There are a number of enterprises that, because of the nature of their business, may elect to depend on a generator to power their day to day operations. This may be for only a short time, such as for the duration of a particular job or project, or it may be because a conventional connection to the electric grid is not feasible or is not available.
Some examples of this type of business may be:
There are situations where a project may be limited to the amount of power that may be drawn from the grid and generator service acts as a supplement to grid supplied power.
The power requirements of these types of enterprises typically require generators that would operate continuously, or for extended periods of time, and would fall into one of two categories: a continuous generator that is designed to operate continually with a consistent load, or a prime generator that is designed to operate for long durations at variable load.
Primary Power Generators are expensive! It is a piece of equipment that is made to operate 24/365. A backup power generator is much less expensive because it is only designed to operate for maybe 200 hours per year when the primary power is unavailable and the lights go out. That is an important slice of time when it is your lights that went out, but when a generator is built to run for over 8,000 hours per year and is expected to provide reliable service for years, there is a degree of sophistication and durability that enters the equation. This is all the more reason to consider the quality of diesel fuel and take steps to assure tank cleanliness when you are operating with Primary Generators powering your enterprise.
Many primary generator applications suffer the most from being dependent on a source of fuel that is, shall we say, inconsistent. Unfortunately, there are distribution channels servicing remote locations that do not have a fuel management plan that calls for reasonable steps to assure that the quality of the fuel that leaves the refinery is maintained until it meets the customer. The other issue is the time frame between the diesel fuel leaving the refinery and when it arrives on the customers doorstep (more on this below).
Our experience has shown that fuel problems cause about 70% of all diesel engine failures. And microbial growth in fuel storage tanks and other degradation of diesel fuel"s stability contributes to 90% of those fuel problems. Why understanding and addressing fuel storage problems is critical to the management primary power generators is clear.
Before 2007, when the Environmental Protection Agency (EPA) mandated a change to Ultra Low Sulfur Diesel (ULSD) in on-road applications, diesel fuel contained 500 ppm of sulfur, providing two positive effects. Sulfur was a lubricant for seals in the fuel injectors and injector pumps. Most diesel engines built prior to the year 2000 relied heavily on this lubrication. Current formulations that include a blend of bio-diesel has helped the lubrications situation, but has presented other problems (see below). Also, sulfur acts as a natural biocide that helps prevent microbial growth in diesel fuel tanks. Removing the sulfur makes the diesel fuel much less resistant to fuel microbes (fungus, mold, and bacteria). Since 2014, on road and off road equipment now must use ULSD.
According to Caterpillar, today’s ULSD has a shelf life, even when all basic fuel storage maintenance practices are followed by the distributor, of one year beginning when the diesel fuel leaves the producer, and six months for bio-diesel and blended bio-diesel. At temperatures above 86 deg. F (30 deg. C), diesel and bio-diesel fuel storage life is cut in half.
Engine Preventative Maintenance is an important part of a periodic engine maintenance program that is common in all major industries today, but fuel condition is often taken for granted. Many of today's maintenance personnel have many years of experience, but until changes were regulated to diesel fuel within the past decade and technology advances in diesel engines were introduced, these maintenance professionals were never presented with the problems we are experiencing today with diesel fuel. With today's advances in design and engineering of diesel engines and the critical requirements that equipment have longer life cycles and near 100% uptime, Fuel Management, as a component of engine preventative maintenance, can no longer be ignored. It is now just as important as changing the oil and ensuring the batteries are charged.
Cat contends that diesel fuels can deteriorate rapidly when fuel is “stressed”. The high pressure (in excess of 30,000 psi) and high temperatures (fuel is used as a coolant for high-pressure fuel injection systems) of today’s engines incorporating High Pressure Common Rail (HPCR) fuel systems results in the fuel enduring these stresses repeatedly as fuel is recirculated back to the fuel tank, causing much of the fuel degradation. Gums and resins that occur in diesel fuel under these stressful conditions are the result of dissolved oxidation products in the fuel that do not evaporate easily and do not burn cleanly. Excessive gum in the fuel will coat the inside of fuel lines, pumps and injectors and interferes with the close tolerances of the moving parts of fuel systems (Caterpillar's publication SEBU6251-17 "Cat Commercial Diesel Engine Fluids Recommendations", Page 45).
As a separate issue, water commonly accumulates in stored fuel and is the most damaging contaminant to diesel fuel and the primary catalyst to additional fuel breakdown. Although some water can be added with a fuel fill, much more common is moisture being introduced through a tank vent as air is drawn in to replace used fuel. Temperature changes of as little as seven degrees (see heated fuel above) cause droplets to form on fuel tank walls and accumulate in the bottom of the tank. Above ground fuel tanks have wide temperature variances daily, and the expansion and contraction of the fuel inside the tank draws air in, and pushes air out as it "breathes" with this expansion and contraction of the fuel. Water is the required component to microbial habitat and growth, and as air is drawn into the tank, so is fungal and other microbial growth. These little critters live in the water, and feed off the components of, and additives in, the fuel. The reproduction process of these microbes produce a black, slimy organic material sometimes seen floating in diesel fuel and on fuel filters (sometimes mistakenly identified as algae). The microbes are too small to filter out, but this black, slimy material shortens filter life, sometimes to minutes instead of hundreds of hours. Uncontrolled microbial growth creates acids that can corrode the fuel tank, fuel systems and injectors. The water in tank bottoms should be periodically tested for pH. Normal pH for Diesel fuel is between 5.5 and 8.0. A reading of below 5.5 is an indicator there could be a problem. Investigations of serious corrosion problems have disclosed fuel pH measured as low as 2.5.
