Oil leak in DG

Fix it. If you don't know how or don't have the time, hire a manufacturer's mechanic to fix it for you.

Same reply as previous Post Fix It. and the sooner the better it will not get better by itself and unless it was overhauled recently and incorrectly assembled. (In which case you should get the company back to repair FOC) this is a sign that the unit is overdue for a full service check

There is no leak. This is unburned fuel from low load mixing with black soot, what we call "slobbering" or "Wet Stacking". The English slang for smoke manifold is 'stack'. I guess your 600 kW has about 75 -100 kW load on it and has unburned fuel coming down the smoke manifold and leaking out the joints of the manifold which are not liquid tight joints. Have this reply translated to your language. Put a heavy load on this at 350 kW - 500 kW and this will go away until you go back to low load.

Thanks for illuminating my ignorance!

Hi Ried

I might be wrong on this. Our guest hasn't reported back or thanked contributors for suggestions so we can't learn what went wrong.

You post was perfect. "Fix it". My suggestion requires no tools to at least eliminate a common problem before he disassembles the engine. Finding load can be a problem though. This problem is so bad we sometimes add parasitic load by resistive load banks to keep minimum 40% load. This unburned fuel causes the lube oil to be washed off of the cylinder walls, it causes low piston ring pressure so no combustion gas sealing takes place and gunk enters the lube oil as high ring "blow by" and finally the valve seals are expecting high pressure to seal them and when there is low pressure (low load) the piston actually sucks lube oil past the valve seals and carbons up the rings and piston top polishing the cross hatch pattern from the liners which intentionally hold lube oil film to lubricate the ring faces (glazing) . . . . etc etc etc . . . a death spiral. The truck drivers that leave their trucks running while they eat or running all night are destroying their engines.

Your comments remind me of recommendations I've always heard about testing diesel fire pumps and emergency generators about testing at full load. I have heard horror stories about "testing" the engines under no-load conditions for years and years, and then when you need it to work right, the engine cannot carry the load.

Hospitals test once a week no load and once a month with whatever load the hospital can give which is rarely full load or even 60% load. Firepumps are typically tested with some load with flow through fire water nozzles but low flow is low load on a centrifugal pump. the highest load on a centrifugal pump is open discharge right out the flange spilling onto the ground. Any type of pressure build up moves the pump curve left and load is decreased accordingly so these guys that think opening one high pressure monitor nozzle and shooting water across the way are not loading up the engine. Constant no load tests screw up the engine to a point it can fail a full load test . . . you are right. Carbon can build up behind the rings and force them out to the cylinder and wear them out; carbon WILL polish the cylinder liners smooth as glass which kills rings; soot in the lube oil screws that up; etc etc.

I now specify that each installation include a dummy load bank and a load demand computer that keeps all engines 40% loaded minimum and cycles in / out accordingly or shuts off engines not 40% loaded if they are paralleled . . . . and during testing, a full load and overload of 120% (which is OK for a few minutes) can be placed on the units. 110% can be done for less than an hour typically.