Understanding Diesel Fuel Cleanliness Standards

With diesel fuel becoming susceptible to contamination after the initial fuel refinement, it should be a concern for fuel managers to understand the quality of the fuel they are receiving.

There are many different types of diesel fuel contamination, each with their own unique challenges in remediating.

Dirt, water, and microbial growth can not only reduce fuel quality, but also impact the operational reliability of the equipment relying on the contaminated fuel supply.

Fuel cleanliness can be measured through the ISO 4406 code that defines the quantity of solid particles in a fluid.

Through this standard, contamination in liquids can be quantified to a degree where necessary actions can be determined.


Part 1:

Fuel Cleanliness Standards

What do ISO numbers mean?

Fuel cleanliness levels using the ISO 4406 method was officially documented as a global standard only as recently as 1998 with the development of the Worldwide Fuels Charter (WWFC).

Since its inception, the charter has established a minimum cleanliness level for each of the diesel fuels under various available categories around the world.

The numbers in the ISO 4406 cleanliness code are used as the industry standard to measure contamination in various liquids, such as fuels and hydraulics.

Since contaminants come in a variety of shapes and sizes, the ISO cleanliness standard specifies measuring the size of particles in microns.

To make contamination levels easier to digest, a 100ml fluid sample is taken to analyze. ISO 4406 measures the number of particles larger than 4µm, 6µm, and 14µm within the 100ml fluid sample.

Chart displaying particle sizes for various ISO 4406 codes.

Using the table below, the ISO code number to the left is used to represent the number of particles per ml. For instance, a reported fluid sample with an ISO of 21 / 19 / 14 would mean that there are 10,000 to 20,000 ppm of particles larger than 4µm (ISO 21), 2,500 to 5,000 ppm of particles larger than 6µm (ISO 19), and 80 to 160 ppm of particles larger than 14µm (ISO 14).

ISO cleanliness chart with ISO code and associated particles per ML count

How big is a Micron?

When talking about things in terms of “micron” measurements (µm), a micron is simply an abbreviation for a “micrometer”, or 1/1,000,000 of a meter. Being equal to roughly .00004 inches, a micron is not visible to the human eye (which is limited to about 40 microns).

Microns are a standard unit of measurement in many sciences, industrial manufacturing, and other industries reliant on fine precision measurements.

The diameter of a human hair, which can be clearly seen by the naked eye, is about 80 microns in diameter. A United States one-cent coin is 19,053 microns in diameter. White blood cells measure at about 25 microns, while bacteria range from a fraction of a micron to about 2 microns in diameter.

Graphic displaying relative micron sizes of things from a grain of salt to a single cell of bacteria.

It is important to note the ISO testing standards of measuring for 4µm / 6µm / 14µm, as all of these micron sizes are invisible to the human eye without the use of a microscope.

These ISO numbers are extremely important to quantify considering mechanical equipment components, such as injectors with specific micron tolerances, or other small openings in pumps that are susceptible to mechanical wear driven by the presence of these microscopic particulates in the fuel.


Part 2:

Fuel Quality Testing

Testing for Fuel Contamination

There are preferred and recommended methods in testing for fuel contamination that are considered the standard in many industries. From bulk fuel storage sites to construction operations relying on petroleum energy, fuel quality is directly responsible for the operability and reliability of these industries and many others.

This is why fuel is to be regularly tested, adequately maintained, and properly remediated should it not meet the recommended cleanliness standards.

Chart displaying mechanical ISO code requirements for mechanical components and their tolerance sensitivity.

Fuel Contamination & Fuel Degradation

Creating a proactive fuel maintenance program requires an understanding of the processes that occur within the tank. In order to properly react to changes in your stored fuel supply, it is important to distinguish the differences between fuel contamination and fuel degradation.

Fuel contamination is typically some type of impurity that has entered the fuel supply, and often starts with water. Some forms of contamination can be removed through remediation or prevented through proper maintenance. Other contamination forms can lead to fuel degradation and eventual fuel breakdown.

Graphic depicting the development of fuel contaminates in diesel fuel overtime

To learn more about the water-driven microbial growth in diesel fuel: check out our article on Addressing Algae In Diesel Fuel.

Fuel degradation is classified as molecular fuel breakdown or changing of fuel chemical characteristics over time. Fuel can interact with its environment and change molecular form over time, leading to forms of contamination or being incompatible with your engine or the demanding equipment.

SAE Fuel Testing Standards

SAE International is an association within the engineering industry that develops international industry standards around sectors such as aerospace, automotive, and more.

SAE has developed technical standards that are universally understood such as horsepower ratings and aerospace engineering standards. 

J1488 & J1839

SAE J1488 is an emulsified water/fuel separation test procedure as recommended by SAE International.

J1488 is specified to be used when the water that is in the fuel has water droplets that are relatively small in size. This SAE standard lab test measures a fuel filtration system’s effectiveness at removing emulsified water.

The type of emulsified water that is targeted in J1488 testing is best remedied through water-absorbing filters or through using coalescing media.

SAE J1839 is a coarse droplet water/fuel separation test procedure. This lab test evaluates water emulsion where droplets are of larger size.

This type of emulsified water is best mitigated through centrifugal water separation and the use of hydrophobic filter media.

ASTM Testing Standards

The ASTM, originally known as the American Society for Testing and Materials produces technical standards for a variety of industries to enhance operability, efficiency, and effectiveness of many critical standards.

ASTM has various categories where their determined standards fall, and they also provide training and testing for those in the industry.

These standards are utilized in hundreds of industries, including manufacturing, construction, medical devices, nuclear services, water technologies, and more.

The ASTM updates their Annual Book of ASTM Standards each year, and ASTM has 143 technical writing committees that work on developing and updating these standards.

ASTM compliance has grown to be the standard in many industries, with many vendors, contractors, engineers, and architects exclusively requesting products and services to meet ASTM’s renown standards.

ASTM D2709

ASTM D2709 is a testing method for water and sediment in middle distillate fuels by centrifuge.

The “Water and Sediment” test is used to provide an indication of free water or sediment that is suspended within the fuel as a haze or cloudiness for No. 1 and No. 2 diesel fuels.

While the test doesn’t provide analysis for the type(s) of fuel contamination, it provides a basis for how much contamination is within your fuel supply. Further testing may be required after remediation to determine the source of fuel contamination.

ASTM D6469

ASTM D6469 is the standard guide for microbial contamination in fuels and fuel systems.

Microbial contamination within your fuel supply can lead to fuel degradation and more severe tank contamination. The microbes grow at the interface of water and fuel and can propagate into much larger issues.

In order to prevent this problem from spiraling out of control, it is important to identify the issue and handle it properly.

Many microbial tests require additional caution and more stringent methods to properly collect and isolate the fuel sample to prevent contamination from the environment (additional microbes getting inside the sample).

ASTM D7371

ASTM D7371 is the standard test method for determination of biodiesel content in diesel fuel using mid infrared spectroscopy.

Biodiesel consists of fatty acid methyl esters (FAME) and is blended with ULSD for use in most industries.

A 5% bio-blend can be sold as straight ULSD without notifying the customer (still falls under ASTM D975). Due to its production from fats and oils, it is particularly susceptible to oxidation (environmental breakdown), microbial growth, and has a higher affinity for water (holds more water in the fuel)).

For these reasons, it can be important to know the amount of the biodiesel within your tank. Backup power fuel sources sit for longer than normal amounts of time, leading to excessive time for fuel breakdown within the tank.

ASTM D7545

ASTM D7545 is the standard test method for oxidation stability of middle distillate fuels–Rapid Small-Scale Oxidation Test (RSSOT).

The RSSOT test is used to project the lifespan of a fuel supply (including biofuel blends and pure biofuel).

Under high pressure and a high oxygen environment, fuel will break down more rapidly (oxidize).

This test is used to predict how well a fuel blend will do in the field over a longer duration. Fuel that scores low on the RSSOT test may want to be replaced instead of remediated.

For fuel scoring very low on this test, contaminants may build up very shortly after remediating the fuel supply. This test replaced older oxidation tests due to its ability to handle biofuel.

ASTM D4176

ASTM D4176 is a distillate fuel bar chart test that is used to determine contamination through “haziness” in a distillate fuel.

A fuel sample is taken from the fuel source, and is contained in a see-through glass jar for visual testing.

The ASTM bar chart has a series of ratings from 1 to 5 used to determine a pass/fail rating.

By putting the ASTM chart behind the fuel, the test can be completed by comparing the appearance of the fuel with the associated ratings on the chart.


Part 3:

The Cycle of Fuel Maintenance

Fuel Maintenance Cycle

When managing bulk storage fuel in often large volumes, it is important to prioritize fuel integrity, ensuring that the fuel is ready for use when a demanding system requires it.

To make this process easier to manage, we have simplified the fuel sampling and testing cycle into four revolving steps.

Graphic showing the 4-step cycle of fuel sampling and testing, 1. sample 2. analyze 3. react 4. repeat

Sampling Fuel

To gather a sample that best represents the current status of your energy source (the fuel), it is important to sample fuel directly from the storage tank.

