Wet stacking, a common but often misunderstood issue, occurs in diesel generators when unburned fuel, carbon particles, and sometimes lubricating oil accumulate in the exhaust system. This buildup creates a thick black liquid that can lead to engine inefficiency and long-term damage. Here’s what you need to know about wet stacking, its causes, and how to prevent it.
What is Wet Stacking?
Wet stacking, also known as “exhaust slobber,” manifests as thick black liquid seeping from exhaust connections, turbochargers, or pipes. This liquid results from a combination of unburned fuel and carbon particles, giving it the appearance of dirty oil.
Key Quote:
“Wet stacking happens when your engine runs below its designed operating temperature for extended periods, causing unburned fuel to collect in the exhaust system.”
Causes of Wet Stacking
The primary cause of wet stacking is low-load operation:
- Running the generator at less than 30% of its rated load for extended periods.
- Generators often sized for worst-case scenarios frequently operate at loads far below their maximum capacity.
This light loading prevents the engine from reaching its optimal operating temperature, leading to incomplete fuel combustion and accumulation in the exhaust system.
Effects of Wet Stacking
While wet stacking may not initially seem harmful, prolonged instances can lead to:
- Fuel Injector Fouling: Unburned fuel can clog injectors, reducing performance.
- Carbon Buildup: Deposits on exhaust valves, turbochargers, and exhaust systems increase back pressure and reduce efficiency.
- Oil Contamination: Unburned fuel can bypass piston rings, diluting engine oil and compromising lubrication, which accelerates wear.
- Reduced Power Output: Overall engine performance declines due to these combined factors.
Best Practices to Prevent Wet Stacking
Preventive measures can significantly reduce the risk of wet stacking and its associated problems:
- Run Generators with Adequate Load: Ensure the generator operates at or above 30% of its rated load to maintain optimal temperature.
- Regular Exercise: Follow guidelines such as NFPA 110, which recommends running the generator monthly for at least 30 minutes with sufficient load to maintain proper exhaust temperature.
- Use Load Banks:
- Portable Load Banks: Ideal for temporary solutions.
- Permanently Installed Load Banks: Provide consistent load when the generator operates below its design load.
Conclusion
Wet stacking is a manageable issue with the right preventive practices. By maintaining sufficient load, conducting regular engine exercises, and utilizing load banks, you can ensure your diesel generator operates efficiently and avoids long-term damage. Take the time to monitor your generator’s performance and invest in preventive measures to protect its lifespan and reliability.
