Wet stacking on a generator or other diesel engine refers to a condition where a diesel engine has a thick, dark liquid substance dripping from its exhausts.
It's called wet stacking because the diesel engines mostly have stacks for exhausts such as on Semi Trucks.
The thick, dark, liquid substance would drip from the exhaust stacks on the diesel engines and run down the pipe when the engine was not under much of a load.
When you run your diesel generator under a light load then it can lead to wet stacking.
The wet stacking condition on a generator that operates with a diesel engine is caused by operating the diesel engine at light load for extended periods, sending unburned fuel and soot into the exhaust system.
If you discover wet stacking within your unit early enough, you can fix it by running your generator at its properly designated operating temperature with a 75 percent load.
Wet stacking is a serious condition affecting diesel generators that operate for extended periods at light load.
It can be avoided by proper generator selection, and by properly performing routine generator testing.
Wet stacking is detectable by the presence of a black ooze around the exhaust manifold, piping and turbocharger, if fitted.
It can be mistaken for lubricating oil in some cases, but it consists of the "heavy ends" of the diesel fuel which do not burn when combustion temperature is too low.
Wet stacking has several bad effects on a diesel engine generator, and if unchecked for a long period of time.
The wet stacking of the diesel engine can result in reduced engine performance or permanent engine damage requiring an expensive major engine overhaul.