Patent Publication Number: US-2022212129-A1

Title: Fluid Filtering System With Backflush Valve And Methods Of Operating The Same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage Application of International Patent App. No. PCT/US2020/033035, filed May 15, 2020, which claims the benefit of U.S. Provisional Patent App. No. 62/848,456, filed May 15, 2019, the entire disclosures of both of which are hereby incorporated by reference as if set forth in their entirety herein. 
    
    
     TECHNICAL FIELD 
     This disclosure generally relates to filtering systems for filtering fluids, such as high-viscosity fluids, and in particular, to systems and methods for cleaning filter elements of filtering systems. 
     BACKGROUND 
     A filtering device, known as a piston type screen changer, is commonly used for filtering high-viscosity media such as plastic melts. The filtering device typically has a housing, feed channels, and a pair of pistons arranged movably in the housing. Each of these pistons has at least one cavity, and at least one filter element or screen is disposed in each cavity. In a production mode of operation, the feed channels in the housing branch off towards the cavities in such a way that melt is guided through the respective filter elements. Provided behind the filter element, when viewed in the direction of flow, are outlet channels through which the plastic melt is discharged. The outlet channels are combined at some point in the housing. When flowing the melt through the at least one filter element, impurities and agglomerations in the melt can become embedded in the at least one filter element. 
     The filtering device with two pistons bearing the filter elements and being movable in a direction basically perpendicular to the flow-through direction of the fluid has several advantages. One of these is that the piston is not only a filter carrier but closes and opens flow paths with its movement so that no additional valves are needed. By a suitable design of flow channels, the piston can be moved from a production mode of operation into a backflushing mode of operation. In the backflushing mode of operation, the fluid is led from a downstream side of a filter element and through the filter element in a reverse flow direction (i.e., upstream direction) in order to detach impurities stuck to the filter and to flush them out of the housing. Furthermore, the piston can be partially moved out of the housing in order to give access to a filter element when cleaning or replacement thereof has become necessary. 
     SUMMARY 
     In one example, a filtering device configured to filter a fluid comprises a housing, first and second pistons, first and second filter elements, and a backflush valve. The housing defines at least one inlet opening, first and second bores, at least one first inlet channel extending from the at least one inlet opening to the first bore and at least one second inlet channel extending from the at least one inlet opening to the second bore, first and second outlet channels in communication with the first and second bores, respectively, and first and second backflush channels. The first and second pistons are movably disposed in the first and second bores, respectively. The first piston defines a first cavity therein that is in fluid communication with the at least one first inlet channel and the first outlet channel when the first cavity is in a production mode. The second piston defines a first cavity therein that is in fluid communication with the at least one second inlet channel and the second outlet channel when the first cavity of the second piston is in the production mode. The first filter element is disposed in the first cavity of the first piston, and the second filter element is disposed in the first cavity of the second piston. The first backflush channel extends between the first bore and the backflush valve and the second backflush channel extends between the second bore and the backflush valve. The backflush valve comprises an inner surface that defines a valve chamber therein that is configured to fill with the fluid such that, when the filtering device is operated in a backflush mode, the backflush valve (1) compresses fluid from the valve chamber into the first cavity via the first backflush channel so as to increase a pressure of the fluid in the first cavity, and (2) opens so as to discharge the compressed fluid from the first cavity out the backflush valve. 
     Another example includes a method of operating a filtering device having a housing and first and second pistons disposed in first and second bores of the housing. The method comprises a step of moving the first piston so as to move a first cavity in the first piston from a production mode, in which the first cavity is in fluid communication with at least one first inlet channel and a first outlet channel of the housing, to a first isolated position in which the first cavity is not in fluid communication with the at least one first inlet channel or the first outlet channel of the housing. The method comprises a step of pressuring the first cavity with fluid by causing a fluid to flow from a first cavity in the second piston to a first filter element disposed in the first cavity of the first piston via at least one backflush channel of the housing and then isolating the first cavity in the second piston from the at least one backflush channel. The method comprises a step of opening a backflush valve of the filtering device to cause the pressurized fluid in the first cavity to flow from the first cavity, through the first backflush channel, and out the backflush valve. The method comprises a step of backflushing the first filter element by moving the first piston to a second isolated position, in which the cavity is in fluid communication with the first outlet channel but not in fluid communication with the at least one first inlet channel, such that the fluid flows from the first outlet channel through the first filter element along an upstream direction, through the first backflush channel, and out the backflush valve. 