Be sure to pull samples from problematic areas of the tank that are often hard-to-reach, where fuel stagnation can rapidly degrade fuel. 

Fuel contamination “falls out” of the fuel and towards the bottom of the tank, where it will collect. When using a fuel sampler, be sure to pull the fuel from the bottom of the tank to be sure you are sampling the fuel where the contamination is most abundant.

If your fuel system has multiple fuel sources, be sure to test all sources to be sure the fuel quality is consistent and/or that contamination has not spread farther from your original testing point.

Analyzing Fuel

When it comes to analyzing your fuel sample, there are many accepted tests and methods to gain an understanding of the current quality of your fuel samples.

There are tests, as mentioned in our SAE/ASTM section above, that can be used to turn your sampled fuel into relevant information regarding your current energy source.

For analyzation and testing, you can send your fuel samples to labs that specialize in fuel testing, where they will give you a breakdown of the different contamination levels that were found in your fuel. This method is thorough, however it can take up to a couple weeks to receive results.

There are other testing methods which can be carried out on-site, and can give fuel managers the insight needed to make critical operations decisions in 15 minutes or less.

Particle counters are used to translate fuel quality into an ISO 4406 standard, using laser technology to account for contamination particles of different micron sizes.

Proper Fuel Sampling & Testing

Fluid sampling pumps are often used to obtain fluid samples from hard-to-reach spots using flexible tubing. This allows for fluids to be drawn without the worry of cross contamination, as the fluid never comes into contact with the pump.

Fuel tank samplers, also known as “bacon bombs”, are industrial-strength stainless steel devices used to remove liquid samples from a bulk fuel storage tank. The device is lowered into a fuel tank until the sampler’s plunger makes contact with the bottom of the tank.

The plunger then opens, which admits a sample into the unit. To sample from any desired level in the tank, the plunger can be actuated by a pull-chain attached to the device.

Once fluid samples are obtained, they must be sent to a lab for testing. Getting results from the lab could take days, up to waiting periods of weeks.

For quicker results, Kolor Kut ® Water Finding Paste is a product used to instantly report if there is a presence of water in petroleum fluids such as gasoline, kerosene, diesel, and heavy fuel oil. The paste is applied to a rod and dipped into the tank, with the color of the paste changing instantly upon contact with water.

FUELSTAT ® PLUS is a simple fuel testing kit that provides results in less than 10 minutes. The objective of the test is to provide rapid screening of fuel samples to give a quick and accurate assessment of H. Res., bacteria & other fungi within the fuel.

Liqui-Cult Microbial Test Kits accurately detects and quantifies bacterial and fungal growth in a variety of fluids. Liqui-Cult tests for microbial growth in fuel samples over a period of a few days.

Through frequent fuel testing, the presence of contamination can be determined and action plans can begin to be determined. Depending on the scope of contamination levels and volume of fuel contaminated, some solutions may be more practical to implement than others.

Fuel Sampling & Testing Tools

To be proactive and catch fuel contamination early, fuel should be sampled and tested from a bulk fuel storage tank at least once every six months. Testing for different contaminants can be achieved in a number of ways, here are the most common tools for fuel sampling and testing:

Reacting to Fuel Results

Once fuel testing results are received, it is time to take the action needed to improve or maintain the quality of the stored fuel you are managing. 

In Part 4 of this article, we will review different fuel maintenance methods and equipment that are suited for both improving and maintaining the quality of bulk fuel storage tanks.

It is important to act quickly when receiving less-than-desirable fuel test results, as prolonged contamination issues can quickly elevate into bigger issues, and even lead to complete equipment failure if that fuel makes it to critical engine components.

Repeating & Prevention

Regular fuel testing is critical in being able to manage an energy source. If unnoticed, contamination in a fuel tank can compromise an entire fuel system, leaving room for vulnerabilities and unnecessary lapses in system integrity.

Fuel can fall out of desired spec in the matter of months to even weeks, so through persistent testing, you can be made aware of undesirable trends in your fuel quality and be able to make proactive decisions.


Part 4:

Keeping Diesel Fuel Clean

Fuel Filtration

When it comes to fuel filtration, there are recognized and preferred ratings that industrial professionals, equipment operators, and filter manufacturers prefer.

Three types of common types of filter ratings are absolute ratings, nominal ratings, and beta ratings.

Other than beta filter ratings (or ratios), an absolute filter rating is one of the preferred rating systems for those working in industries that utilize filters, as absolute filter ratings give operators and mechanical engineers a much more consistent result when compared to nominal ratings.

Absolute Ratings

Absolute filter ratings are absolute in that they are rated to the diameter of the largest particle that will pass through the filter media.

The absolute filter rating indicates the filter media pore size, and ultimately, what maximum particle size will be allowed to pass through the filter.

Filters that are “absolute rated” usually have (on average) a more consistent pore size, enabling them to achieve higher filtration efficiency, increasing their beta ratios as a result. 

Nominal Ratings

Nominal filter ratings are expressed in being able to filter a certain % of a given micron size, for instance, “90% of 25 micron” – meaning that the filter is able to stop 90% of all 20+ micron particles from passing through.

The nominal rating is considered by most to be an inaccurate and inconsistent rating system because of the many variables around liquid flow through a filter media.

Between the concentration of contamination and the system operating conditions like pressure and temperature, it is nearly impossible to rely on nominal ratings for accurate measurements of filter effectiveness.

Beta Ratios (ISO 16889)

Beyond both absolute and nominal filter ratings is the most preferred rating system in the fluid filtration industry, the beta rating.

Derived from ISO 16889, the Multipass Method for Evaluating Filtration Performance of a Fine Filter Element, the beta rating is the most accurate measurement of filter effectiveness, which bridges the gap between manufacturer claims and end-user results.

Chart displaying beta ratio and corresponding filter efficiency percentage.

The beta rating system uses particle counts both upstream and downstream of the filter element to measure controlled quantities of contaminants in the fluid.

The beta ratio is then determined by dividing the number of particles of a certain size measured upstream of the filter by the number of particles of the same size measured to be downstream of the filter.

Referencing the chart below, you can see what particulate differentials correspond to what beta ratio.

Chart demonstrating the beta ratio and efficiency of upstream vs. downstream particle counts.

Filter Types

Filter medias are especially important in that they are responsible for capturing contaminants in passing liquids, in this case fuel.

Through choosing efficient and effective filter media, fuel systems can be kept at an optimal state where risk of failure from fuel contamination is dramatically reduced.

However, the lack of optimized fuel filtration medias can also provide its own set of unique challenges, that could put the fuel system at risk.

There are two common types of filter medias primarily used in the filtration industry today, cellulose and microglass filters.

Cellulose

Cellulose filter media is a widely used filter type that is made of larger diameter fibers than microglass.

Because of the media quality, cellulose filters are cheaper than other media types but that initial cost saving often comes with a greater cost of its own.

Due to the larger fibers in the cellulose filter media, the contaminants that are captured in the filter can severely restrict fuel flow and develop into a rapid pressure drop in the system.

This leads to more frequent filter changes, and less effective filtration overall.

Because of this, cellulose filter medias are seen to be much less efficient when compared to microglass media filters.

Microglass

Microglass filter medias are made of synthetic media that is of a smaller diameter than cellulose media.

This smaller diameter media allows the microglass filter to capture more contaminants with less severe impact on fuel flow and pressure.

The increased surface area of the microglass filters also provide more surface area for the filter media to be able to remove contaminants from the fuel.

These microglass filters translate into higher efficiency filters for the fuel system, allowing optimal fuel filtration as well as an extended filter lifetime.

Graphic displaying the difference in cellulose and synthetic (microglass) filter media

What is Fuel Polishing?

Fuel polishing is a fuel filtration technique used across many industries to increase and maintain fuel quality in stored fuel. Through these fuel filtration systems, various forms of contamination are removed and prevented.

Mobile Fuel Polishing

These polishing systems can be mobile units built onto carts or skids, or these systems can be mounted (sometimes in an enclosure) that is plumbed into the bulk fuel storage tank.

Graphic depicting periodic fuel polishing with a mobile fuel polishing system

The mobile polishing systems are advantageous when having to maintain a number of different fuel tanks without having to incur the financial cost of installing multiple fixed systems. Mobile systems come in a number of different sizes and flow rates, and we recommend you visit our Mobile Fuel Polishing page to view the different systems that are available.

Mobile fuel polishing may seem like the perfect solution especially if you have multiple tanks, however that is not always the case.

As these units are not fixed onto the fuel storage tank, these systems must be hauled out on a scheduled basis to maintain fuel cleanliness. The problem arises not when fuel is cleaned to the desired fuel cleanliness standard, but rather when fuel is again left to sit untreated.

This causes the fuel to fall back out of the desired cleanliness specifications where it must be polished again. This creates a cycle, which is illustrated below, that gives chance that the fuel fails to maintain the quality requirements if stringent polishing cycles are not maintained.

