Patent Description:
One factor which influences the efficiency of self-cleaning of filtration systems is the amount of fluid, e.g. fresh water in a water filtration system, wasted in performing the self-cleaning (as a percentage of the total amount of fluid flowing through the system).

Excessive waste of self-cleaning water may result from unnecessary prolongation of the self-cleaning session beyond the required for effective cleaning of the screening member.

The time duration for cleaning a screening member to its full extent, depends on unstable factors such as the pressure of water in the water supply system during the self-cleaning, amount of filtride and residue on the screening member, and properties thereof. The water pressure may be unpredictable because it may depend on factors that may vary in real-time, e.g. the water consumption rate from the system during the self-cleaning session, and the number of filters which happen to undergo backflush simultaneously. Similarly, the amount and properties of the filtride may also be unpredictable, depending on the raw fluid that is being filtered and particles therein.

In some cases, a controller of the self-cleaning filtration system may be configured to activate the cleaning process for a predetermined time duration. Setting the time duration may be challenging, as too short duration may be insufficient for full extent cleaning on the one hand, and on the other, excessively long duration causes undue waste of fluid.

It is therefore among the objects of the following disclosure to provide for optimization of the duration of automatic self-cleaning sessions in filtration systems.

<CIT> discloses a device for filtering for treating ballast water by means of a filtering method, and more particularly, to a multicage-type device for filtering ballast water to prevent back pressure.

<CIT> discloses a filtering apparatus for treating ballast water. constructed so that a housing cover plate and an exhaust unit are removably coupled to each other at an upper position of a housing. The exhaust unit includes a base flange on a portion thereof coupled to the housing cover plate and the base flange includes a projecting step that projects to be inserted into a core through hole formed in the housing cover plate. A core serving as a discharge passage of foreign substances includes a shaft coupling unit on a portion thereof coupled to the driving shaft, and is coupled at the shaft coupling unit to the driving shaft via a coupling means.

It is an object of the presently disclosed subject matter to provide for timely termination of self-cleaning sessions in filtration systems in which screening elements (filters) are cleaned by scanners (which scan the screen by relative motion between the screening element and a respective scanner), for minimizing waste of self-cleaning fluids and for avoiding termination of a self-cleaning session before completion of scanning the screening element by the scanner.

A first solution according to the presently disclosed subject matter is to determine whether a change in the respective position between the screening element and the scanner (resulting from the relative motion between the scanner and the screening element) has reached an end, wherein the determination is based at least on a signal free from real-time variations in parameters (e.g. pressure, flow-rate, transparency) of the self-cleaning fluid.

A second solution according to the presently disclosed subject matter is to provide the filtration system with electronic controller, and to communicate the signals generated by the location tracker to the electronic controller, wherein the electronic controller is configured to determine whether a cleaning session is to be terminated, based on at least the signals generated by the location tracker.

<FIG> illustrate three respective schematics of an embodiment of a filtration system <NUM> according to the presently disclosed subject matter, in three situations which normally occur during the operation cycle of the system. <FIG> illustrates the system during its filtration mode of operation. <FIG> illustrates the system at the beginning of a self-cleaning operation mode (referred to also as "self-cleaning session"). <FIG> illustrates the system at the end of a self-cleaning session, shortly before it resets and takes the filtration-mode position shown in <FIG>.

The filtration system <NUM> comprises a filtration chamber <NUM>, a pre-filter (coarse screen) <NUM>, a screening element (fine screen) <NUM> located within the filtration chamber <NUM>, a suction scanner <NUM> comprising a main-tube <NUM> and at least one nozzle 104n for self-cleaning the screening element by suctioning fluid through the screening element upon activation of a self-cleaning session, and a switching mechanism configured to terminate the self-cleaning session when a condition is met.

One of the suction scanner <NUM> and the screening element <NUM> is configured to move linearly with respect to the other, during a self-cleaning session. The relative linear motion between the scanner and the screen (which, as a matter of design, is combined with rotational motion between the suction scanner <NUM> and the screening element <NUM>) allows for scanning and cleaning by suction the screening element to its entire extent. The relative motion results also with a predetermined linear offset of positions between these two elements when their relative position in the moment before activation of a self-cleaning session is compared to their relative position in the moment of termination of a successful self-cleaning.