     Yet another example is a filtering device configured to filter a fluid. The filtering device comprises a backflush valve, a housing, and first and second pistons. The housing defines at least one inlet opening, first and second bores, at least one first inlet channel, at least one second inlet channel, and first and second backflush channels. The at least one first inlet channel extends from the at least one inlet opening to the first bore. The at least one second inlet channel extends from the at least one inlet opening to the second bore. The first and second outlet channels are in communication with the first and second bores, respectively. The first backflush channel extends between the first bore and the backflush valve and the second backflush channel that extends between the second bore and the backflush valve. The first piston is movably disposed in the first bore and defines a first cavity therein that is in fluid communication with the at least one first inlet channel and the first outlet channel when the first cavity is in a production mode. The first piston defines a groove at an upstream side thereof that extends away from the first cavity of the first piston. Further, the first piston is movable so as to align the groove of the first piston with the first backflush channel. The second piston is movably disposed in the second bore and defines a first cavity therein that is in fluid communication with the at least one second inlet channel and the second outlet channel when the first cavity of the second piston is in the production mode. The second piston defines a groove at an upstream side thereof that extends away from the first cavity of the second piston. Further, the second piston is movable so as to align the groove of the second piston with the second backflush channel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following description of the illustrative examples may be better understood when read in conjunction with the appended drawings. It is understood that potential examples of the disclosed systems and methods are not limited to those depicted. 
         FIG. 1  shows a front perspective view of a filtering device according to one example; 
         FIG. 2  shows a rear perspective view of the filtering device of  FIG. 1 ; 
         FIG. 3  shows a front perspective view of a piston of the filtering device of  FIG. 1  according to one example, with first and second filter elements of the piston in an exploded position; 
         FIG. 4  shows a rear perspective view of the piston of  FIG. 3 ; 
         FIG. 5  shows a front view of the filtering device of  FIG. 1  with the first and second pistons in a production mode and inlet channels shown in hidden lines; 
         FIG. 6  shows a cross-sectional top view of the filtering device of  FIG. 1  with the first and second pistons in a production mode and with inlet channels and manifold channels of the filtering device shown in hidden lines; 
         FIG. 7  shows a rear view of the filtering device of  FIG. 1  with outlet channels of the filtering device shown in hidden lines; 
         FIG. 8  shows a perspective view of a manifold of the filtering device of  FIG. 1  with manifold channels shown in hidden lines; 
         FIG. 9  shows a cross-sectional side view of the filtering device of  FIG. 1  according to one example taken through one of first and second backflush valves of the filtering device and with the backflush valve in an open position; 
         FIG. 10  shows a cross-sectional side view of the filtering device of  FIG. 1  according to one example taken through one of first and second backflush valves of the filtering device and with the backflush valve in a closed position; 
         FIG. 11  shows a simplified flow diagram of a method of operating the filtering device of  FIG. 1  according to one example; 
         FIG. 12  shows a perspective view of the filtering device of  FIG. 1  with the first and second pistons in fluid communication with one another via backflush channels and with the backflush channels and inlet channels of the filtering device shown in hidden lines; 
         FIG. 13  shows an enlarged view of a portion of the view in  FIG. 12 ; 
         FIG. 14  shows a front view of the filtering device of  FIG. 1  with the first and second pistons positioned as shown in  FIG. 12 ; 
         FIG. 15  shows a rear view of the filtering device of  FIG. 1  with the first and second pistons positioned as shown in  FIG. 12 ; 
         FIG. 16  shows a perspective view of the filtering device of  FIG. 1  with a first filter element of the filtering device in an isolated position, wherein the first filter element is isolated from inlet and outlet channels of the filtering device but is in fluid communication with a second filter element via a backflush channel; 
         FIG. 17  shows an enlarged view of a portion of the view of  FIG. 16 ; 
         FIG. 18  shows a front view of the filtering device of  FIG. 1  with the first and second pistons positioned as shown in  FIG. 16 ; 
         FIG. 19  shows a rear view of the filtering device of  FIG. 1  with the first and second pistons positioned as shown in  FIG. 16 ; 
         FIG. 20  shows a perspective view of the filtering device of  FIG. 1  with the first filter element in an isolated position, wherein the first filter element is isolated from inlet and outlet channels of the filtering device and isolated from the second filter element; 
         FIG. 21  shows an enlarged view of a portion of the view of  FIG. 20 ; 
         FIG. 22  shows a front view of the filtering device of  FIG. 1  with the first and second pistons positioned as shown in  FIG. 20 ; 
         FIG. 23  shows a rear view of the filtering device of  FIG. 1  with the first and second pistons positioned as shown in  FIG. 20 ; 
         FIG. 24  shows a front view of the filtering device of  FIG. 1  with the first filter element in a backflush position, wherein the first filter element is isolated from the inlet channels of the filtering device and is in fluid communication with an outlet channel of the filtering device; 
         FIG. 25  shows a rear view of the filtering device of  FIG. 1  with the first and second pistons positioned as shown in  FIG. 24 ; 
         FIG. 26  shows a front perspective view of a filtering device according to another example; 
         FIG. 27  shows a rear perspective view of the filtering device of  FIG. 26 ; 
         FIG. 28  shows a cross-sectional side view of the filtering device of  FIG. 26  according to one example taken through a pair of opposing backflush valves of the filtering device and with both backflush valves in closed positions; 
         FIG. 29  shows a cross-sectional side view of the filtering device of  FIG. 26  according to one example taken through a pair of opposing backflush valves of the filtering device and with one a first one of the backflush valves in a closed position and a second one of the backflush valves in an open position; and 
         FIG. 30  shows a cross-sectional side view of the filtering device of  FIG. 26  according to one example taken through a pair of opposing backflush valves of the filtering device and with one a first one of the backflush valves in an open position and a second one of the backflush valves in a closed position. 
