STS 7000 Series Enclosed Automated
Fuel Cleaning & Maintenance Systems

The fuel flow first enters the Fuel Conditioner immediately upon exiting the fuel pump. Operating on the principal of induction on the process of combining kinetic and magnetic energy to influence the behavior of electrons, the Fuel Conditioner provides a powerful magnetic field and the flow of fuel provides the kinetic energy.

As fuel deteriorates, clusters of fuel components break down and residue begins to accumulate, resulting in dark, hazy fuel with poor combustibility. This residue is composed primarily of asphalt components of the crude oil from which diesel fuel is refined that have fallen out of solution.  The fuel becomes dark as the asphaltenes agglomerate and gain weight. The increase in size and mass of the fuel breakdown products lead to clogged filters and the build up of tank sludge.

Accumulation of water in the fuel tank provides habitat for bacterial and microbes brought into the tank through the breather vent or with fuel. As this microbial growth grows and reproduces, a bio-film accumulates and attaches to the tank walls and baffles of the fuel tank and may be seen floating in the fuel (and sometimes referred to mistakenly as “algae”).

This accumulation of bio-mass and fuel breakdown clogs filters, adversely impacts combustion efficiency, produces dark smoke from the exhaust, form acids that degrade injectors and fuel pumps, and adversely impacts performance.  Eventually fouled diesel fuel will clog fuel lines and ruin your equipment.

The Fuel Conditioner dissolves the clusters, stabilizes the fuel, and eliminates tank sludge. The results are Clear & Bright Fuel, improved filterability, optimal combustion and clean fuel systems. It also adversely impacts the reproduction process of the microbes and prevents further growth (see the article “Why Bacteria Hate Magnets“, allowing continuing use of the fuel to eliminate the microbes. The process of how the Fuel Conditioner makes clear, bright and more combustible fuel as well as restoring degraded fuel and eliminating the effects of microbial contamination is compelling. As the Fuel Conditioner does not filter the fuel, but treats it as it passes through the unit, there is seldom any reason to suspect that a restriction is in the Fuel Conditioner. But you can remove the face plate, remove the magnet and wipe it off with a shop rag and replace the magnet and face plate. A spare parts kit for the Fuel Conditioner includes a new face panel O-Ring and replacement screws to fasten the face plate.

A centrifuge, when used as a filtration system, as with the FP Series of Fuel / Water Separators,  is a piece of equipment that puts the fluid in rotation around a fixed axis (the center of the FP Series cylinder) and spins it in a circle applying a force perpendicular to the axis of spin (outward force) that can be very strong.  The centrifuge works using the sedimentation principal where the centrifugal acceleration causes the denser substances and particles to move outward in the radial direction.  In the case of the FP Series, the water is more dense than the diesel fuel and it is forced to the outside of the cylinder as the flow spins, and then the water drops down the sides of the cylinder to the bottom of the centrifuge.  Particles, sludge, and debris all are also more dense than the diesel fuel, so they collect in the bottom of the cylinder with the water.

Because the removal of water, sludge and debris occurs due to the mechanical action of the fluid, there is no filtration media, such as with a bag filter or spin on filter elements that are consumed, making this type of water and particulate removal system attractive from a cost-of-operation standpoint.  As this system, however, removes only “free” water (i.e.: water that is in the form of droplets) and does not remove water that is emulsified or absorbed into the water, and particulate removal is only effective at higher levels, perhaps 10 microns or larger, the FP Series System’s use is limited to that of a Primary Filtration unit and secondary or tertiary filtration for removal of fine particulates and emulsified water using water block filter elements is common.

In installations such as in the STS Series 6020 and 6040, the STS Series  7020 and 7040, a sensor is included near the bottom of the cylinder that connects to the System Controller to provide an alert that the FP Series Centrifuge has reached the point that drainage is required, and the system shuts down so that the water and other materials may be removed via a port and ball valve on the bottom of the cylinder.

The MTC Cart Mounted Systems utilize the FP Centrifuges, but as there is no controller on these systems, the need for draining the FP Centrifuge is determined by the sound of the MTC System’s Pump as it suctions fuel through the Centrifuge.

The MTC HC Pallet Mounted Mobile Tank Cleaning Systems all utilize the same FP Series Centrifuges  as the primary filtration unit and has the same sensor and alerts as the above STS Series Systems.

