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Main engine crankpin defects

Main engine crankpin defects

Main engine crankpin defects

(OP)
Hi all.

I'm new in the forum. I'm in a new buildings site team for some tankers. After sea trials we open one unit of the main engine to discover that the crankpin had 2 different kind of defects. one looks like watermark (imagine a map with 7 different countries that the borders have a depth of 0.1mm on the surface of the pin). It seems like oily water was left there and touched the pin while the engine was idle but we had nothing on the bearing which is strange.

The second one is a straight line that looks like pitting for 100mm but completely straight.

Can somebody help me identify exactly what it is and why it happened?

RE: Main engine crankpin defects

First of all what brand and size is the engine? And a photo is what is needed. Any discoloration may have been present the day the engine was assembled. Those engines aren't exactly built up by the same caliber of people that assemble an F1 racing engine, its like any other job in the manufacturing world, where employees are pushed in time constraints. Pitting ? what does the pitting look like? Someone tapping to music on their last day of work before getting layed off? Or
cavitation type pitting, rust pitting, ??? Again need some pictures.

RE: Main engine crankpin defects

I have seen that before on an MAN v8 and ran fine. It miked out fine therefore we decided to put it back into use. Add some pictures of it if possible.

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