     
    
    
     DETAILED DESCRIPTION 
     Described herein are fluid filtering devices and methods of operating the same. In some examples, a first cavity of a first piston of a filtering device can be isolated from inlet and outlet channels of the filtering device, so as to remove the first cavity from a production mode. The first cavity can then be pressurized by applying fluid flow from a first backflush channel to a first filter element disposed in the first cavity. In some examples, the pressure in the first cavity can be increased above the normal operating pressure of the first cavity in the production mode. The fluid in the pressurized cavity can then be discharged to atmosphere and fluid flow through the first filter element in a reverse direction (i.e., an upstream direction) so as to clean impurities and agglomerations from the first filter element. This process can be similarly performed for one or more other cavities of the filtering device. 
     Referring to  FIGS. 1 and 2 , a filtering device  100  is shown according to one example. In general, the filtering device  100  comprises a plurality of filter elements, each of which can be selectively switched between a production mode and a backflushing mode. When a filter element is in the production mode, the filter element is configured to receive a fluid, filter the fluid so as to remove impurities and agglomerations, and communicate the filtered fluid to processing downstream of the filtering device  100  for further processing. The fluid can be a high-viscosity fluid, such as a molten thermoplastic, or any other suitable fluid. When a filter element is in the backflushing mode, the filtering device  100  is configured to reverse a flow of fluid through the filter element so as to detach impurities and agglomerations for the filter element and flush them from the filtering device  100 . 
     The filtering device  100  comprises a housing  102  that defines a first bore  104 ( 1 ) and a second bore  104 ( 2 ) therethrough. The first and second bores  104 ( 1 ) and  104 ( 2 ) can extend through the housing along a lateral direction A. The filtering device  100  comprises a first piston  106 ( 1 ) disposed in the first bore  104 ( 1 ) and a second piston  106 ( 2 ) disposed in the second bore  104 ( 2 ). The first piston  106 ( 1 ) is configured to translate within the first bore  104 ( 1 ) along the lateral direction A. The filtering device  100  can comprise a first actuator  108 ( 1 ) that is configured to translate the first piston  106 ( 1 ) within the first bore  104 ( 1 ) along the lateral direction A, although it will be understood that the first actuator  108 ( 1 ) can be distributed as a separate component from the filtering device  100 . Similarly, the second piston  106 ( 2 ) is configured to translate within the second bore  104 ( 2 ) along the lateral direction A. The filtering device  100  can comprise a second actuator  108 ( 2 ) that is configured to translate the second piston  106 ( 2 ) within the second bore  104 ( 2 ) along the lateral direction A, although it will be understood that the second actuator  108 ( 2 ) can be distributed as a separate component from the filtering device  100 . Each actuator  108 ( 1 ) and  108 ( 2 ) can be any suitable actuator, such as a linear actuator, such as (without limitation) a hydraulic cylinder, pneumatic cylinder, or piezoelectric actuator. 
     The filtering device  100  can have at least one backflush valve that is configured to enable backflushing of the filtering device  100 . In one example, the filtering device  100  can comprise a first backflush valve  134 ( 1 ) and a second backflush valve  134 ( 2 ). Each backflush valve  134 ( 1 ) and  134 ( 2 ) can be disposed at an upstream side  102   a  of the housing  102 . However, it will be noted that, in alternative embodiments, one or both of the backflush valves  134 ( 1 ) and  134 ( 2 ) can be disposed at a downstream side  102   b  of the housing  102 . The first backflush valve  134 ( 2 ) can be offset from the second backflush valve  134 ( 2 ) along the lateral direction A. 
     The housing  102  can have an upstream side  102   a  and a downstream side  102   b  that are offset from one another along a longitudinal direction L. The housing  102  can have first lateral side  102   c  and a second lateral side  102   d  that are offset from one another along a lateral direction A. The housing  102  can have an upper end  102   e  and a lower end  102   f  that are offset from one another along a transverse direction T. The housing can be shaped as a cuboid as shown or can have any suitable alternative shape. The first and second bores  104  and  106  can extend through the housing  102  along the lateral direction A. The first and second bores  104  and  106  can be offset from one another along the transverse direction T. 
     Turning to  FIGS. 3 and 4 , an example of the first piston  108 ( 1 ) of the filtering device  100  is shown. Each of the first and second pistons  108 ( 1 ) and  108 ( 2 ) can be implemented as shown in  FIGS. 3 and 4 . The piston  108  has a first end  108   a  and a second end  108   b  that are offset from one another along the lateral direction A. The piston  108  has an outer surface  108   c  that extends between the first and second ends  108   a  and  108   b.  In one example, the piston  108  can have a circular cross-sectional shape along a plane that is perpendicular to the lateral direction A. Thus, the piston  108  can have a cylindrical shape, and the outer surface  108   c  can be a curved outer surface. However, in alternative examples, the piston  108  can have other suitable cross-sectional shapes, such as a rectangular shape. 
