
In GT, high vibration in Hydraulic starter(24 mm/sec rms) Particularly showing 7 times. Indicating might be plungers(7)How we could finalise really plunger is making or flow related???? Previously (2-3 year back condition was good)
Thanks in Advance.

Hi Gurusamy,

Is the high vibration reading only during GT startup or are you seeing this during steady state operation? Could please post some spectral profiles of your measurements?
Thanks

Rajan Muthukrishnan

Dear Rajan,
During GT start up only. But previously the level was low only. We called GE for doing analysis, they have given Plungers to be checked. (4 years back)
Now the trend is incresing.

Gurusamy,

It is difficult to make a call without seeing the vibration spectra. Based on what you have described it could very well be one of the pistons/plungers may be damaged. If this is the case, you may need to check the bearings, too; you should see bearing fault frequencies in the spectra, may not be as pronounced as the 7x. harmonic.

Cheers...Rajan Muthukrishnan

Once i receive the FFT from my consultant i will post it. Please bear with me....Presently i am having Old FFTs (1 Years Old one)Attaching the same for your ready ref.

This is a one year old plot, is the Starter still running at the amplitude seen here or has it changed? There are quite a few high amplitude harmonics and modulations, coupled with raised floor noise, on the plot. Can't see flow/pulsation alone generating this type of spectral profile. I'd be more inclined to suspect one or more plungers to be damaged. If your current level/profile is similar to the attached, you very likely have damaged starter.
If you have a stethoscope handy, it would be an idea to listen to it while it is disengaged. But, please make sure you have applied for relevant permits and work safely. Let us know what your findings are.

Cheers...Rajan Muthukrishnan

We are waiting for a start up...soon i will get back in this ...
Thanks...Hope r u from Tamilnadu?
Gurusamy TA

Hi Gurusamy,

Is the unit shutdown at the moment or R U awaiting startup to check the starter?
My grandparents are from Tamil Nadu but, I hale from Malaysia and residing in Canada, now.

Cheers...Rajan Muthukrishnan

while pressure shoots up to 300 bar that time the vibration goes very high 22 mm/sec rms. After two to three minutes it came to 8 mm/sec. and further it goes down...
Its Rubber mounted base.
Regards
Gurusamy TA

Dear Mr.Rajan
We started our hydraulic machine found 18mm/sec in pump Vertical. 1X and 2X and small 7X observed. What will be cause....


FFT we cant send it to you, bcos VT 60 we are using our software is not working.

Hi Gurusamy,

The amplitude continues to be high and assuming the spectral profiles are unchanged when compared to previously posted signatures. I still believe you potentially have damaged plunger/s. Remember, the starter is compact and assembled to tight tolerance and so, even if the internal parts are damaged/worn, it will very likely continue to function as designed; until there is severe damage/seizure. I see that the unit is shutdown from time to time. If you have a spare starter, new or refurbished, it would be an idea to swap this with the installed unit; during the shutdown. On the hind side, the starter seem to be performing thus far, with the high vibration condition it is in, all this while....do you really wish to intervene at this point?? Something to ponder over before acting.


Regards...Rajan Muthukrishnan

Dear Mr Rajan,
Please tell me whether it leads to catastropic fail. These pumps are running in same condition and developing the rated pressure to rotate the Gas turbine.
Tell me when pump reaches around 300 Bar, what max. can go.....
Expecting your reply.
Gurusamy TA

Gurusamy,

I've not had this experience and so, can't really relate to real life situation. But, worse case scenario, when 300 bar pressure is attained and the torque cannot be delivered due to seized plunger/s, I guess two things can possibly happen ie. 1) the turbine may fail to start and/or, 2) the pump seals may rupture due to pressure buildup and leak. However, your best bet is to consult OEM for their opinion/advise.

Regards....Rajan Muthukrishnan

Gurusamy, I have found that a partially clogged suction filter in a positive displacement pump can produce a high vibration while pumping satisfactorily.
Regards,
Joe Mc Cormack

Guarasamy,
How long running until vibes smooth out? is the oil cold when you start up? does the oil tank have a heater? I'm not familiar with equipment you mention but these are just some thoughts

Jonesy, Good thoughts! I'm with you, check the simple things first. Take a step back and ask yourself what has changed over time. Get some oil analysis done, its cost effective and can help determine if there is any wear particles in the system. A filtergram on these particles will also help determine whet type of wear is present.


Hooch

gurusamy,
I have seen also on positive displacement pumps, they tend to have pulsation dampeners on both suction and discharge of the pumps. Lack of pressure on these dampeners tend to have a similar spectrum that you had back there which is X number of times = number of plungers.

Just my 5 cents...