Graphic comparing periodic fuel polishing against automated fuel maintenance as solutions for preventing harmful levels of fuel contamination

Now, you can see where this fuel polishing cycle could turn into something that proves to be quite taxing, especially in situations where multiple fuel tanks on a specific site need to be treated on a regular basis.

Automated Fuel Polishing

Automated fuel polishing systems can be beneficial to fuel storage in facilities where frequent access for mobile polishing isn’t preferred or practical.

Our Automated Fuel Maintenance and Enclosed Fuel Maintenance systems are engineered to allow for the scheduling of periodic fuel polishing so that fuel is constantly being cycled and polished. This eliminates the concern for fuel to fall out of the desired fuel cleanliness and quality standard.

Graphic depicting the installation of an enclosed and compact fuel maintenance system for automated fuel filtration

For facilities that are reliant on backup power systems, this is immensely important. Mission critical facilities, such as hospitals and data centers, cannot risk electrical downtime in the event of a power outage.

With these facilities having large volumes of stored fuel to power the backup generators, it is important that fuel quality is maintained to ensure quality fuel is delivered to the backup power system at a moment’s notice. Any fuel quality issues could render the backup generator inoperable, putting critical systems at risk.

Levels of Fuel Filtration

Fuel polishing systems have a number of components necessary to ensure that fuel is being cleaned and contamination is removed in an appropriate manner.

Micron filtration removes clumps of fuel and other particulate that could harm equipment. By passing fuel through micron filters, contaminants such as dirt, grime, and sludge can be caught by the filter and removed from the fuel.

With water separation, free water is captured and removed from the fuel to prevent the proliferation of microbial growth. By capturing the water, fuel polishing systems effectively remove the conditions to which “the diesel bug” thrive.

Not only that, but by removing the water from the fuel it keeps the engine and fuel injection system from receiving water that could pose harm to the integrity of the equipment.

AXI International’s LG-X Inline Magnetic Fuel Conditioners are a proprietary part of our fuel polishing systems that use a magnetic field to achieve a number of things.

Through running fuel through the magnetic chamber, metallic particles and fragments are captured and thus prevented from making their way into critical engine components. These metals could be comprised of various ferrous metals or even rust.

Rust is typically a sign of the presence of water within a fuel tank. Rust can only develop where there is water, and if fuel was previously clean but rust was found during the polishing cycle of a fuel tank, chances are that there is water present as well.

The magnetic field is also responsible for breaking down clumps of diesel fuel known as agglomeration where the fuel molecules in diesel fuel, over time, naturally pull together creating thick clumps of fuel. By passing these clumps through a magnetic field, the intermolecular bonds are weakened, allowing clusters to fall apart and return to a more fluid-like state.

Fuel Additives

Fuel additives can also prove to be beneficial for those concerned with fuel contamination issues. However, with such a wide variety available on the market, it could be hard to decide which additive is best suited for your unique needs.

Fuel stabilizers as a fuel additive work in a manner that prolongs the stability of fuel in storage. These fuel stabilizers are often used in circumstances where fuel is expected to sit for an extended period of time without any fuel maintenance.

By dosing the fuel tank appropriately, this fuel additive prevents fuel from oxidizing and experiencing a chemical breakdown.

Combustion catalysts can be used to not only enhance engine performance, but also provide for a more complete burn of fuel being supplied to the combusting cylinder, which results in reduced carbon deposits. This, in turn, reduces engine emissions as less unburnt fuel is released from the exhaust system.

By increasing power output, combustion catalysts can often result in a healthier engine response.

Corrosion inhibitors in certain fuel additives prevent corrosion on metal surfaces, which prolong engine life and equipment operability. This reduces the amount of “surprise” equipment maintenance that is needed due to the failure of certain parts within an engine’s mechanical system.

The corrosion inhibitor is comprised of compounds that attach to component surfaces and form a film that acts as a lubricant which reduces engine wear and extends the lifetime of mechanical components.

We recommend AFC Fuel Additives as the go-to fuel additive to add to your fuel maintenance schedule. As the only fuel additive offering all of these features and benefits within a single formula, AFC Fuel Additive is the smart choice for your equipment. With a concentrated formula, just eight ounces of AFC Fuel Additive is able to treat 320 gallons of fuel. AFC is also available in 1 Gallon (treats 5,000 gallons), 5 Gallon (treats 25,000 gallons), and 55 Gallon (treats 275,000 gallons) quantities.

Summary

Through gaining an understanding of what diesel fuel contamination is, what causes it, how to test for it, and how to treat and prevent it, we hope to give you greater in-depth knowledge on just how critical your fuel quality is.

From lawnmowers to tractor trailers, fuel quality is something that affects everyone logistically- for it could be the reasons behind your car not running and your generator failing. Sometimes, the application is small, and fuel is simply replaced before damage is done and you are on your way again.

But, in many cases, this can be a costly solution especially when there are thousands of gallons of fuel at risk. And in the worst-case scenario, this fuel can not only be contaminated, but also further contaminate and cause detrimental mechanical issues within the equipment the fuel was being supplied to.

Engines and equipment rely on quality fuel to operate as designed, and when that standard of fuel isn’t being supplied (which is often the case), gradual wear and breakdown of components could lead to costly repairs, particularly in and around the fuel injection system.

To ensure fuel quality and mitigate the effects of contamination, it is recommended to instill fuel maintenance systems and procedures. At the general consumer level, this could mean using a fuel additive when you fuel up your vehicle. At the business operational level, this could mean installing automated fuel management systems to polish bulk fuel and prevent contamination from proliferating.

Diesel 101: DPF or Dangerous Potential Fire?

As the global market continues to push for reductions in harmful emissions, Diesel Particulate Filters (DPF) have grown to be an important product in fighting pollution from diesel-powered vehicles.

But without adequate long-term testing on the feasibility of DPF systems and associated maintenance/repair costs, are DPFs becoming a pain point that outweighs its potential benefits for consumers who rely on their vehicles for work or pleasure?

There is plenty of information and research to back up the fact that DPFs reduce harmful vehicle emissions, but there is little research conducted to quantify the financial impact DPFs have on the general consumer market.

To understand diesel particulate filters and their potential pitfalls, first one must understand just how these systems grew to have such widespread use.


Part 1:

Emissions Requirements and DPF Systems

Section icon for laws and legislature around DPF and emissions

Emissions Regulations in the US & EU

Starting in 1993, Euro 1 regulations set emissions limits for new vehicles in the EU. From 1997 to 2015, Euro 2-6 regulations were incrementally introduced to further reduce the emissions of both diesel and petrol vehicles.

With the December 2000 adoption of EPA rule-making in the United States, strict standards were established that aimed at reducing harmful emissions from new heavy-duty trucks and buses, and the stateside automotive industry would forever be changed.

This change would begin with the 2007 model year, requiring 100 percent of on-road diesel vehicles to use a DPF to reduce exhaust emissions.

Aiming to reduce the particulate matter, NOx, and other harmful emissions of the automotive exhaust systems, manufacturers were required to develop and implement a change in the exhaust management systems of their vehicles.

Because of the known health concerns that come with automotive pollutants, the EU & EPA’s rulemaking regulated the particulate matter (PM) and NOx emissions in on-road vehicles, with the purpose of reducing the impact exhaust emissions has on human health.

Diesel particulate filter (DPF) systems have been around for decades. With the EPA working alongside diesel engine manufacturers, these bodies were able to focus on reducing NOx and PM in exhaust emissions through using these DPF systems.

Diesel Particulate Filter and Regeneration

DPFs work to reduce exhaust emissions through capturing exhaust particulates in the filter within the canister. DPFs are typically installed close to the engine side of the exhaust system. By capturing particulates, these filters are able to keep a majority of harmful emissions from ever entering the air.

Over time, these filters do need to be cleaned of the captured particulate matter (PM). This is when the DPF system enters regeneration mode, also known as “regen”.

The computer is made aware that regeneration is necessary, and the engine is able to heat up the DPF to burn off the PM, cleaning the filter. There are two different types of regeneration, passive and active.

Passive regeneration occurs when an engine operates at significant speed, passing heat into the exhaust system. This hot exhaust is able to heat up the DPF, burning off the trapped PM in the filter.

Active regeneration is activated by a PCM command that increases the amount of fuel, allowing the DPF to experience higher exhaust temperatures. This PCM command usually comes from an input that senses the excess back pressure in the DPF from filter blockage, letting the PCM know that a PM burn-off is needed. As the DPF experiences this temperature increase, PM is oxidized from the filter. During this regeneration, the DPF temperature is raised to roughly 1,000° F.

Other types of DPF regenerations can be activated through programmed mileage counters (i.e. every 500 miles). Regeneration can also be deactivated should the vehicle operator be in a situation where a prolonged high temperature regeneration could be potentially dangerous.


Part 2:

The Potential for DPF Failures

Icon for DPF failure section

DPF Fires, Failures, and Lawsuits

DPF systems have come under fire by a group of California trucking companies after filing a lawsuit against the California Air Resources Board.

The truckers claim that the so-called pollution preventer is causing dangerous truck fires.