     The piston  108  can define at least one cavity therein. In some examples, the at least one piston  108  can include a first cavity  109  and a second cavity  110 . Each cavity  109 ,  110  can extend into the outer surface  108   c  of the piston  108  along a select direction. In one example, the select direction can be the longitudinal direction L. Each cavity  109 ,  110  can extend into the piston  108  on an upstream side of the piston  108  that is configured to receive the fluid. Each cavity  109 ,  110  can have a circular cross-sectional shape in a plane that is perpendicular to the select direction, although it will be understood that each cavity can have another suitable cross-sectional shape. 
     The piston  108  can define a groove  107  that extends from each of the at least one cavity. Each groove  107  can extend into the outer surface  108   c  of the piston  108 . Each groove  107  can be defined at an upstream side of the piston  108 . However, in alternative examples, such as where one or both of the backflush valves  134 ( 1 ) and  134 ( 2 ) is at the downstream side  102   b  of the housing  102 , each groove  107  can be defined at a downstream side of the piston  108 . Each groove  107  can extend outwardly away from a corresponding one of the cavities  109 ,  110  along the lateral direction A and can be open to the corresponding one of the cavities  109 ,  110 . Each groove  107  can be used for pressurizing the corresponding one of the cavities  109 ,  110  as will be discussed in further detail below. In one example, each groove  107  can have a triangular shape in a plane that extends along the lateral direction A and transverse direction T, although other shapes are contemplated within the scope of this disclosure. Each groove  107  has a cross-sectional dimension along the transverse direction T that is less than a cross-sectional dimension of a corresponding one of the cavities  109 ,  110  along the transverse direction T. Each groove  107  is in fluid communication with a corresponding one of the cavities  109 ,  110 . 
     The piston  108  can define at least one piston outlet. In some examples, the at least one piston outlet can include a first piston outlet  111  and a second piston outlet  112 . Each piston outlet  111 ,  112  can extend into the outer surface  108   c  of the piston  108  along the select direction towards a respective one of the cavities  109 ,  110 . Each piston outlet  111 ,  112  can extend into the piston  108  on a downstream side of the piston  108  that is configured to dispense the fluid. Thus, each piston outlet  111 ,  112  can be offset from a corresponding cavity  109 ,  110  along a downstream direction. In one example, the downstream direction can be aligned with the longitudinal direction L. Each piston outlet  111 ,  112  can be in fluid communication with a corresponding cavity  109 ,  110 . 
     Each piston outlet  111 ,  112  can be elongate along the lateral direction A. Thus, each piston outlet  111 ,  112  can have a width along the lateral direction A that is greater than a height of the piston outlet  111 ,  112  along the transverse direction T. The elongate shapes of the piston outlets  111  and  112  allows one cavity  109 ,  110  to remain in fluid communication with at least one inlet channel  118  and an outlet channel  120  (both discussed below) of the housing as piston  108  is moved between different positions so as to backflush the other cavity  109 ,  110 . Each piston outlet  111 ,  112  can have a first end  111   a,    112   a  and a second end  111   b,    112   b  that are offset from one another along the lateral direction A. Each piston outlet  111 ,  112  can have an intermediate portion  111   c,    112   c,  between its first end  111   a,    112   a  and its second end  111   b,    112   b.  The first end  111   a,    112   a  and the second end  111   b,    112   b  of each outlet  111 ,  112  can each be enlarged relative to the intermediate portion  111   c,    112   c.  For example, the first end  111   a,    112   a  and the second end  111   b,    112   b  can each have a height that is greater than a height of the intermediate portion  111   c,    112   c.  In one example, the first end  111   a,    112   a  and the second end  111   b,    112   b  of each outlet  111 ,  112 , can each have a circular cross-sectional shape, and the intermediate portion  111   c,    112   c  can have a rectangular cross-sectional shape. However, it will be understood that each piston outlet  111 ,  112  can have another suitable shape. 
     The filtering device  100  can comprise at least one filter element for each piston  108 . Each cavity  109 ,  110  is configured to receive at least one of the filter elements. For example, the first cavity  109  can be configured to receive a first filter element  114 , and the second cavity  110  can be configured to receive a second filter element  115 . Each filter element can be a screen, such as a woven metal mesh with small openings that create a flow resistance, or any other suitable filter element that is suitable for filtering the particular fluid that is received by the filtering device  100 . 