All of the Fuel Polishing and Tank Cleaning Systems  that are available on this web site, any one of which you may find meeting your fuel maintenance requirements, incorporates one or up-to four spin on fuel filter elements for the purpose of capturing and holding fine particulates or water (dissolved or emulsified).

The removal of water and fine particles to a level considered extreme in the past is now considered critically important, especially for today’s engines that utilize a High Pressure Common Rail Fuel Injection system that engine manufacturers have adopted.  These engine manufactures now require filtration of all materials larger than 4 micron.  Review the article “Diesel Fuel and Injector Failures” on this web site to understand why fuel cleanliness is more important now than ever before.

It is difficult to project how often these hard-working filters might need to be changed, and sometimes difficult to determine when they need to be changed during the fuel polishing process.  Many of our systems incorporate Filtration and System Controllers that utilize pressure and/or vacuum sensors to determine when fuel flow through filter elements is being restricted necessitating the replacement of these filters.

Other systems, such as the TK Series or MTC Series Cart Mounted systems do not have automated controllers, but in each case we do utilize pressure gauges that will tell you when the flow of fuel through the filter element is restricted, increasing the back-pressure in the fuel flow and alerting that the filter is “used up”.

It is very typical that the first few times that a re-circulation tank cleaning is undertaken on a tank that has been in service for many years, without any prior cleaning being performed, that several filters are quickly used up in cleaning the tank.  But after these several intense cleanings, the filters should last much longer, but only experience and maintaining a log of the fuel flow that has been passed through a set of filters, and how many times a tank has been cleaned will you begin to determine going forward how many filters you are likely to consume and how many filters should be kept on hand.

Many commercial tank cleaning companies that often tackle the cleaning of tanks that have never been cleaned before will regularly go through many filters.  In these situations, using systems, such as the MTC Series Cart Mounted and HC Pallet Mounted systems that use mechanical centrifugal primary filtration prior to directing fuel flow through the more expensive spin on filters saves considerable money.

Also, when you know that many tanks you will tackle are bad, using the PF Series Pre-filter Bag Units can give you a great deal of savings.  The PF Series Bag Units can be used without bags initially to remove water and “the big pieces”, and then incorporate large micron bags (as high as 800 microns) in the early phases of the tank cleaning process, and work your way down to 5 micron bags before using the more expensive but much more efficient spin-on filters.  The bags may be dumped out, flushed and re-used for a limited number of times, and replacement bags are quite inexpensive.

It is critically important to re-circulate the fuel through the Fuel Polishing and Maintenance System that best suits your requirements, whether it is a hand held TK Series System, an MTC Series Mobile System, an FPS Series Compact System, or an STS Advanced Automated Enclosed Fuel Maintenance System.  But the re-circulation process does not create sufficient fuel flow and agitation in the tank, in many instances, to really knock the slime and sludge off the sides and inside top of the tank, and not enough force to loosen the sludge that has been accumulating on the floor of your fuel tank for years!

What you need is something to clean the tank and put this bio-film and slime into the fuel flow so that the Fuel Polishing and Maintenance System can filter out the debris and the Fuel Conditioner can get to the microbes and break apart the agglomerated asphaltene component of the fuel.

Moving the suction hose stinger (an extension to the hose, usually rigid, allowing for the control of the suction line intake end) of the Fuel Polishing System around the bottom during the fuel re-circulation phase does stir up considerable material for the suction line to deliver to the Fuel Polishing System, but there needs to be something that can dissolve the slime and organic material off the tank walls, top, and floor prior to the re-circulation process that will also keep working between Fuel Polishing Treatments.

It is recommended that the diesel fuel tank be treated with the AFC Series Broad Spectrum Additive Concentrate appropriate to your application a day or two prior to the first re-circulation.  It should be added to a full tank of fuel or the tank filled just after the additive is introduced to the tank.

After completing the initial fuel polishing re-circulation, continue the use of AFC Series Additives at least once or twice every six months thereafter to assure the fuel tank remains clean and the fuel is stabilized. This will enhance and accelerate the long term tank cleaning process, mainly the hardened sludge in the tank bottom, by breaking down and dissolving the existing tank sludge.

Check the Tank Bottom for Water at Regular Intervals

Always check the fuel tank for an accumulation of water in the bottom of the tank prior to doing a re-circulation. Using a rod, sometimes used to measure fuel in a storage tank, or a length of PVC pipe, spread a line of Kolor Kut Water Finding Paste on the side of the rod or pipe and insert to the bottom of the tank. If the paste touches water, it will change colors, showing how much water is in the tank requiring removal.