Approximately one million trucks in the state of California have a DPF, and one of those trucks belonged to Keith Daniels. In 2016, Keith Daniels watched his 2009 Peterbilt truck burn to the frame in only eight minutes.

Moments before it erupted into flames, Daniels pulled into a truck stop to use the restroom.

Walking back, he looked up to his beloved truck in flames.

His suspicions are that the truck fire started during the DPF regeneration process.

He was stunned from the incident, reflecting on the close call and how he could have easily been in the cab sleeping when this fire started.

This is not the first recorded incident with suspected DPF origins.

A major DPF manufacturer closed its doors after numerous fires and recalls stemming from their DPF systems. With a reported price tag of $20,000 for the DPF to be installed, it is an astonishing price to pay for a system that proved to be unreliable and unpredictable.

There have been numerous reports of DPF regeneration being the possible catalyst for engine fires, and there has even been a DPF fire responsible for burning down more than 5,000 acres.

Around the globe, automotive manufacturers are facing lawsuits. In Australia, a Federal class action lawsuit by consumers alleges faulty DPF filters installed by Toyota are reducing fuel efficiency and harming engines.

Beyond the suspected risk for fires, DPFs also have other failure points that should be addressed.

A common issue with DPF systems is the deactivating of cleaning cycles because of untimely regenerations leading to the build-up of soot and particulate which can clog the filter. This can disable a vehicle, and leave operators stranded.

The exhaust restrictions that come with the DPF filters increase back pressure and can cause engine strains which can harm the integrity of the engine over extended periods of time.

When DPFs are blocked, there are many symptoms that can be felt by an equipment operator. These symptoms include vehicles being stuck in “limp” mode, premature engine & turbo failure, reduced engine power, continuous regeneration failure, strong diesel failure, excessive exhaust smoke, loss of power, and reduced fuel economy.

DPF system failure indicators graphic showing examples of warning lights and failure symptoms

DPF Maintenance and Replacement

As a DPF forms blockage over time, there is an increased likelihood of the DPF system becoming clogged if required regeneration cycles are not met.

Once the DPF becomes clogged to the point where DPF will not activate and maintenance will not be effective, it must be replaced and can become a costly expense.

DPF systems are a post-combustion filter element used to prevent diesel exhaust particulate and soot from emitting from the vehicle. From the exhaust inlet, these DPF systems flow exhaust through oxidizing catalysts to control harmful emissions.

These diesel oxidation catalysts (DOCs) are a honeycomb filter that oxidizes carbon monoxide. The hot exhaust gas makes contact with the DOC and converts harmful pollutants into carbon dioxide and water. The filter’s “honeycomb” flows exhaust gases through channels to pass through the filter media, capturing the particulates in the process.

These filter channels have various cell plugs which redirect exhaust flow to continue through an optimized exhaust filtration path.

DPF system overview showing components and how the particulate matter is captured

During regeneration, the metal casing that encloses the DPF elements expands and contracts with the heating and cooling within the unit. Over time, this continuous cycle has the potential to crack or rupture the casing which results in DPF failure and likely requires replacement.

The costs associated with DPFs is something that has grown to be a big concern to users who have them equipped. There have been many reports of consumers who have been alerted to required DPF servicing just weeks after the last service.

This is a far cry away from the suggested 150,000 – 200,000 miles between DPF service intervals that many OEMs recommend.

DPFs have been proven to prevent up to 95% of the harmful soot and pollution produced by diesel engines from being released into the atmosphere.

Preventing pollution is a positive thing, since the pollution from diesel exhaust has been shown to cause lung cancer, asthma, premature death, and other health problems.

In conclusion, the effectiveness of DPF systems can’t be ignored, however the issues that come along with using them begs the question: Are the consumer-facing issues worth the emissions benefit?


Part 3:

Alternative Methods to Reduce Emissions

Section icon for fuel additives to reduce emissions

Improving Fuel Quality to Enhance Fuel Efficiency

As determined by the United Nations Economic Commission for Europe, “fuel quality is key to deliver on sustained low emissions from cars, as both cleaner fuels and advanced emission control systems are needed to deliver on cleaner tailpipe emissions.”

Through decades of study on emissions, the UN determined that the quality of the fuel being used is critical for the automobiles and engines to perform both reliably and properly. This includes the emissions control systems that were engineered by auto manufacturers to combat harmful exhaust emissions.

In turn, many developed countries around the globe mandated the reduction of sulfur levels in gasoline and diesel fuel. This led to the development of ULSD to reduce harmful exhaust emissions, to improve the quality of the air, and improve both human and environmental health.

With sulfur being known to impair the effectiveness of emission control systems, a majority of countries took this big step towards using low sulfur fuel to improve air quality around the world.

The International Maritime Organization is following suit in reducing sulfur emissions in the international marine shipping industry with the introduction of IMO 2020 regulations.

Reducing Emissions Pre-Combustion

Emissions devices such as DPF systems do possess one critical flaw.

These systems are designed to combat emissions through post-combustion measures, meaning that the harmful pollutants are still being created during the engine’s mechanical operation.

Harmful emissions are simply captured through the DPF element of the exhaust system.

To best reduce harmful emissions, it is important to seek pre-combustion measures to combat the reactions that produce these harmful pollutants.

This includes the use of high quality fuel, and maintaining stored fuel for optimized engine operation.

Whether used on their own, or in tandem with systems that utilize a DPF, fuel additives act as a catalyst that optimizes the combustion of the fuel.

In doing so, pollutants are minimized during engine combustion and harmful emissions are reduced.

This is achieved through reducing the amount of unburned fuel that is able to pass through the engine and out the exhaust, providing for a higher-efficiency engine and reduced exhaust emissions.

AFC Fuel Additives has an extended history of reducing exhaust emissions through its use.

Through numerous case studies conducted over its 30+ year history, the use of AFC fuel additive has been linked to increases in fuel efficiency as well as reductions in exhaust emissions such as sulfur oxides (SOx), carbon monoxide (CO), hydrocarbons, smoke/particulate matter, and nitrogen oxides (NOx).

The Effects of Diesel Fuel Contamination

Fuel contamination can be felt in many ways, particularly in the mechanical operability of your engine or equipment. Some of these symptoms often go unnoticed, or ignored, while other symptoms can be severe and impossible to ignore.

Not only can these failures be extremely costly to repair, but these catastrophic failures can be dangerous, especially when they occur on the road or at high speeds.

Fortunately, many of these failures can be prevented through frequent fuel testing and the implementation of preventative solutions.

In this article we will cover the symptoms, causes, testing, and solutions for all types of diesel fuel contamination.


Part 1:

Symptoms of Fuel Contamination

Don't Ignore Your Engine Check Light

Many people have been or have known someone that was in a situation where the “check engine” light comes on in their vehicle out of seemingly nowhere. Anxious at first, they tone down their driving to see if they can feel any difference in how the vehicle is running.

Strangely enough, it doesn’t feel any different than before- so they convince themselves it probably isn’t anything other than the car or truck being a bit “finicky”.

At first a few days go by, then a few months. The light is still on and since the vehicle doesn’t feel to be running any different, it’s being ran just as often and hard as it normally would.

Under the hood however, components are not operating as designed, and the continuous operation of worn parts are damaging the very systems that keep the vehicle running.

At this point, detrimental engine failure could be just a matter of time, turning a repair of a couple hundred dollars into one that could quickly incur costs deep into the thousands.

Clogged Fuel Filters

Frequently clogged fuel filters are oftentimes one of the first initial signs of possible diesel fuel contamination. The filter is designed to capture particles in your fuel before they pass into the engine, and these pieces of matter can be made up of clumps of fuel sludge, metallic particles, or other unwanted particulate.

If a fuel system is experiencing an atypical recurrence of fuel filter replacements, the problem’s root could lie in the quality of the fuel being supplied to the filter.

Heavily contaminated fuel would consistently provide particulates and other undesired material that would quickly clog up the filters and possibly be leading to other issues in the fuel system.

This contamination could be stemming from either the fuel source itself, or from the internal corrosion of the very fuel tank being used to fuel the engine.

Failing Fuel Pump

With frequent fuel filter clogging, fuel pump failure is often to follow. Because of the restriction caused by the clogged filters, the fuel pump could be working harder than designed to deliver fuel from the tank to the engine.

While a fuel pump is failing, the fuel pump will not be able to deliver a steady flow of fuel, interrupting the mechanical stroke and function of the engine. This can be especially noticeable under acceleration, where fuel demand is increased however the fuel pump is unable to deliver the fuel at the requested rate.

Symptoms of a failing fuel pump may include:

When a fuel pump is exerted to the point of failure, it is past the point of simple maintenance to get the engine running again. When a fuel pump fails, fuel line pressure is lost thus not being able to deliver any fuel for the engine to fire up. Downtime of equipment for major repair is expected at this point to get the fuel flowing properly again.

Partial Injector Failure

Unfortunately, partial functional failure of an engine will often go unnoticed until it is too late.

Engine inefficiencies are seldom felt by a user but can result in serious losses in operability and revenue.