     Turning now to  FIGS. 5 and 6 , front and top views of the filtering device are shown, respectively, of the filtering device  100  in the production mode. In  FIGS. 5 and 6 , the housing  102  is shown as transparent to illustrate a plurality of channels of the housing  102 . The first piston  106 ( 1 ) can include a first cavity  109 ( 1 ) with at least one filter element  114 ( 1 ) disposed therein. In some examples, the first piston  106 ( 1 ) can include a second cavity  110 ( 1 ) with at least one filter element  115 ( 1 ) disposed therein. Similarly, the second piston  106 ( 2 ) can include a first cavity  109 ( 2 ) with at least one filter element  114 ( 2 ) disposed therein. In some examples, the second piston  106 ( 2 ) can include a second cavity  110 ( 2 ) with at least one filter element  115 ( 2 ) disposed therein. When the first and second pistons  106 ( 1 ) and  106 ( 2 ) are in the production mode, the first cavities  109 ( 1 ) and  109 ( 2 ) can be aligned with one another along the transverse direction T, and the second cavities  110 ( 1 ) and  110 ( 2 ) can be aligned with one another along the transverse direction T. 
     The housing  102  defines at least one inlet opening  116  therein. The inlet opening  116  can be defined at the upstream side  102   a  of the housing  102 . The housing  102  defines a plurality of inlet channels  118  therein, where each inlet channel extends from the at least one inlet opening  116  to a respective one of the bores  104 ( 1 ),  104 ( 2 ). The housing  102  can define at least one inlet channel  118  for each cavity  109 ( 1 ),  110 ( 1 ),  109 ( 2 ),  110 ( 2 ). In some examples, the housing  102  can define two or more inlet channels  118  for each cavity  109 ( 1 ),  110 ( 1 ),  109 ( 2 ),  110 ( 2 ). Each channel  118  can extend away from the at least one inlet opening  116  along a direction that has a directional component along the lateral direction A. Additionally, or alternatively, each channel  118  can extend away from the at least one inlet opening  116  along a direction that has a directional component along the transverse direction T. 
     The housing  102  can define at least one inlet channel  118 ( 1 ) for the first cavity  109 ( 1 ) of the first piston  106 ( 1 ) and at least one inlet channel  118 ( 2 ) for the first cavity  109 ( 2 ) of the second piston  106 ( 2 ). The at least one inlet channel  118 ( 1 ) for the first cavity  109 ( 1 ) of the first piston  106 ( 1 ) is in fluid communication with the first bore  104 ( 1 ), and the at least one inlet channel  118 ( 2 ) for the first cavity  109 ( 2 ) of the second piston  106 ( 2 ) is in fluid communication with the second bore  104 ( 2 ). The at least one inlet channel  118 ( 1 ) for the first cavity  109 ( 1 ) of the first piston  106 ( 1 ) is in fluid communication with the first cavity  109 ( 1 ) when the first piston  106 ( 1 ) is in the production mode. The at least one inlet channel  118 ( 2 ) for the first cavity  109 ( 2 ) of the second piston  106 ( 2 ) is in fluid communication with the first cavity  109 ( 2 ) when the second piston  106 ( 2 ) is in the production mode. 
     Similarly, in examples in which the first and second pistons  106 ( 1 ) and  106 ( 2 ) each have first and second cavities, the housing  102  can define at least one inlet channel  118 ( 3 ) for the second cavity  110 ( 1 ) of the first piston  106 ( 1 ) and at least one inlet channel  118 ( 4 ) for the second cavity  110 ( 2 ) of the second piston  106 ( 2 ). The at least one inlet channel  118 ( 3 ) for the second cavity  110 ( 1 ) of the first piston  106 ( 1 ) is in fluid communication with the first bore  104 ( 1 ), and the at least one inlet channel  118 ( 4 ) for the second cavity  110 ( 2 ) of the second piston  106 ( 2 ) is in fluid communication with the second bore  104 ( 2 ). The at least one inlet channel  118 ( 3 ) for the second cavity  110 ( 1 ) of the first piston  106 ( 1 ) is in fluid communication with the second cavity  110 ( 1 ) when the first piston  106 ( 1 ) is in the production mode. The at least one inlet channel  118 ( 4 ) for the second cavity  110 ( 2 ) of the second piston  106 ( 2 ) is in fluid communication with the second cavity  110 ( 2 ) when the second piston  106 ( 2 ) is in the production mode. 
     With reference to  FIGS. 6 and 7 , the housing  102  defines a plurality of outlet channels  120  (e.g.,  120 ( 1 ),  120 ( 2 ),  120 ( 3 ),  120 ( 4 )) therein, where each outlet channel  120  extends from a respective one of the bores  104 ( 1 ) and  104 ( 2 ). Each outlet channel  120  is positioned downstream from the inlet opening  116  with respect to the direction of fluid flow through the filtering device  100 . The housing  102  can define at least one outlet channel  120  for each cavity  109 ( 1 ),  110 ( 1 ),  109 ( 2 ),  110 ( 2 ). When in the production mode, each outlet channel  120  can extends away from a respective one of the cavities  109 ( 1 ),  110 ( 1 ),  109 ( 2 ),  110 ( 2 ) along the downstream direction. In the production mode, fluid flows from the inlet channels  118 ( 1 ),  118 ( 2 ),  118 ( 3 ),  118 ( 4 ), through the filter elements  114 ( 1 ),  114 ( 2 ),  115 ( 1 ),  115 ( 2 ), and to the outlet channels  120 ( 1 ),  120 ( 2 ),  120 ( 3 ),  120 ( 4 ). The filter elements restrict the fluid flow through the cavities  109 ( 1 ),  110 ( 1 ),  109 ( 2 ),  110 ( 2 ), and as a result, a pressure at the inlet channels can be higher than a pressure at the outlet channels. In other words, in the production mode, the fluid in the inlet channels  118 ( 1 ),  118 ( 2 ),  118 ( 3 ),  118 ( 4 ) can be at a first pressure, and the fluid in the outlet channels  120 ( 1 ),  120 ( 2 ),  120 ( 3 ),  120 ( 4 ) can be at a second pressure, less than the first pressure. Thus, each filter element  114 ( 1 ),  114 ( 2 ),  115 ( 1 ),  115 ( 2 ) can have a higher pressure side upstream of the filter element, and a lower pressure side downstream of the filter element. 
