Big End Bearing Failure in PD Pump - Seeking Expert Insight 1

[Bravo6]

Greetings fellow engineers,

I am facing a persistent issue with repeated big end bearing failures in a positive displacement (PD) pump, and I am seeking your expert insight to help me diagnose the cause and address this problem effectively.

Problem Description:
We have installed 03 heavy duty PD pump of make PERONI POMPE which make pressure up-to 250 bar, these pumps are installed in parallel arrangement and all remain in service as per process requirement.

We have been facing a recurring pattern of big end bearing failure on one specific pump. Despite thorough maintenance and regular oil changes, the bearings fails after 8-10 months, resulting in unplanned downtime and increased maintenance costs. This issue has become a significant concern for our operations, and we are determined to find a lasting solution.

Details and Observations:
The big end bearings are in two halves and babbit lined. The lubrication mechanism is as such that an auxiliary pump supplies oil to small end bearing at pressure ranging from 10-14 bar and this oil travels through machined ports from small to big end. Following are the re-current observations of failure
•On first bearing, out of five, counting from driving end, Babbit is found chipped off from top half in a spider-web pattern (picture attached).
•Babbit of 4th and 5th big end bearing chipped off at the edges (picture attached).

Maintenance Checks
Following extensive maintenance checks are performed on this pumps, but the problem is persistent. Let me reiterate that same maintenance procedure is followed on other two pumps but this specific unit failing on recurrent basis.

•Casing level checks.

•Thrust line run out.

•Crankshaft end run out.

•Crankshaft web deflection.

•Big end bore face straightness.

•Cross head bore concavity and ovality checks.

•Cross head straightness.

•Connecting rod deflection.

•Pump main bearing bore alignment.

•Main & Big end bearing clearance and ovality.

•Lubrication system port checks for blockage

Expert advise is required on the following :
1) Probable causes of this failure.
2) What steps can be taken to avoid recurrence in future.

Link to pictures

https://files.engineering.com/getfi...-4e3d-8cba-020f215aa87f&file=1st_Bearing.jpeg

https://files.engineering.com/getfi...8cf6-acb749f3a4e5&file=4th_&_5th_Bearing.jpeg

 

[1503-44]

People are going to ask what are all the observed differences between the installation of the problem pump and the other two.

Use the image camera icon to post photos.

I didn't find any photos in the second link.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[hydtools]

Looks like cavitation.

Ted

 

[electricpete]

I work with motor bearings but nothing like this so I doubt I can help. But some general questions

1. Each bearing has 2 holes, are they:
__1A both oil supplies to this bearing?
____ OR
__1B one is a supply to this bearing and the other is a discharge port to provide oil to another bearing. (in this case it seems like a heckuva lot of pressure and volume will be lost with such a short / low L/D bearing although I'd be interested to know what clearances / restrictions there are to stationary parts on the side)

2. What is direction of rotation in the photo?

 

[electricpete]

A few more thoughts fwiw

Cavitation was mentioned. I assume that would apply primarily at the edges.

There looks to be large patches of babbitt missing but no indication of melting or wiping. To my thinking it resembles damage from babbitt fatigue which cracks the babbitt and eventually chunks come out like in the bottom section (there are other cracks further up which look like an earlier stage of babbit fatigue). Babbit fatigue is most commonly associated with excess cyclic loading. It might also be caused/exacerbated by design factors like poor selection of babbitt thickness. The fact that the failure tends to recur after a repeatable number of operating months would be consistent with a fatigue failure mechanism.

 

[1503-44]

The broad surface eaten away like that looks like cavitation. Is this the pump with the longest distance from source to inlet, or is it unusually close to an elbow near the intake?

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[pierreick]

Hi,
Can we get pictures of the pumps set up and or Isometrics?
Always good to start with the big picture.
Pierre