A major reason for engine inefficiency stems from partial failure of an engine’s fuel injection system, which isn’t well understood by a majority of people.

Injector partial functional failure isn’t a failure point that is well-documented in many industries, leaving a lapse in understanding of the symptoms that come with this kind of failure.

Although the equipment is still operable, partial functional failure of a fuel injection system is generally one that reduces engine efficiency or performance. The symptoms of such failures within an injection system may include the following:

Many of the symptoms mentioned here are difficult to diagnose without the proper tools and equipment, which makes needed repairs something that often falls behind.

By continuous operation of the equipment, the user is at risk of experiencing events of catastrophic engine or component failure.

To understand the role fuel injection plays in the engine mechanically, one must understand the stroke cycle as referenced below.

Graphic depicting the combustion process in a diesel engine

During the power stroke, fuel is injected into the cylinder and ignites, creating the energy needed to transfer to the mechanical output that drives the vehicle or equipment.

Prior to manufacturing, diesel fuel injectors are designed with specific functional tolerances. If these injectors begin to fail, or veer from the designed tolerances in any way, then the fuel spray trajectory within the combustion chamber is drastically affected.

Injectors can deviate from their tolerances through the introduction of contaminated fuel. Contaminated fuel can deteriorate and corrode the metal surfaces in injectors, with a higher likelihood after prolonged use of contaminated fuel.

Any number of these factors can alter the engineered functionality of a fuel injector, leading to a snowball effect of internal engine damage that could eventually progress into full functional engine failure.

Catastrophic Engine Injector Failure

When catastrophic engine injector failures are experienced, the engine fails to continue operation due to these sudden occurrences. Typically, these experienced events can only be restored through costly repairs that often result in prolonged equipment downtime.

Operations and equipment managers rely on proper equipment functionality to maintain revenue margins and business profitability. It is for these reasons that attention should be directed at managing, predicting, and preventing these failures from occurring through proper equipment maintenance and operation.

Equipment specialists and OEMs typically operate their equipment around recommended maintenance procedures that are designed to limit component failure and prolong equipment life.

It is common for OEMs to recommend these maintenance procedures to uphold warranties. Fuel injector replacements are a critical component to these OEM warranties, with recommendations often being at the engine’s half-life.

This is recommended because OEMs are aware that engines are not commonly supplied with quality fuel and are instead typically supplied with contaminated fuel that can damage injectors over time and jeopardize reliability.

Although equipment maintenance personnel are responsible for managing engine equipment and remediating potential issues, not all can be predicted and/or prevented. This is often the case with contaminated fuel, as operations managers are often limited in the fuel they can procure.

With the use of contaminated fuel, erosion of the injector valve seat is likely, which can result into partial functional failure that will eventually lead into full functional failure of the fuel injector valve.

The Failure Chain Reaction

  1. Contaminated fuel is sent through fuel injectors
  2. Fuel injector valve deterioration begins
  3. Fuel pressure through injector nozzle reduces
  4. Fuel volume through the injection system reduces
  5. Engine ECU increases fuel load to compensate
  6. Reduced fuel atomization
  7. Soot generation within the cylinder
  8. Emissions increased
  9. Experienced power loss
  10. Partial injection failure point
  11. Injector wear continues
  12. Fuel consumption increases
  13. Visible and audible signs of engine distress
  14. Full injection failure

Within a high-pressure common rail fuel injector, there are three main components that are harmed the most by the effects of diesel fuel contamination. These are:

Fuel Injector Nozzle

Fuel injector nozzles are designed to spray a mist of fuel into the cylinder for piston compression and fuel combustion. These fuel nozzles primarily come in two designs today: the SAC (area around pintel tip) nozzle and the VCO (valve covered orifice) nozzle.

High-pressure common rail (HPCR) injectors primarily use the VCO type. This design allows the injector to quickly and totally shut off the fuel as the fuel injection action ends. This allows for increased control of the fuel injection action, as it is critical in HPCR injectors.

This design enables the injector to abruptly and completely shut off the fuel at the end of an injection event, thus providing a more stringent control of the fuel injection event. The two designs can be seen below.

Graphic depicting SAC and VCO types of fuel injectors

VCO type injection needle valves are known for having particularly fine tolerances and are extremely sensitive to partial failure during the rise and fall actions.

The rise and fall injection actions can occur dozens of times every second in a diesel engine. That is why injector tolerances are critically important in maintaining reliable operation and avoiding partial failures in the fuel injection function.

Typically, fuel injector nozzle holes are susceptible to two circumstances which can lead to injector failure. These two circumstances are blockages and erosions.

Graphic depicting the internals of a high pressure common rail (HPCR) system

The precision involved in the operation of HPCR fuel injectors, although impressive, makes for components that require proper circumstances for combustion to take place as designed.

When achieved as designed, the fuel mist that is injected into the combustion chamber is burned out before the fuel droplets reach the lining of the engine cylinder. This ensures that all the fuel combustion does not damage the cylinder, and it is especially critical for the fuel injection system to function as intended by the OEM.

When fuel is unable to complete combustion as it should, soot builds up within the engine and harmful exhaust emissions are created such as Nitrogen Oxide, Carbon Monoxide, and Particulate Matter.

HPCR fuel injectors ordinarily have 5-8 holes that are machined into the injector tip which allow for fuel to be injected into the combustion chamber and achieve atomization.

When the fuel injection action occurs, diesel fuel is sprayed into the combustion chamber. During the power stroke, the piston moves downward and pulls injector fuel spray deeper into the combustion chamber.

When injector tolerances have been compromised, fuel droplets from the injector nozzle may not be able to achieve combustion, and often results in smoke and soot emissions. If the issue is not addressed, soot will build on the injector tips and eventually cause blockages. These blockages can also occur within the engine valves, the cylinder walls, and the exhaust system.

When injector nozzle holes are blocked due to this build up, fuel velocity through the open nozzle holes increases because more fuel is forced to exit the injector through the remaining non-blocked holes.

These blockages in the injector nozzle result in ineffective atomization which contributes to engine inefficiencies and harmful emissions.

When these partial functional failures within the injector occur, it is perceived as best practice to use diesel fuel additives that are chemically designed to clean soot build-up from the fuel injectors.

Although the use of these additives can help, these additives do not rectify the true underlying issues that contribute to injector blockages. Contaminated fuel will still wear down injectors, and the fuel additive solution may only act as a bandage on a much more significant issue.

Graphic depicting the injector needle valve and nozzle

Fuel Injector Needle Valve & Control Valve

There are two commonly used fuel injectors in modern engines, electronically controlled unit injectors (EUI) and high-pressure common rail injectors (HPCR). The needle valve in both of these fuel injection types is engineered to stop the fuel from running through the injector tip after the fuel injection action.

When a needle valve fails to properly seal, fuel will drip down into the engine cylinder and onto the piston(s). This dripping fuel can be the catalyst for severe engine problems and catastrophic failures.

In HPCR injection systems, the fuel injectors are continuously under sustained pressure while the engine is running. This leads to a higher likelihood of harm if a fuel injector’s needle valve fails.

Both types of electronic fuel injectors have a control valve that functions to manage the timing of fuel injection sequences.

The control valve in EUI injectors are controlled by an electronic solenoid. HPCR injectors are controlled with a Piezoelectric actuated valve. These Piezoelectric valves are often seen as the most critical injector component because they enable the injection system to have more control of the distance of valve movement and valve speed.

The Piezoelectric valves are especially sensitive to fuel contamination because it wears and damages the components and compromises the designed injection tolerances.

With prolonged exposure to contaminated fuel, contaminants can build up within the injector and result in lethargic movement of the needle valve. This causes wear on the valve, and eventually leads to partial, if not full, functional failure of the needle component within the fuel injector.


Part 2:

Causes of Fuel Contamination

Particulates in the Fuel

Undesired particulate within diesel fuel is one of the most common contaminants. From microscopic fragments of ferrous metals to dirt and grime that is introduced to the fuel, various contaminants can be to blame for a majority of fuel-related issues.

Following the refinement process, fuel most likely passes through numerous tankers, trucks, vessels, and storage before it reaches you. Because of this, there are many potential sources of unwanted particulate contamination. Older fuel tanks, particularly those made of black iron, are highly susceptible to rust and corrosion.

Because of corrosion, fuel that was previously clean could be contaminated when introduced to a tank that has rust build-up within. If in a transport tanker or truck, constant vibrations and sloshing could mix the particulates with the fuel to a point where all of the fuel is contaminated.

This fuel can often find its way into other tanks for distribution and bulk storage, where it can then contaminate other tanks or equipment, as well as other fuel that will eventually find its way there.

This cycle evolves into a constant problem for equipment and engine operators, making it difficult to pin-point the source or cause of contaminated diesel fuels.

Rarely is it known exactly where fuel has been passed through before making it to you, leaving the likelihood of receiving contaminated fuel to chance.

Water Contamination

Water in diesel fuel is one of the most troubling types of contaminants, and also one of the toughest to combat in large bulk fuel tanks.