     Each outlet channel  120  can define an inner opening  122  at a corresponding one of the bores  104 ( 1 ),  104 ( 2 ). In some examples, the size and shape of each inner opening  122  can match a size and shape of a corresponding one of the piston outlets  111 ,  112 . For example, each inner opening  122  (e.g.,  122 ( 1 ),  122 ( 2 ),  122 ( 3 ),  122 ( 4 )) can be elongate along the lateral direction A. Thus, each inner opening  122  can have a width along the lateral direction A that is greater than a height of the inner opening  122  along the transverse direction T. Each inner opening  122  can have a first end  122   a  and a second end  22   b  that are offset from one another along the lateral direction A. Each inner opening  122  can have an intermediate portion  122   c,  between its first end  122   a  and its second end  122   b.  The first end  122   a  and the second end  122   b  of each inner opening  122  can each be enlarged relative to the intermediate portion  122   c.  For example, the first end  122   a  and the second end  122   b  can each have a height that is greater than a height of the intermediate portion  122   c.  In one example, the first end  122   a  and the second end  122   b  of each inner opening  122  can each have a circular cross-sectional shape, and the intermediate portion  122   c  can have a rectangular cross-sectional shape. However, it will be understood that each inner opening  122  can have another suitable shape. 
     Each outlet channel  120  can define an outer opening  124  (e.g.,  124 ( 1 ),  124 ( 2 ),  124 ( 3 ),  124 ( 4 )). Each outer opening  124  can be defined downstream of the inner opening  122  of the channel  120 . For example, each outer opening  124  can be defined at the downstream side  102   b  of the housing  102 . Each outer opening  124  can have a circular shape as shown, or any other suitable shape. Each channel  120  can taper inwardly from its inner opening  122  to its outer opening  124  as the channel  120  extends along the downstream direction. 
     As shown in  FIG. 7 , the housing  102  can define an outlet channel  120 ( 1 ) for the first cavity  109 ( 1 ) of the first piston  106 ( 1 ), the outlet channel  120 ( 1 ) having an inner opening  122 ( 1 ) and an outer opening  124 ( 1 ). The housing  102  can define an outlet channel  120 ( 2 ) for the first cavity  109 ( 2 ) of the second piston  106 ( 2 ), the outlet channel  120 ( 2 ) having an inner opening  122 ( 2 ) and an outer opening  124 ( 2 ). The outlet channel  120 ( 1 ) for the first cavity  109 ( 1 ) of the first piston  106 ( 1 ) is in fluid communication with the first bore  104 ( 1 ), and the outlet channel  120 ( 2 ) for the first cavity  109 ( 2 ) of the second piston  106 ( 2 ) is in fluid communication with the second bore  104 ( 2 ). The outlet channel  120 ( 1 ) for the first cavity  109 ( 1 ) of the first piston  106 ( 1 ) is in fluid communication with the first piston outlet  111  of the first piston  106 ( 1 ) when the first piston  106 ( 1 ) is in the production mode. The outlet channel  120 ( 2 ) for the first cavity  109 ( 1 ) of the second piston  106 ( 2 ) is in fluid communication with the first piston outlet  111  of the second piston  106 ( 2 ) when the second piston  106 ( 2 ) is in the production mode. 
     Referring now to  FIGS. 2 and 8 , the filtering device  100  can include a manifold  126  disposed at the downstream side  102   b  of the housing  102 . The manifold  126  can be configured to receive fluid streams from the plurality of outlet channels  120 ( 1 ),  120 ( 2 ),  120 ( 3 ), and  120 ( 4 ), combine the fluid streams to an outlet  126   c  of the filtering device  100 . The manifold  126  can have an upstream side  126   a  and a downstream side  126   b.  The outlet  126   c  can be disposed at the downstream side  126   b.  The manifold  126  can have a plurality of manifold channels  128 ( 1 ),  128 ( 2 ),  128 ( 3 ),  128 ( 4 ). Each manifold channel  128 ( 1 ),  128 ( 2 ),  128 ( 3 ),  128 ( 4 ) can define a manifold inlet opening  130 ( 1 ),  130 ( 2 ),  130 ( 3 ),  130 ( 4 ) at the upstream side  126   a.  Thus, each manifold channel  128 ( 1 ),  128 ( 2 ),  128 ( 3 ),  128 ( 4 ) can extend from the outlet  126   c  to a corresponding one of the manifold inlet openings  130 ( 1 ),  130 ( 2 ),  130 ( 3 ),  130 ( 4 ). Each manifold channel  128 ( 1 ),  128 ( 2 ),  128 ( 3 ),  128 ( 4 ) can extend away from the outlet  126   c  along a direction that has a directional component along the lateral direction A. Additionally, or alternatively, each manifold channel  128 ( 1 ),  128 ( 2 ),  128 ( 3 ),  128 ( 4 ) can extend away from the outlet  126   c  along a direction that has a directional component along the transverse direction T. It will be understood that, in alternative examples, the manifold  126  can be omitted from the filtering device  100 . For example, the channels  128 ( 1 ),  128 ( 2 ),  128 ( 3 ),  128 ( 4 ) and outlet  126   c  can be defined by the housing  102 . 