This situation does not happen overnight. Many maintenance managers will blame a fuel fill and complain to the fuel distributor, but this situation can take six and even nine months to develop to where the slime becomes problematic. The fuel distributor recommends a biocide additive. The problem is that a biocide will shock the organic growth in a tank creating a grit in the tank bottom akin to sand. This debris is then stirred up every time fuel is added to the tank and drawn into the fuel system, further clogging filters. Treating the symptom instead of the real cause of the problem, in this instance, results in creating an additional problem. And with all likelihood, the added biocide becomes diluted and less effective, cannot penetrate the slime and other organic build-up on the tank walls and bottom, and does not eradicate 100% of the microbial growth. And so the cycle begins again.
Another problem less recognized by the maintenance personnel is the process involving the agglomeration of asphaltenes, a component of diesel fuel, in clogging fuel filters. Asphaltenes are present in all diesel fuel as a function of the process of refining crude oil, are less than 2 microns in size and suspended in the diesel fuel. But stored fuel allows the asphaltene time to form clusters, and as these clusters grow in size, and achieve sizes of 100-200 microns, the fuel begins to appear dark, sometimes black, and filters become black and clogged with these clusters of asphaltenes (see accompanying before-and-after pictures). In storage tanks, they can gain size and weight and drop to the tank bottom adding to the tank sludge in the tank bottom. Inspections of tank bottoms often disclose an appearance of being painted with roofing tar. This is the accumulated asphaltenes.
Fuel injector nozzle holes generally have two failure conditions, which result in a partial functional failure of a fuel injector. These two conditions are blockage, caused by the contaminants in the fuel discussed above, and erosion of the injector ports from the acids formed by the microbial contamination. These conditions lead to fuel non-atomization and leakage of fuel onto the piston crown. The degraded fuel spray pattern results in carbon buildup on injectors, valves and the piston as a result of larger droplets of fuel not fully burning. Leaked fuel results in an increase in piston crown temperature, which can cause the crown to deform or melt, resulting in engine failure. As this may only occur in one cylinder, even an experienced operator or mechanic may not properly diagnose this problem before total engine failure occurs.
Diesel fuel cleanliness is the ultimate goal. For a more complete understanding of fuel cleanliness and how that term is defined, see the Diesel Fuel and Injector Failure page on this web site. Caterpillar, like most engine makers, recommends a final filter rated at 4 microns and the use of fuel with an ISO Cleanliness (ISO4406:1999) of ISO 18/16/13. This level of filtration is assumed to allow injectors and other fuel system components to live happy, long lives as the tolerances in injectors are in the 4 to 5 micron range. But the reality is this final filter should not be your first line of defense against nasty fuel. Even with a primary filter rated at 10 microns that may double as a water separator, it is not wise to put a lot of faith in a belief that the fuel is not-so-bad so as to overpower the engine manufacturer's safeguards. Keep in mind that filters do not stop the acids, and the gums and resins can still get through a 4 micron filter to wreak havoc on your pocketbook.
Caterpillar, as will all engine manufacturers, set standards and make recommendations for a reason. If there should be a failure of components in the fuel system within the warranty period, it is not unheard of for the servicing dealer to check the fuel. If fuel being sourced from the storage tank for use in the generator is not within recommended standards (ISO Cleanliness), warranty claims could be denied.
Diesel fuel that is maintained in a condition as close to "refined" as possible will out perform fuel that is under, or poorly, maintained. In order to achieve optimal fuel quality, the contaminants in fuel must be filtered out, water must be separated and removed, and the fuel must be conditioned. This process of filtration, separation, and conditioning (commonly referred to as the Fuel Polishing process) is the foundation for achieving, and maintaining, the quality of fuel necessary for ultimate reliability. Review the page about Diesel Fuel Polishing, as what some folks call "fuel polishing" is really only filtering the fuel after the use of a biocide. Returning fuel to its clear and bright condition and restoring optimal fuel quality requires a Fuel Conditioner.
Although filtration and de-watering is critical, fuel conditioning is paramount. You cannot filter microbes out of fuel, and the asphaltene agglomeration will not be reversed without the use of the Fuel Conditioner.
We recommend you establish a Fuel Management Plan that allows the manufacturer's filters to be the last line of defense instead of the only line of defense. Place protections in front of those filters by establishing a Fuel Management Plan that keeps your diesel fuel water free, clear, bright, and providing optimal performance. The AXI MTC 3000 Mobil Tank Cleaning System is an example of a cart mounted Tank Cleaning and Fuel Conditioning System that will provide for a single unit that can manage dozens of fuel tanks. Using this unit only once per year on each generator set in most locals (in some locals, depending on temperatures, humidity and other factors, treatments more than once per year may be necessary), will assure that your fuel is in optimal condition, clear and bright, and ready to go to work for you on a moments notice. Larger diesel fuel tanks used for distribution may be better served with a dedicated Series 6000 or Series 7000 Automated Fuel Management System that will automatically, at predetermined times, clean and filter the storage tank.
Your generator units filters will last longer and your engines will enjoy the longevity that you expect from them. As a bonus, the same Mobil Tank Cleaning System can also be used on various other equipment and diesel vehicles that are part of your equipment inventory to clean all fuel storage tanks and equipment tanks, and polish the fuel so you are ready when the power goes out and your community is in need.
Now that you have decided to institute a Fuel Management Plan for your operations, there is work to do. Consider the following as the basis for your Fuel Management Program to further assure that your equipment will run when it is needed most and repair costs are under control:
With only moderate effort, you can be assured that your diesel fuel will provide optimal performance and enjoy the expected life of your fuel filters, diesel engine and engine components.