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Fuel Polishing Explained

Posted May 18, 2022 by Tyler Moore

Globally, there are hundreds of millions of gallons of diesel fuel sitting in fuel storage tanks awaiting use. The demanding equipment can range from truck fleets and marine vessels to military bases and hospitals.

The fuel stored on-site is a critical asset that must be managed and maintained appropriately. Failure to maintain fuel properly can lead to a number of issues and impacts can be severe.

In this article, we will go over everything you need to know about fuel polishing and the impact fuel quality has on bulk fuel sotrage applications.

Why Should Fuel Be Polished?

Through the logistical chain of fuel transportation and fuel storage, it is not uncommon for fuel to “pick up” contaminants along the way.

These fuel contaminants come in many forms including water, sludge, dirt, and other particulates that could jeopardize the integrity of the fuel or cause critical damage to the demanding engines that rely on the fuel as an energy source.

This could potentially cause downtime for mission-critical facilities such as data centers and hospitals, or could leave fleet truckers stranded and ship captains “dead in the water”.

According to a study conducted by the Ponemon Institute, the average cost of a total data center outage was approximately $901,500.

Fuel Storage Tank

The financial pitfalls of these potential vulnerabilities are a big reason why mission-critical facilities are prioritizing fuel quality and maintenance so that the backup power systems are reliable in the event of an unexpected power outage.

For marine applications, contaminated fuel can lead to constant headaches. As a vessel rocks through the waters, the fuel within a tank is sloshed around constantly.

This sloshing causes contaminants to be kicked up from the bottom of the tank, dramatically increasing the likelihood of engine filter clogging compared to fuel stored in more stationary applications.

How Effective is Fuel Polishing?

For facility managers, fuel polishing procedures have become a vital part of maintaining the operation of any facility or site that stores large quantities of fuel, especially for prolonged periods of time.

When power systems rely on an energy source, it is critical for that energy source to be of optimal quality for the demanding system(s). In this case, our energy source is the fuel, and optimal quality is achieved through proper fuel management and fuel maintenance procedures.

Fuel polishing equipment effectively removes various contaminants from the fuel. These fuel polishing Fuel maintenance systems that offer polishing features effectively remove harmful contaminants from the fuel.

These fuel polishing systems typically operate automatically on a programmed schedule. These systems will feature multiple stages of filtration that the fuel will flow through, each with its own unique filtration purpose.

Filtration Stages and Fuel Polishing

Fuel polishing systems often feature multiple phases of filtration, where the fuel is decontaminated.

Recommended filtration systems and stages can vary depending on fuel volume and the users’ unique needs. The placement of these filtration stages between systems may differ depending on the engineering & design.

By filtering out contamination and separating water from the fuel, fuel polishing systems maintain the quality of stored diesel fuel.

In AXI’s LX-F Fuel Maintenance System, for example, fuel will first flow through filtration Stage 1 which features a magnetic fuel conditioner. This in-line device will capture loose metals and aid in breaking up clusters of fuel before passing into Stage 2.

Stage 2 is the primary filter of the system, and multiple filter media types are available.

There are different micron filtration options available for the primary filters, with the best option depending on the users' unique needs. 

The micron (µ) level tells us the smallest size particles the filter media can capture. A 50-micron filter (50µ) will capture particulates as small as 50µ but any particles smaller than that (1µ, 10µ, 30µ, etc.) will still be able to pass through the filter media. LX-F users can opt for either 10µ or 30µ particulate filters. Instead of particulate filters, users can also opt to use a 60µ stainless steel screen.  

In instances where the fuel may be heavily contaminated, the 60µ filter will capture the largest particulates while the fuel is being conditioned. This is because in some situations low micron count fine filters may have to be continually changed as they clog due to the severity of the fuel contamination.

After passing through either the particulate filter or screen, the fuel will then flow into Stage 3. When the fuel enters the centrifugal water separator, water is “spun” out of the fuel using centrifugal force.

With water being heavier than the fuel that it resides in, the fuel water separator can successfully remove the majority of the water present in the fuel by spinning the fuel and its contents at a high velocity.

Once the fuel leaves the fuel water separator, fuel will now enter the pump. It is important to note that the primary filtration happens before the pump, which helps to keep the pump from being damaged by heavy particulates.

After flowing through the pump, the fuel will then enter the 4th stage of filtration which features a highly-efficient filter element.

These spin-on elements can capture particulates as small as 3 microns (3µ) in size and can use either fine or water blocking filters. Water block filters actively absorb water from the fuel that passes through them.

Fuel Polishing Stage Diagram

What can be perceived as redundancies, the strategic use of multiple filter stages can extend filter life, increase filtration efficiency and system effectiveness, as well as prolong the lifetime of critical operating equipment within these polishing systems.

