Feature 4 | DIESEL ENGINE REPAIR AND MAINTENANCE
Cost effective solution for main bearing saddle repairs
MAN Diesel & Turbo has come up with an engine repair solution that is said to save time and money.
O
ver the past few years MAN Diesel & Turbo has seen a number of cases where a specific type of
filter has been flushed into marine engines with the oil, thereby damaging the bearings and consequently the saddles. Due to the design of the engines, which have a narrow gap between the journal and saddle in the bedplate, the A-frame and crankshaſt had to be liſted in these cases to enable access for repair. With traditional methods, this type of major repair could take up to three months to complete. MAN Diesel & Turbo has recently
developed a new, and it claims revolutionary way of repairing the saddle by machining it in situ, without the need for the time consuming dismantling of large engine parts. A new patented machining tool developed by the company has made it possible to reduce repair time by more than a month, claims Peter Michael Nielsen, technical service senior manager, MAN Diesel & Turbo. He adds: “Another benefit is the safety aspect. By reducing the overall repair time and manpower and by avoiding the heavy liſting of the cylinder frame, A-frame and crankshaſt, the risk of an accident is significantly reduced.” The new solution incorporates a
sophisticated tool that is glued onto the crankshaſt. Using this as a lathe to machine the saddle it is possible to achieve a perfect shape for the bearing shell. By putting a number of semi-finished machining tools in stock and then modifying them according to the specifications of the individual engine in need of a repair, MAN believes it will be able to ensure a fast response covering the entire MC-C engine population in service. Shortly aſter the development of the tool
it was successfully tested on a vessel with a 6L60MC-C engine having a main bearing failure. Te vessel was towed to Rotterdam and PrimeServ engineers managed to remove the damaged shell. Mr Nielsen says: “Tis is not an easy assignment as experience shows that depending on the
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The new machining tool.
heat ingress the shell can weld itself to the saddle. Te owner was offered a choice between a traditional repair with the removal of the crankshaſt or the new in situ machining procedure. Facing time savings of 33% the owner agreed to be the first and the project was started.” Before the saddle could be machined the
crankshaſt had to be aligned within 1/100 of a millimetre and the journal machined. Te alignment was undertaken using specially fabricated supports in the neighbouring saddles. In this case another company, Metalock, undertook the machining of the journal. Te base of the tool was glued to the journal and leſt for 24 hours for hardening. The cutting tips were fitted and the machining went exactly as it had during the test phase. Te final geometry was checked and found to be excellent and no edges from using multiple tips could be detected,” says Mr Nielsen. As it turned out, in this case the collapse
of the saddle was not of a magnitude that required a special solution for the bearing cap. Machining of the outer face was sufficient and the original bearing cap was reused. Aſter adaption and fitting of the
A damaged saddle showing heat ingress due to a main bearing failure.
bearing cap the engine was reassembled and a successful sea trial was carried out. Te whole repair had taken about one and a half months as opposed to three months with more traditional methods. Mr Nielsen adds: “This development
of this new tool and its implementation is a showcase for innovation and gives us a significant advantage when it comes to in situ machining, saving time and money for the owners.” Development of various procedures related to the repair is still ongoing and the results will be implemented on a continuous basis, the company says. SCRT
Shiprepair and Conversion Technology 4th Quarter 2010
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