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Selecting the Right Filtration Solution for Your Fuel Tank

Posted October 22, 2020 by Caleb Courville

Navigating multiple product lines to find the optimal fuel filtration solution can be a daunting task. In this guide, we will walk you through how our fuel quality experts recommend the best fuel filtration system for each use case and tank size. We will cover the key differences between mobile and stationary filtration solutions, outline when a passive or active fuel filtration system should be used, and when to opt for an enclose or compact stationary solution. 

Mobile vs. Stationary Fuel Filtration Systems

The most obvious difference between our mobile and stationary filtration systems lies in the name. All of our mobile fuel polishing systems are in fact mobile and can be moved from tank to tank as opposed to our stationary systems which are permanently installed and usually manage a single fuel tank.

A key difference that may not be so obvious is the use case for both system categories. Mobile polishing systems are designed to restore highly contaminated fuel through manual servicing. The stationary systems, often referred to as fuel maintenance systems, are intended to maintain fuel cleanliness by recirculating fuel from the connected tank for routine filtration.

Note, that although both system types are designed to filter contaminants from the fuel, stationary systems are not nearly as efficient at remediating heavily contaminated fuel as the mobile systems. This why AXI often recommends users employ a mobile polishing service before connecting a stationary system to a pre-existing tank with potentially high levels of fuel contaminants. This saves the end customer from running through an exorbitant number of expensive fine filters to remove larger contaminants such as sludge.

Another point to emphasize is stationary systems, unlike mobile systems, do not require an operator to function. Users set run schedules for these systems to automatically filter the fuel throughout the week. Beyond initial setup and routine filter changes, the stationary systems are completely independent.

Equipped with this information, our fuel quality experts will usually recommend mobile or stationary filtration systems based on the end-users needs. Most purchasers of a mobile polishing system usually aim to provide fuel polishing services to a portfolio of facilities, requiring them to travel to multiple sites for the remediation of various fuel tanks. These individuals or companies usually hold several maintenance contracts in which they are the primary means of fuel filtration for those clients.

It is not uncommon for these customers to purchase a smaller MTC system to start only to later look at high capacity systems to capture bigger contracts that involve polishing larger tanks. For these large high capacity systems, custom trailers are sometimes built to aid in the transportation from site to site.

Mobile systems are usually recommended based on the volume and port sizes of the tanks the user will be servicing. We have included a table below that breaks this down for you:

MTC System Recommended Tank Volumes Min. Port Size
TK-240 XT < 1,000 Gallons 1/2" Port
MTC-1000 < 2,000 Gallons 1" Port
MTC-3000 < 5,000 Gallons 2" Port
MTC-X < 5,000 Gallons 2" Port
MTC HC-50 > 5,000 Gallons 2" Port
MTC HC-90 > 5,000 Gallons 2" Port
MTC HC-150 > 10,000 Gallons 3" Port
MTC HC-300 > 10,000 Gallons 4" Port

In contrast, purchasers of stationary fuel filtration solutions like an FPS or STS system are usually the facilities themselves or yachts owners who cannot afford a lapse in fuel quality/reliability. Although mobile fuel polishing systems are great at bringing even the worst cases of fuel contamination down to ideal levels, they lack the consistency needed to ensure there are no periods of time where the fuel quality is sub-optimal. We often refer to these periods as zones of liability and they usually occur between scheduled fuel polishing services. The following graph illustrates this key difference between periodic fuel polishing and automated fuel maintenance:

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

Passive vs. Active Fuel Filtration Systems

All stationary systems are either active or passive solutions. Active filtration solutions include a pump to pull fuel from the connected tank while passive solutions rely on an external pump to push the fuel through the system. Both of these solution categories are recommended on a circumstantial basis. 

Active filtration systems are the popular option and may be considered a more complete solution due to them not relying on an external pump to function. Yet, having the pump on the system does present some limitations. To pull the fuel from the tank, each system pump has to create a vacuum which, regardless of the pump size, is limited to a maximum horizontal and vertical lift of 100 ft. and 15 ft. respectively. Meaning, if the bottom of an underground storage tank was more than 15 ft. below the system’s pump head, the system would not be able to effectively pull the fuel from the tank.

In cases like this, an external submersible pump would be installed to instead push the fuel out of the tank, freeing one from the limitations of a vacuum pull. With a submersible pump installed, an active filtration solution would be considered redundant due to adding another pump to the process. In these cases, a passive system would make more sense.

AXI currently offers one standard passive system along with a portfolio of more custom solutions designed for various clients.

STS System Flow Rate Recommended Tank Volumes
STS 6/7000 P-35 30 GPM (113.6 LPM) 15,000 - 45,000 Gallons (56,782 - 170,344 Liters)

Enclosed vs. Compact Fuel Filtration Systems

If it has been determined that an active stationary system is the preferred fuel filtration solution, it must then be decided whether a compact or enclosed system is most appropriate based on the installation.

