MAN DIESEL D2840 LE401piston failures

[fork]

The organisation that i work operates these marine engines and is suffering from piston failures at around 1150 hrs total running time.I believe that the problem has not yet been resolved or fully investigated.They are rated at 860 hp at 2300 rpm for this installation

Have any of you out there had similar experiences with these engines ?

 

[MotoGuzzi]

Threr a re a number of things which will effect affect an answer including:
Are they being used as main propulsion of generator sets?
Are they new or refurbished?
Type and state of oil
Injector condition

 

[longbl]

What kind of piston failure are you having? Is it a crown to skirt seperation? or are you burning a hole in the top.

 

[fork]

Hi All
Some further info fot you
The engines are used for propulsion in a twin installation running on a 15/40 grade lube oil.
The piston failures are melting of the crown followed by disintegration.I believe that some pistons have been found with cracks on the crown.

 

[hvammur]

Hi fork
If you have foulty injectors the Piston Crown temp can increase 150°C-200°C and reach melt down temp.

 

[Paramagurubaran]

The failure projected seems to be due continous operation on overload or due to poor scavenging and/or sealing inside the combustion chamber or improper fuel atomisation. Further, piston cooling circuits might have developed restrictions by way of blocks in the cooling medium passages, during operation. How about the L.O. analysis reports? Do they indicate presence of carbonaceous substances which might have entrained into the crankcase due heavy blowpast? These substances would get into the drilled passages, eventually blocking them & preventing the piston cooling oil from flowing past to cool the piston. Further badly leaking fuel injectors & malfunctioning fuel pumps would lead to after burning inside the cylinder. Due to the above reasons, the pistons would have been running hot, leading to their failures.

 

[romke]

I agree with Paramagurubaran. It seems that the whole proces starts with pistons getting way to high in temperature. There are a few things to check here: what is the avarage air temperature entering the combustion chambers, how efficient are intercoolers/aftercoolers working, is the injection timing correct, is the cetanenumber or cetane index of the fuel used adequately high? These questions relate to the quality of the combustion proces.

If all those things are correct, cooling of the pistons should be investigated. Check whether sufficient oil is sprayed against the piston crown and/or whether the oil passages in the piston crown are not blocked. A black undercrown is a sure sign of insufficient cooling.

A third possibility for the failure might be the type of loading of the engines. If they are idling for prolonged periods and then occasional bursts of full power are needed, it may happen that the temperature rise in the piston is much faster then of the surrounding liners with consequently a temporary mismatch in the clearance between piston and liner.