Since fuel is often kept, transferred, and purchased out-of-sight, contamination and build-up of water in diesel fuel can be extremely difficult to spot, unless it is properly tested for.

Not only this, but engine damage from water contamination in fuel can be very costly.

Water can enter the fuel in a number of different ways.

Diesel fuel is a hygroscopic fluid, meaning that it is able to absorb moisture from the air around it. This can become a problem in fuel tanks where full capacity is not maintained for extended periods of time.

By allowing the fuel in a storage tank to have more air overhead to pull water from, emulsified water can develop and become mixed with the fuel in suspension.

Combined with water from condensation, this results in an unfavorable ratio of fuel to water, which can result in contaminated fuel being introduced into the engine or equipment it is being supplied to.

In some cases, water contamination can cause fuel injector tips to explode, should the water make it through the fuel filter and into the engine.

As a potentially catastrophic contaminant, excessive levels of water in fuel can reduce engine performance because of the reduction of energy available within the fuel.

Not only this, but water in fuel can increase the temperature the fuel will freeze at within engine components. This can be especially problematic in cold climates where fuel gelling is already a concern.

Another type of water contaminant is free water. Free water develops as a layer beneath stored fuel after phase separation occurs.

With the presence of free water in a fuel storage tank comes the possible proliferation of microbial growth within the fuel.

When the presence of free water is ignored, the microbial growth will live and grow in the layer where the water meets the fuel. Hydrocarbons in fuel provide food and energy for the “diesel bug” (that is often referred to as “algae”) to rapidly spread.

Once microbial growth exists in a fuel tank, sludge develops as a waste byproduct of the hydrocarbons being consumed by the microbes.

Graphic depicting the development of fuel contaminates in diesel fuel overtime

To learn more about the diesel bug and possible solutions: check out our article on Addressing Algae In Diesel Fuel.

Fuel Degradation

Fuel indeed “goes bad” over extended periods of time in storage.

Many people aren’t aware that diesel fuel has a shelf life, however fuel stability is important to the mechanical operability of your engine.

Good fuel samples are typically bright in color and clear. Degrading fuel samples can often be determined visually, with fuel turning dark and murky because of the development of tar and asphaltenes within the fuel.

High sulfur diesel shelf life recommendations are less than a year, while ULSD and biodiesel blends have an even further reduced long-term stability.

When fuel loses stability during degradation, the gums and waxes that develop can contribute to corrosion and damaging deposits on engine components.

Many automotive mechanics will first flush fuel lines and replace the fuel if a troubled vehicle was known to be sitting for even a few months.

With most engines designed to be in frequent use, such as fleet vehicles, fuel stability isn’t something most consumers have at the top of mind.

If you have fuel that is going to be sitting for extended periods of time, such as bulk fuel storage for a fleet or on-site fuel storage for backup generators, equipment managers should be aware of fuel stability timelines.

Diesel fuel composition can begin to change within a month of sitting in storage, with recommended maximum storage timelines without significant degradation of six months to one year.

However, these recommendations are contingent on the fuel being purchased from suppliers and stored in tanks with the appropriate cleanliness and quality standards.

To properly store fuel (especially in large amounts) for extended periods of time, fuel should be polished to maintain optimum fuel quality that is ready for use at any moment.


Part 3:

How to Test for Fuel Contamination

Fuel Testing Tools

To be proactive and catch fuel contamination early, fuel should be sampled and tested from a bulk fuel storage tank at least once every six months. Testing for different contaminants can be achieved in a number of ways, here are the most common tools for fuel sampling and testing:

Proper Fuel Sampling & Testing

Fluid sampling pumps are often used to obtain fluid samples from hard-to-reach spots using flexible tubing. This allows for fluids to be drawn without the worry of cross contamination, as the fluid never comes into contact with the pump.

Fuel tank samplers, also known as “bacon bombs”, are industrial-strength stainless steel devices used to remove liquid samples from a bulk fuel storage tank. The device is lowered into a fuel tank until the sampler’s plunger makes contact with the bottom of the tank.

The plunger then opens, which admits a sample into the unit. To sample from any desired level in the tank, the plunger can be actuated by a pull-chain attached to the device.

Once fluid samples are obtained, they must be sent to a lab for testing. Getting results from the lab could take days, up to waiting periods of weeks.

For quicker results, Kolor Kut ® Water Finding Paste is a product used to instantly report if there is a presence of water in petroleum fluids such as gasoline, kerosene, diesel, and heavy fuel oil. The paste is applied to a rod and dipped into the tank, with the color of the paste changing instantly upon contact with water.

FUELSTAT ® PLUS is a simple fuel testing kit that provides results in less than 10 minutes. The objective of the test is to provide rapid screening of fuel samples to give a quick and accurate assessment of H. Res., bacteria & other fungi within the fuel.

Liqui-Cult Microbial Test Kits accurately detects and quantifies bacterial and fungal growth in a variety of fluids. Liqui-Cult tests for microbial growth in fuel samples over a period of a few days.

Through frequent fuel testing, the presence of contamination can be determined and action plans can begin to be determined. Depending on the scope of contamination levels and volume of fuel contaminated, some solutions may be more practical to implement than others.


Part 4:

Solutions to Fuel Contamination

What is Fuel Polishing?

Fuel polishing is a fuel filtration technique used across many industries to increase and maintain fuel quality in stored fuel. Through these fuel filtration systems, various forms of contamination are removed and prevented.

Mobile Fuel Polishing

These polishing systems can be mobile units built onto carts or skids, or these systems can be mounted (sometimes in an enclosure) that is plumbed into the bulk fuel storage tank.

Graphic depicting periodic fuel polishing with a mobile fuel polishing system

The mobile polishing systems are advantageous when having to maintain a number of different fuel tanks without having to incur the financial cost of installing multiple fixed systems. Mobile systems come in a number of different sizes and flow rates, and we recommend you visit our Mobile Fuel Polishing page to view the different systems that are available.

Mobile fuel polishing may seem like the perfect solution especially if you have multiple tanks, however that is not always the case.

As these units are not fixed onto the fuel storage tank, these systems must be hauled out on a scheduled basis to maintain fuel cleanliness. The problem arises not when fuel is cleaned to the desired fuel cleanliness standard, but rather when fuel is again left to sit untreated.

This causes the fuel to fall back out of the desired cleanliness specifications where it must be polished again. This creates a cycle, which is illustrated below, that gives chance that the fuel fails to maintain the quality requirements if stringent polishing cycles are not maintained.

Graphic comparing periodic fuel polishing against automated fuel maintenance as solutions for preventing harmful levels of fuel contamination

Now, you can see where this fuel polishing cycle could turn into something that proves to be quite taxing, especially in situations where multiple fuel tanks on a specific site need to be treated on a regular basis.

Automated Fuel Polishing

Automated fuel polishing systems can be beneficial to fuel storage in facilities where frequent access for mobile polishing isn’t preferred or practical.

Our Automated Fuel Maintenance and Enclosed Fuel Maintenance systems are engineered to allow for the scheduling of periodic fuel polishing so that fuel is constantly being cycled and polished. This eliminates the concern for fuel to fall out of the desired fuel cleanliness and quality standard.

Graphic depicting the installation of an enclosed and compact fuel maintenance system for automated fuel filtration

For facilities that are reliant on backup power systems, this is immensely important. Mission critical facilities, such as hospitals and data centers, cannot risk electrical downtime in the event of a power outage.

With these facilities having large volumes of stored fuel to power the backup generators, it is important that fuel quality is maintained to ensure quality fuel is delivered to the backup power system at a moment’s notice. Any fuel quality issues could render the backup generator inoperable, putting critical systems at risk.

Levels of Fuel Filtration

Fuel polishing systems have a number of components necessary to ensure that fuel is being cleaned and contamination is removed in an appropriate manner.

Micron filtration removes clumps of fuel and other particulate that could harm equipment. By passing fuel through micron filters, contaminants such as dirt, grime, and sludge can be caught by the filter and removed from the fuel.

With water separation, free water is captured and removed from the fuel to prevent the proliferation of microbial growth. By capturing the water, fuel polishing systems effectively remove the conditions to which “the diesel bug” thrive.

Not only that, but by removing the water from the fuel it keeps the engine and fuel injection system from receiving water that could pose harm to the integrity of the equipment.

AXI International’s LG-X Inline Magnetic Fuel Conditioners are a proprietary part of our fuel polishing systems that use a magnetic field to achieve a number of things.

Through running fuel through the magnetic chamber, metallic particles and fragments are captured and thus prevented from making their way into critical engine components. These metals could be comprised of various ferrous metals or even rust.

Rust is typically a sign of the presence of water within a fuel tank. Rust can only develop where there is water, and if fuel was previously clean but rust was found during the polishing cycle of a fuel tank, chances are that there is water present as well.

The magnetic field is also responsible for breaking down clumps of diesel fuel known as agglomeration where the fuel molecules in diesel fuel, over time, naturally pull together creating thick clumps of fuel. By passing these clumps through a magnetic field, the intermolecular bonds are weakened, allowing clusters to fall apart and return to a more fluid-like state.

