Wednesday, 21 June 2017

A Close Look at Wet Stacking of Diesel Generators – Effects, Prevention and Solution

Diesel as a source of fuel is conveniently independent and its compression ignition systems have a higher thermal efficiency than that of gas engines that use the spark ignition systems. That said, an important factor to be considered when choosing a diesel generator is its potential for ‘wet stacking’. Diesel generator designers must bring into account the potential for wet stacking when they determine the equipment for the system, maintenance, service programs and load calculations. Further, this post will discuss the adverse effects of wet stacking on your diesel generator and methods you can use to eliminate the condition.

What is wet stacking?

Just like all internal combustion engines, a generator must have exactly the right amount of air-to-fuel ratio to operate at its best efficiency and deliver optimum results. It should be able to utilize its designed operational temperature so that the fuel can burn out completely. Diesel generators rely on the hot compressed air in the cylinder to ignite the fuel. Because the air is cooler than the design temperature, the conditions for combustion are not ideal. Thus, the fuel ignites, but it doesn’t burn completely. The unburned fuel exhausts and results into wetness in the exhaust system. Hence, the phrase, wet stacking.

How do you know if your generator is wet stacking?

Your diesel generator may likely be performing inefficiently if one or all the below conditions exist:-

There’s a continuous release of black exhaust smoke from your diesel generator’s exhaust pipe.
A thick, dark substance is continually dripping from the exhaust pipes.
There’s a formation of deposits of soot or hard carbons.

Effects wet stacking has on your generator

Raised expenses: Wet stacking can shorten the life of the engine of your diesel generator by many years and you may have to replace it much before than you planned to.

Air pollution: The level of smoke emissions produced due to wet stacking is restricted in many urban areas.

Low power: The deposits caused due to wet stacking will reduce the maximum power of your diesel generator even before the engine is damaged.

Higher maintenance: A diesel generator that is experiencing wet stacking will need considerably higher maintenance than one which is adequately loaded.

Prevention and Solution:

The basic solution for wet stacking is a few hours of operation at a load of about 75% of the generator’s nameplate rating (or more) to raise the exhaust temperature high enough so that the unburned fuel in the exhaust system can be vaporized and the soot can be blown out away. At the same time, the exhaust temperature at that load is higher than the auto-ignition temperature for diesel which on rare occasions can ignite fuel and soot within the exhaust system. In case a unit has a history of extended operation at low load, or if there’s no proof that it’s been exercised recently at adequate load, it’s vital to get a professional generator maintenance report to manage the load testing procedure. If a generator is made to prolong operations at low loads, it can lead to permanent damage of the engine which will need a major engine overhaul. The costs of an overhaul can run high and so, replacing the unit altogether is the more economical option.

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