Pump vibration

The difference of 1" is quite high and if the design does not provide for alternating distances the impeller is suspect.

I may be wrong but the shaft may not be positioned in the exact centre of the vanes / impeller.

If only one space is bigger the vanes might not have been placed at the correct pitch.

Is it a pirate part?

The balancing is done without water (must have been quite an effort) and more material had to be taken of from one side. With water (or fluid) the balance seem to be disturbed.

I would demand a replacement impeller.

since when have you been using this pump? if tou were using the same thing before, try to check the pipeline intake & output there is a posibility of choke up problems lead to overload and this causes severe vibration & overheat. too much vibration creates bigger sideplay on the bearings and tend offcenter your impeller.

It certainly sounds like the impeller to me. Do you see any cavitation damage on the impeller or your wearplate?

Hi G, You didn't say whether the balance was static or dynamic. The location of the balance mass along the shaft axis, either plus or minus, will not effect a static balance, but can cause a severe dynamic(in motion) unbalance. Just a thought...Clintb32

Hi

In order to fix the problem I have these qustions:

1. Did you check the vibration level after repaired pump start? What is the overall level? Could you take some spectra? If yes send this one to my address AMares@Petrotel.LUKoil.com.

2. The vibration level is increasing after an operation period?

3. The operation parameters are altered in operation?

4. Did you check the lubrication oil temperature periodically before to pump trip?

5. How you described your impeler configuration seems to be a hydraulic unbalance, but in his condition the vibration level should be high since the pump start. Any way the spectra must confirm this hydraulic unbalance.

Looking forward for you

Aurel Mares

I was using this pump for many years, I shutdown the pump for routine maintenance but when I open the casing, I found the impeller to be scraped. so the pump goes to workshop for impeller replacement.

yes, I use pirated impeller ,I dynamic balance the rotor per API standard, nothing changes with the piping.

Thank you to all of you

Addendum to the above suggestions:

1.Check motor to pump alignment (ie. Coupling)

2.Make sure your motor is of correct RPM

3.Make sure correct pump seal and installation procedure

Hope this helps!

Ron

Does old impeller have 1" discrepancy also? Probably good idea to check all dimensions against old impeller, if nothing else, just for reference.

I am wondering , why you didn't replace the damaged impeller with origional one !! , second It's preffered to send the new one to a laboratory who can balance it , this is important , and finally be sure that the new impeller has the eame weight and design of the damaged one.

as it is mentioned before , 1 inche is too much my friend , it's logical.

Hydrolic cavitation could also be a culprit.. a pump that large needs a serious amount of slution fed through it in order to run correctly, unless itis a VFD, Im assuming it is not.

also on Items that are of this much value, (labor intensive) to replace, I would go with the OEM model impellar instead of a pirated. You may save 30% up front with the Pirated, but you (as you are now finding out) will eventually pay for it in the end. If not realizing that the cheaper "pirated" impellars do not go through the quality check points, inspections or maybe even worse are made in CHINA!!!

You will pay for this pump twice in te long run using sub-grade materials.

Sir,

GREETINGS from EGYPT

Well, briefly we have to chech for the followings:

1- Are RPM, diameter and Imp material the same? more likely to be different

2- Do you check for static and dynamic palamcibg?

3- Are Suc. and Disch. conditions the same?

What are the detailed performance consitions? Why you did not refer to the original pump manufacurer?

PUMPMAN

If you are looking to improve the design, or redesign..then when you mention "investigation" in my world that means taking an advanced engineering approach, ie CAE coupled with CFD. This is structural analysis problem but also a computational fluid dynamics problem. One method would be to create a detailed finite element model and conduct a CFD simulation which includes flow rates, rpm, material properties etc to gain understanding the forces and cavitational effects transmitted into the shaft, bearings etc. Then bring those results in to a structural analysis code like Abaqus to understand vibrational effects and identify how to modify the geometry to remove the undesirable frequencies outside the excitable range. Thermal effects could also be evaluated using data from the two previous analyses. If this is a "one off" problem and no geometry modifications can be made or is feasible, then the trial and error method is your path based on the previous recommendations.

good luck,

Chris