Partial linear offset between their relative positions in the moment of activation of a self-cleaning session and in the moment of termination of a self-cleaning session occurs in case of premature termination of the self-cleaning, i.e. before a full-extent scanning. Premature termination is desired e.g. in case the self-cleaning session exceeds a predefined maximal time limit.

The linearly moving part of the suction scanner is a main-tube <NUM> of the suction scanner through which the suctioned dirt is communicated to a draining port <NUM>. The suction scanner is <NUM> is stationary with respect to the filtration chamber. The screening element <NUM> is configured to move linearly with respect to the filtration chamber and the suction scanner, thereby constituting the moving part of the suction scanner, to which a moving body of the location tracker is coupled for the purpose of monitoring the respective linear offset of positions between the suction scanner and the screening element.

For the condition to be met, a predetermined change in a signal indicative of the respective linear offset between the screening element <NUM> and the suction scanner <NUM> need to be recorded, with, without, or as an alternative to additional criteria to be met.

For the condition to be met a value calculated based on a signal indicative of a respective linear motion between the screening element <NUM> and the suction scanner <NUM> need to exceed a predetermined threshold value indicative of the respective linear offset between the screening element <NUM> and the suction scanner <NUM>, with, without, or as an alternative to additional criteria to be met.

The signal to be used in determining whether the condition is met, is generated by a location tracker <NUM> having a moving body 106p coupled to a moving part <NUM> of the suction scanner <NUM>, for moving outside the filtration chamber <NUM> in an environment 106c isolated from fluid content of the filtration chamber, wherein said moving corresponds to a motion of the moving part of the suction scanner within the filtration chamber.

The termination of the cleaning session is based on additional criteria. The additional criteria to be met for automatic termination of the self-cleaning session includes one or more of the following: (i) a lapse of a predetermined time from the time of recordation of the predetermined change in the signal; (ii) a lapse of a predetermined time from the activation of a recent self-cleaning session; (iii) a pressure differential between a first pressure P1 and a second pressure P2 measured respectively from opposite sides (upstream and downstream) of the screening element <NUM> has reached a predetermined value; (iv) a predetermined change in a pressure differential between a first pressure P1 and a second pressure P2 measured respectively from opposite sides of the screening element <NUM> has been recorded.

In the illustrated embodiment, the signal by which the offset between the screening element <NUM> and the suction scanner <NUM> is revealed, is a fluid pressure P3 measurable in an outlet port 106t of the location-tracker <NUM>.

In the illustrated embodiment, the switching mechanism comprises an electronic controller <NUM> coupled to an electromechanical latch valve <NUM>. The latch valve <NUM> has a first state in which a fluid-outlet 115e is in fluid communication with a first fluid inlet 115f, and a second state in which the fluid outlet 115e is in fluid communication with a second fluid inlet 115c. Additionally or alternatively, other forms of valves is utilized, such as an AC valve, DC valve, DC latch valve, solenoid valve, or the like.

The outlet 115e of the latch valve <NUM> is in fluid communication with an inlet port of the location-tracker 106t through a pipe-line <NUM>.

The location tracker <NUM> comprises a piston 106p, movable within a cylinder 106c. The piston is coupled to and is linearly comoving with a linearly moving part <NUM> of the suction scanner <NUM>.

A draining compartment <NUM> separates between the filtration chamber <NUM> and the cylinder 106c. A proximal end of the draining compartment <NUM> is connected to an end of the filtration chamber <NUM> near an end portion 103e of the screening element <NUM> to be scanned by the suction scanner <NUM> closely to the termination of the self-cleaning session. The cylinder 106c is connected to a distal end of the draining compartment <NUM>, opposite said proximal end. A draining-opening 104d of the suction scanner located at an end of a main tube <NUM> of the suction scanner <NUM> is opened to the draining compartment. A turbine <NUM> configured to rotate the suction scanner by means of kinetic energy extracted from the flow of draining fluid suctioned by the scanner, is housed by the draining compartment <NUM> and is connected to a top end of the suction-scanner's main tube <NUM>.

