WO2017221226A1

WO2017221226A1 - Systems and method for cleaning fuel

Info

Publication number: WO2017221226A1
Application number: PCT/IL2016/050648
Authority: WO
Inventors: Yair Harel
Original assignee: Yair Harel
Priority date: 2016-06-19
Filing date: 2016-06-19
Publication date: 2017-12-28

Abstract

A fuel cleaning system includes one or more primary fuel separators for removing water and other contaminants from the fuel, each primary fuel separator may include a fuel input port, a fuel output port and a sump having a draining port. One or more secondary depth filters may be fluidically connected in parallel to the primary separator fuel outlet(s) and receive fuel from the primary separator for further fuel cleaning. The system may also include a pump. The system may include a controller for performing automatic sump draining and/or automatic detection of depth filter clogging and/or automatic pump shutoff in case of malfunctioning of a sump draining valve and/or depth filter clogging. The system may also provide warning signals or system status signals to a user.

Description

SYSTEMS AND METHOD FOR CLEANING FUEL

FIELD OF THE INVENTION

The present invention, in some embodiments thereof, relates to systems and methods for cleaning hydrocarbon based fuels and fuel oils, and more particularly, but not exclusively to methods and systems for polishing heavy fuel oil.

BACKGROUND OF THE INVENTION

Hydrocarbon based fuels such as, kerosene, diesel fuels, heavy fuel oil, jet fuel and the like are produced and used in very large quantities world-wide, for operating internal combustion engines and diesel engines (for automotive and marine use), burners for industrial and domestic heating, power generating turbines, jet propulsion turbines and many other applications.

The recent introduction of new standards for sulfur free fuels and the recent worldwide transition to use ultra-low sulfur fuel (completed in 2010) have resulted in removal of sulfur containing compounds from such fuels in order to reduce harmful environmental effects from emissions including sulfur compounds However, the removal of such sulfur containing compounds from fuels resulted in a substantial change in certain fuel properties which create new problems associated with the behavior of such sulfur free fuels. For example, such fuels may be more susceptible to biological contamination resulting from growth and accumulation of bacteria and/or other microorganisms in the fuel during storage. In addition, the new low-sulfur fuel is more susceptible to contamination with water and to oxidation. Water contamination in such fuels which may again increases the susceptibility of water contaminated fuel to biological contamination. The water contamination may include water which is dissolved in the fuel as well as water which is suspended as tiny droplets in the fuel (free water). Thus, in many small or large tanks which are being used for fuel storage there accumulates a residue containing water and/or bacteria or other microorganisms and/or some heavy hydrocarbon based semisolid particles. The mixture of these materials accumulating in such fuel storage tanks is called "sludge" and may need constant monitoring and removal. The presence of any such contaminants may adversely affect the performance of devices using such contaminated fuel Including, among others, reducing the fuel efficiency of engines or turbines using the contaminated fuel, clogging and blocking small diameter passages in such engines and in general decreasing the useful life-span and causing increased wear and tear and deterioration in such engines or turbines or other devices using contaminated fuels.

Devices and methods known in the art and used to clean fuel may include fuel separators which separate water and some solid and/or or semi-solid particulate matter. Such fuel separators usually include two different classes of fuel separators. The first type of such fuel separators are centrifugal separators which impart a circular motion to fuel pumped into such separators. Due to the action of such centrifugal forces water and some solid or semi-solid particles which have a higher specific gravity than the specific gravity of the fuel are physically separated from the fuel and may accumulate in the lower part (sump) of the separator from which the heavier water and other contaminants may be periodically drained as the need arises, an advantage of centrifugal separators are that they have very long service life, and require very little maintenance.

Another type of separator is a coalescing filter also referred to throughout the present application as a "coalescer". A coalescer is typically a cartridge or container filled with an active material having a high surface area per gram of active material. The active material packed within the container is typically in the form of crystals or beads and may sometimes be supported by an inert support matrix. The container has an input port for allowing contaminated fuel including water and other contaminants to flow into the container and pass through the active material. The container also has an output port that allows the separated fuel (from which some water and some of the other contaminants has been removed) to exit the container. The active material has chemical and physical properties which cause the separation of water from fuel due, in part, to the hydrophilic properties of the active material and the hydrophobic properties of the fuel. Other physical processes may also be involved in the separation of water from fuel by such coalescers. Irrespective of the actual mechanisms of the water/fuel separation, as the fuel flows through the active material, tiny water drops suspended in the fuel are adsorbed to the active material and may merge to form larger drops. Once a certain the degree of water coalescing is reached the water adsorbed on the surface of the active material accumulates to form large drops which drop to the bottom part (sump) of the container due to gravity's action where they accumulate in the sump of the separator from which the heavier water and other contaminants may be periodically drained as the need arises. An advantage of such coalescers is that they may be even more efficient than centrifugal separators in removing the water from the fuel, have a relatively long service life, and require little or no maintenance. The active material in some coalescers is, typically, active alumina, but other types of materials having an active surface and high values of surface area per unit weight may be used.

Finer filters for further cleaning residual water and finer particles which may remain in fuel are known in the art. Typically, such filters are membrane filters which contain a single layer of porous filtering material, such as, for example, paper, reinforced paper, synthetic paper, thin porous sheets of polymer based material, or other filtering materials. When such membrane filters are used, fuel is passed through the membrane, which stops and traps fine particulate matter or semi-solid particles and passes the fuel therethrough. If the membrane material has hydrophilic properties (such as in paper membrane based filters, the membrane may also adsorb and retain some of the water dissolved or suspended in the fuel. In such single membrane filters the filtering capacity of the filter is limited by the surface area of the membrane. In some such filters, the membrane surface area is increased by folding or corrugating the membrane. However, while such single membrane filters are inexpensive, they have relatively low filtering capacity and may become clogged relatively quickly and require frequent replacement. As such they are not usable in filtering applications requiring high fuel flow rates, high fuel cleaning capacities and low maintenance requirements.

There is therefore a long felt need for devices and methods for efficiently and cost effectively cleaning fuel from water and other contaminants to maintain or increase fuel performance characteristics, and prevent or reduce engine degradation due to fuel contamination.

SUMMARY OF THE INVENTION

According to an aspect of some embodiments of the present invention, there is provided a system for cleaning fuel the system includes one or more primary fuel separators for removing water and/or coarse particulate matter from said fuel. Each primary fuel separator includes a separator fuel inlet port, a separator fuel output port and a sump having an openable and closable draining port. The system also includes one or more secondary depth filters. Each depth filter has a depth filter inlet port and a depth filter output port. The filter inlet port is fluidically connected to the fuel separator outlet for receiving fuel from the primary separator and for removing residual water and fine particulate matter from the fuel.

In accordance with some embodiments, the system is configured to be installed in a vehicle. The fuel inlet port of the primary separator(s) is fluidically connectable to a fuel pump of the vehicle and the fuel outlet port of the secondary depth filter(s) is fluidically connectable to an engine of the vehicle for providing cleaned fuel to the engine.

In accordance with some embodiments, the sump is a transparent sump to enable visual inspection of the water accumulated in the sump.

In accordance some embodiments, the primary separator is a coalescer including an active material having a high surface area per unit weight.

In accordance with some embodiments, the coalescer is a coalescer comprising active alumina.

In accordance with some embodiments, the primary separator(s) have a maximal fuel flow rate in the range of 5 - 50,000 liter per hour.

In accordance some embodiments, the depth filter(s) have a maximal flow rate in the range of 0.1 - 2,500 liter per hour

In accordance with some embodiments, the system may clean a fuel selected from gasoline, kerosene, light to heavy petroleum distillation fraction, diesel fuel, marine diesel fuel, aviation turbine fuel, Jet A fuel, Jet A-l fuel, Jet B fuel, heavy fuel oil, number 2 fuel oil, Number 3 fuel oil, Number 4 fuel oil, JP-4 jet fuel, JP-5 jet fuel, JP-7 jet fuel and JP-8 jet fuel.

In accordance with some embodiments, the system is configured for cleaning fuel disposed in a fuel storage tank and the system also includes a pump having a pump inlet port for receiving fuel from the storage tank through a incoming fuel conduit and a pump outlet port for pumping the fuel into the fuel inlet port(s) of the primary fuel separator(s). The system also includes a return fuel conduit for receiving fuel from the depth filter output port(s) of the depth filter(s). The fuel exiting the depth filter output port(s) is returned to the fuel storage tank by the return fuel conduit. In accordance with some embodiments, the system also includes a strainer fluidically connected between the fuel storage tank and the pump inlet port for straining the fuel before the fuel enters the pump inlet port.

In accordance with some embodiments, the system also includes one or more bypass conduits. Each bypass conduit of the bypass conduits is fluidically connected between the fuel output port of a primary fuel separator of the primary fuel separator(s) and the return fuel conduit. Each bypass conduit of the bypass conduits includes an openable and closable bypass valve. When the bypass valve(s) are closed, the fuel exiting the fuel output port(s) of the primary fuel separator(s) flows into the inlet ports of the depth filter(s) connected to the primary fuel separator(s). When the bypass valve(s) are open, the fuel exiting the fuel output port(s) of the primary fuel separator(s) flows directly into the return fuel conduit bypassing the depth filter(s).

In accordance with some embodiments, the openable and closable draining port of a sump includes a controllable sump draining valve for controllably opening and closing the draining port of the sump.

