For an internal combustion engine to work at its peak performance, it is imperative that it has an optimal air-to-fuel ratio. Additionally, such an engine must also be able to sustain its operational temperature efficiently, to utilize the complete fuel. In other words, the complete burning of fuel must be supported by the engine. When engines operate on lighter loads, the process of fuel burning is compromised. When a diesel engine runs on lower temperatures for prolonged periods, the unburned fuel is eliminated and is noticed as wetness in the exhaust system. This phenomenon is termed as ‘wet stacking.’
Effects of wet stacking
Unburned fuel that is eliminated through the combustion chambers starts to build up on the exhaust side of the engine. This gives rise to fouled injectors and a thick carbon build up on the exhaust valves, turbocharger and exhaust. Such an excessive deposit can result in the engine to underperform. Additionally, such gasses impact the turbo efficiency as they begin to deposit on the turbo blades. Though permanent damage may not occur immediately, prolonged exposure can scratch and erode the engine’s surface.
It may also be imperative to note that in case of engines that run below the designed operating temperature, the piston rings cannot seal the space between the pistons and the cylinder walls. This additionally contributes to the escaping of unburned fuels and gasses which eventually deposit in the oil pans. These tend to dilute the lubricating properties of the oil, ageing the engine rapidly than normal rate.
Preventing cold/wet stacking
One of the easiest and straightforward solutions to prevent cold/wet stacking is using a heater load. Start by setting the electrical load at the designed operating temperature of the diesel. Alternatively, you can set it at approximately 75% of full build up. Get rid of built-up fuel deposits and carbon by running the diesel engine for several hours at the needed operating temperature. Continue doing so until the wet stacking reaches a level where carbon build up can only be removed through a major engine overhaul.
You can prevent the recurrence of wet stacking by using the following load bank solutions.
Automatic auxiliary loading
If your diesel generator is the primary source of power, this solution can be used. The auxiliary load bank will be switched onto the system only in case of lighter loads
Facility manual load bank
This technique works similar to automatic loading. One can use a manually operated system for initiating larger loads by manual initiation. A load bank can be utilized for load testing a system for standby power.
Portable load bank
Distributors who deal with diesel generator sets are the best people to approach for maintaining a system. Most standby generator system owners today outsource the complete maintenance of their system through planned maintenance (PM) contract with a full-service generator set supplier. During a typical maintenance schedule, a distributor will bring in a portable load bank and test run the generator at a designed operational temperature. Such a portable load bank runs from a few kW to 3MW units which are basically mounted on large-sized trailers.
While avoiding wet stacking is an extremely crucial aspect of diesel generator maintenance, generator maintenance requires skills and machinery from thorough professionals. Electric Horsepower can offer experienced and valuable advice pertaining to all such aspects of the generator. Speak to our crew member today for a detailed, comprehensive and customized maintenance plan.