     Turning to  FIGS. 9, 10, 12, and 13 , the housing  102  can define at least one backflush channel, such as a plurality of backflush channels  132 ( 1 ),  132 ( 2 ),  132 ( 3 ),  132 ( 4 ), therein. Each backflush channel extends from the upstream side  102   a  of the housing  102  to a respective one of the bores  104 ( 1 ),  104 ( 2 ). The housing  102  can define a backflush channel for each cavity  109 ( 1 ),  110 ( 1 ),  109 ( 2 ),  110 ( 2 ). Each backflush channel  132 ( 1 ),  132 ( 2 ),  132 ( 3 ),  132 ( 4 ) can be outwardly offset from the at least one inlet  116  along the lateral direction A. Each backflush channel can be spaced entirely from the at least one inlet  116  and from the inlet channels  118 ( 1 ),  118 ( 2 ),  118 ( 3 ),  118 ( 4 ). 
     The housing  102  can define a first backflush channel  132 ( 1 ) and a second backflush channel  132 ( 2 ). The first and second backflush channels  132 ( 1 ) and  132 ( 2 ) can be offset from one another along the transverse direction T. The first backflush channel  132 ( 1 ) extends between an inlet of the first backflush valve  134 ( 1 ) and the first bore  104 ( 1 ). Thus, the first backflush channel  132 ( 1 ) is in fluid communication with the first backflush valve  134 ( 1 ) and the first bore  104 ( 1 ). The first backflush channel  132 ( 1 ) is configured to be in fluid communication with the first cavity  109 ( 1 ) of the first piston  106 ( 1 ) when the first piston  106 ( 1 ) is in the backflushing mode. The second backflush channel  132 ( 2 ) extends between the inlet of the first backflush valve  134 ( 1 ) and the second bore  104 ( 2 ). Thus, the second backflush channel  132 ( 2 ) is in fluid communication with the first backflush valve  134 ( 1 ) and the second bore  104 ( 2 ). The second backflush channel  132 ( 2 ) is configured to be in fluid communication with the first cavity  109 ( 2 ) of the second piston  106 ( 2 ) when the second piston  106 ( 2 ) is in the backflushing mode. The second backflush channel  132 ( 2 ) can also be in fluid communication with the first backflush channel  132 ( 1 ). 
     Similarly, in examples in which the first and second pistons  106 ( 1 ) and  106 ( 2 ) each have first and second cavities, the housing  102  can define a third backflush channel  132 ( 3 ) and a fourth backflush channel  132 ( 4 ). The third and fourth backflush channels  132 ( 3 ) and  132 ( 4 ) can be offset from one another along the transverse direction T. The third backflush channel  132 ( 3 ) extends between an inlet of the second backflush valve  134 ( 2 ) and the first bore  104 ( 1 ). Thus, the third backflush channel  132 ( 3 ) is in fluid communication with the second backflush valve  134 ( 2 ) and the first bore  104 ( 1 ). The third backflush channel  132 ( 3 ) is configured to be in fluid communication with the second cavity  110 ( 1 ) of the first piston  106 ( 1 ) when the first piston  106 ( 1 ) is in the backflushing mode. The fourth backflush channel  132 ( 4 ) extends between an inlet of the second backflush valve  134 ( 2 ) and the second bore  104 ( 2 ). Thus, the fourth backflush channel  132 ( 4 ) is configured to be in fluid communication with the second backflush valve  134 ( 2 ) and the second bore  104 ( 2 ). The fourth backflush channel  132 ( 4 ) is configured to be in fluid communication with the second cavity  110 ( 2 ) of the second piston  106 ( 2 ) when the second piston  106 ( 2 ) is in the backflushing mode. 
