The Dangers of a Load Too Small for a Diesel Power Generator

The generator starts up, and not long after, white smoke and oil are seen coming out of the exhaust. It is new, and tested, good quality diesel... I wonder what happened? This is the classic symptom of a diesel generator operating at a load far below its specification. And it's a more common mistake than you might think. When connecting a 100 kVA generator to power a load that consumes 10 kVA, it will not work “quietly” as one could deduce from a layman. On the contrary, she will be making a greater effort than if she were fully loaded. Why does it happen?

First, it is important to understand that generator sets are designed to run on load. This may sound trivial, but properly sizing and running a generator set is critical to engine availability and long life. Manufacturer's maintenance intervals and component life projections are based on statistical data from operations with proper workload.

Incorrect operation of the generator set can result in reduced power, component damage, reduced life and unscheduled downtime.

In general, diesel generator sets, standby and prime, are designed to operate between 50 and 85 percent load, while continuous diesel generator sets operate best between 70 and 100 percent load. Operating diesel generator sets at loads below 30 percent for extended periods can impact engine life. This is because it needs to reach a minimum temperature to function properly, which is not achieved with a load below the specified.

The most common consequence of underloading is exhaust manifold lubricant leakage, or carbonization, which is a black, oily liquid that can leak from the exhaust gaskets when the engine does not reach the minimum temperatures and pressures. Visible leaks in the engine do not necessarily indicate a problem, but they do signal possible underload, low ambient temperature or very low temperature of the cooling ducts. In addition, long periods of operation at lower loads can cause deposits of material behind the piston rings, on the spark plugs or inside the cylinders, which can lead to loss of power, poor performance, accelerated wear and in extreme cases, damage. to the cylinder lining.




But if in certain situations, it is absolutely necessary to operate with low loads, there are some procedures to minimize its impact, in particular a specific maintenance for this type of situation. After underloading, the generator sets must be run at higher loads (you can use a load bank, for example) to increase the pressure and temperature in the cylinders, which will clear the combustion chamber of deposits. Continuous operations at low loads require a more aggressive maintenance plan to reduce excessive component wear and may require engine modifications.

Power system underload impacts both individual components and overall performance, so it should not be overlooked. While the simple solution is to run generator sets at loads according to design requirements, the truth is that system needs change at times. This makes underloading common in the field of power generation — especially in standby applications. However, the effects of underloading can be minimized with a meticulous operation and maintenance plan to preserve system health and avoid extra costs down the road.

Load levels in percentages of continuous maximum rated power  0-25%   extremely low charge   25-40%   low load   40-80%   Normal generator operating load   80-90%   high load   90-100%   extremely high load 

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Designed for demanding job sites, our Chicago Pneumatic mobile air compressors allow operators to run multiple hand tools and hammers at the same time for maximum efficiency. They’re also ideal for sandblasting, irrigation blow-outs and general construction applications.

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Ash Air's range of Chicago Pneumatic Mobile CPDG diesel generators have been designed to meet the tough demands of the construction industry.

Using proven technology, sturdy design and ease of operation, the CPDG provides you with a dependable source for all your electrical power needs. With integrated forklift slots and a lifting beam, the CPDG range of generators are easy to move and designed to be highly impact resistant.

Other features include easy to read gauges, easy to access maintenance points and a reinforced structure. Chicago Pneumatic products are backed by more than a century of experience working with construction industry customers.

We understand what it takes to be productive on the job, and it shows in our CPPG portable generator and CPDG mobile diesel generator line. Get in touch with our team today!

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Ash Air has been around in New Zealand since 1979, and we’ve grown into a nationwide company with international support and a reputation for quality and reliability.We look after all things compressed air for your business!

  • Reciprocating, Screw, air compressors
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Ash Air's range of Chicago Pneumatic, Alup, Pneumatech, and Quincy compressors are used extensively around the world in industries ranging from oil and gas to food, automotive and farming, and we bring you these world class compressors here in the land of the long white cloud.Our technicians are compressed air equipment experts and are dedicated to addressing customer needs. Supported by a 13 locations nationwide, Ash Air offers one of the widest selections of compressed air equipment and parts available today in New Zealand.

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