What can cause a breakdown of a submissible pump which is completely submerged in seawater and designed almost maintenance free? What are the major areas to look into in a RCA exercise?

From the engineering glossary

Engineer says: Low maintenance or maintenance free.
Engineer means: Impossible to repair.

http://driedger.ca/classics-1/Classics-1.html



On this website there is information about pumps, don't know which type you have, but the first thing I would do is go to the "battlefield" armed with magnifying glass, flashlight and camera

Josh,
All the normal failure modes for submersible pumps should apply: Bearings, seals, wiring, impeller, foreign debris, degredation due to environment - corrosion, build up, etc, damage, poor installation, power system /control system disruption, operating conditions, service duty....etc....

I got the pcitures & inspection report. Vertical 3-stage submissible pump driven by a motor cooled by potable water. Now need to do rca.

Who might have these articles?

Electric Submersible Pump System Failure Analysis by Mike A. Swatek, Centrilift

Development of a Condition Monitoring and Protection Program for High Horsepower ESP Systems by D.J. Cohen, et al

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quote:

Originally posted by Josh:
What can cause a breakdown of a submissible pump which is completely submerged in seawater and designed almost maintenance free? What are the major areas to look into in a RCA exercise?

Seawater? Impacted by a shark, whale or dolphin?

Josh, the articles are listed here: http://www.espworkshop.com/PostSummaries/PastAgendas/PastAgendas.html

Josh,
I would recommend a review of your system requirements and pump specs to ensure you have the right pumps and features for the job.

Eugene, I got the tittles from the same link.

What would happen if the coolant to the motor has been cut off unintentionally?

Josh, we still do not know what your pump looks like, or what happened.

I am visualizing a big pump on the bottom of the sea, probably connected by some hose to a production platform, but with potable cooling water. Did they ran two hoses from the cooling tower on the platform to the equipment down under? Somebody tripped on the hose?

GA: The pump-motor set is hanged from a platform floor and submerged in the seawater. The motor is below the pump (upside down intead of motor on top). The pump is directly coupled to the motor. The whole set is housed in casing. Power cable and coolant to the motor are run from the platform along the pump-motor rising main pipe. The coolant is contained in a header tank on the platform. there is also a dosing line to the bottom of the motor. The total vertical length is 3.5m. Flow capacity is 270 m3/h. Motor is 140kW.

Inspection: Mech seal stationary face broke into several positions. Motor bearing badly damaged and bushes completely worn out.

So what can cause these effects?

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Josh,
As mentioned before, you may want to check the system requirements versus the pump specs. Operating the pump outside the design limits can cause overloading of the thrust bearing and the consequential damage you mention.


You don't mention how many hours on this pump. I assume this is a premature failure.

My experience with this kind of pump is on offshore drilling rig applications. 25-30k hours is reasonable life. What are life are you getting?

Regards,
Charlie

The pump was commissioned Aug last year ie (9mthsx24hrsx30days)/2nos (A&B). Now pump A kaput & B running.

25k to 30k / 8k per yr is abt 4 to 5 years, right? Is this life achieved with or without motor testing condition monitoring?

The application is seawater lift pump.

I saw the thrust bearing on the motor on the sectional drawing.

Can coolant starvation to the motor cause the same damage?

I will try to check then system reqts vs pump specs. Any guide how to do this?

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What about some pictures?

Put yourself in our place, how can we give intelligent answers if we do not see what you have, think, smell or see?

Yes Josh, it would be good to visit the "battlefield" maybe they just screw up the tags when reporting, just like the maintenance guy who parked the service car in front of Haulpack Truck 16, while Truck 60 was down...

You keep saying battlefield but I'm gathering as much info as possible. So any best guesses are good for brainstorming purposes. Unlikely they mixed up the tagging.

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Josh,

I understand you and your colleagues have had formal RCA training recently.

The best people to understand your pump failure are your own operating and maintenance staff, not some of us guessing from 000.s of miles away. Others can tell what they found in their situation, but that may not apply in your case. All they can suggest is a laundry list of failure modes for you to investigate.

With these provisos, it would appear from the pictures that you might have had a lubrication failure. So one line of inquiry should be to verify that possibility with factual data.

Svanels advice on 'battlefields' is good, and one that I would support.

Point noted. I agree that the nearest people should know better. However, sometimes it opens the mind a bit by listening to external views at the brainstorming stage.

What can cause journal bearings inside a motor to fail?