In accordance with some embodiments, the bypass valve(s) and/or the sump draining valve(s) are electrically openable and closable valves.

In accordance with some embodiments, the electrically openable and closable valves are solenoid based valves.

In accordance with some embodiments, the system also includes a controller for controlling the operation of the system.

In accordance with some embodiments, the controller is electrically connected to the pump, the bypass valve(s) and the sump draining valve(s) for controlling the operation of the pump, the bypass valve(s) and the sump draining valve(s).

In accordance with some embodiments, the system also includes a water level sensing sensor disposed within the sump(s) for detecting when the water level within the sump(s) reaches a threshold level.

In accordance with some embodiments, the controller is programmed to automatically open the draining valve of a sump when the water level sensing sensor of the sump detects that the water level within the sump is equal to or exceeds the threshold level. In accordance with some embodiments, when the water level sensing sensor detects that the water level within a sump is equal to or exceeds the threshold level, the controller opens the sump draining valve for a preset time period and closes the sump draining valve at the end of the preset time period.

In accordance with some embodiments, the preset time period is a factory set fixed time period or a user programmable time period.

In accordance with some embodiments, the system also includes a fuel overflow tank for receiving any water and fuel drained from the sump(s) of the primary fuel separator(s).

In accordance with some embodiments, the overflow tank includes an overflow sensor connected to the controller for sensing when the fluid level within the overflow tank reaches a threshold level.

In accordance with some embodiments, whenever the overflow sensor senses that fluid level within the overflow tank has reached the threshold level, the controller is programmed to stop the operation of the pump, and (optionally) provide a warning signal to check the sump draining valve and/or the water level sensor.

In accordance with some embodiments, the overflow tank includes an openable and closable draining port for draining any fluids from the overflow tank.

In accordance with some embodiments, the system also includes a pressure sensor connected to the controller and disposed before the fuel inlet port(s) of the depth filter(s) for sensing the fuel pressure level at or before the inlet port(s) of the depth filter(s).

In accordance with some embodiments, if the pressure level sensed by the pressure sensor exceeds a threshold pressure level, the controller is programmed for either providing a warning signal indicative of the need to replace the one or more depth filters, or for switching off the pump, or for providing a warning signal indicative of the need to replace the one or more depth filters and switching off the pump.

In accordance with some embodiments, the amount of water in the fuel exiting the one or more primary fuel separators is in the range of 400-700 parts per million by weight.

In accordance with some embodiments, the one or more primary fuel separators remove particles exceeding an average diameter of 30 micron. In accordance with some embodiments, the amount of water in the fuel exiting the one or more depth filters is in the range of 30-70 parts per million by weight.

In accordance with some embodiments, the one or more depth filters remove particles exceeding an average diameter of 1-3 micron from the fuel.

In accordance with some embodiments, the system includes a single primary fuel separator.

In accordance with some embodiments, two or more depth filters are fluidically connected in parallel to the output port of the single primary fuel separator by a secondary fluid manifold.

In accordance with some embodiments, the system includes a single depth filter fluidically connected to a single primary fuel separator.

In accordance with some embodiments, the system includes two or more primary fuel separators connected in parallel to the output port of the pump through a primary fuel manifold.

In accordance with some embodiments, each primary fuel separator of the two or more primary fuel separators is fluidically connected to the input port of a single depth filter and the fuel exiting the single depth filter is returned to the fuel storage tank.

In accordance with some embodiments, each primary fuel separator of the two or more primary fuel separators is fluidically connected to the input ports of two or more depth filters through a secondary fuel manifold.

In accordance with some embodiments, the output ports of all of the depth filters of the system are fluidically connected to a fuel output manifold that feeds the fuel back to the fuel storage tank.

In accordance with some embodiments, the system is a fixed system or a mobile system.

There are also provided methods for cleaning fuel. In accordance with some aspects of fuel cleaning methods of the present application, the method includes the steps of pumping the fuel into one or more primary separators for removing water and coarse particulate matter from the fuel and passing the fuel exiting the one or more primary separators through one or more depth filters for removing at least part of the residual water and at least some fine particulate matter remaining in the fuel after the fuel exits the one or more primary separators. In accordance with some embodiments, the step of pumping the fuel is performed by a fuel pump of a vehicle.

In accordance with some embodiments, the step of passing includes providing the fuel exiting the one or more depth filters to an engine of the vehicle.

In accordance with some embodiments, the one or more primary separators each include a sump, and the method also includes the step of draining fluid from one or more sumps of the one or more primary separators into an overflow tank included in the system.

In accordance with some embodiments, the step of draining fluid is performed by manually draining fluid from the one or more sumps.

In accordance with some embodiments, the step of draining fluid includes automatically draining fluid from the one or more sumps into the overflow tank when the water level within the one or more sumps exceeds a threshold level.

In accordance with some embodiments, each sump of the one or more sumps includes a draining valve and the step of automatically draining includes automatically opening the draining valve(s) of the sump(s) for a set time period and closing the draining valve(s).

In accordance with some embodiments, the system includes a pump for performing the step of pumping, the overflow tank includes a sensor for sensing the level of fluid disposed in the overflow tank, and the method also includes the step of checking if the level of fuel in the overflow tank exceeds a threshold level and turning off the pump if the level of fuel in the overflow tank exceeds the threshold level.

In accordance with some embodiments, the step of checking also includes the step of providing a warning signal indicative that the overflow tank is full if the level of fuel in the overflow tank exceeds the threshold level.

In accordance with some embodiments, the system includes one or more pressure sensors for sensing the pressure of the fuel at the input port(s) of the one or more depth filters and the method also includes the step of providing a warning signal when the pressure of the fuel at the input ports of the one or more depth filters exceeds a first pressure level.

In accordance with some embodiments, the system includes a pump for performing the step of pumping and one or more pressure sensors for sensing the pressure of the fuel at input ports of the one or more depth filters and wherein the method also includes the step of turning off the pump when the pressure of the fuel at the input ports of the one or more depth filters exceeds a second pressure level.

In accordance with some embodiments, the system also includes one or more bypass valves, each bypass valve of the one or more bypass valves is fluidically connected to an output port of one primary separator of the one or more primary separators and is configured for controllably bypassing the one or more depth filters connected to the primary fuel separator to flow the fuel exiting the one or more primary separators directly into a main fuel output port of the system, and the method also includes the step of activating one or more of the bypass valves when the pressure at input ports of the one or more depth filters exceeds a second pressure level.

In accordance with some embodiments, the system also includes one or more bypass valves, each bypass valve of the one or more bypass valves is fluidically connected to an output port of one primary separator of the one or more primary separators and is configured for controllably bypassing the one or more depth filters associated with each of the one or more primary separators, to flow the fuel exiting the one or more primary separators directly into a main fuel output port of the system, and the method also includes the step of activating all of the one or more bypass valves prior to performing the step of pumping to initially recycle the fuel only through the one or more primary separators until at least some of the water and coarse particulate matter is removed from the fuel at which time the one or more bypass valves are deactivated resulting in the fuel passing through the one or more depth filters.

Finally, in accordance with some embodiments, the step of activating all of the one or more bypass valves is performed at an initial part of a cleaning run performed by the system to reduce the contaminant load reaching the one or more depth filters for increasing the serviceable lifetime of the one or more depth filters.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings in which like components are designated by like reference numerals. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1 is a schematic block diagrams illustrating the components and fuel flow directions in a fuel cleaning system, in accordance with some embodiments of the present application;

FIG. 2 is an isometric view of a fuel cleaning system using a primary fuel separator and a depth filter connected in series, in accordance with some embodiments of the cleaning systems of the present application;

FIG. 3 is a schematic block diagram, illustrating a fuel cleaning system used as an in line system, in accordance with some embodiments of the fuel cleaning systems of the present application;

FIG. 4 is a schematic block diagram illustrating the components of a fuel cleaning system, in accordance with some embodiments of the present application;

FIG. 5 is a schematic diagram illustrating some of the components in the fuel flow pathway of a fuel cleaning system including two primary fuel separators and four depth filters, in accordance with some embodiments of the fuel cleaning systems of the present application;

FIG. 6 is a schematic part cross- sectional diagram, illustrating a fuel cleaning system re-circulating the fuel in a storage tank for cleaning the fuel, in accordance with an embodiment of the fuel cleaning systems of the present application; FIGs. 7-9 are schematic flow charts illustrating the steps of three different methods of cleaning fuel using fuel cleaning systems in accordance with some embodiments of the fuel cleaning systems of the present application; and

FIG. 10 is a schematic front view of a mobile fuel cleaning system, in accordance with an embodiment of the fuel cleaning systems of the present application.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates systems and methods for cleaning hydrocarbon based fuels and fuel oils, and more particularly, but not exclusively to methods and systems for polishing heavy fuel oil.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

As used herein the term "about" refers to ± 10 %. The word "exemplary" is used herein to mean "serving as an example, instance or illustration." Any embodiment described as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments.

The word "optionally" is used herein to mean "is provided in some embodiments and not provided in other embodiments." Any particular embodiment of the invention may include a plurality of "optional" features unless such features conflict.

The word "preferably" is used herein to mean "preferably but not obligatorily".

The terms "comprises", "comprising", "includes", "including", "having" and their conjugates mean "including but not limited to".

The term "consisting of means "including and limited to".