One or more suction nozzles 104n of the suction scanner extend between the main-tube <NUM> of the suction scanner and the internal surface of the screening element <NUM>, such that intake-openings of the nozzles touch or nearly-touch the porous inner surface of the screening element <NUM>. The nozzles are angularly or linearly spaced along the main-tube <NUM>, in a design guaranteeing full coverage of the screening element <NUM> during a full extent suction-scanning. Suction scanner <NUM> is configured to move the suction nuzzles 104n in a helical-like trajectory while scanning the screening element <NUM>. Additionally or alternatively, suction nozzles 104n are shaped as a disk so as to concurrently engage an entire inner circumference of a cylindrical portion of the screening element <NUM>. Suction scanner <NUM> may or may not rotate about its axis. Linear movement of the suction nozzles 104n provides a full scanning of the filter element <NUM>. The main tube <NUM> of the suction scanner is provided with a single longitudinally extending nozzle having an intake opening elongated parallel to the main tube along a certain extent of the screening element, wherein scanning of the entire extent of the screening element is achieved by the intake opening of the single nozzle following a helical trajectory.

The draining compartment <NUM> comprises a draining port <NUM> in fluid communication with a drain valve <NUM>. The drain valve <NUM> is connected to a draining environment (e.g. a collection tank, or e.g. free atmosphere) through evacuation tube (not illustrated).

Activation of self-cleaning includes opening the draining valve <NUM>. The draining valve is in fluid communication with the inner porous surface of the screening element <NUM> through the draining port <NUM>, the draining compartment <NUM>, and the main tube <NUM> of suction scanner <NUM> (which its exit-opening 104d is opened in the draining compartment). Since the fluid pressure in the filtration chamber <NUM> is greater than the pressure in the draining environment to which the drain valve <NUM> is open, fluid from the filtration chamber is suctioned into the intake openings of the nozzles of the suction scanner <NUM>, thereby cleaning the screening element <NUM> and draining the removed dirt through the main tube <NUM>, the draining compartment <NUM>, and the drain valve <NUM>.

Once a fluid flow is established through the suction-scanner's main tube <NUM>, the turbine <NUM> connected at the top of the main tube starts to rotate due to kinetic energy supplied by the drain flow emerging from the opening 104d at the top of the main tube <NUM>, such that a screen portion 103b at a first end of the screening element becomes suctioned and cleaned, and linear motion of the scanner <NUM> is started, and is to be tracked by the location tracker <NUM>.

For the location to be tracked, the fluid pressure P3 at an end of the cylinder 106c facing a first side of the piston 106p, away from the filtration chamber <NUM>, is communicated to the electronic-controller <NUM> from the outlet port of the location tracker through a pipe-line <NUM>.

In the illustrated embodiment, the moving part of the suction scanner <NUM> is the main tube <NUM>. The piston 106p of the location tracker <NUM>, is coupled to the main tube <NUM> of the suction scanner <NUM> by means of a piston-stem 106r.

The piston stem 106r is pivotably coupled to the suction scanner (in the illustrated embodiment, the piston 106p is coupled to the scanner <NUM> through the turbine <NUM>, wherein the piston stem 106r has hollow end and the turbine <NUM> has an axial pin protruding into the hollow of the stem), thereby allowing for free rotation of the suction scanner <NUM>, without rotation of the piston 106p. Thus, the suction scanner <NUM> and the piston 106p comove linearly during a suction scanning, while only the suction scanner rotates.

During the filtration mode of operation (<FIG>), the latch valve <NUM> is in said first state. In the first state of the latch valve, the inlet port 115f is connected to the exit port 115e, therefore the valve <NUM> communicates to the cylinder 106c a high-pressure fluid HP supplied from the latch-valve inlet 115f. The high-pressure fluid is greater than the pressure fluid inside the filtration chamber <NUM> which presses the piston from its second side (the side of the piston facing the filtration chamber), thus maintains the piston 106p closer to the filtration chamber and full-stroke remotely from the cylinder end 106e, as illustrated by <FIG>.