For yachts, a compact system is almost always preferred due to the limited space available in the engine rooms. This also holds for base/belly tanks that reside below enclosed generators. For these tanks, customers will often opt to have a system installed inside the generator enclosure, limiting the installation space but also negating the need for the system to have an enclosure of its own. Typically, compact fuel maintenance systems are more cost-effective than enclosed systems due to their installation locations not requiring them to have NEMA rated enclosures.

Selecting amongst the available compact systems is largely determined by tank size followed by other supporting factors such as filtration capabilities, system size, and desired upgrade options. We have included table below that outlines the recommended system based on tank size:

FPS System Flow Rate Recommended Tank Volumes
FPS Compact 1.3 GPM (5 LPM) < 1,000 Gallons (< 3,785 Liters)
FPS DX-S 1.3 GPM (5 LPM) < 1,000 Gallons (< 3,785 Liters)
FPS FX 2.5 GPM (9.5 LPM) < 2,000 Gallons (7,571 Liters)
FPS SX-F 2.5 GPM (9.5 LPM) < 2,000 Gallons (7,571 Liters)
FPS MX-F 4 GPM (15 LPM) < 6,000 Gallons (22,712 Liters)
FPS LX-F 10 GPM (38 LPM) 6,000 – 15,000 Gallons (22,712 – 56,781 Liters)

Should it be determined the recommended system is too large for the available installation space, we typically will suggest the largest system option compact enough to fit. We have also included a table outlining the dimensions of the systems and their controllers below:

System Name System Dimensions Controller Dimensions
FPS Compact 14” x 10” x 8” (36 x 25 x 20 cm) 6.54” x 6.54” x 4.01” (16.6 x 16.6 x 10.19 cm)
FPS DX-S 15” x 18.5” x 7.5” (38 x 47 x 19 cm) Controller Included on System Backplate
FPS FX 20” x 17” x 7” (51 x 43 x 18 cm) Controller Included on System Backplate
FPS SX-F 23” x 26” x 9” (58 x 69 x 23 cm) SFC-50: 10” x 12” x 8” (25 x 30 x 20 cm)
SFC-55: 13.4” x 16” x 7.4” (34 x 41 x 19 cm)
TSC-7000: 16.0” x 13.4” x 7.4” (40.6 x 34.0 x 18.8 cm)
FPS MX-F 23” x 26” 9” (58 x 69 x 23 cm) SFC-50: 10” x 12” x 8” (25 x 30 x 20 cm)
SFC-55: 13.4” x 16” x 7.4” (34 x 41 x 19 cm)
TSC-7000: 16.0” x 13.4” x 7.4” (40.6 x 34.0 x 18.8 cm)
FPS LX-F 26” x 34” x 12” (66 x 86 x 31 cm) SFC-50: 10” x 12” x 8” (25 x 30 x 20 cm)
SFC-55: 13.4” x 16” x 7.4” (34 x 41 x 19 cm)
TSC-7000: 16.0” x 13.4” x 7.4” (40.6 x 34.0 x 18.8 cm)

When addressing large bulk storage tanks, such as cylindrical tanks, an enclosed STS system is typically recommended. This is usually due to the STS system having higher flow rates than what can be found amongst the compact FPS systems.

In addition to higher flow rate options, all STS systems feature NEMA rated enclosures to protect their components from the elements. These enclosures allow the STS systems to be installed outdoors, closer to the bulk tanks they are intended to maintain.

Much like the FPS systems, all STS systems are usually recommended based on the volume of the tanks they are servicing. We have included a table outlining the suggested STS system based on tank volumes:

STS System Flow Rate Recommended Tank Volumes
STS 6000 SX-F 2.5 GPM (9.5 LPM) < 3,000 Gallons (< 11,365 Liters)
STS 6/7003 3 GPM (11.4 LPM) < 3,000 Gallons (< 11,365 Liters)
STS 6/7004 4 GPM (15 LPM) < 3,000 - 6,000 Gallons (11,356 – 22,712 Liters)
STS 6/7010 10 GPM (38 LPM) < 6,000 - 15,000 Gallons (22,712 – 56,781 Liters)
STS 6/7020 20 GPM (75.7 LPM) 10,000 – 25,000 Gallons (37,854 – 94,635 Liters)
STS 6/7030 30 GPM (113.6 LPM) 15,000 – 45,000 Gallons (56,782 – 170,344 Liters)
STS 6/7040 40 GPM (151.4 LPM) 20,000 – 60,000 Gallons (75,708 – 227,125 Liters)

When it comes to selecting a compact or enclosed fuel maintenance system, there is a multitude of other factors to consider that are not covered in this guide; the number of filtration stages, filter element types, and system options just to name a few. To gain an even deeper insight for selecting the right system for your fuel tank, feel free to reach out to our fuel quality experts by filling out the contact form here.

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