The term "consisting essentially of" means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure. As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases "ranging/ranges between" a first indicate number and a second indicate number and "ranging/ranges from" a first indicate number "to" a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

The terms "separator", "fuel separator" "primary separator" and "primary filter" and their plural forms and conjugates are interchangeably used throughout the specification and claims and mean a device or filter for separating water and coarse particulate matter from a fuel by passing the fuel into a bed containing active material having a high surface area per unit weight which causes the water in the fuel to coalesce or aggregate and separate from the fuel.

The term "coalescer" means a device including an active material having a high surface area per unit weight which can separate water dissolved and/or suspended in fuel into a liquid phase separate from the fuel, based on physical and/or /chemical properties of the active material and on the force of gravity.

The term "depth filter" means a filter including multiple layers of porous filtration material disposed adjacent to each other, such that a liquid may be passed through the multiple layers of filtration material to trap and stop particulate matter, semi- solid matter and other contaminants included in the filtered liquid. Depth filters may include, but are not limited to, spirally wound filters, stacked disc filters or any other type of arrangement of multiple filtration material layers were the arrangement of multiple layers has a depth substantially larger than the thickness of a single layer of the filtration material. Depth filters also include filters having a block of porous material having any shape and a substantial thickness (in the direction of passage of the filtered liquid), through which the filtered liquid passes through during filtration.

The filtration material used in such depth filters may include but is not limited to, paper, synthetic paper, long fiber paper, chemically modified cellulose based materials, polymer based materials, hydrophobic materials, hydrophilic materials and combinations of such materials. Depth filters may also (optionally) have multiple alternating layers made of different filtration materials. Depth filters including layers of paper or other hydrophilic materials may adsorb water from the filtered liquid.

Reference is now made to Fig. 1 which is a schematic block diagrams illustrating the components and fuel flow directions in a fuel cleaning system, in accordance with some embodiments of the present application.

The fuel cleaning system 10 includes a primary filter 2 and a depth filter 4. Contaminated fuel enters the primary filter 2 (as schematically represented by the arrow 1. The primary filter 2 may be any type fuel coalescing filter (coalescer) known in the art. Preferably, the primary filter 2 is a coalescing filter including active alumina. The primary filter 2 has a sump 2A into which most of the water separated from the fuel primary filter 2 settles and accumulates. The sump 2A may be periodically drained through a draining port (as schematically represented by the arrow 7) to let out excess water accumulated in the sump 2A. The primary filter 2 may remove some of the water contaminating the fuel and may also remove some of the coarse particulate matter and semi- solid contaminants (which may typically accumulate in the sump 2A together with the water removed from the fuel). The partially cleaned fuel exiting the primary filter 2 enters the depth filter 4 (as schematically represented by the arrow 3). The depth filter 4 further cleans the fuel by absorbing some of the water remaining in the fuel and by trapping finer particulate matter and semi-solid contaminants within the filtering material or matrix of the depth filter 4 which were not removed from the fuel by the primary filter 2. The cleaned fuel then exits the depth filter 4 as schematically represented by the arrow 5.

Reference is now made to Fig. 2 which is an isometric view of a fuel cleaning system using a primary fuel separator and a depth filter connected in series, in accordance with some embodiments of the cleaning systems of the present application.

The fuel cleaning system 20 includes a primary fuel separator 22 fluidically connected in series to a depth filter 24. The fuel separator 22 may be any type of coalescer (coalescing filter) including an active material in the form of beads and/or crystals and or active material particles. The contaminated fuel may enter the fuel separator 22 through a fuel inlet port 21. The fuel separator 22 may have a sump 22A disposed at the bottom part thereof. During passage of the fuel 11 within the fuel separator 22, water 9 and some coarse contaminants (solid and/or semi-solid) are separated from the fuel 11 by the active material (preferably, active alumina) included within the fuel separator 22 and gravitationally settle into the bottom part of the sump 22A, due to the water 9 being heavier than the fuel 11. Preferably, the sump 22A is a transparent sump made of glass or another visually transparent material such as, for example, a clear plastic or other strong polymer based transparent material. The transparent sump 22A may allow visual inspection of the contents of the sump 22A to determine when the sump 22A needs to be drained. The sump 22A has a draining port 27 which allows the sump 22A to be drained by manually opening a stopcock 27A of the draining port 27 until most or all of the water 9 is drained from the sump 22A and then closing the stopcock 27A. The partially cleaned fuel 11 exits the fuel separator 22 through a fuel output port 23 which is fluidically connected to the fuel input port 24A of the depth filter 24. The depth filter 24 further cleans the fuel by absorbing at least some of the water 9 remaining in the fuel exiting the fuel separator 22 and by trapping some of the finer contaminant particles and semi-solid material which were not removed from the fuel 11 by the fuel separator 22.

In accordance with one non-limiting example of the fuel cleaning system 20, the fuel separator 22 may be an active alumina based coalescing filter, such as, for example a model 8X20X2 diesel fuel purifier commercially available from Diesel Craft fluid engineering division (Magnum group), CA, U.S.A., and the Depth filter 24 may be a Model SDFC1888 super duty filter cartridge depth filter commercially available from FLAC GUARD, South Africa or from Kleenoil, UK. However, some embodiments of the fuel cleaning systems of the present application may include any other activated alumina based filters commercially available from Diesel Craft fluid engineering division (Magnum group), CA, U.S.A., including but not limited to models 3X8X0.5, 5X8X0.5, 5X12X1, 5X16X1, 5X32X1, 8X47X2, 18X56X3 and 18X74X4. Such models may have maximal fuel flow rate in the range of 114 liters per hour (LPH) to 756 liters per minute (LPM). The particular model of the activated alumina based primary filter used may depend, inter alia, on the required maximal fuel flow rate needed in the particular application, and the depth filter 24 may be any other depth filter commercially available from FLAC GUARD, South Africa or from Kleenoil, UK.

While depth filters have been previously used for filtering engine lubrication oils and hydraulic oils, to the best knowledge of the inventor, depth filters have not been used for cleaning fuel either by themselves or in combination with other fuel cleaning filters such as fuel separator coalescing filters including activated alumina.

It is noted that fuel cleaning systems of a type similar to the fuel cleaning system

20 may be used in several different applications. One such exemplary application is as an in-line system for cleaning fuel in vehicles.

Reference is now made to Fig. 3 which is a schematic block diagram, illustrating a fuel cleaning system used as an in line system, in accordance with some embodiments of the fuel cleaning systems of the present application. The fuel cleaning system 3 receives the fuel from a vehicle fuel pump 28, cleans the fuel as disclosed in detail hereinabove and outputs (feeds) the cleaned fuel directly into the vehicle engine 32. The fuel cleaning system may be constructed and may operate as disclosed in detail hereinabove with respect to the fuel cleaning systems 10 and 20 of Figs. 1 and 2, respectively. For example, the fuel cleaning system 30 may be installed in a truck or other motor vehicle using a diesel engine and may feed the cleaned diesel fuel directly into the fuel intake manifold (not shown in detail in Fig.3) of the diesel engine. It is noted that the arrangement of the cleaning fuel 30 is not limited to use in a vehicle but may also be used in any type of application requiring cleaning of fuel, such as, for example, in marine application in which the system 30 may be use for cleaning the fuel fed into an engine of a motorized boat, small ship, yachts, hovercraft, tanks, military vehicles, trains, or any other type of motorized vehicle. The fuel cleaning systems illustrated in Figs 1-3 may be typically used in applications which require relatively small to medium fuel flow rates. Typically, such in line fuel cleaning systems may be implemented for applications requiring output fuel flow rates in the range of 5-500 liter per hour.

The advantages of in-line fuel cleaning systems of the type illustrated in Figs.

1-3 is that they are relatively small and compact in size, require little maintenance (mainly periodic draining of the water in the sump and periodic replacement of the depth filter of the system, are relatively inexpensive and provide excellent performance in reducing fuel contaminants and water which in turn improve fuel energy efficiency, improve engine performance, and reduce engine maintenance and wear.

Another type of fuel cleaning system, in accordance with some embodiments of the fuel cleaning systems of the present application, may be used for performing fuel cleaning for fuel storage tanks.

Reference is now made to Fig. 4, which is a schematic block diagram illustrating the components of a fuel cleaning system, in accordance with some embodiments of the present application. The fuel cleaning system 50 may include a pump 51 and an (optional) strainer 49 fluidically connected between a fuel inlet 55 of the system 50 and the pump 51. The fuel inlet 55 may be fluidically connected to a fuel reservoir (not shown in Fig. 4, but see Fig. 6 hereinafter) through a suitable pipe or fuel line (not shown in Fig. 4 for the sake of clarity of illustration) for receiving fuel to be cleaned. The strainer 49 may be any suitable type of fuel strainer (such as, for example a strainer including a mesh or any other type of straining suitable for straining fuel, as is known in the art) for stopping and retaining any relatively large particles from entering the pump 51. The pump 51 may be any suitable pump for pumping fuel at a desired flow rate. Such pumps are well known in the art, are not the subject matter of the present invention and are therefore not described in detail hereinafter. The system 50 may also include a primary filter 52.