Fuel Additives

Fuel additives can also prove to be beneficial for those concerned with fuel contamination issues. However, with such a wide variety available on the market, it could be hard to decide which additive is best suited for your unique needs.

Fuel stabilizers as a fuel additive work in a manner that prolongs the stability of fuel in storage. These fuel stabilizers are often used in circumstances where fuel is expected to sit for an extended period of time without any fuel maintenance.

By dosing the fuel tank appropriately, this fuel additive prevents fuel from oxidizing and experiencing a chemical breakdown.

Combustion catalysts can be used to not only enhance engine performance, but also provide for a more complete burn of fuel being supplied to the combusting cylinder, which results in reduced carbon deposits. This, in turn, reduces engine emissions as less unburnt fuel is released from the exhaust system.

By increasing power output, combustion catalysts can often result in a healthier engine response.

Corrosion inhibitors in certain fuel additives prevent corrosion on metal surfaces, which prolong engine life and equipment operability. This reduces the amount of “surprise” equipment maintenance that is needed due to the failure of certain parts within an engine’s mechanical system.

The corrosion inhibitor is comprised of compounds that attach to component surfaces and form a film that acts as a lubricant which reduces engine wear and extends the lifetime of mechanical components.

We recommend AFC Fuel Additives as the go-to fuel additive to add to your fuel maintenance schedule. As the only fuel additive offering all of these features and benefits within a single formula, AFC Fuel Additive is the smart choice for your equipment. With a concentrated formula, just eight ounces of AFC Fuel Additive is able to treat 320 gallons of fuel. AFC is also available in 1 Gallon (treats 5,000 gallons), 5 Gallon (treats 25,000 gallons), and 55 Gallon (treats 275,000 gallons) quantities.

Summary

Through gaining an understanding of what diesel fuel contamination is, what causes it, how to test for it, and how to treat and prevent it, we hope to give you greater in-depth knowledge on just how critical your fuel quality is.

From lawnmowers to tractor trailers, fuel quality is something that affects everyone logistically- for it could be the reasons behind your car not running and your generator failing. Sometimes, the application is small, and fuel is simply replaced before damage is done and you are on your way again.

But, in many cases, this can be a costly solution especially when there are thousands of gallons of fuel at risk. And in the worst-case scenario, this fuel can not only be contaminated, but also further contaminate and cause detrimental mechanical issues within the equipment the fuel was being supplied to.

Engines and equipment rely on quality fuel to operate as designed, and when that standard of fuel isn’t being supplied (which is often the case), gradual wear and breakdown of components could lead to costly repairs, particularly in and around the fuel injection system.

To ensure fuel quality and mitigate the effects of contamination, it is recommended to instill fuel maintenance systems and procedures. At the general consumer level, this could mean using a fuel additive when you fuel up your vehicle. At the business operational level, this could mean installing automated fuel management systems to polish bulk fuel and prevent contamination from proliferating.

Addressing "Algae" in Diesel Fuel

There is nothing worse than opening your tank and seeing diesel fuel contaminated with “algae“.

If this fuel were ever to be used, it could wreak havoc on your fuel system.

You may be asking yourself how do I get rid of this “algae” and prevent it for good?

Luckily, we have the answers to those very questions.

In this article, we’ll explain what the “algae” really is, where it comes from, common methods to combat it, and best practices to prevent it for good.


Part 1:

Understanding the Problem

A Common Misnomer

In order to address “algae” in diesel fuel we must first understand the problem in its entirety.

It was a common misconception that the dark sludge growing in your tank is “algae”.

As a result, many still refer to it as such.

What you are actually dealing with is microbial growth.

How do we know this?

For starters, your fuel tank is far too dark.

Algae are plant organisms and they cannot survive without sufficient sunlight.

On the other hand, there are plenty of microbes (bacteria and fungi) that reside in your diesel fuel.

Graphic depicting different cartoon microbes

When water present in the diesel separates into a distinct layer below the fuel (phase separation), you may notice a dark layer begin to form.

A term often coined to describe this phenomenon is the “diesel bug”.

Graphic depicting the development of fuel contaminates in diesel fuel overtime

The interface between the diesel fuel and the water creates the perfect breeding ground for various bacteria and fungi to thrive.

The microbes live and proliferate in the water while consuming the hydrocarbons in the diesel fuel.

In time, the accumulation of microbes will form a visible biomass (rag layer) between the water and diesel fuel.

By-products and dead cells from the growing microbial communities also fall towards the bottom of tank to create a viscous sludge.

The Effects of Microbial Growth

The sludge by-product of microbial growth, when churned up, can clog any engine filter with ease.

A clogged engine filter, especially one clogged at a time of importance, can cause serious problems.

For example, data centers relying on diesel generators for backup power may experience unexpected downtime due to clogged filters.

This can result in costs of hundreds to tens of thousands of dollars a minute for maintenance.

On a smaller scale, clogged filters on boats can often leave owners stranded.

“The diesel bug may start on a microscopic level, but it is clear it can lead to macroscopic consequences.”


Part 2:

Common Solutions

Common Methods to Prevent “Algae” in Diesel Fuel

There are a lot of opinions on how to best prevent “algae”/microbial growth in fuel.

Some will push for the use of biocides which use hazardous chemicals to kill most of the microbes directly.

Others prefer fuel additives that pull water back up into the fuel to help prevent conditions (phase separation) best suited for microbial growth.

At AXI International, we understand that neither of these solutions are perfect for every situation, but recognize they embody the two methodologies for controlling microbial growth in diesel fuel.

You can either kill them directly or prevent the very conditions they thrive in.

Biocides

Although initially effective, biocides are not the end all solution to microbial growth and sludge formation.

Placing health, safety, and environmental concerns aside, frequent use of biocides can create resistant microbes that no longer die upon application.

This is due to the fact that it is nearly impossible to sterilize diesel.

As a result, the surviving microbes, through means of natural selection, will exhibit increasingly resistant traits that will eventually render biocides ineffective.

Graphic depicting a biocides eventual ineffectiveness on microbes in diesel fuel

Part 3:

Best Practices

Removing Microbial Sludge

If microbial growth has progressed to a point that it is noticeable, no treatment mentioned will effectively remove the sludge.

In order to restore the fuel, you must employ a mobile fuel polishing service or system.

Mobile fuel polishing systems work by circulating the fuel out of the tank for filtration.

Graphic depicting periodic fuel polishing with a mobile fuel polishing system

These systems are designed to effectively remove both small and larger contaminates like sludge and can prevent microbial growth through the removal of water.

Beyond restoring the fuel, it is not recommended to use mobile fuel polishing as a long term preventative measure to “algae“/microbial growth when compared to other options.

Preventing Microbial Growth

In some cases, fuel additives that pull water up into the fuel by the means of an emulsifier can be an appropriate response to preventing microbial growth.

The additives address the problem at its source.

Without water, microbes cannot proliferate in the fuel.

By pulling the water into the fuel, it will eventually vaporize in the engine and exit out the exhaust.

In cases involving a Tier-4 engine, water emulsifiers will only create more problems.

Tier 4 engines feed fuel into the combustion chamber at extremely high pressures with very little tolerance for fuel contaminants.

Internals of an injector tips nozzle

Emulsified water, being much larger than the 2-4 micron injector openings, can cause abrasive wear and eventual failure of the injector tips.

Due to this reality, Tier 4 engines require a more technical solution.

Tier-4 Preventative Solutions

For Tier-4 engines, fuel maintenance systems are the best approach to prevent “algae”/microbial growth in the diesel fuel.

Fuel maintenance systems are permanent installations that work on a programmed schedule to regularly pull fuel from the tank to filter out contaminants.

Graphic depicting the installation of an enclosed and compact fuel maintenance system for automated fuel filtration

Unlike fuel polishing systems, fuel maintenance systems are better at maintaining the fuel as opposed to restoring or remediating it from a highly contaminated state.

By the same effect of fuel polishing systems, fuel maintenance systems prevent “algae“/microbial growth through the removal of water.

The Failure Chain: When a Power Outage Can Spell Downtime

For mission critical facilities, downtime is not an option.

When the power goes out, multiple systems must function in sequence for a smooth, uninterrupted transition to backup power.

If just one of these systems fails, the whole backup power system fails.

This is what we call the Failure Chain.

In this article, we cover how oversights in maintenance can lead to the dreaded Failure Chain and how you can prevent downtime.


Part 1:

When the Power Goes

Mission Critical Facilities

Mission critical facilities house any number of operations that, if interrupted, will cause substantial losses of revenue, reputation, and, in the worst cases, life.

This definition can include a large range of facilities such as:

When a power outage occurs, these facilities must rely on a seamless transition to backup power to avoid the damaging effects of downtime.

According to Gartner, even a lapse of just minutes could cost companies thousands of dollars, not including the loss of customer goodwill.

Uptime Statistics (2018)

The 2018 Global Data Center Survey compiled by the Uptime Institute reported infrastructure outages increased to 31% among respondents, a 6% rise from last year’s 25%.

