Be Aware of the Cam Effect (Ridge Wear) that Affects Four-Stroke Crankshafts!

Whenever a four-stroke engine has accumulated around 60,000 running hours or more, then its crank pins are in all likelihood affected by what is called the “cam effect” or “ridge wear”.

This phenomenon develops over time and manifests itself in an uneven wear pattern that is, with the right tools, easily detectable as a protruding band (“cam”) that goes around the circumference of the crank pin. It usually only develops on engines equipped with grooved bearing shells and its development is a function of time. The more impurities (abrasive particles) the lubricating oil contains, the faster the cam effect develops.

The two major makers of medium-speed diesel engines, MAN Diesel & Turbo and Wärtsilä, have booth issued Service Letters to make their customers aware.

The following pictures are typical and exemplify well how the cam effect develops and what damage it can cause. The pictures were taken during an attendance on a German-owned small tanker, where QuantiServ’s specialists machined one crank pin and polished all the others on the vessel’s single 50/54 main engine. The damage was in fact so severe that in-situ heat treatment (annealing) had to be performed too in order to reduce the crankpin’s hardness, which had increased as a result of the failure.

QuantiServ very much recommends to all owners and operators of medium-speed four-stroke engines to keep a close eye on the condition of the crankpins and to regularly inspect them once they have surpassed around 60,000 running hours. The cost of rectifying the pin geometry in good time pales in comparison to the cost of a repairing a failed crankpin bearing. And fail they will, if no action is taken.

Read more

 

 

Polishing All Main Journals and Crankpins on one of the World’s Largest Engines

QuantiServ in-situ machining specialists from China, Sweden and Singapore joined forces in a shipyard in China to carry out in-situ polishing on one one of the world’s very largest diesel engines. The 14-cylinder, 96-bore engine is installed on a 14,000 TEU container ship.

Our engineers and technicians worked in two shifts, around the clock, seven days a week to machine-polish 17 main journals and 14 crank pins while the vessel was docked in Beihai Shipyard, Qingdao, undergoing steel work. It was one of the most extensive polishing jobs that we have ever carried out. And it was done in record time!

All the necessary dismantling and reassembling work was carried out by us as well. In a case like this it pays off that many of our in-situ personnel are multi-skilled – they don’t only do the machining work, but can conduct any mechanical work as well if required.

In addition, our reconditioning centre in Shanghai also carried out cylinder cover reconditioning for a sister ship, belonging to the same customer, that was docked in the same shipyard a few weeks earlier.