The primary filter 52 may be any coalescing filter (coalescer) based on an active material having a high surface area per unit weight, as disclosed in detail hereinabove. Preferably, the primary filter 52 is a fuel separator including activated alumina, such as, but not limited to, the activated alumina fuel separators available from Dieselcraft, USA disclosed hereinabove. The pump 51 is fluidically coupled to the primary filter 52 and pumps the fuel into the primary filter 52. The primary filter 52 may have a sump 52A for receiving water and some coarse contaminants (including particular matter and/or semi-solid contaminants) separated from the fuel by the primary filter 52. In some embodiments, the sump 52A may have a manually operated draining port (not shown in Fig. 4, for the sake of clarity of illustration) as disclosed in detail with respect to the sump 22A of Fig. 2. However, in other embodiments of the system 50, the sump 52A may be a controllably drainable sump and may include an electrically operated draining valve 52B which may be opened and closed by receiving suitable control signals (such as, for example, an electrical voltage or current signal). For example, the draining valve 52B may be a solenoid operated valve as is known in the art. It is noted that electrically controlled valves are well known in the art, are not the subject matter of the present invention and are therefore not described in detail hereinafter. Any water and/or contaminants which are drained from the sump 52A may be drained into an overflow tank 60 included in the system 50. The primary filter 52 feeds the partially cleaned fuel to a secondary fuel manifold 58 from which the fuel is fed into the input ports (not shown in detail for the sake of clarity of illustration) of two secondary filters 54 and 56 which are fluidically connected in parallel to a fuel output manifold 62. The secondary filters 54 and 56 are depth filters as disclosed hereinabove. The system 50 may also (optionally) include a pressure sensor 63. The pressure sensor 63 may be any type of pressure sensor capable of sensing pressure in a fuel, as is well known in the art. For example, the pressure sensor 63 may be a Model FST800- 211P241C, pressure sensor commercially available from Firstrate Sensor Co. Ltd., China. However, any other suitable pressure sensor may also be used. The pressure sensor 63 may be disposed within the secondary manifold or anywhere in the (fuel filled) space between the fuel outlet (not shown in detail in Fig. 4) of the primary filter 52 and the inlet ports (not shown in detail in Fig. 4) of the secondary filters 54 and 56. The fuel passing through the secondary (depth) filters 54 and 56 is further cleaned by the secondary filters 54 and 56 which may remove some of the water and/or other contaminants remaining in the fuel exiting the primary filter 52. The fuel exiting the secondary filters 54 and 56 is fed into the fuel output manifold 62 and therefrom to a fuel outlet port 65. The fuel outlet port 65 of the system 50 may be suitably fluidically connected to a fuel line or pipe (not shown in Fig. 4 for the sake of clarity of illustration) for returning the cleaned fuel into the storage tank (not shown in Fig. 4).

The system 50 may also (optionally) include a bypass fuel line (bypass conduit) 67 which may include a bypass valve 69. The bypass fuel line 67 may be fluidically connected between the output port 57 of the primary filter 52 and the fuel output manifold 62. When the bypass valve 69 is closed, the fuel flows from the output port 57 of the primary filter 52 into the secondary manifold 58 and from the secondary manifold 58 into the two secondary filters 54 and 56 as disclosed hereinabove. When the bypass valve 69 is closed, the fuel flows through the bypass fuel line 67 directly into the fuel output manifold 62, bypassing the secondary filters 54 and 56. The bypass valve may be a manually operated valve or an electrically operated valve (such as, for example, a solenoid operated electrical valve) as disclosed hereinabove.

It is noted that the type, placement and arrangement of the bypass valve 69 is given by way of example only and may be varied. For example, in an alternative embodiment of the system 50, the bypass valve may be positioned at the T-junction 70 and the bypass valve may be a three-way valve having two states. In such an alternative embodiment, in a first state of the bypass valve the bypass valves fluidically connects the outlet port 57 of the primary filter 52 with the secondary manifold 58 and fluidically closes the connection between the outlet port 57 and the bypass line 67 resulting in the fuel passing from the primary filter 52 into the secondary manifold 58 and from the secondary manifold 58 into the secondary filters 54 and 56 as disclosed hereinabove. In a second state of the bypass valve of this alternative embodiment, the bypass valve fluidically disconnects the fluid outlet port 57 from the secondary manifold 58 and fluidically connects the fluid outlet port 57 to the bypass fuel line 67 such that the fuel bypasses the secondary filters 54 and 56 and flows through the bypass fuel line 67 into the fuel output manifold 62. In such an alternative embodiment, the bypass valve may be manually operated or electrically operated.

In operation of the system 50, when the system starts cleaning the fuel in a fuel storage tank (not shown), the initial content of water and/or other contaminants in the fuel may be quite high. In order to avoid excessive or premature clogging of the secondary (depth) filters 54 and 56, the operator of the system 50 may either manually or through the user interface of the controller 80 activated the bypass valve 69 into a bypass (open) state in which the fuel bypasses the manifold 58 and flows directly into the fuel output manifold 62 of the system 50 and is returned into to the fuel storage tank without passing through the secondary filters 54 and 56. In this state, the system 50 may be operated for a certain time by circulation the fuel coming from the storage tank only through the primary filter 52. Once the amount of water and other contaminants in the re-circulating fuel is reduced by the action of the primary filter 52, the operator may actuate the bypass valve 69 into an open state in which the fuel exiting the primary filter 52 may pass through the secondary filters 54 and 56 and re-circulated back into the storage fuel tank for the rest of the cleaning operation run time. Such an initial bypass operating mode of the system 50 may advantageously extend the operating life of the depth filters of the system 50 by using the primary filter 52 to remove a substantial portion of the water and/or other fuel contaminants before the fuel is re-circulated by passing the fuel also through the secondary filters 54 and 56. Alternatively, the system 50 may be configured and programmed to automatically begin each cleaning run by automatically switching the system 50 into a bypass operating mode by opening the bypass valve as described hereinabove for a first time period initiated at the beginning of a cleaning run of the fuel in a storage tank and by automatically switching the system into a second operating mode in which the fuel is passed through both the primary filter 52 and the secondary filters 54 and 56 during recirculation of the fuel through the system 50. The switching between the two different operating modes may be performed after a set time period or a user programmable/adjustable time period or, in some embodiments may be performed when a water content sensor (not shown in Fig. 4) disposed in the fuel entering the system 50 may indicate that the water content in the fuel is below a set value (the set value may be factory set or user adjustable).

The system 50 may also include a controller 80. The controller 80 may be any type of controller and may include analog circuitry, or digital circuitry or both analog and digital circuitry, as is well known in the art. The controller 80 may include a processor (which may be any type of processor or combination of processors known in the art, including but not limited to microprocessor(s), microcontroller (s), digital signal processor(s) (DSP) or any suitable combinations of processing and controlling circuitry and software program(s) operating on such a controller. The controller 80 may also include any type of user interface known in the art ( such as, but not limited to, a display screen, operating switches, pointing devices, touch screens) or any other types of user interfaces suitable for being operated by a user to control the operation of the system 50 and to provide system status signals and/or warning signals to a user (such system status signals, system data signals and system warning signals may be, inter alia, visual signals, auditory signals, audio-visual signals, alphanumeric data output, textual output, numerical output displayed on a screen or display, or any other type of signals known in the art). In alternative embodiments of the system 50, the controller 80 may also include any suitable wireless transmitter or transceiver or communicating device capable of wirelessly communicating with a remote user or remote operator for remotely receiving control signals from a remote operator and/or sending status information and /or warning signals to a remote communication device used by a user. For example, the controller 80 may include a cellular communication transmitter and/or transceiver capable for sending data and status signals to a cellular telephone of the user and for receiving control signals or commands from the cellular telephone of a user through a suitable application or program installed on the cellular telephone of the user. Alternatively and/or additionally, the controller 80 may include a software program for bi-directionally communicating with a remote terminal or a remote computer of a user by using a communication network (including, but not limited to, a local area network a digital cellular network, a wide area network, the internet, a virtual private network, or any other suitable communication network known in the art). The controller 80 is suitably coupled or connected to the pump 51 for controlling the operation of the pump 51. While the user of the system 50 may manually start and stop the operation of the pump 51 by using the user interface of the controller 80, the controller 80 may also automatically control the operation of the pump 51 as is disclosed in detail hereinafter.

The system 50 may also include an overflow sensor 82 disposed in the overflow tank 60. An exemplary overflow sensor is a model MK-SFS 15010 float ball switch, commercially available from Maker Electric, Zhejiang, China. However, the overflow sensor may be any fluid level sensor capable of sensing the level of fluid in the overflow tank 60. Any type of fluid level sensor may be used, including, for example, mechanical fluid level sensors, capacitive fluid level sensors, ultrasonic fluid level sensors, optical fluid level sensors or any other suitable fluid level sensor known in the art. The overflow sensor is suitably coupled to the controller 80 and may send a signal to the controller 80 when the fluid level in the overflow tank exceeds a set threshold value. The set fluid level threshold value may be a user adjustable threshold value but is preferably a factory set value. The system 50 may also include a water level sensing sensor 83. The water level sensing sensor may be disposed within the sump 52A of the primary filter 52. The water level sensing sensor 83 is suitably connected to the controller 80. When the water level in the sump 52A is equal to or exceeds a set threshold level, the sensor may provide a signal to the controller 80 which may automatically open the draining valve 52B for a set time period to drain the water (and possibly some small amount of fuel) from the sump 52A into the overflow tank 60. At the end of the set time period, the controller 80 automatically closes the draining valve 52B. The set threshold for the water level within the sump 52A may be adjustable by the user but is preferably factory preset. Similarly, the set time period for opening the draining valve 52B may be user adjustable but is preferably factory preset to avoid too much fuel from being drained into the overflow tank 60.

