Hey Guys (& gals),
Need some help!

Attached are some spectrals and TW's from a 150HP pump/motor assembly that's exhibiting some very defined vibration - .8315 in/s @ 5454 CPM which is 3x's Operating Speed (1818 RPM - ASD @ 61Hz). At the moment I'm a little baffled and although I'm still looking, I'm looking for some help/ideas/comments and or other avenues to chase.

The pump is a Goulds 8x10-14 in a paper stock application driven by a 150 HP @ 1800, Siemens with a Toshiba ACVF drive.

41PMP4014_-_2006-11-08.doc (154 Kb, 42 downloads)

Hello there!

That looked very familiar.See my post further down.
Looks like one of mine.Especially in the waveform.
Can't tell anything usefull, because im still struggling myself.

Likely it has been already verified but I will ask anyway. Does # of vanes have something to do with # 3?

Dave_G,
The impeller is a 2/4 configuration.

Denny C,

Is this a new installation (Pump/Motor), Vertical/Horizontal machine? The amplitude is quite severe...do you have an increasing trend or is this a sudden occurence? Is the 3X appearing at the Motor (DE/NDE) or is it at the Pump only?

Thanks...Rajan

RajSha,
This is a horizontal pump application that been in service for years. The vibration at 3x's is across the unit although most severe at the pump DE.

The onset of the 3x's is new. I've attached some additonal info as well.

41PMP4014_-_2006-11-09.doc (126 Kb, 19 downloads) Vibration Analysis

Denny C,

Looking at the waterfall plots of both Motor & Pump, I wouldn't say the 3X is a recent occurence; increase in level may be recent.
Is the Pump experiencing seal problems/ failures...was there any Maintenance done recently or prior to the increase in amplitude? Is the Motor/Pump installed on grouted foundation or I-Beam Skid?
Answers to these may shed some light.

Thanks...Rajan

Rajan,
You're correct the 3x's isn't new although the levels have increased dramatically. The WO history doesn't reveal any problems with seal and/or other components. Unfortunately I have to be somewhat sceptical of what's recorded as the mechanics don't always log there actions.

The pump is set on a grounted cast base and secure. Vibration levels on the base are minimal.

Denny,

What type of shaft coupling is in use?

Good Luck,

Denny C,

Thanks for the info. What I suspect may be a potential contributor to your vibration problem is, misalignment...not just at shaft/coupling but very likely caused by piping strain. Perhaps look at the last alignment readings, if you have the records.
Also, I suggest you look for tell-tale signs at site such as, cracked grouting particularly anchor bolt locations, leaky seal and pipe joints...doesn't have to be severe faults.
Your vibration amplitude is quite severe hence, would require prompt action.
Keep us posted.

Good Luck...Rajan

Danny,
The coupling is a Dodge paraflex (elastomeric element)spacer coupling with taper-lock flanges.

Rajan,
Thanks for the great input. Our alignment guys are very good so I suspect it's OK although I will follow-up with them. They do keep good records.

I haven't noticed any cracking, etc. although I'll do a closer inspection now that you've raised the subject. I'll also take a look at the other items you mentioned.

This pump is critical to this 24/7 operation and thus any downtime at all is undesirable. Identifying the source (of this vibration)would be very beneficial both tot he company and our PdM program.

Thanks for your help!