WHY IT’S NECESSARY TO ADDRESS WET STACKING Wet stacking doesn’t damage the engine in the short term, but over time it can lead to poor performance and reduced engine life. In extreme cases the exhaust stream can combust under rapid application of the high exhaust temperatures.
This combination of common rail systems and improved ring designs enables lower-exercise loading by containing combustion gases and enabling a shaped charge to be created. See Figure 3 .
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Increasing cylinder pressures also increases cylinder temperatures at lower loads.
Figure 2
Figure 3
Diesel Oxidation Catalyst (DOC)
REHLKO KD SERIES TM DIESEL
Hydrocarbon
Carbon Monoxide Soluble Organic Fraction
Water
H 2 0
CO
HC
CO 2
SOF
HC
Carbon Dioxide
CO
Particulate Matter
Normal Exhaust Gas Flow
Empty DPF Filter
Selective Catalytic Reduction (SCR)
Urea
Injection
Catalytic Converter
Pressure Sensor
SCR
Exhaust Gases with Particulates
h
- P
Diesel Exhaust Gas
Diesel Particulate Filter (DPF)
Figure 3
-Load Exercising for Diesel Generators Figure 2
Load-Bank Testing Loading to Minimum Load
reduce the gaps between pistons and rings that allow unburnt fuel to escape. Other advances include: • Common rail systems allow better atomization of fuel into the cylinder and the ability to have multiple injections per cycle. This allows the combustion process to be better tailored to the requirements of emissions and/or cylinder temperatures, a process called “fuel mapping.” • Charge air cooling allows more air to be delivered to the cylinder at a lower temperature, which permits fuel to be combusted more completely. • Modern piston and ring assemblies are engineered to a much finer degree of tolerance than those of older engines. This significantly reduces the blow-by that allows fuel to escape the combustion chamber. The result is that the engine burns more efficiently and the conditions that lead to wet stacking are significantly mitigated. This combination of common rail systems and improved ring designs enables lower-exercise loading by containing combustion gases and enabling a shaped charge to be created. See Figure 3. Increasing cylinder pressures also increases cylinder temperatures at lower loads. Revisiting Old Maintenance Assumptions Rehlko ® KD Series TM Field Experience These and other efficiency improvements should enable generator operators to reconsider old assumptions about
5 / Benefits of No-Load Exercising for Diesel Generators
The simplest way to avoid wet stacking during monthly exercise is to run the generator at the manufacturer’s recommended minimum loading. Because many operators do not wish to transition to building load, the monthly exercise requires use of a load bank, which can be used to supplement or perform loaded maintenance activities. This load-bank testing artificially boosts the load placed on the generator to burn the accumulated buildup. Most generator manufacturers recommend that load-bank testing be done monthly for a minimum runtime of 30 minutes. In addition to runtime, operators also need to consider the time it takes to set up the load bank, which can add up to a significant time commitment by operations personnel as well as fuel consumption for facilities that manage multiple generators. Revisiting Load-Bank Testing Procedures Many facilities conduct load banking according to maintenance procedures that were drawn up years ago and have never been revised. Technology improvements can now simplify this monthly procedure. In an industry that has historically moved rather slowly, the news has probably not reached many operators. Loading Modern Diesel Engines Taking Account of the Latest Diesel Technology Modern diesel engine designs now incorporate several technologies that enhance operating efficiency and
POWERLINE Summer 2026 | 45
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