By continual removal of contaminants, fuel polishing systems consistently ensure your fuel is of optimal quality, therefore, protecting the demanding equipment from premature onboard filter clogging, damage, and unexpected downtime.

Fuel polishing systems may also be equipped with additional features that work to maintain fuel quality. Fuel heaters can be integrated into systems where cold temperatures have caused the diesel fuel to gel, therefore being too viscous to flow through the system. A fuel heater will warm up the fuel as it enters the system so that it can be polished effectively.

Biocides Do Not Solve The Contamination

Biocides are often sold/bought with the idea that it will solve all contamination issues rooted in microbial growth. Unfortunately, it is impossible to perfectly sterilize your fuel, meaning there will always be microbes waiting to repropagate, especially with water still present within the tank.

Microbial growth, often mistaken as algae, is responsible for the development of a sludge-like byproduct that is usually responsible for the premature clogging of onboard engine filters.

The use of biocides to address microbial contamination presents a number of issues in its use.

First, through “killing” the microbes, you are left with the same levels of unwanted biomass within the fuel. Introducing biocides does nothing to remove the sludge or particulate present in the fuel.

Second, using biocides doesn’t do anything to solve the root cause of rampant microbial growth, water.

These microbes thrive where the fuel and water layers meet, living in the water while consuming the hydrocarbons in the fuel. By removing water from the fuel, you are reducing the ability of the microbes to proliferate in the first place.

Biocides simply add more foreign non-petroleum contaminants to the tank, diluting your fuel further. This does nothing to remove the contaminants from your fuel.

The use of biocides may just cause you to clog filters more frequently, while not addressing the water that is in your fuel tank. After initial biocide treatment, this residual water source will allow new microbial growth, adding to the contamination problem that the biocides were originally intended to treat.

How Does Water Get Into Fuel?

Typically, condensation occurs within the fuel tank resulting in water droplets getting into the fuel. The more headspace (the space between the top of the fuel load and the top of the fuel tank) there is the more room for condensation to develop. In time, free water will accumulate as its own layer beneath the fuel.

Water can also be introduced into the fuel during transportation. After fuel is refined, it is often “passed through” multiple tanks and trailers before reaching its final destination. Many of these tanks hold the potential to have accumulated condensation and water of their own.

This leaves multiple opportunities for the fuel load to be exposed to and contaminated with water that may have already been present in one of these tanks or trailers.

Logistically, it is tough for fuel providers to properly vet the fuel, creating a lapse in time between the intended fuel quality and the actual fuel quality the consumers may receive.

This is why it is important for consumers to be vigilant regarding the quality of the fuel they receive.

How Do I Know I Need To Polish My Fuel?

There are a number of ways to determine if the fuel you have stored is in need of polishing. With fuel quality being so important to operational reliability, it should be a priority for maintaining the integrity of this critical energy source.

The most accurate way to know if your fuel is contaminated is to sample the fuel and get it tested for microbial growth and other forms of contamination. 

Bacon bombs are a popular choice for sampling, as they allow the user to dip the sampler into the bottom of the tank and pull fuel from areas that may be denser with contamination.

Many testing labs can take more than a few days to receive, test, and report on the results of the tested fuel sample. There are alternatives to this method of testing, and FUELSTAT® instant fuel test kits are available to test fuel on-site and report results within fifteen minutes.

Fuel Sampling, Testing, and Polishing

When testing is not an immediate option to determine fuel quality, there are also ways to tell visually and circumstantially if the fuel quality likely isn’t where it needs to be.

Instances, where fuel polishing would be recommended, include:

  • If the fuel has been sitting for an extended period of time
  • If the fuel access port wasn’t sealed properly and water, dirt, or other contaminants have seeped into the fuel supply
  • If unusual amounts of water are being captured by onboard filters and water separators
  • If fuel was received through the supply chain and was not tested for contamination prior to loading

If engine filter changes are becoming more frequent than usual, the buildup of fuel contamination can likely be the cause. If large amounts of thick sludge are found in your filters, it is likely that there is a much greater presence of sludge within the fuel tank.

When the equipment/engines that the fuel is supplying experience rough idle, operational inconsistencies, or smoke, contaminated fuel may also be the culprit of these issues.

Visually, clean fuel will be yellow, orange, or red in hue (depending on fuel type and dye) and shouldn’t be extremely cloudy or difficult to see through. When the fuel has been sitting for a prolonged period of time (6 months or longer), it is best practice to polish the fuel as stored fuel becomes more susceptible to degradation and contamination over long periods of time.

How Often Should I Polish My Fuel?

Fuel polishing cycles can vary between volume and conditions, but there are a few recommended best practices known to keep fuel within the desired fuel quality range.

t is recommended to run an ASTM-approved fuel test annually, with some specialized facilities recommending more frequent testing.