A majority of downtime instances averaged at four hours with 50% of respondents reporting losses under $100,000 and 3% at over $10 million.

Chart Depicting the top causes of Data Center downtime in 2018

The leading cause of data center downtime were power outages, accounting for 33% of all reported cases.


Part 2:

The Failure Chain

The Backup Power System

The typical backup power system includes multiple components that combine into a coordinated system aimed at providing a seamless transition to and from backup power.

Graphic showing an automatic power transfer switch

The instant a power outage is detected, the Automatic Transfer Switch (ATS) shifts power draw to an uninterruptible powersource (UPS).

A signal is simultaneously sent to the backup power generator (usually diesel powered) to begin startup.

Graphic of a Uninterruptible Power Supply (UPS) system

To maintain power during the time taken to start the generator, the UPS acts as a temporary source of electricity.

These systems, usually large batteries, are relatively limited in both storage and output.

As a result, only critical functions receive power until the main source of backup power, the generator, is fully running.

Graphic of a Diesel Power Generator with base tank of contaminated fuel

It is at this point in the backup power chain that problems are most likely to arise.

Fuel is drawn out of the storage tank and into the generator.

If not maintained properly, the diesel fuel can carry contaminants such as:

With the implementation of High Pressure Common Rail (HPCR), an advancement in fuel system efficiency, the tolerance for fuel contaminants has significantly decreased to 4μ in size.

Any contaminant larger than 4μ can clog or, in the case of water, even blow injector tips.

To prevent this, diesel generators have filters to prevent such contaminants from reaching the injectors but with poor fuel quality these filters can clog quickly.

Once generator filters are clogged a facility is left with two options:

#1 Shutdown the generator for maintenance

In order to replace filters, the generator must be shut down for maintenance.

Graphic of a individual replacing a on-board filter on a diesel powered generator

If the facility is relying on this generator for power, downtime is unavoidable.

#2 Bypass the filters

By bypassing the filters, there is nothing preventing the contaminated fuel from clogging or even blowing the injector tips.

Internals of an injector tips nozzle

Clogged injector tips will produce inefficient spray patterns which can result in:

Blown injector tips require immediate shut down for replacement and maintenance.

Either way, contaminated fuel significantly increases the risk of damage to the generator and downtime for the facility.


Part 3:

A Proactive Response

Addressing Fuel Contamination

Your backup power system is only as reliable as its weakest link.

Addressing fuel contamination is quickly becoming the standard for mission critical facilities.

AXI International provides two approaches to keep your diesel fuel emergency-ready:

#1 Fuel Polishing

Scheduled fuel polishing can be achieved internally with the purchase of a Mobile Fuel Polishing System (MTC) or outsourced to a fuel polishing company.

fuel polishing stored fuel to prevent downtime

With this approach, a mobile fuel polishing system is brought to your fuel storage tank.

Fuel is then pumped through the system where water, sludge, and particulate are filtered from the diesel fuel.

It is recommended you test your fuel regularly to ensure it remains within ISO cleanliness standards.

#2 Fuel Maintenance – Recommended*

Compared to fuel polishing, fuel maintenance systems are the more proactive approach to ensuring fuel cleanliness.

These permanent systems run automatically on a programmed schedule to maintain fuel quality indefinitely.

Much like dialysis, fuel maintenance systems pull contaminated fuel from the connected tank(s) for filtration and return clean fuel back to the tank(s).

fuel maintenance system for mission critical downtime

Ultra Low Sulfur Diesel (ULSD): the Good, the Bad, and the Rusty

You have probably heard mixed reviews about ultra low sulfur diesel (ULSD).

Some say it is great for the environment.

Others claim it causes more problems than it solves.

If you are looking for an unbiased take on what exactly is going on, you are in the right place.

Below we will cover why ULSD exists, its benefits and disadvantages vs. traditional diesel, and what you can do to protect your equipment in response to these changes.


Part 1:

ULSD: A Timeline

Clean Air Act Amendment (1990)

Congress passed the Clean Air Act in 1970 as a means to reduce harmful emissions from automobiles.

In 1990, it amended the Clean Air Act to require stricter emission reductions of:

The amendment also included, among other things, stricter tailpipe emission standards and emission testing procedures.

Concurrently, the EPA started imposing sulfur content limits in diesel fuel in an effort to specifically target sulfur oxide emissions.

Highway Diesel Program (2001)

In 2001, the EPA finalized a federally-mandated program called the 2007 Heavy-Duty Highway Diesel Program.

This program was established to further lower emissions from highway diesel engines.

Effective June 2006, the maximum sulfur limit in diesel decreased from 500 to 15 parts per million (ppm).

Chart of sulfur content (ppm) in on-road diesel overtime

This reduction marked the switch from Low Sulfur Diesel to Ultra Low Sulfur Diesel.

Clean Air Off-Road Diesel (2007)

Shortly after the highway diesel program’s inception, the EPA issued the Clean Air Non-Road Diesel – Tier 4 Final Rule.

This rule mandated sulfur reductions for off-road diesel engines, effective 2007.

Chart of sulfur content (ppm) in off-road diesel overtime

As a result, the maximum sulfur limit in off-road diesel fuel initially dropped from 3,000 to 500 ppm in 2007, and then again from 500 to 15 ppm in 2010..


Part 2:

ULSD: The Good, The Bad...

Emission Reductions

Since the 1990s, the EPA has mandated an overall 99.7% reduction in fuel sulfur content.

It has done so in order to cut diesel fuel emissions and pollution.

Sulfur oxides (SOx), specifically SO2are a threat to public health and the environment.

sulfur oxides and the threat to public health

Health concerns related to exposure from SOx include respiratory problems and lung damage.

SOx also causes environmental harm in the form of tree, plant, and stone damage, acid rain, and reduced visibility (haze).

The less sulfur content in fuel, the less polluting SOx emissions that fuel will release.

The Change in Fuel Chemistry

Reducing sulfur content greatly alters the lubricity and overall chemical composition of diesel fuel.

Refineries use severe hydrotreating to remove sulfur from diesel fuel.

Hydrotreating affects diesel fuel in the following ways:

Increases production costs

Fuel economy decreases by an estimate of 1%.

According to the EPA, severe hydrotreating increases fuel production costs by 5 to 7 cents per gallon.

However, these costs may be significantly higher depending on market, distribution, and other production factors.


Part 3:

ULSD: The Rusty

Same Tank, Different Fuels

In 2007, pollution awareness and prevention was on the rise as emission mandates came into full effect.

Since then, fuel tank corrosion damage has hit an all-time high in both gasoline and diesel fuel tanks.

ULSD fuel tankers labeled with ULSD and ethanol describing switch loading

This is because fuel hauling tanker trucks participate in something called switch loading.

For example, a truck could be hauling ethanol-based gasoline one day and ULSD the next.

ULSD causes fuel tanks to rust because of the increased water content and retention

This due to ULSD having a higher affinity to water than traditional diesel.

Water is essential for microbial growth.

However, as the EPA has confirmed, accelerated tank corrosion occurs when ULSD blends with small quantities of biofuel.

Therefore, when ULSD combines with ethanol, or other types of biofuel, even in small quantities, a problematic chain reaction occurs that not only accelerates tank corrosion but can also pose a risk to backup power systems:

ULSD problem flow chart that come from the increased microbial growth and sludge from using ULSD

Part 4:

ULSD: Problem Prevention

Addressing Low Sulfur

To combat problems with ULSD effectively, including decreased lubricity, energy density, and fuel economy, use of broad spectrum fuel additive  is considered best practice.

fuel additive can restore many of the lost properties of diesel while continually reducing emissions.

This is achieved through a fuel catalyst which allows for a more complete combustion of the fuel.

Benefits of using a fuel additive can include:

Preventing Corrosion & Downtime

As previously discussed, tanks containing ULSD have corrosion problems.

If ULSD mixed with biofuel during transportation, those problems will manifest at an accelerated rate.

To combat these issues, along with the formation of sludge, clogged filters, and downtime, you have to look at the chain of events that lead to these outcomes.

In this particular case, everything traces back to microbial growth.

Microbes that proliferate in diesel fuel love areas where water and fuel meet.

ULSD microbial growth from fuel contamination image

If you remove water, you effectively halt microbial growth along with the development of previously mentioned problems.

So how do you remove water?

You have two options:

#1 Hire a mobile fuel polishing company

A mobile fuel polishing company will bring specialized equipment to your location and filter out water, particulate, and sludge from your fuel.

Graphic depicting periodic fuel polishing with a mobile fuel polishing system

Note: Without a permanent installation, like a fuel maintenance system, it is recommended you test your fuel regularly to prevent future contamination due to condensation of new water or introduction of new fuel to the tank.

#2 Invest in a fuel maintenance system

A fuel maintenance system is a permanent installation that regularly maintains the fuel by removing water and other contaminants. These solutions run automatically.

Graphic depicting the installation of an enclosed and compact fuel maintenance system for automated fuel filtration

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