While it's not advisable to run generators below their optimal workload-to-fuel-consumption level, the reality on job sites and in emergency situations sometimes demands it. If this happens to be the case, regularly scheduled and preventative maintenance regimens become even more crucial for maintaining the health of the power system. Generators regularly expected to run on light loads should be subject to more rigorous maintenance regimens to ensure there's no excessive wear or deposit buildup.
If generators must be run at a light load for a period of time, then they generally should afterward be run under an increased load. This raises the temperature and pressure within the generator's cylinders, which helps to clean off deposits in the combustion chamber.
Light-loading should be even more limited for natural gas generator sets. It's recommended that they be run at a 0- to 30-percent load level only for half an hour, and from 31- to 50-percent load level for only two hours. All light-loading should be followed by at least two hours of running at no less than a 70-percent load level.
Scheduled and Preventative Maintenance
Scheduled and preventative generator maintenance plans are a must for users looking to prolong the life of their generator equipment. For generators in critical applications, such as standby generators at hospitals, data centers and laboratories, generator maintenance plans are critical.
Some components of a scheduled maintenance plan may be as simple as the user making sure generator exercisers are in place and functioning properly. These turn on the generator at set intervals to verify that everything is working correctly.
Load bank testing is another essential element in a preventative generator maintenance plan. This test artificially boosts the load placed on the generator, usually to about the height of the generator's output capacity. This helps to erase any effects of wet stacking or other buildup and to confirm that a generator is actually capable of performing at its peak output rate. It is normally recommended that load bank testing be conducted at least once per year.
The ambient conditions in which a generator operates will also have an effect on how often it should be serviced. Dust, moisture, salinity, altitude and extreme temperatures will all have a bearing on how often routine generator maintenance should be conducted.
In general, regularly scheduled "life-cycle" maintenance can save time and money by preventing downtime, allowing for small issues to be addressed before they become large ones and by prolonging the service life of the generator.
Diesel Generator Efficiency and Tier 4
As is the case in many sectors of the power generation industry, the Environmental Protection Agency's final Tier 4 regulations are shaking up the way we buy and maintain diesel generators. Many of the diesel generators designed to meet Tier 4's new emission standards are even less tolerant to light-loading than previous models were. This is largely due to the fact that the selective catalytic reduction (SCR) components, which were introduced to reduce nitrogen-oxide (NOx) emissions, must operate within a very narrow temperature range.
It's also important to realize that final Tier 4 diesel generators cannot be operated without the additive diesel exhaust fluid (DEF). DEF is a non-hazardous solution that's sprayed into the exhaust stream of diesel engines to help reduce NOx emissions. In addition to confirming a Tier 4 diesel generator is running with the proper levels of DEF, it's also key to verify beforehand that a particular type of DEF is approved for use with the specific generator model.
Final Tier 4 engine standards are tweaking best practices for running diesel generators efficiently. While some of the effects are new to all of us, it's always best to consult experienced engineers who know how this type of machinery will function with new components and additives. Consulting a professional before any adverse effects of inefficient operation have time to add up will help to prolong the life of final Tier 4 generator equipment.
About the Author
Clayton Costello is the operations manager at CK Power, a leading manufacturer of power units and power generation solutions for a variety of markets and customers. In addition to its manufacturing capabilities, CK Power has been a leading distributor of new and remanufactured diesel and natural gas engines.