Treating a full tank of fuel is important as you don’t want to clean just the bottom half of the tank.  You want the additive treated fuel to touch every part of the sides and, if possible, the top of the tank — anywhere the fuel touches during equipment operation.

The AFC Series Fuel Additives are industrial strength and concentrated for the focused dual-purpose of:

• First – working hand-in-hand with the Fuel Conditioning and Tank Cleaning Systems cleaning fuel tanks in preparation for periodic circulation and treatment of the fuel; and
• Second – as a continuing part of a Fuel Management Plan to maintain the cleanliness of storage tanks and fuel systems and assuring that your fuel maintains Optimal Fuel Quality, that we define as fuel that is like it was when it left the refinery, for as long as you depend on the fuel to efficiently operate your equipment.

Removal of Residual Water

Prior to the initial and any subsequent fuel polishing re-circulation, pump any measurable accumulated water out of the tank for proper disposal. It is, however, often impossible to remove all of the water.  The AFC-705 Catalyst and Tank Cleaning Additive contains a surfactant that will emulsify this residual water up into the fuel for removal by a Water Block Filter on the Fuel Polishing System.

The AFC-710 Catalyst and Tank Cleaning Additive, which is Tier 4 Compliant, does not include the surfactant component, but otherwise works the same as the AFC-705 to dissolve deposits and stabilize the fuel.  As and option to the liquid AFC-710, a powdered form of AFC-710 is also available.  It is easier in certain instances to handle, store and transport.

Additive Dosage

Depending on the condition of the fuel and the amount of sludge build-up, it is recommended to initially use a double dose of one to twenty-five hundred (1:2500 – one oz. to 20 gallons of fuel) and circulate the capacity of the tank five times.  The use of AFC Fuel Catalyst has proven to be essential in accelerating the tank cleaning process. AFC-705 and 710 contains detergent, dispersant, corrosion inhibitor, lubricity enhancer and combustion catalyst. AFC Additives do not contain biocides.

For engines manufactured in 2007 and later, use AFC-710, available in both liquid and powdered form. AFC-710 does not contain the surfactant (used to emulsify residual water into the fuel for removal in the circulation process as does AFC-705), a component that does not allow for qualification as a Tier 4 product.

Tank Cleaning & Fuel Treatment for Cold Weather Use

For cold weather operations, AFC Fuel Catalyst AFC-805 is a unique and powerful anti-gelling broad-spectrum fuel additive specifically formulated for use in Diesel, Bio-fuels, Gasoline, Kerosene, and HFO.  AFC-805 can be used as part of any preventative fuel maintenance program, and is ideal for use in bulk storage fuel tanks in cold weather environments. AFC-805 enhances the breakdown and removal of sludge, slime, and bio-fouling from tank walls and baffles that are difficult to access.  It continues to work in storage tanks cleaning and stabilizing fuel for up to 12 months with a single dose.

It is not unusual that a Fuel Polishing and Tank Cleaning System is installed at a level above the fuel that is to be maintained, especially in underground tanks or base (or “belly”) tanks of generators.  How do you maintain the prime on the pump in such an installation?

Foot Valves are handy little devices that can be installed at the end of a pipe line in a suction lift application.  They function as a check valve to maintain the prime and also have a strainer affixed to the open end. The check valve is spring assisted.  When the pump is turned on, the suction opens the valve and the fluid flows. When the pump stops, the valve responds again by closing. This stops fluid from draining out of the pump column and causing the pump to lose prime every time it turns off.  

The strainer also keeps debris from becoming lodged in the foot valve. This would result in the valve being stuck in the open position, and all the fluid draining from the pump column. That nullifies the point of the foot valve! Some foot valves offer tight mesh, others offer a wider grid strainer.

Any installation of a Fuel Maintenance System dedicated to the cleaning and conditioning of fuel in one or multiple tanks would benefit from the inclusion of a foot valve.  The efficiency of a system that is programmed to operate on a periodic basis would suffer if an operator must prime the pump each time a tank is due for maintenance.

The Multi-Port Flowpath Actuated Valve System is available to operate in unison with several of the FPS Fuel Polishing Systems.  Each MP-VS Valve Set includes two (2) Solenoid Valves (one for the suction and one for the discharge line) and one Foot Vale to be installed on the end of the suction pipe.  One valve set is typically installed in each partitioned section of the base tank.