Some recommend that a fuel quality test be conducted every 6 months, and in certain applications this 6-month periodic testing is required.

What Fuel Polishing Options Do I Have?

Facilities have a few different options available for fuel polishing solutions. Depending on the operational application, some solutions may better align with the user’s needs than others. 

Mobile Fuel Polishing

Mobile fuel polishing is a popular solution, as it allows a single system to be transported between different fuel tanks that are in need of polishing.

This portability gives users the flexibility to reach fuel supplies that may not have the space needed for a permanently-installed system.

Mobile fuel polishing systems are typically mounted on a cart or trailer. These are brought on-site to the fuel storage tank(s) periodically to polish the fuel.

Most fuel polishing services bring mobile fuel polishing systems on-site to service the fuel. These systems are typically mounted on a cart that can be moved independently between tanks. However, depending on how much fuel needs to be serviced, heavy-duty mobile systems designed for bulk volumes of fuel may be needed.

These heavy-duty fuel polishing systems are transported in enclosed trailers and can be unloaded, or operators can use industrial hoses to reach and circulate the fuel supply without the equipment having to be removed from the trailer.

Depending on how many fuel tanks are in need of polishing, a single mobile system may not be practical enough to keep all of the fuel within the desired fuel quality specification.

Also, one of the critical drawbacks of mobile polishing solutions, is that this process can not be automated for operational efficiency. Because these systems are not permanently affixed to the fuel supply, the fuel will not be kept in-spec at all times. The fuel quality will often fall out of the desired quality spec before the fuel is polished again.

Although not a practical option for larger volumes of fuel, there are handheld fuel polishing systems available like the TK-240 XT. 

These systems are highly portable and compact, allowing for easy transportation between fuel tanks or into tight areas, such as vessel engine rooms, to access fuel ports.

These systems feature a flow rate of 240 gallons per hour with primary and secondary filtration designed to remove problematic fuel contaminants.

Automated Fuel Polishing

If mobile systems are not used often enough, this could cause the fuel in the storage tanks to fall out of the desired fuel quality specification.

Depending on how many fuel tanks are in need of polishing, a single mobile system may not be practical enough to keep all of the fuel within the desired fuel quality specification.

Automated fuel polishing systems are typically mounted near the fuel storage tank and have programmable features that allow for fuel polishing schedules to be determined and executed without human intervention. These timelines can be “tightened”, resulting in more frequent polishing cycles that keep the fuel from falling out of the desired quality spec.

This outshines mobile systems in that the fuel is routinely being cycled through the polishing system. In doing so, the fuel does not sit for long periods of time, preventing degradation and contamination.

Because these systems are permanent installations, the polishers can turn over larger volumes of fuel without “having to keep an eye” as system alarms will alert the user of any fault that requires user intervention. 

Bigger systems can also be engineered to maintain fuel across multiple tanks, with users having the ability to determine which fuel supply loop they want polished and when.

What To Remember About Fuel Polishing

Biocides are not an effective alternative to fuel polishing when combating fuel contamination. Fuel polishing is critical to maintaining the operational integrity of your energy source.

Contaminated fuel can spell disaster in many applications, and by prioritizing fuel cleanliness you are increasing the overall reliability of your engine, equipment, site, or facility.

By creating a fuel maintenance procedure that includes fuel polishing, the stored fuel can last much longer than if it wasn't being polished. Keeping the fuel free of harmful contaminants allows the fuel to be a long-term reliable energy source that is less likely to harm the equipment it is meant to supply.

Do I Need To Empty The Tank?

One major misconception about fuel polishing is the idea that the fuel needs to be completely removed from the tank for polishing.

This is false, as it would be not only a colossal task but also impossible to displace all of the fuel in many bulk storage applications. It is an impractical concept as there simply isn’t anywhere else to transfer tens of thousands of gallons of fuel for holding while the fuel is being polished. 

Fuel polishing equipment cycles through the entire load of the fuel tank through intentionally-designed fuel pick up and return lines that are placed in a manner that allows the system to cycle through all of the fuel from the top of the tank to the messy bottom. 

Fuel Replacement vs. Fuel Polishing

Fuel polishing is considered an alternative to expensive fuel replacement. With some bulk tanks storing tens of thousands of gallons of fuel, fuel replacement costs would be high.

With some storage tanks holding over $100,000 worth of fuel, this fuel is considered an asset that needs to be maintained. It wouldn’t make fiscal sense to simply replace that much fuel when specialized equipment can bring new life to the “old” fuel at a much lower cost.

This is why facilities with bulk fuel storage will implement serious fuel maintenance procedures. Facility managers see fuel as a critical asset that must be protected and maintained.

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