The controller <NUM> is configured to turn the filtration system <NUM> into a self-cleaning mode, either manually (e.g. by a pushbutton to be pressed by a user), or upon detection of a predetermined pressure difference between an upstream pressure P1 and a downstream pressure P2. The controller <NUM> is configured to turn the filtration system <NUM> into a self-cleaning mode on periodic basis, e.g. upon counting a predetermined time interval T1 from a successful termination of a previous cleaning session, or upon counting a predetermined time interval T2 from an unsuccessful termination of a previous cleaning session, when the termination was recognized by the controller as resulting from inappropriate external conditions (e.g. occasional severe drop in the upstream pressure occurring during a cleaning session) and not as resulting from a failure of the self-cleaning mechanism.

The upstream pressure P1 is measurable, e.g. in a pressure sampling port t1 near the inlet 101i of the filtration chamber <NUM>, in an inlet side of the screening element <NUM> (which is in fluid communication with the inlet 101i of the filtration chamber through the coarse screen <NUM>), and is communicated to the controller through line 105p1. The downstream pressure P2 is measurable in an outlet side of the screening element <NUM> (e.g. in a pressure sampling port t2 near the outlet 101e of the filtration chamber <NUM>, connected to the controller through line 105p2).

The controller <NUM> is configured to measure both said pressures by a pair of dedicated pressure gauges and to calculate the differential pressure. The differential pressure is detected by a differential pressure gauge and the differential pressure alone is communicated to the controller. Regardless of the method by which the differential pressure is detected, the controller <NUM> is configured to activate a self-cleaning session whenever the differential pressure exceeds a predetermined threshold value. The threshold is indicative of filtride accumulated on the screening element <NUM> and reducing its open-area. As a result, when the threshold is met, self-cleaning session is performed to improve the effectiveness of the screening element <NUM> after removing the filtride.

Upon activation of a self-cleaning session by turning the drain valve <NUM> open, the controller sends a switching command to the latch valve <NUM>, and the latch valve disconnects the valve inlet 115f from and connects the valve inlet 115c to the valve outlet 115e, as shown by <FIG>.

The fluid pressure supplied through the valve inlet 115c is open to the atmosphere, thus communicates atmospheric pressure to the inlet port of the cylinder 106c. The fluid pressure inside the draining compartment <NUM> is greater than atmospheric. As a result, the piston 106p starts moving in a direction away from the filtration chamber <NUM>, into the cylinder 106c, as illustrated by <FIG>.

The electronic controller is configured to delay the switching command of the latch valve <NUM>, for a predetermined amount of time to be counted from the time of outputting the draining command that initiates the self-cleaning session by turning the drain valve <NUM> open. The delay is optimized for allowing at least one full rotation of the suction scanner <NUM> before linear motion of the suction scanner begins, thereby providing for full extent cleaning of the screening element first end portion.

The pressure P3 in the end of cylinder 106c, is responsive to the motion of the piston 106p, since the motion of the piston presses against the fluidic content located in the cylinder 106c between the piston's first side and the cylinder's end (where the pressure P3 is monitored).

The electronic controller <NUM> is programmed to calculate the current location of the piston with respect to the cylinder (which reflects the location of the suction scanner <NUM> with respect to the screening element <NUM>), based on the current value of the pressure P3 as measured by a pressure gauge to which the pipe-line <NUM> is connected. An electronic signal indicative of the pressure value is outputted by the pressure-gauge to respective circuitry in the electronic controller.

The controller is pre-programmed with the rate of evacuation of fluid out of the cylinder 106c per a given pressure P3 (or is pre-programmed with a table of positions of the piston as a function of time and of the pressure P3), thus calculating (or determining) the position of the piston 106p, based on the actual pressure P3 and the lapse of time since switching the latch valve <NUM> to the self-cleaning mode.

