Wet-Stacking in Generator Set
1.
Diesel Engines
All diesel engines operated for extended periods under light load may develop a
condition commonly referred to as wet-stacking. This condition results from the
accumulation of unburned fuel in the exhaust system. It is recognizable by fuel oil
wetness around the exhaust manifold, pipes, and muffler. Liquid fuel, in the form of
droplets, may be spewed from the exhaust outlet.
Wet-stacking is common, and may be expected in diesel engines operated under light
load. Light loads do not allow the engine to reach most efficient operating
temperature for complete combustion of fuel. The unburned fuel collects in the
exhaust system to create the wet condition known as wet-stacking.
To alleviate wet-stacking in lightly loaded engines, it is recommended that the
machine be connected to a load bank after each 200 hours of use and operated
under full rated load for one hour. This will burn away and evaporate the
accumulation of fuel in the exhaust system. This clean-out procedure should be
considered as a regular maintenance operation for machines operated under light
load. The time schedule of 200 hours may be changed as required to suit each
user’s particular needs and operating conditions.
OM-2084 / Operation and Maintenance Manual
90CU24 / Series 500392 Generator Set
November 27/1997
Wet Stacking
Page 1
