OM-2245 / Operation and Maintenance Manual
ITW GSE 4400 / 400 Hz. Generator Set
March 15, 2015
Appendix C
Page 1
Appendix C Wet Stacking in Generator Set
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, as well as, excessive soot
around the exit point area. Liquid fuel, in the form of droplets, may be also 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 the 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 loads. The time schedule of
200 hours may be changed as required to su
it each user’s particular needs and
operating conditions.