The same cylinder which constitutes a part of the location-tracker, is used also to control the linear motion of the suction scanner <NUM> with respect to the screening element <NUM>. In the illustrated embodiment, the location tracker <NUM> serves not only for tracking the linear motion of the suction scanner <NUM>, but also to propel the linear motion. Moreover, in case the linear motion is faster than desired (as pre-programmed), the electronic controller switches the latch valve <NUM> during the cleaning session for stopping the linear motion of the suction-scanner <NUM> several times during the self-cleaning session, while rotational motion of the suction scanner is maintained (by maintaining the drain valve <NUM> open).

The electronic controller is configured to identify when the pressure P1 has dropped below predetermined threshold value, for thereby identifying the piston stroke has been completed. When the piston stroke is completed, i.e. the piston approached the end of its stroke and is the closest to the end 106e of the cylinder 106c, it ceases pressing the fluid residuals in the cylinder and the pressure in the cylinder becomes equal to the atmospheric pressure communicated by the latch valve through the inlet port 115v. Said predetermined pressure value is considered an identification that the suction scanner has completed its linear motion for a current self-cleaning session. The predetermined pressure is a pressure above the atmospheric pressure. The predetermined pressure is a pressure indicative of the piston stroke nearing its completion, in which a relatively minor pressure is still applied.

As is appreciated, the fluid accommodated within the cylinder 106c between the cylinder end 106e and the piston 106p is substantially isolated from the dynamics of fluid accommodated in the filtration chamber <NUM>, thus allowing for noise-free tracking of the linear offset between the screening element <NUM> and the suction scanner <NUM>, by monitoring the pressure P3. The electronic-controller <NUM> is configured to use the monitoring of pressures P1 and P2 for supplemental calculations and for doublechecking the location data revealed from the monitoring of P3. The pressures monitored at P1 and P2 during the movement of suction scanner <NUM> are affected by the cleaning process, and are not suffice for clearly and accurately signal that the cleaning process removed the filtride and the screening element <NUM> regained a desired effectiveness level. Using the monitored pressure of P3, such disadvantage of relying solely on P1 and P2 is overcome.

<FIG> illustrates the position of the suction scanner <NUM> closely to the termination of a self-cleaning session, with the leftmost nozzle 104n situated in front the end portion 103e of the screening element, and with the main-tube's base axis 104a nearly fully withdrawn from the coarse filter <NUM>. The piston 106c is full-stroke into the cylinder 106c, and the pressure P3 drops to the atmospheric pressure communicated to the cylinder from the inlet 115c of the latch valve <NUM>. Upon recognition of such a change in the pressure P3, the electronic-controller <NUM> outputs a self-cleaning termination command, after a predetermined time-delay during which the suction scanner <NUM> completes at least a single rotation, thereby guaranteeing full cleaning of the end band 103e of the screening element. The self-cleaning termination command include a shutting-signal communicated through electrical line 105d to the drain-valve <NUM>, and a switching signal communicated through electrical line 105v to the latch valve <NUM>. The high-pressure HP communicated to the cylinder 106c through the latch valve <NUM>, drives the piston back, full-stroke remoter from the cylinder's end 106e, thereby resetting the system <NUM> to the position illustrated by <FIG>.

A single moving body (such as piston 106p) of a location tracker is commonly coupled to and is linearly comoving with a plurality of linearly moving parts of a respective plurality of suction scanners, which clean simultaneously a respective plurality of screening elements. The electronic controller <NUM> receives a signal from a single location tracker, wherein said signal is indicative of the respective linear offset between a plurality of screening elements and a respective plurality of suction scanners. The electronic controller <NUM> is configured for terminating an ongoing cleaning session of a multi-screen filtration system, when a condition is met, similarly to the way it is configured for terminating the cleaning session of a single screening element. Likewise, the same electronic controller <NUM> is configured to activate a cleaning session upon detection of a differential pressure exceeding a predetermined threshold value, between the upstream and the downstream of the multi-screen filtration system.

The multi-screen filtration system comprises a single hydraulic turbine and a gear to activate the plurality of suction scanner. Additionally, or alternatively, multiple turbines are used, each to activate a corresponding suction scanner.

<FIG> shows a flowchart diagram of a method for performing filtration of a fluid by a screening element, self-cleaning of the screening element, and termination of the self-cleaning, in accordance with embodiments of the disclosed subject matter.

