Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations pierreick on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

PD Pump Big End Bearing Failure

Status
Not open for further replies.

Turbo1123

Mechanical
Apr 2, 2024
2
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 2-2.5 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 3rd, 2nd and 4th 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.

•Connecting Rod Distortion.
•Cross Head Liner and cross head clearance.
•Cross head liner and housing clearance.
•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

The power end is inspected so far and no such issue has been found. The hydraulic end valve bodies are changed preventively after 2-2.5 months interval. Now it is doubted that the hydraulic end clearance volume might be changed due to some reason.

Expert advice is required on the following :
1) Does increased or decreased clearance volume affect the load on crank-shaft and subsequently affect the bearings?
2) Probable causes of this failure.
3) What steps can be taken to avoid recurrence in future.
 
 https://files.engineering.com/getfile.aspx?folder=832490a5-1b70-4f04-8b05-e4b3f6038a0a&file=WhatsApp_Image_2024-06-06_at_6.01.07_PM.jpeg
Replies continue below

Recommended for you

download.aspx_jf3pav.jpg


--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
 
Vibration sensing on reciprocating machinery can be useful, but the signals are not the same as for rotating machinery. Look for signs of impact.


Journal impact can result from excessive journal clearance. Increased clearance makes the oil wedge smaller, concentrating any impact loading on a smaller area. Can you measure the journal clearance and compare that with the factory specified clearance?

Screenshot_from_2024-06-18_20-23-24_ilyvc1.png


Plastigage is one way to measure in service clearance of bearing journals.
Screenshot_from_2024-06-18_20-27-40_bzwaj8.png


Reference
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor