Understanding Wet Stacking in Diesel Engines
What is Wet stacking?
In reference to diesel engines, “wet stacking” refers to unburned fuel mixed with carbon soot that builds up in the exhaust pipes. This is usually caused by operating the engine for long periods of time at less than 60% of its rated output. This does not allow the engine to reach the 1500 to 1800 degrees necessary to run at optimum temperatures. It is well known that prolonged operation at low loads can lead to permanent engine damage and even catastrophic failure.
Wet stacking can also come from over-fueling, faulty fuel injectors, improper air to fuel ratio and even running the diesel generator engine in cold weather for too short a period of time.
How can you tell if you have wet stacking?
Excessive black smoke that lasts longer than a few seconds is usually a cause to be concerned. If there is noticeable thick, black sludge building up around the generator engine exhaust manifold, exhaust pipes or the even the turbocharger, you should definitely assume the unit is wet stacking.
What can you do if you have wet stacking?
The general rule of thumb for clearing out the effects of wet stacking in diesel generators is to run the unit at approximately 75% of the output rating for three to four hours. However, you must be wary of generators that have a history of being run for extended times at low load. Exhaust temperatures at load are much higher than the auto-ignition temperature of diesel fuel and can cause soot and unburned fuel to ignite within the exhaust system creating a serious fire hazard!
We highly recommend utilizing one of the many professional diesel generator maintenance firms to manage load bank testing when the unit’s history isn’t clear or the visual signs of wet stacking are apparent.
How can I prevent wet stacking?
Selecting the right size diesel generator for your application is key to preventing wet stacking and many other issues, so let the professionals help. We highly recommend that you follow all manufacturer testing schedules, procedures, and fuel specifications exactly as stated in the operating manual. Most professionals recommend you test your generator engine every 36 months for no less than 60% of the stated output rating.
If you have any questions about used generators, load bank testing or wet stacking, feel free to send us a message or give us a call and we will be happy to help.