- Microbial Growth
How Do I Get Clean Fuel?
Clean fuel is obtained by filtering your fuel upon delivery, protecting it from ambient dirt and moisture while it is in storage, and filtering it again when dispensing into your equipment. The methods for obtaining clean fuel are fairly straightforward, if not always easy to implement.
The best way to prevent problems before they occur is to ensure that only clean, dry fuel reaches your equipment. Unfortunately, you often don’t know you have a problem until it is too late. First, we will address what to do if you already have a problem in your tank or are experiencing fuel-related equipment failure.
Removing Dirt Protects Engines
When people think about fuel contaminants, the first thing that comes to mind is dirt. It seems obvious that abrasive wear cannot be good for a fuel system, and it’s not. So, why don’t people pay more attention to keeping dirt out of their fuel?
Fuel is generally clean when it leaves the refinery, but contamination enters each time it is transferred or stored, all the way through to the moment when it is burned. Is hard particulate damaging your equipment or rapidly clogging your filters? If so, the first thing to do is to isolate the problem by testing the cleanliness of your fuel at each critical point: at delivery, inside your bulk tank, and at the dispenser. This will help you prioritize the action steps that will improve your fuel quality the most: cleaning fuel before it is delivered, improving tank conditions, installing filtration your dispensers, or other.
Protect the Fuel Investment In Your Tank
Work sites tend to be dirty places, and fuel continues to be contaminated each time it is transferred or stored. The task at hand is to prevent additional dirt from getting into the fuel after it is in your bulk tank. This is something every fuel user can and should take steps to control. Dirt can get into your bulk or on-board fuel tank upon delivery, from the air, from the tank, or from direct contact. This can be prevented or minimized by good handling practices.
Protect the Fuel Investment In Your Tank
- Inspect all tanks to ensure that they are properly sealed, with no cracks, loose fittings or other openings where dirt could get through.
- Inspect all breathers. Many breather pipes have little to no protection from airborne dirt and contaminants. Install high efficiency breather filters to protect from dirt. Combination air filter and desiccant (deliquescent) breather styles are best, since they protect from both ambient dirt and humidity.
- Inspect all transfer and dispensing points and take measures to ensure that dirt is not introduced into the system through negligence.
- Inspect the inside of the bulk storage tank on a regular basis. Test samples from the bottom, middle and top to determine the presence of dirt, water or other contaminants.
- Drain and clean tank periodically if it is contaminating your new fuel deliveries.
Not all fuel filters are created equal. Some remove only “rocks and sticks”, while others remove over 99.9% of all contaminant down to the size of a single cell of bacteria. It is important to use a filter that will clean fuel to recommended levels.
To accomplish this, the bulk filter should be just as efficient as the on-board secondary fuel filter specified by the manufacturer of your equipment. Numbers of particles and total contamination amounts increase dramatically at smaller particle sizes under 4 microns.
If you are not filtering out particles of this size at a high efficiency rate, then you are doing little to protect your equipment or extend the life of your on-board filters. No matter which filter you select, testing your fuel is the only way to know for sure that it is clean enough.
Water Management Techniques
Fuel will always contain a certain percentage of water. The goal is to keep water levels within acceptable limits, well below the saturation point. Removing excessive water from fuel can be a challenge; therefore, the most effective approach is to take every reasonable measure to prevent water from entering your tank and monitor it regularly. This way the need for water removal can be kept to a minimum. In order to develop a good water management strategy, it is important to understand how to measure water content and evaluate the results.
Measuring Water Content
There are several methods for measuring water content in fuel. Some are done in a laboratory, some can be done onsite. It is important to understand the type of information these different tests can provide. Perhaps the most common method for testing for water in fuel tanks is to “dip” the tank using a special indicator paste on a long dip stick. This method is fast, easy and can be done on site, it will tell you if there is free water in the tank bottom.
Water monitors (sensors) can be installed inline and give reliable real time results. They measure the dissolved water content in fuel and return the relative humidity of the fuel as a percentage. The maximum result is 100%, meaning that the fuel has reached its saturation point and can hold no more water in solution. This test method will not tell you how much free water there is in the tank.
The Karl Fischer titration method is a laboratory test used since 1935 for determining water content in a fluid sample. The test is highly precise and requires only a small sample size. It detects even small amounts of dissolved water, down to about 50 ppm in diesel fuel. It can measure water content both below and above saturation level (dissolved and free water). In laboratory practice it can be used to determine water saturation level of fuel under different conditions. While laboratory tests are typically more precise than field tests, they can be much less accurate. This may seem confusing. The reason that the laboratory test may be less accurate is that the sample itself may have changed between the time it was taken from the tank and the time it is tested in the lab.