It is noted that one of the reasons that prior art fuel cleaning systems including fuel separators do not perform automatic sump draining was that electrically operable draining valves are not highly reliable and may occasionally fail to close due to mechanical failure or other reasons. If such a valve fails to close, such failure may result in serious fuel loss because fuel may be continually drained from the sump of the primary filter. When such draining valve malfunctions (fails to close) during cleaning of fuel from a large fuel storage tank this may result not only is catastrophic loss of very large amounts of fuel but may also pose a serious risk of environmental contamination by the fuel continuously exiting the sump of the primary fuel filter. The system 50 may avoid such undesirable fuel loss and environmentally detrimental fuel spills by automatically checking or monitoring the fluid level within the overflow tank 80. In accordance with some embodiments of the fuel cleaning system, the controller 80 may be programmed to shut of the pump 51 if the fluid level in the overflow tank 60 reaches (or exceeds) a set threshold fluid level. The overflow tank fluid threshold level is, preferably, a factory preset threshold level. Therefore, in such an embodiment, if the draining valve 52B malfunctions by failing to close for any reason, the excess fuel draining from the sump 52A into the overflow tank 60 gradually increases the fluid level within the overflow tank 60 until the fuel level reaches the threshold level and the overflow sensor 82 sends a signal to the controller 80. In response to the signal sent by the overflow sensor 82, the controller shuts off the pump 51 terminating the fuel flow through the system 50 to avoid any fuel loss and/or fuel spills.

The safety level, reliability and fault tolerance of the system 50 may be even further improved if more than one overflow sensor is included within the overflow tank 60 and the controller 80 is programmed to shut of the pump 51 is any single overflow sensor of the multiple overflow sensors 82 senses that the fluid level within the overflow tank 60 has reached the threshold fluid level. In such an embodiment having multiple overflow sensors, while a failure of the draining valve 52B to close may occasionally happen, the probability that all of the multiple overflow sensors 82 simultaneously fail may be reduced to acceptable levels by suitable choice of the mean time before failure (MTBF) of the overflow sensors.

The system 50 may also (optionally) be programmed to use the (optional) pressure sensor 63 to detect clogging of the secondary (depth) filters 54 and 56. As the system 50 operates, the secondary filters 54 and 56 become gradually clogged by the water and other contaminants that gradually accumulate within the filtering material within the secondary filters 54 and 56. Such clogging causes the resistance of the filters to fuel flow to gradually increase. As the flow resistance of the secondary filters 54 and 56 increases, the pressure of the fuel within the secondary manifold 58 (as well as the pressure level of the fuel disposed between the output port of the primary filter 52 and the input ports of the secondary filters 54 and 56) also increases. The pressure sensor 63 may continuously sense the fuel pressure at or before the input ports of the secondary filters 54 and 56 (or within the secondary fuel manifold, depending on the positioning of the fluid sensor 63) and sends to the controller 80 signals representing the fuel pressure level. The controller 80 may (optionally) be programmed to process the signals received from the pressure sensor 63 sensed by the pressure sensor 63. If the pressure level exceeds a first threshold pressure level, the controller 80 may continue the operation of the system and provide a warning signal that the secondary filters 54 and 56 may need to be replaced soon (or within a certain time from the providing of the warning signal). This warning signal may alert the user or operator to the state of the secondary filters 54 and 56 and may provide enough time for changing the filter. However, during the operation of the system 50, if the pressure level sensed by the pressure sensor 63 exceeds a second pressure threshold level (higher than the first pressure threshold level), the controller 80 may shut off the pump 51 to terminate the fuel cleaning operation of the system 50 and may also provide a warning signal indicating that the secondary filters 54 and 56 are excessively clogged and that the system operation has been terminated and replacement of the clogged secondary filters is required.

It is noted that the system 50 is an exemplary system having a single primary filter 52 and two secondary depth filters 54 and 56. This may be a configuration dictated by the required fuel flow rate and by the fuel flow ratings of the primary filter 52 and of the secondary filters 54 and 56. However, some embodiments of the fuel cleaning systems may be implemented to include a single primary filter and a single secondary (depth) filter or with a single primary filter and more than two secondary filters operating in parallel, depending, inter alia, on the particular fuel flow ratings of the selected primary filter and secondary filters.

As there is a limit to the fuel maximal flow rate of commercially available primary filters, in fuel cleaning systems requiring higher fuel throughput it may be necessary to include multiple primary filters operating in parallel to increase the system throughput. Each of such multiple primary filters may be fluidically coupled to one or more secondary depth filters operating in parallel depending, among others, on the nominal flow rates of the primary filters and secondary filters available for the implementation. Practically the fuel flow characteristics of commercially available primary filters and secondary depth filters are dictated by the manufacturer and may not be available in unlimited nominal flow rates values, it may be necessary to mix and match commercially available such available filters and to vary the number of secondary filters connected to each primary filter depending on the flow rates of available filters.

Reference is now made to Fig. 5 which is a schematic diagram illustrating some of the components in the fuel flow pathway of a fuel cleaning system including two primary fuel separators and four depth filters, in accordance with some embodiments of the fuel cleaning systems of the present application. It is noted that some of the components of the fuel cleaning system illustrated in Fig. 5 are not shown for the sake of clarity of illustration. The fuel flow arrangement of the fuel cleaning system 100 includes a first primary fuel separator 102 and a second primary fuel separator 103 that are fluidically connected in parallel to a primary fuel manifold. The fuel may be fed into the primary fuel manifold 101 through a fuel inlet port 99.

The first primary separator 102 includes a sump 102A that is drainable through a draining port 102C by opening a draining valve 102B and the second primary separator 103 includes a sump 103A that is drainable through a draining port 103C by opening a draining valve 103B, as disclosed hereinabove with respect to the primary filter 52 of Fig. 4. In some embodiments the sump 102A and the sump 103A may each include a water level sensor (not shown in Fig. 5, for the sake of clarity of illustration) similar in construction and operation to the water level sensor 83 of Fig. 4. An outlet port 107 of the first primary filter 102 is fluidically connected to a three way valve 111 and an outlet port 109 of the second primary filter 103 is fluidically connected to a three way valve 112. The three- way valve 111 may feed the fuel entering it either to a first fuel bypass conduit 117 or to a secondary manifold 108. The three- way valve 112 may feed the fuel entering it either to a second fuel bypass conduit 119 or to a secondary manifold 110. The bypass valves 111 and 112 may be manually operated valves or automatically operated electrical valves.

The secondary manifold 108 may have a pressure sensor 163 disposed therein for sensing the fuel pressure within the secondary manifold 108 and the secondary manifold 110 may have a pressure sensor 165 disposed therein for sensing the fuel pressure within the secondary manifold 110 as disclosed hereinabove in detail with respect to the fuel pressure sensor 63 of Fig. 4. Two (secondary) depth filters 116 and 118 are fluidically connected in parallel to the secondary manifold 108 to receive fuel partially cleaned by the first primary separator 102. Two (secondary) depth filters 120 and 122 are fluidically connected in parallel to the secondary manifold 110 to receive fuel partially cleaned by the first primary separator 103. The outlet port 116A of the depth filter 116, the outlet port 118A of the depth filter 118, the outlet port 120A of the depth filter 1206 and the outlet port 122A of the depth filter 122 are each fluidically to a fuel output manifold 130 which feeds the fuel to a fuel outlet 135. The bypass conduits 117 and 119 are also fluidically connected to the fuel output manifold 130.

When the three way valve 111 is in a first state, the fuel entering the valve 111 is passed into the secondary manifold 108 and from the secondary manifold 108 to the depth filters 116 and 118 for further cleaning. When the valve 111 is in a second state, the fuel entering the valve 111 is diverted into the bypass conduit 117 from which it flows directly into the fuel output manifold 130, bypassing the secondary manifold 108 and the depth filters 116 and 118. Similarly, when the three way valve 112 is in a first state, the fuel entering the valve 112 is passed into the secondary manifold 110 and from the secondary manifold 110 to the depth filters 120 and 122 for further cleaning. When the valve 112 is in a second state, the fuel entering the valve 112 is diverted into the bypass conduit 119 from which it flows directly into the fuel output manifold 130, bypassing the secondary manifold 110 and the depth filters 120 and 122.