At step <NUM>, fluid flow between an inlet and an outlet of the filtration system is provided. The fluid flows through a screening element that filters the raw fluid received in the inlet and provides the treated fluid through the outlet. In some embodiments, a fluid flow is provided between the inlet 101i and the outlet 101e, through a screening element <NUM>.

A self-cleaning session is determined automatically, such as based on a detection of differential fluid pressure (<NUM>). Additionally, or alternatively, the self-cleaning session is manually activated.

At Step <NUM>, a pressure differential P1 minus P2 is monitored. P1 is the pressure value at or near a fluid inlet 101i of a filtration chamber <NUM> of the system. P2 is the pressure value at or near a fluid outlet 101e of the filtration chamber <NUM>. When the differential pressure value DP exceeds a predetermined threshold, the system interprets the event as indicative of a too clogged screening member <NUM>, requiring activation of a cleaning session to remove filtride and residue therefrom.

The controller <NUM> of the filtration system is configured to provide alerts, whenever the detection made in step <NUM> reveal a positive determination, or when the cleaning-session is in progress. The alerts are provided in the form of a blinking LED light, a beeping sound, a text message appearing on the controller, a text message transmitted to a mobile device of an administrator of the controller, or the like.

At step <NUM>, a drain valve <NUM> is turned on and opened. In some embodiments of the disclosed subject matter, the activation is automatic, such as using an electronically controlled drain. In other embodiments of the disclosed subject matter the activation is performed manually, e.g. by a user pressing a press-button causing the drain valve <NUM> to turn on.

Either of the inlet 101i and the outlet 101e are shut, either automatically by the controller <NUM> or manually by a user, before or during the drain valve <NUM> is turned on in method step <NUM>. For the self-cleaning steps starting with step <NUM>, a pressurized fluid for the cleaning is communicated to either the inlet 101i or the outlet 101e of the filtration chamber <NUM>.

Once the drain valve <NUM> is turned on, a low (e.g. atmospheric) pressure is communicated through the drain valve to a drain port <NUM> of a draining compartment <NUM>, and a portion of the fluid entering the inlet 101i of the filtration chamber, is thereby suctioned into one or more nozzles 104n of a suction scanner <NUM>, which a main tube thereof <NUM> is opened at its end 104d to the draining compartment <NUM>.

In some embodiments of the disclosed subject matter, the fluid flow outputted through the opening 104d of the suction scanner drives the rotation of a turbine <NUM> connected to the top end of the main tube <NUM>, thereby spinning the suction scanner <NUM> and making intake opening of the nozzles 104n scan the inner surface of the screening element <NUM> while suctioning fluid through the screen and filtride off its inner surface.

At step <NUM>, a lapse of time since the previous step is counted to cause a delay before proceeding with the next step <NUM>. The counting of lapse of time includes a counting TD1 (Time Delay <NUM>) between <NUM> and a predetermined number of seconds (e.g. between <NUM> and <NUM> seconds) depending on what desired portion of the cleaning session (corresponding to what approximate number of rotations) the suction scanner <NUM> is about to spend in spinning, before start moving linearly about the screening element <NUM>.

Upon completion of counting TD1, step <NUM> is performed.

At step <NUM>, a latch valve <NUM> is switched for making the suction scanner <NUM> move linearly with respect to the screening element <NUM>. The state of latch valve <NUM> is switched to the position illustrated by <FIG>, which initiates the linear motion of the suction scanner <NUM>, and the comoving of the piston 106p within the cylinder 106c.

At step <NUM>, the pressure P3 near the end 106e of the cylinder 106c is monitored.

At step <NUM>, a determination is made whether or not the value of P3 has reached a threshold value indicative of desired completion of the stroke of piston 106p within the cylinder 106c, which in turn is indicative of completion of the linear motion of the suction scanner <NUM> with respect to the screening element <NUM>.

Additionally, or alternatively, in <FIG>, based on the monitored value of P3 (<NUM>), at step <NUM>, a calculation is performed. The calculation estimates the relative linear location of the suction scanner <NUM> with respect to the screening element <NUM>. The estimated location calculated in step <NUM> is used in step <NUM> for determining whether the estimated location is the final desired location.