One of the characteristics of fuel is that it holds more water in saturation when it is warm compared to when it is cold. If the fuel in your tank is cold it may be over the saturation point. In this case there will be free water entering your equipment, which can cause huge problems. If you send this same sample to a lab, it will likely be warmer in the lab than in your tank. The fuel will warm up, the water will go back into solution, and it may look like you have no problem at all. The same sort of diagnosis difficulties can happen with ice crystal problems. The “evidence” goes away at room temperature.
How Much Water Is Okay?
The easiest answer would be none. But this is neither practical nor realistic. All fuel contains some percentage of water. The most important thing is to keep the water below its saturation point so that it stays dissolved rather than entering your equipment as free water. Equipment manufacturers specify that ZERO free water must reach the engine.
Saturation points vary from roughly 50 ppm to 1800 ppm based on temperature and on the petro fuel/biofuel ratio. As you can see on the chart above, biofuel can hold significantly more water in saturation than than its petro equivalent. Blending bio and petro fuel together, however, does not result in a mathematically proportional moisture content. The blend will hold less in solution that the sum of the parts, meaning that free water precipitation may occur when the two are mixed.
And as we now know, ultra low sulfur diesel that contains just 15 ppm of sulfur is especially susceptible to having the water fall out of solution. One of sulfur's surfactant properties is to help the water stay in solution as the diesel passes through combustion. Without the sulfur, the water is more likely to fall to the bottom of the tank.
Ambient moisture and condensation can be prevented from entering the fuel through the use of good desiccant breathers in combination with a blanket of dry air (or nitrogen) fed into the tank’s headspace and out through the breather. As explained earlier, the relative humidity of the fuel will tend toward the relative humidity (or “dryness”) of the air. Moisture in the fuel will, with time, be released back into the dry air until the fuel is just as dry as the air.
Microbes Must Be Eradicated
Microbial colonies can proliferate in any fuel tank. All they need is food (fuel) and water to grow. Warm weather and the presence of biofuels will accelerate this process. Once these microbes have gained a foothold in your fuel tank, they can be hard to eliminate. The first step, of course, is to diagnose the problem and its severity.
Microbial contamination varies in appearance, but looks very different from typical dirt. Most people don’t realize they have a problem with their system until they experience filter plugging. By this time the situation is far more severe than just a few microbes.
Diagnosing Microbial Growth
One easy indicator may be found in your used fuel filters. Open up a clogged filter, if it is coated with stinky, slimy, black filth; then you probably have a microbe problem. One ASTM test method for diagnosing microorganisms in fuel is described in ASTM D7463-08. This test detects the presence of Adenosine Triphosphate (ATP) in fuel and fuel/water mixtures. ATP is an energy-bearing molecule found in all living cells. If ATP is present, it means that micrboes are living in your fuel tank.
The test helps estimate the concentration of microorganisms, which is useful in diagnosing a microbial problem, validating the effectiveness of the treatment, and for ongoing monitoring of your fuel supply. The advantages of this test method are that it is fast and easy. The user can do it and see the results in about 10 minutes.
Work with your local Fuel Professionals expert to have a member of our team come out with the necessary equipment to pull a sample of fuel from your tank. Most microbial issues are very evident when looking at the color and clarity of the diesel sample. However, independent lab tests can confirm if you have issues that should be addressed, and an acceptable timeframe for you to get that resolved.
Eliminating Microbial Colonies
Microbes are everywhere. But when they have acclimated to your fuel system, half-measures will probably not eliminate the problem. If you don’t remove the system’s free water and substantially reduce the active colony, they will simply grow back.
You never truly sterilize a fuel system, but you can reduce and control biological activity to a level where it is not a problem. Numerous good biocides are available for proactive use. DO NOT USE what many call “maintenance dosing”. These are usually sub-lethal and actually make things worse. A better proactive strategy is to periodically treat the system with a kill dose. The time frame for this can be determined by a systematic testing program to determine how frequently your system gets re-infested. Also, it is very important to institute a vigorous water removal program. This alone will significantly reduce future contamination issues.
If your fuel is of critical need, then a less expensive (and more effective) option is fuel polishing. Through fuel polishing, The Fuel Professionals are able to clean your tank by sucking the microbial growth off the inside walls of the tank like a vacuum cleaner.
For most microbial infestations, a combination of fuel polishing and biocide treatment will together solve the problem. However, if the tank is too contaminated for the fuel polishing equipment to effectively remove the sludge from the inner walls, then a more intense multi-step process may be necessary.
