Hi,
I have a problem with this pump recently. It's ebara’s multistage boiler feed water pump (10 stages) drive by 6.6KV motor with a inducer gearbox. Input speed 2800rpm and output speed 4600rpm. The spectrum show dominant 7x peak at Pump DE and dominant 9x peak at MDEA. The number of blades was unknown so I just assume that 7x peak is blade pass frequency and 9x peak is due to resonance. How to confirm this? If it is true how to correct it??? Your help are really appreciated. Thanks.

Regards,
Rizal

I'm posting some of the vibration spectrum. Please help me.Thanks.

Regards,
Rizal

P3200B.doc (93 Kb, 103 downloads) BFW-B

The impellors don't have to have the same number of vanes. You need to track down this information.

Hi Bill,
Thanks for your reply. The pump has 10 impellers. Sorry, i missed your point can you advice more? Thanks in advanced.

How many blades (vanes) are on each of impellor? The impellors may not all have the same number of vanes.

Hi Rizal,
What is in your gearbox? Could the 9x be a multiple of the gear mesh?

Best regard, Marcel

Bill,
Thanks for your guide. I will find the information later because i'm at home right now. Can we just assume that the 1st impeller has 7 vanes due to it's the one very near to Pump DE? Errm...it seem that 7x peak also appeared at Pump NDE but with very low amplitude compare to Pump DE.

Regards,
Rizal

I wouldn't assume anything, just ask the pump vendor if this information isn't in any manuals. Has anyone opened the pump before? They may know.

Besides this, where is the pump operating on the pump curve? If you have the individual stage curves this could be of benifit. Vary the flow to determine the affect on the vibration (Are you operating around BEP?).

Did the pump vendor stagger the vanes, or did he line them up?

Check on the various operating parameters; does the piping have an automatic minimum flow by-pass or problems with it - else Bill gave the things you must know - gather information first.

Marcel,
The GMF is more than 9x it’s 46x I believe. Thanks.

Regards,
Rizal
**Ping**
My internet connection is too slow....I think I need to seek for broadband
<End>

It would not be unusual for one impeller to have 7 vane and another to have 9 vanes, as Bill said, you need to find out from the OEM what the configuration is.

Hello Rizal,

Kenal saya tak Bang?? Sorry guys for the Double-Dutch...use to be an ex-colleague!
Rizal has gone quiet, unsure if the Pump has suffered an outage or his internet speed/connection is toast.
Can you provide vibration levels recorded on the train...spectral data would be better??
Hope all is well.

Regards...Rajan

If my eyes do not prove me wrong, is that a 1XTS side band appearing just around your motor spectrum around your 9th order?

Hi,
Thanks all for your input.

Bill,
I manage to get the pump curve but I have no idea what is BEP? Is it Best Efficiency Pressure? And where the BEP suppose to be in this pump curve? Could you help me? Regarding the vanes, the vendor still waiting reply from Japan.

Hi Rajan,
Rajan yang mana ye? Yups….bad connection…. Streamyx much better….hahahaha I’ve attached the overall vibration report.

Hello Wookp,
Yes there’s side band 8x & 10x. Errm…..what the side band surrounding 9x means?

Actually we have 3 pumps (A/B/S) running parallel during high plant load. But during normal plant load normally only 2 pumps were running. A & B pumps drive by motor meanwhile S pump drive by small steam turbine. Both motor has been observed having humming sound when running during coupled with gearbox and free load (Solo run). Appreciate any input. Thanks.

Regards,
Rizal

P-3200B(31-10-06).pdf (15 Kb, 48 downloads)

Pump curve attachment

DataSheet(P-3200ABS).pdf (290 Kb, 48 downloads)

Some drawings.

Regards,
Rizal

Drawings.pdf (1,161 Kb, 52 downloads)

BEP is the best efficiency point, the flow rate with the greatest efficiency for the pump. The curves you show look like the theoretical ones, not from test data.

You have 3 curves rated for minimum diameter (?, rated, max - what do you have). Since there is only one curve at rated diameter, this should be a fixed speed pump (Constant speed motor and gear,true? The curve states that it is for 4600 rpm, the same speed you have. Is S pum the same type, same speed, variable speed?). Where are you on the curve, and do you have the individual pump parameters or just combined flow?

Bill,
Thanks for your quick reply. It’s rated curve. Yes this is constant speed type pump at 4600 rpm. All 3 pumps are same type and running with combined flow. S pump run at 4600 rpm directly with steam turbine.

Regards,
Rizal

Hi Rizal,

Rajan, Rotating Engr. from TPC and later Reliability Supt. of TPE; I set up your CBM programs-lah.
Anyway, I'm not sure if my earlier reports on these BFPs are still available. You potentially have worn Impeller/Casing wear ring and possible wear/damage at the 1st Stage impeller. The Pump DE-ENV (gE) has increased by 137% and you are starting to see a drop in velocity reading (16.6 - 13.6 mm/s)...not a good sign.
The Motor 9X and "Hum" is very likely due to alignment related problem...Check coupling condition and alignment...Motor to Gearbox.
My regards to Lim Soon Hua & Kamal Kassim, if they are still there, that is.
Good Luck.

Rajan

Hi Rizal,

Vane pass syndrome - usually due to low clearance between the impeller tip and volute - for new pumps or where impellers have been changed recently - if not wearing siezure or damage in the impeller - the BEPs usually have a low NPSH req impeller in the first stage followed by the normal sized impellers in the later stages - the number of vanes in all stages not necessarily can have the same number of vanes.
9 X remains a mystery - as maunfacturers refrain from making 9 vaned impellers
Can u furnish us the waterfall spectra ?

Regards

Ramesh Rao