It is noted that the system 100 of Fig. 5 may include a controller (not shown) and a pump (not shown) for pumping the fuel into the inlet port 99 of the primary manifold 101. The water level sensors (not shown) in the sumps 102A and 103A may be similar in construction and operation to the water level sensor 83 of Fig. 4 and may be connected to the controller (not shown) of the system 100. The pressure sensors 163 and 165 may be similar in construction and operation to the pressure sensor 63 of Fig. 4. The draining valves 102A and 103A and the three way bypass valves 111 and 112 may be electrically connected to the controller (not shown) of the system 100. The pressure sensors 163 and 165 may be connected to the controller (not shown) of the system. The software program operating on the controller of the system 100 may be a different than the program operating the controller 80 of Fig. 4. For example, the program operating on the controller of the system 100 may independently and separately monitor the water level sensors in the sumps 102A and 103A and the controller may independently automatically drain the sumps 102A and 103A as disclosed hereinabove with respect to the controller 80 and the draining valve 52B of the system 50 of Fig. 4. The system 100 may include an overflow tank (not shown in Fig. 5) for the sake of clarity of illustration. The overflow tank may be similar to the overflow tank 60 of the system 50 and may include one or more overflow sensors (not shown in Fig. 5) similar in construction and operation to the overflow sensor(s) 82 of Fig. 4. If any single overflow sensor in the overflow tank signals that the level of fluid in the overflow tank has reached or exceeded a set threshold level, the controller of the system 100 may shut off the pump (not shown) of the system 100. It is noted that the system 100 may be operated in a "bypass mode" in which the fuel passes only through the primary separators 102 and 103 and bypasses the depth filters 116, 118, 120 and 122 and in a "normal mode" in which the re-circulating fuel passes through the primary separators 102 and 103 and the depth filters 116, 118, 120 and 122. The system may be switched between these operating mode either manually by an operator, or automatically switched by the controller after a preprogrammed or user set time period, or, alternatively may switch from a bypass mode to a normal mode automatically after an (optional) fuel water content sensor ( not shown) that is immersed in the fuel (preferably, at the fuel inlet 99) senses that the water content in the fuel has decreased below a preset or a user set or determined water content threshold level.

It is noted that the fluidic flow path arrangement illustrated in Fig. 5 allows the total maximal fuel flow rate to be double the maximal flow rate of a single primary separator such as the primary separator 102 or 103 (assuming the primary separator 102 and 103 have the same nominal maximal fuel flow rate). By similar arrangements including several such primary separators (and a suitable number of depth filters to match the fuel flow rate of each primary separator) arranged in parallel, it is possible to increase the fuel flow rate of the system 100 to very high nominal maximal flow rates for very high throughput applications.

Reference is now made to Fig. 6 which is a schematic part cross-sectional diagram, illustrating a fuel cleaning system re-circulating the fuel in a storage tank for cleaning the fuel, in accordance with an embodiment of the fuel cleaning systems of the present application. The fuel cleaning system 200 may be fluidically connected to a fuel storage tank 205 by an incoming fuel line 202 which may be any type of suitable fuel line or conduit. The pump (not shown in detail) of the fuel cleaning system 200 pumps the contaminated fuel through the primary and secondary filter(s) (not shown in detail) of the fuel cleaning system 200 for cleaning the fuel 11 and removing water and contaminants from the fuel 11 as disclosed in detail for the fuel cleaning systems 10, 20, 50 100 and 300 of the present application. The cleaned fuel 11 is returned into the storage tank 205 through an outgoing fuel line 204 which may be any type of suitable fuel line or conduit.

The system 200 may be operated in the "bypass mode" in which the fuel 11 passes only through the primary filter(s) of the system 200 for removing a substantial amount of water (and possibly other contaminants) from the fuel 11. After the system is operated in the bypass mode for some time, the system 200 may be switched to operating in a "normal mode" in which the fuel 11 is passed through both the primary filter(s) and the depth filter(s) of the system 200 to further clean (polish) the fuel 11 in the storage tank 205. Such a dual operating mode cleaning cycle may advantageously extend the useful life time of the depth filter(s) of the system 200 by removing a substantial amount of the water and other fuel contaminants using only the primary filter(s) to decrease the total load of water and other contaminants passing through the depth filter(s). If sampling and testing of the fuel 11 in the storage tank 205 (prior to starting the fuel cleaning operation) indicates that the level of water contamination is sufficiently low (for example, the water contamination is about 500 parts per million), the system 200 may be operated in the "normal mode" without using the "bypass mode".

It is noted that the fuel cleaning systems of the present application may have a fuel flow rate in the range of 5-50,000 liter per hour, depending, inter alia, on the type of application and on the amount of fuel that needs to be cleaned (such as, for example, the total volume of the fuel 11 in the fuel storage tank 205 of Fig. 6). However, in certain high volume/high throughput applications the fuel throughput of the system may be greater than 50,000 liters per hour.

Reference is now made to Figs. 7-9, which are schematic flow charts illustrating the steps of three different methods of cleaning fuel using fuel cleaning systems in accordance with some embodiments of the fuel cleaning systems of the present application.

Turning to Fig. 7, the method includes pumping the fuel into the primary separator(s) of the fuel cleaning system for removing water and coarse particular matter contaminants, such as, for example, solid contaminant particles, semi-solid contaminant particles, sludge particles, and other contaminants (step 230). The fuel exiting the primary separator(s) is then passed through the depth filter(s) of the fuel cleaning system for removing at least part of the residual water and at least some of the fine particulate matter remaining in the fuel after the fuel exits the primary separator(s) (step 232). The method of Fig. 7 is applicable to all the embodiments of the fuel cleaning systems disclosed in the present application. Turning to Fig. 8, the method includes the steps 230 and 232 as described in detail with respect to the fuel cleaning method of Fig. 7. The system checks if the pressure level at the input of the depth filter(s) exceeds a pressure threshold level (step 234). The threshold pressure level may be a factory set threshold level or may be a user adjustable threshold level. If the pressure level at the input of the depth filter(s) exceeds the pressure threshold level, the system provides a warning signal (step 236) and may also (optionally) turn off the pump of the fuel cleaning system (step 238). If the pressure level at the input of the depth filter(s) does not exceed the pressure threshold level, the system proceeds to step 240.

The system checks if the sump water level in the sump(s) of the primary filter(s) exceeds a threshold level (step 240). The threshold level of the sump water level may be a factory preset threshold level but may also be a user adjustable threshold level. If the sump water level exceeds the threshold level, the system automatically opens the sump draining valve for a set time period to drain the water in the sump (preferably, into an overflow tank such as, for example the overflow tank 60 of the system 50 of Fig. 4) and then closes the sump draining valve (step 242). The set time period may be factory set but may also be a user set and user adjustable time period. If the sump water level does not exceed the threshold level, the system transfers control to step 244.

The system checks if the overflow tank fluid level exceeds a threshold level (step 244). If the overflow tank fluid level exceeds the threshold level, the system turns off the pump (such as, for example, the pump 51 of Fig. 4) and may (optionally) provide a warning signal (step 246) the overflow tank threshold level may be a factory set threshold level but may also be a user set and adjustable level. If the overflow tank fluid level does not exceed the threshold level, the system transfers control to Step 234.

The warning signals which may (optionally) be provided in steps 236 and 246 may be any of the warning signal types disclosed hereinabove. For example, the warning signals may be, inter alia, visual signals, auditory signals, audio-visual signals, alphanumeric data output, textual output, numerical output displayed on a screen or display, or any other type of signals known in the art). The warning signals may be provided locally on the system (such as, for example by being visually displayed on a display device included in the controller 80, or as a warning tone or beep provided by a loudspeaker included in the controller 80 or by turning on or blinking one or more light emitting diodes installed in the controller 80, or by using any combinations of any such visual and/or auditory signal types described herein). In systems including remote communication capabilities as disclosed in detail hereinabove, the warning signals may include sending warning messages over a communication network to a cellular communication device such as a cellular telephone use by the operator, or to a computer operated by the user or to any other remote communication device used by an operator of the system.

Turning now to Fig. 9, the method illustrated in Fig. 9 may start with steps 230 and 232 as disclosed in detail with respect to Fig. 7. The system checks if the overflow tank fluid level exceeds a threshold level (step 250). If the overflow tank fluid level exceeds the threshold level, the system turns off the pump (such as, for example, the pump 51 of Fig. 4) and may (optionally) provide a warning signal (step 252) the overflow tank threshold level may be a factory set threshold level but may also be a user set and adjustable level. If the overflow tank fluid level does not exceed the threshold level, the system transfers control to Step 254.

The system checks if the pressure level at the input of the depth filter(s) exceeds a second pressure threshold level (step 254). The second threshold pressure level may be a factory set threshold level or may be a user adjustable threshold level. If the pressure level at the input of the depth filter(s) exceeds the second pressure threshold level, the system turns off the pump of the fuel cleaning system and may also (optionally) provide a warning signal (step 256). If the pressure level at the input of the depth filter(s) does not exceed the second pressure threshold level, the system transfers control to step 258.

The system checks if the pressure level at the input of the depth filter(s) exceeds a first pressure threshold level which is lower than the second pressure level (step 258). The first threshold pressure level may be a factory set threshold level or may be a user adjustable threshold level. If the pressure level at the input of the depth filter(s) exceeds the first pressure threshold level, the system may provide a warning signal (step 260). If the pressure level at the input of the depth filter(s) does not exceed the first pressure threshold level, the system transfers control to step 262.

The system checks if the sump water level in the sump(s) of the primary filter(s) exceeds a threshold level (step 262). The threshold level of the sump water level may be a factory preset threshold level but may also be a user adjustable threshold level. If the sump water level exceeds the threshold level, the system automatically opens the sump draining valve for a set time period to drain the water in the sump (preferably, into an overflow tank such as, for example the overflow tank 60 of the system 50 of Fig. 4) and then closes the sump draining valve (step 264). The set time period may be factory set but may also be a user set and user adjustable time period. If the sump water level does not exceed the threshold level, the system returns control to step 250.

It is noted that the methods disclosed in Figs. 8 and 9 may be used in the systems 50, 100, 200 and 300 of Figs. 4, 5, 6 and 10, respectively.

