pump bearing problem 2

[mechanver]

dear fellows,
I have problem with a multistage centrifugal pump known as VEB pump the problem is that from one month ago it was found that loud noise come from the rear bearing so pump was shut down and dis assembled to view what is wrong with it
there were bad deterioration in back bearing and mechanical seal damaged
we install new bearing and mechanical seal identical with its manual recommendations but the new bearing work only for 3 hours and then damaged this problem occurred 3 times and untl now i cant find where is the real problem with the pump despite the pump was install with high degree of alignment check and when stars no high vibration
i need your expert to help in this problem

 

[Artisi]

The problem could be caused by many problems, none of which are even likely to be guessed from the limited info you have supplied -- you will need to supply a lot more information for any meaningful answers, such as pump brand, type, size, speed, operating conditions, ie, the flow and head the pump was selected to operate at, the actual operating flow and head, NPSHa/r, motor size and the operating power input. etc.

Is this a new or existing installation - has anything been changed in the system, pipe work added or reduced, more equipment installed or removed etc.



It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[1gibson]

Ask the manufacturer.

 

[LittleInch]

Have you checked lube oil system?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[chamjam09]

@1gibson "ask the manufacturer" isn't exactly a constructive response. The user has posted on here to gain some thoughts and ideas, if they wanted to ask the manufacturer they would have. These forums are for help, and while I agree in this instance more information is required, we should endeavour to provide some guidance and not merely tell people to ask a 3rd party.

 

[1gibson]

I would disagree, but point taken. The alternative is to provide us with all the information the manufacturer already has (rated fluid properties, allowable operating ranges) and then information the operator has (actual fluid properties, actual operating parameters.) I thought my suggestion was appropriate if they wants to solve the problem (and I'd hardly call the manufacturer of the equipment a 3rd party.)

 

[mechanver]

thank you all my helpful friends and there are some available details:
1- the pumping system is existing one contain 3 pumps
2- H=700 psi Q=20000 BPD RPM=3000 no. of stages =5 HZ=50
Booster pump pressure = 75 psi
3- working fluid: crude oil @ T=50 Celsius degree

 

[H4Marine]

What is the bearing material and what is the lubricant for the bearing? is the lubricant the pumped fluid or a closed loop system separate lubricating fluid?

 

[Artisi]

If you want help you will need to supply more data such as pump detail(configuration etc) pump curve, application etc and clarify if 1 or3 of your pumps have the same problem. Your information to date is meaningless in terms of looking at your problem.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[mechanver]

i have this problem with pump 1 only
the application of my pump is to charge crude oil
it has closed loop lubrication system

 

[Artisi]

Have you contacted the manufacturer?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[LittleInch]

Still sounds like lube oil failure to me. Have you thoroughly checked that you are getting sufficient lube oil flow through the bearings?

Otherwise it's a pump strip down to check shaft run out, alignment, damage to any of the impellers, any blockage etc

If your process conditions changes that could cause problems, but not for three running hours before failure.

A pump bisection drawing would help...



My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[electricpete]

I agree lub is prime suspect based on timing.
Some assembly errors might also fall in same category.

Along with other requested info (drawing, description of bearing configuration), perhaps some pictures:
Would like to see the OD of outer ring and ID of inner ring.
Would like to see the axial faces.
Would like to see if possible mating surfaces on bearing housing and shaft for all the above.
Would like to see the inner and outer races of all available bearings (not just the failed one) to see if there is a sign of the loading pattern prior to damage.

The info may or may not be available. If not, I want to at least point out the value of close inspection of the damaged bearing by an experienced bearing evaluator (I'm not saying that's me...I send a lot to OEM for inspection/evaluation). You'd be surprised at what kinds of clues may be there.

Other miscellaneous shotgun questions
alignment checked ok, but is there thermal growth?


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(2B)+(2B)' ?

 

[QualityTime]

I assume a qualified miilwright was used to look at the problem. A good millwright will be able to look at the condition of the bearings to determine the cause. A good engineer will also be able to interpret the condition of the bearings by looking at it AND he will also separately be able determine if the lube oil pump is delivering the required flow. One check is to put your hand on the bearing collar and feel if the temperature is abnormally high. Also place the metal end of a very heavy screw drive on the shaft collar and put your ear to the end of the screwdriver handle. You will be able to hear any bearing vibration problems.