Diesel engine damage?

[MN6RB]

Can a diesel engine get severely damaged because of back pressure from fire water system? The engine drives fire water pump and the check valve was found passing. Is there any relation between possible engine piston+crank shaft damage and back pressure from fire water system? 

[G B Reid MIMechE, SIMarEST]

The short answer is unlikely (though, never say "never"...anomalies do occur!).

In the instance of back pressure, the most likely thing is the Engine will stall, the clutch slip, the pump housing split (due to internal pressure) etc. 

That said, it does depend on the pressure and forces involved, hence the "never say never" comment. 

Though, that said, you did say the "check valve was found passing"...do you mean the pressure relief/bypass valve...?  If that is what you mean, that would REDUCE the loading on the engine, so make such a failure less likely. 

 

There would need to be a LOT more information, but my initial suggestion would be it sounds like a blocked oilway within the engine. Pistons are cooled from behind by oil-spray from a crank-oilway outlet. If these oilways become blocked, the oil pressure at the end of the circuit drops resulting in insufficient spray and the piston can overheat, swell and seize in the cylinder. If this occurs, the con-rod will bend or shatter and the crankshaft can do too!

The diagnosis would be "insufficient maintenance" - regular oil and filter changes remove residue and minimises the risk of oilway blockage and resulting engine failure. This becomes far more critical in high dust environments (so should increase in frequency), where oil top-ups (with the best of intensions) can actually introduce significant levels of contaminants.

Hope this helps

Bruce