The fuel cleaning systems of the present application may be mobile systems but may also be fixed systems. For example, the system 20 of Fig. 2 may be installed in a vehicle or boat as disclosed hereinabove and may carried with the vehicle or boat. In another example, the system 200 may be fixedly installed in the vicinity of the fuel storage tank 205 and may be used periodically to clean the fuel 11 stored in the storage tank 205. This type of fixed system may be referred to as "on-site installation".

Alternatively, the fuel cleaning system 200 may be configured as a mobile system. Such a mobile system may be carried on a suitable vehicle to any site at which a fuel cleaning service needs to be performed (such as, for example, the site at which the fuel storage tank 205 is disposed. The system may then be temporarily fluidically connected to the fuel tank as illustrated in Fig. 6 by using either flexible fuel lines or any other type of existing fuel lines installed in the fuel storage tank 205. The fuel 11 in the fuel storage tank 205 may then be cleaned as disclosed hereinabove. During the cleaning of the fuel 11, the system 200 may either remain on the truck which mobilized it to the storage tank 205, or alternatively may be taken off the truck ( by using a fork- lift or any other suitable type of winch or motorized crane (preferably installed on the truck). After cleaning of the fuel 11 is completed, the fuel cleaning system may be disconnected from the fuel storage tank 205 and may be loaded again on the truck and carried away from the cleaning site. If the system 200 is fixedly installed on the truck, the cleaning of the fuel 11 may be performed as the system 200 mounted on the truck and after disconnecting the system from the fuel storage tank 205, the truck may simply drive off the site of cleaning. In another example, a large capacity cleaning system may be fixedly mounted on a freighter ship or large tanker ship and may be fixedly fluidically connected to the fuel tank providing the fuel to the engine(s) of the ship and may be periodically or continuously used to keep the fuel clean. Furthermore, such a system may also be installed on a commercial tanker ship carrying fuel such as diesel fuel or any other types of fuel disclosed hereinabove and may be operated continuously or periodically to clean the fuel at sea or at a port.

Reference is now made to Fig. 10 which is a schematic front view of a mobile fuel cleaning system, in accordance with an embodiment of the fuel cleaning systems of the present application. The fuel cleaning system 300 includes a housing 301 having two closable doors 302A and 302B. The system 300 includes a fuel pump 351, a controller 300, a primary coalescing filter 352 and three depth filters 354, 356 and 359. Fuel may enter the system 300 through a fuel inlet port 355. The inlet port 355 is fluidically connected to a strainer 349 for straining very coarse debris or particulate matter from entering the pump 351 and is fluidically connected to the inlet port of the pump 351. The outlet port of the pump 351 is fluidically connected to the fuel inlet port of the primary coalescing filter 352. The fuel outlet port of the primary coalescing filter 352 is fluidically connected to an input manifold 358. The input manifold 358 is fluidically connected to the fuel inlet ports of the three depth filters 354, 356 and 359 for feeding the fuel exiting the primary coalescing filter 352 into the depth filters 354, 356 and 359. The fuel exiting the outlet ports of the depth filters 354, 356 and 359 flows into manifold 362. The fuel output manifold 362 feeds the cleaned fuel into a system a fuel output port (not seen in the front view of Fig. 10). A pressure sensor (not shown) is installed in the fuel input manifold 358 for sensing the pressure level at the input ports of the depth filters354, 356 and 359 to determine the degree of clogging of the depth filters 354, 356 and 359, as disclosed in detail hereinabove with respect to the pressure sensor 63 of Fig. 4 and the pressure sensors 163 and 165 of Fig. 5.

A manual bypass valve 369 is fluidically connected to the output port of the primary coalescing filter 352, the input manifold 358 and the fuel output manifold 362. The bypass valve 369 has two states. A first "bypass" state in which the bypass valve diverts the fuel exiting from the primary coalescing filter 352 directly to the output fuel manifold 362, bypassing the depth filters 354, 356 and 359 by blocking filter entry into the input manifold 358. In the second "normal" state, the bypass valve 369 diverts the fuel exiting from the primary coalescing filter 352 into the input manifold 358 while blocking of the fuel exiting from the primary coalescing filter 358 from directly entering the fuel output manifold 362. When the bypass valve 369 is in the normal state, the fuel exiting the primary coalescing filter 352 must pass through the depth filters 354, 356 and 359.

The primary coalescing filter 352 includes a sump 352A and an electrically operated draining port 352B which includes an electrically operated draining valve (not seen in detail in the front view of Fig. 10) installed in the draining port 352B and electrically controlled by the controller 380. The sump 352 may include a water level sensor (not seen in Fig. 10) as disclosed in detail hereinabove. The water level sensor is may be suitably connected to the controller 380. The sump 352A may be drained from water through the drainable port and the drained water is drained into the overflow tank 360 disposed at the bottom part of the housing 301. The overflow tank 360 includes a fluid level sensor (not seen in the front view of Fig. 10) that is suitably connected to the controller 380. And the controller 380 and the fluid level sensor may be operated to shut off the pump 51 and (optionally) provide a warning signal) if the fluid level in the overflow tank 360 exceeds a threshold level, as disclosed in detail in steps 244 and 246 of the method of Fig. 8 or the steps 250 and 252 of the method of Fig. 9.

The system 300 also includes a sampling port ending in a manual sampling valve 370. By opening the sampling valve 370, it is possible to collect samples of the fuel exiting the primary coalescing filter 352. The fuel samples may be tested to determine the amount of water and/or other contaminants if desired.

The system 300 may also include an overflow tank draining port (not shown in Fig. 10) for draining any fluids which has accumulated in the overflow tank 360.

The bottom part of the housing 301 also includes a tool drawer 305 for storing tools and has four supporting feet (only the two from supporting feet 307A and 307B are seen in the front view of Fig. 10). The fuel cleaning system 300 is a movable (mobile) system and may be lifted by a fork-lift or any other suitable lifting device and loaded into, or offloaded from a vehicle.

In the system 300, the primary coalescing filter may be a model 8X20X2 diesel fuel purifier commercially available from Diesel Craft fluid engineering division/ Magnum group, CA., U.S.A., and the depth filters 354, 356 and 359 may be a Model SDFC1888 super duty filter cartridge depth filter commercially available from FLAC GUARD, South Africa or from Kleenoil, UK. The pump 351 may be a Polaris gear pump model PL 10 with a fuel pumping capacity of 3200 liter per hour, commercially available from Cassappa Corp., USA., but other types of pumps may also be used.

The pressure sensor (not shown in detail in Fig. 10) used to measure the pressure at fuel input manifold 358 is a Model FST800-211P241C, pressure sensor commercially available from Firstrate Sensor Co. Ltd., China, but other types of pressure sensors may be used.

The System 30 may be operated in accordance with any of the fuel cleaning methods of Figs 7-9. Typically, the amount of water in the fuel after exiting the primary coalescing filter is about 500 parts per million (PPM) and the filter typically removes particles with mean diameters of about 20-30 micron. The level of water in fuel exiting the depth filters 354, 356 and 359 is typically 50 PPM and the depth filters typically filter out particles having a diameter greater than about 1 micron. The nominal fuel flow rate for the system 300 is 3200 liter per hour.

It is noted that In accordance with some embodiments, the systems of the present application may clean different types of fuel, including but not limited to, gasoline, kerosene, light to heavy petroleum distillation fraction, diesel fuel, marine diesel fuel, aviation turbine fuel, Jet A fuel, Jet A-l fuel, Jet B fuel, heavy fuel oil, number 2 fuel oil, Number 3 fuel oil, Number 4 fuel oil, JP-4 jet fuel, JP-5 jet fuel, JP-7 jet fuel and JP-8 jet fuel.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A system for cleaning fuel, the system comprising:

One or more primary fuel separators said one or more primary fuel separator comprise a coalescer including an active material having a high surface area per unit weight for removing water and/or coarse particulate matter from said fuel, each primary fuel separator of said one or more primary fuel separators includes a separator fuel inlet port, a separator fuel output port and a sump having an openable and closable draining port; and

one or more secondary depth filters, each depth filter of said one or more depth filter has a depth filter inlet port and a depth filter output port, said filter inlet port is fluidically connected to said fuel separator outlet for receiving fuel from said primary separator and for removing residual water and fine particulate matter from said fuel.

2. The system according to claim 1, wherein said system is configured to be installed in a vehicle and wherein said fuel inlet port of said primary separator is fluidically connectable to a fuel pump of said vehicle and said fuel outlet port of said one or more secondary depth filter is fluidically connectable to an engine of said vehicle for providing cleaned fuel to said engine.

3. The system according to any of the preceding claims, wherein said sump is a transparent sump to enable visual inspection of said water accumulated in said sump.

4. The System according to any of the preceding claims, wherein said coalescer is a coalescer comprising active alumina.

5. The system according to any of claims 1-2, wherein said one or more primary separators comprises one or more separators having a maximal fuel flow rate in the range of 5 - 50,000 liter per hour.

6. The system according to any of the preceding claims, wherein said one or more said depth filters comprises one or more depth filters having a maximal flow rate in the range of 0.1 - 2,500 liter per hour.

7. The system according to any of the preceding claims, wherein said fuel is selected from the list consisting of, gasoline, kerosene, light to heavy petroleum distillation fraction, diesel fuel, marine diesel fuel, aviation turbine fuel, Jet A fuel, Jet A-l fuel, Jet B fuel, heavy fuel oil, number 2 fuel oil, Number 3 fuel oil, Number 4 fuel oil, JP-4 jet fuel, JP-5 jet fuel, JP-7 jet fuel and JP-8 jet fuel.