For bad infestations, we recommend a multi-step process:
- Drain the tank of all free water.
- Use a high dose of a reputable biocide to “shock” the contaminated tank
- Follow this with a thorough “man down” tank cleaning, scouring the sides and bottom to remove all remnants.
- Prevent reoccurrence by using a periodic kill dose of biocide on a regular basis to protect a clean system.
Be sure to follow dosing instructions carefully and retest your tank periodically, to be sure that your anti-microbial regimen is working.
Some equipment operators choose to skip the tank cleaning step due to downtime, cost considerations or the inability to physically enter the tank. In this case, be aware that you may load up a large quantity of filters with dead microbes before the tank flushes itself out.
Microbes cannot reproduce without water. If your tank is properly maintained and contains no free water, then microbes will not grow.
I’ve been handling my fuel the same way for years. Why should I change now?
You are not alone, with the exception of reducing sulfur content, fuel standards have not changed substantially in over a decade. Engines, however, have changed dramatically. In order for new equipment to run trouble-free, they require much cleaner fuel. This means an increased need for filtration. Manufacturers are insistent that damage caused by fuel contaminants is not a factory defect. Therefore, it is in your best interest to filter your fuel prior to use.
Shouldn’t it be my fuel supplier’s responsibility to deliver clean fuel?
More than likely, your supplier is delivering perfectly in-spec fuel. The problem is that fuel cleanliness specifications are woefully out of date when compared to the needs of the modern engine. Some distributors are starting to go the extra yard and filter fuel prior to delivery, but this is not an industry requirement. An additional note of caution: the term “clean diesel” can also be used when referring to ultra-low sulfur fuel. This is not the same as reduced contamination levels or fuel “cleanliness”.
How can I tell if my fuel is clean enough?
Testing is the only way to know how clean your fuel really is. Any reputable oil analysis lab should be able to help you with this, and here at The Fuel Professionals, we work directly with an independent laboratory who can provide you the results you need to make the best decision for your fuel system. Remember, engine manufacturers do not accept liability for damage caused by fuel contaminants, so the cleaner the better.
My fuel filters are plugging up really quickly; should I change brands?
It is important to use high quality fuel filters to protect your engine. In most cases changing filter brands will NOT solve your fuel problems. Remember, a plugged filter did its job. Rapid filter plugging is an indication that there is a problem with the fuel, not the filter. The key to resolving rapid plugging issues is to determine how filterable solids are getting into or forming inside your fuel tank, and then fixing the root cause. Switching to a lower efficiency filter, regardless of brand, will simply spread the problem throughout your fleet.
The injectors and fuel pumps on my new equipment keep failing; what can I do?
The first step is to speak with your Original Equipment supplier. If you suspect that dirty fuel is behind the problems, a simple test can verify your fuel cleanliness level. Make sure you put the cleanest fuel possible into your equipment and protect your engine with a high-efficiency fuel filter. This should eliminate injector and fuel pump problems due to dirty fuel.
Fuel is fuel, right? Why not buy from the cheapest source?
As with anything, you typically get what you pay for. Fuel is expensive, so it is tempting to minimize operating expenses by purchasing the cheapest fuel possible. While this fuel may meet minimum industry standards, that may not be adequate. Small differences in handling practices can have a huge impact on overall fuel quality and cleanliness. Saving a few pennies on your fuel bill may end up costing you far more in downtime, lost production and equipment repairs. Partnering with a good supplier is one of your best defenses against unforeseen fuel quality issues.
I already have a 10 micron filter on my pumps; shouldn’t that be good enough?
Having a filter on your pumps is always a good idea. However, as modern engines have evolved, they need fuel that is hundreds of times cleaner than just a decade ago. Technology, such as 10 micron filtration, that was effective a few years ago is simply not adequate for modern equipment. With high injection pressures and clearances of only 1 or 2 microns in HPCR fuel systems, much tighter filtration is needed. As a rule of thumb, the filter on your dispenser should be just as efficient as the secondary fuel filter specified for your equipment.
Biodiesel was just introduced to my area. I’ve heard horror stories. What can I do?
While biodiesel has many good qualities, it can be a challenge as it relates to filtration. Biodiesel acts as a solvent, so it tends to clean the infrastructure when first introduced, putting a stress on existing filtration. Biodiesel begins to gel or solidify at much higher temperatures than petro fuel, making it difficult to flow and filter in colder climates. And finally, biodiesel contains glycerin, which even in small quantities can contribute to rapid filter plugging. Your best strategy is to remove any solidified glycerin before it reaches your equipment.