Once either P3 has reached the threshold value according to a first group of embodiments of <FIG>, or the calculation made in step <NUM> revealed in step <NUM> that the suction scanner <NUM> has reached its final linear position with respect to the screening element <NUM>, according to a second group of embodiments of <FIG>, the method continues.

At step <NUM> a lapse of time TD2 (Time Delay <NUM>) is counted. The TD2 is a time duration which the suction scanner continues its spinning for a desired portion (between <NUM> and a predetermined number of seconds) of the cleaning session, before termination thereof in method steps <NUM> and <NUM>. The termination of the cleaning session is achieved successfully regardless of the execution order between steps <NUM> and <NUM> (which is performed also with step <NUM> preceding step <NUM>, or with both executed simultaneously). The cleaning session is terminated by turning the drain valve <NUM> off, in method step <NUM>, thereby shutting the fluid flow through the suction scanner <NUM>. In step <NUM> the latch valve is switched back to its initial position, thereby resetting the system to a filtration mode of operation, and to step <NUM>.

A step of counting a lapse of a predetermined time before allowing activation of a next cleaning session based on the differential pressure between P1 and P2, is e included.

Method steps <NUM> and <NUM> (depending on the group of embodiments concerned), includes also counting a lapse of a predetermined time then skipping to step <NUM> (or to step <NUM>), even in case P3 did not reach the threshold value (step <NUM>) or in case the calculation (step <NUM>) did not reveal that the suction scanner has reach its final position (step <NUM>), e.g. due to a malfunctioning in the mechanism generating the respective motion between suction scanner <NUM> and the screening element <NUM>.

The monitoring of the pressure P3 is either accompanied or substituted by monitoring a signaling device that generate electrical output which corresponds to or allows to reveal by calculation the offset in position of a moving body. The moving body is coupled to a moving part of the suction scanner such that the respective position of the suction scanner <NUM> with respect to the screening element <NUM> is revealed based on the electrical output. The signaling device includes at least one photosensor for optically determining whether the moving body has reached a predetermined location (the photosensor, e.g. a photovoltaic cell is configured to respond to changes in the illumination of a light emitting diode when a sightline between the photodiode and the LED is crossed by the moving body). The signaling device includes at least one actuator, e.g. an electrical switch, to be contacted by the moving body when the moving body has reached a predetermined location. The signaling device includes at least one electric-field (e.g. capacitance) sensor or magnetic field (e.g. induction) sensor for determining whether the moving body has reached the predetermined location, based on variation in capacitance, in inductivity, or in an electrical current or voltage, resulting from the changing distance between a moving body comprising or constituting a first member of the related sensor and between a stationary element constituting a second member of the related sensor.

The calculation in step <NUM>, and the determinations made in steps <NUM> and <NUM>, are thus performed taking account of the signal generated by the signaling device.

Claim 1:
A filtration system (<NUM>) comprising:
a filtration chamber (<NUM>);
a screening element (<NUM>) located within the filtration chamber (<NUM>); and
a suction scanner (<NUM>) for self-cleaning the screening element (<NUM>) by suctioning fluid through the screening element (<NUM>) upon activation of a self-cleaning session, wherein the suction scanner (<NUM>) is configured to move linearly with respect to the screening element (<NUM>); and
wherein the filtration system (<NUM>) is characterized by:
a switching mechanism configured to automatically terminate the self-cleaning session when a condition is met; and
a location tracker (<NUM>) being configured to communicate to the switching mechanism during the self-cleaning session a signal indicative of an axial location of the suction scanner (<NUM>) with respect to the screening element (<NUM>), wherein the axial location of the suction scanner (<NUM>) comprises a relative linear offset of positions between the suction scanner (<NUM>) and the screening element (<NUM>), wherein the switching mechanism is configured to determine whether the condition is met based at least one of: a predetermined change in the signal; and the relative linear offset of the positions between the screening element (<NUM>) and the suction scanner (<NUM>) as indicated by the signal, exceeding a threshold value.