8. The system according to any of claims 1 and 3-7, wherein said system is configured for cleaning fuel disposed in a fuel storage tank and wherein said system also includes a pump having a pump inlet port for receiving fuel from said storage tank through a incoming fuel conduit and a pump outlet port for pumping said fuel into the fuel inlet ports of said one or more primary fuel separators and a return fuel conduit for receiving fuel from the depth filter output ports of said one or more depth filters and wherein the fuel exiting the depth filter output ports of said one or more depth filters is returned to said fuel storage tank by said return fuel conduit.

9. The system according to claim 8, wherein the system also includes a strainer fluidically connected between said fuel storage tank and said pump inlet port for straining said fuel before said fuel enters said pump inlet port.

10. The system according to any of claims 8-9, wherein said system also includes one or more bypass conduits, each bypass conduit of said one or more bypass conduits is fluidically connected between the fuel output port of a primary fuel separator of said one or more primary fuel separators and said return fuel conduit, wherein each bypass conduit of said one or more bypass conduits includes an openable and closable bypass valve of one or more bypass valves, wherein when said one or more bypass valves are closed, the fuel exiting the fuel output ports of said one or more primary fuel separators flows into the inlet ports of said one or more depth filters and when said one or more bypass valves are open, the fuel exiting the fuel output ports of said one or more primary fuel separators flows directly into said return fuel conduit bypassing said one or more depth filters.

11. The system according to any of claims 8-10, wherein said openable and closable draining port includes a controllable sump draining valve for controllably opening and closing said draining port of said sump.

12. The system according to any of claims 10-11, wherein one or more of said bypass valve and said sump draining valve are electrically openable and closable valves.

13. The system according to claim 12, wherein said electrically openable and closable valves are solenoid based valves.

14. The system according to any of claims 10-13, wherein said system also includes a controller for controlling the operation of said system.

15. The system according to claim 14, wherein said controller is electrically connected to said pump, said bypass valve and said sump draining valve for controlling the operation of said pump, said bypass valve and said sump draining valve.

16. The system according to claim 14, wherein said system also includes a water level sensing sensor disposed within each sump of said one or more primary fuel separator for detecting when the water level within said sump reaches a threshold level.

17. The system according to claim 16, wherein said controller is programmed to automatically open the draining valve of a sump when said water level sensing sensor detects that the water level within said sump is equal to or exceeds said threshold level.

18. The system according to claim 17, wherein when said water level sensing sensor detects that the water level within said sump is equal to or exceeds said threshold level, said controller opens the sump draining valve of said sump for a preset time period and closes said sump draining valve at the end of said preset time period.

19. The system according to claim 18, wherein said preset time period is selected from a factory set fixed time period and a user programmable time period.

20. The system according to any of claims 8-19, wherein said system also includes a fuel overflow tank for receiving any water and fuel drained from the sumps of said one or more primary fuel separators.

21. The system according to claim 20 wherein said overflow tank includes an overflow sensor connected to a controller for sensing when the fluid level within said overflow tank reaches a threshold level.

22. The system according to claim 21, wherein whenever said overflow sensor senses that fluid level within said overflow tank has reached said threshold level said controller is programmed to perform an action selected from the list consisting of,

stopping the operation of said pump, and stopping the operation of said pump and providing a warning signal to check said sump draining valve and/or said water level sensor.

23. The system according to any of claims 20-22 wherein said overflow tank includes an openable and closable draining port for draining any fluids from said overflow tank.

24. The system according to any of claims 8-23, wherein said system also includes a pressure sensor connected to a controller and disposed before the fuel inlet ports of said one or more depth filters for sensing the fuel pressure level at or before said inlet ports.

25. The system according to claim 24, wherein if the pressure level sensed by said pressure sensor exceeds a threshold pressure level, said controller is programmed for performing an action selected from the group consisting of,

providing a warning signal indicative of the need to replace said one or more depth filters,

switching off said pump, and

providing a warning signal indicative of the need to replace said one or more depth filters and switching off said pump.

26. The system according to any one of the preceding claims wherein the amount of water in the fuel exiting said one or more primary fuel separators is in the range of 400-700 parts per million by weight.

27. The system according to any of the preceding claims wherein said one or more primary fuel separators remove particles exceeding an average diameter of 30 micron.

28. The system according to any of the preceding claims, wherein the amount of water in the fuel exiting said one or more depth filters is in the range of 30-70 parts per million by weight.

29. The system according to any of the preceding claims wherein said one or more depth filters remove particles exceeding an average diameter of 1-3 micron from said fuel.

30. The system according to any of the preceding claims, wherein said one or more primary fuel separator comprises a single primary fuel separator.

31. The system according to claim 30 wherein said one or more depth filters comprises two or more depth filters fluidically connected in parallel to the output port of said single primary fuel separator by a secondary fluid manifold.

32. The system according to any of claims 1-30 wherein said one or more depth filters comprise a single depth filter.

33. The system according to any of claims 8-29, wherein said one or more primary fuel separators comprise two or more primary fuel separators connected in parallel to said output port of said pump through a primary fuel manifold.

34. The system according to claim 33, wherein each primary fuel separator of said two or more primary fuel separators is fluidically connected to the input port of a single depth filter and wherein the fuel exiting said single depth filter is returned to said fuel storage tank.

35. The system according to claim 33, wherein each primary fuel separator of said two or more primary fuel separators is fluidically connected to the input ports of two or more depth filters through a secondary fuel manifold.

36. The system according to claim 35 and wherein the output ports of all of the depth filters of said system are fluidically connected to a fuel output manifold that feeds said fuel back to said fuel storage tank.

37. A method for cleaning fuel by a fuel cleaning system, the method comprising the steps of:

pumping said fuel into one or more primary separators for removing water and coarse particulate matter from said fuel; and

passing the fuel exiting said one or more primary separators through one or more depth filters for removing at least part of the residual water and at least some fine particulate matter remaining in said fuel after said fuel exits said one or more primary separators.

38. The method according to claim 37, wherein the step of pumping comprises pumping said fuel by a fuel pump of a vehicle.

39. The method according to claim 38, wherein the step of passing comprises providing the fuel exiting said one or more depth filters to an engine of said vehicle.

40. The method according to claim 37, wherein said one or more primary separators each include a sump, and wherein the method also includes the step of draining fluid from one or more sumps of said one or more primary separators into an overflow tank included in said system.

41. The method according to claim 40, wherein said step of draining fluid comprises manually draining fluid from said one or more sumps.

42. The method according to claim 40, wherein said step of draining fluid comprises automatically draining fluid from said one or more sumps into said overflow tank when the water level within said one or more sumps exceeds a threshold level.

43. The method according to claim 42, wherein each of said one or more sumps includes a draining valve and wherein said step of automatically draining comprises automatically opening one or more draining valves of said one or more sumps for a set time period and closing said one or more draining valves.

44. The method according to any of claims 40-43, wherein said system includes a pump for performing said step of pumping, said fuel overflow tank includes a sensor for sensing the level of fluid disposed in said fuel overflow tank, and wherein the method also includes the step of checking if the level of fuel in said overflow tank exceeds a threshold level and turning off said pump if the level of fuel in said overflow tank exceeds said threshold level.

45. The method according to claim 44, wherein sais step of checking also includes the step of providing a warning signal indicative that the overflow tank is full if the level of fuel in said overflow tank exceeds said threshold level.

46. The method according to any of claims 37-45, wherein the system includes one or more pressure sensors for sensing the pressure of the fuel at input ports of said one or more depth filters, and wherein the method also includes the step of providing a warning signal when the pressure of the fuel at said input ports of said one or more depth filters exceeds a first pressure level.

47. The method according to any of claims 37 and 40-46, wherein the system includes a pump for performing said step of pumping and one or more pressure sensors for sensing the pressure of the fuel at input ports of said one or more depth filters and wherein the method also includes the step of turning off said pump when the pressure of the fuel at said input ports of said one or more depth filters exceeds a second pressure level.

48. The method according to any of claims 37 and 40-46, wherein said system also includes one or more bypass valves, each bypass valve of said one or more bypass valves is fluidically connected to an output port of one primary separator of said one or more primary separators and is configured for controllably bypassing said one or more depth filters to flow the fuel exiting said one or more primary separators directly into a main fuel output port of said system, and wherein said method also includes the step of activating one or more of said bypass valves when the pressure at input ports of said one or more depth filters exceeds a second pressure level.

49. The method according to claim 37, wherein said system also includes one or more bypass valves, each bypass valve of said one or more bypass valves is fluidically connected to an output port of one primary separator of said one or more primary separators and is configured for controllably bypassing said one or more depth filters associated with each of said one or more primary separators to flow the fuel exiting said one or more primary separators directly into a main fuel output port of said system, and wherein the method also includes the step of activating all of said one or more bypass valves prior to performing said step of pumping to initially recycle said fuel only through said one or more primary separators until at least some of said water and coarse particulate matter is removed from said fuel at which time said one or more bypass valves are deactivated resulting in said fuel passing through said one or more depth filters.

50. The method according to claim 49, wherein said step of activating all of said one or more bypass valves is performed at an initial part of a cleaning run performed by said system to reduce contaminant load reaching said one or more depth filters for increasing the serviceable lifetime of said one or more depth filters.