     Referring more specifically to  FIGS. 9 and 10 , the first backflush valve  134 ( 1 ) can be configured to selectively moved between an open position ( FIG. 9 ) and a closed position ( FIG. 10 ). In the open position, the first backflush valve  134 ( 1 ) places the first and second backflush channels  132 ( 1 ) and  132 ( 2 ) in fluid communication with the atmosphere outside of the filtering device  100 . In the closed position, the first backflush valve  134 ( 1 ) closes such that the first and second backflush channels  132 ( 1 ) and  132 ( 2 ) are not in fluid communication with the atmosphere outside of the filtering device  100 . The first backflush valve  134 ( 1 ) can be a pressure-boosting shutoff valve that is configured to increase a pressure within the first and second backflush channels  132 ( 1 ) and  132 ( 2 ) during a backflush operation as will be described in further detail below. Alternatively, the first backflush valve  134 ( 1 ) can be a standard shutoff valve, such as (without limitation) the shutoff valve  134 ( 1 ) shown in  FIGS. 28 to 30  or any other suitable shutoff valve, that can be opened or closed without increasing pressure within the first and second backflush channels  132 ( 1 ) and  132 ( 2 ). 
     Similarly, the second backflush valve  134 ( 2 ) can be configured to selectively moved between an open position ( FIG. 9 ) and a closed position ( FIG. 10 ). Note that the cross-sections at the first and second backflush valves  134 ( 1 ) and  134 ( 2 ) may be identical, and thus  FIGS. 9 and 10  can depict either of the first and second backflush valves  134 ( 1 ) and  134 ( 2 ). In the open position, the second backflush valve  134 ( 2 ) places the third and fourth backflush channels  132 ( 3 ) and  132 ( 4 ) in fluid communication with the atmosphere outside of the filtering device  100 . In the closed position, the second backflush valve  134 ( 2 ) closes such that the third and fourth backflush channels  132 ( 3 ) and  132 ( 4 ) are not in fluid communication with the atmosphere outside of the filtering device  100 . The second backflush valve  134 ( 2 ) can be a pressure-boosting valve that is configured to increase a pressure within the third and fourth backflush channels  132 ( 3 ) and  132 ( 4 ) during a backflush operation as will be described in further detail below. Alternatively, the second backflush valve  134 ( 2 ) can be a standard shutoff valve, such as (without limitation) the shutoff valve  134 ( 1 ) shown in  FIGS. 28 to 30  or any other suitable shutoff valve, that can be opened or closed without increasing pressure within the third and fourth backflush channels  132 ( 3 ) and  132 ( 4 ). 
     As discussed above, in one example, the first backflush valve  134 ( 1 ) and/or the second backflush valve  134 ( 2 ) can be implemented as a pressure-boosting backflush valve.  FIGS. 9 and 10  show one example of a pressure-boosting backflush valve; however, it will be understood that the pressure-booting backflush valves can be configured in another suitable manner. The pressure-boosting backflush valve has a valve inlet  134   a  and a valve outlet  134   b.  The valve inlet  134   a  can be in fluid communication with at least one backflush channel, such as backflush channels  132 ( 1 ) and  132 ( 2 ). The pressure-boosting backflush valve  134  can have an inner surface  134   c  that defines a valve chamber  134   d  therein. The valve chamber  134   d  can have a first end and a second end that are offset from one another along a valve axis A. In one example, the valve axis A can extend along the transverse direction T. The valve inlet  134   a  can extend through the inner surface  134   c  such that the valve inlet  134   a  is open to the valve chamber  134   d  at a position that is between the first and second ends of the valve chamber  134   d.  The valve outlet  124   b  can be defined at the second end of the valve chamber  134   d.  The valve outlet  124   b  can be positioned such that the valve axis A extends through the valve outlet  124   b.    
     The pressure-boosting backflush valve can have a valve stem  134   e  that is configured to translate within the valve chamber  134   d.  The valve stem  134   e  can be configured to translate along the valve axis A. The valve can comprise a valve seat  134   f  that is fixedly attached to the valve stem  134   e  such that the valve seat  134   f  translates with the valve stem  134   e.  The valve is configured to translate the valve seat  134   f  along the valve axis A on opposing sides of the valve inlet  134   a.  The valve seat  134   f  has an inner surface  134   g,  an outer surface  134   h  opposite the inner surface  134   g,  and a sealing surface  134   j  that extends between the valve seat inner surface  134   g  and the valve seat outer surface  134   h.  The sealing surface  134   j  is configured to seal against the inner surface  134   c  of the valve chamber  134 . 
     The valve stem  134   e  can have a cross-sectional dimension in a plane that is perpendicular to the valve axis A that is less than a cross-sectional dimension of the valve chamber  134   d  in the same plane. Thus, when the valve is in the closed position, a space can be defined between the inner surface  134   c  of the valve chamber  134   d  and the valve stem  134   e.  In one example, the space can have an annular cross-sectional shape in a plane that is perpendicular to the valve axis A. The space can be sized so as to receive fluid therein. The sealing surface  134   j  of the valve chamber  134  can have a cross-sectional dimension in a plane that is perpendicular to the valve axis A that is greater than a cross-sectional dimension of the valve stem  134   e  in the same plane and substantially equal to a cross-sectional dimension of the valve chamber  134   d  in the same plane. As will be described further below, during a backflushing operation, the space can be filled with the fluid, and the fluid can be forced into the backflush channels by opening the valve so as to increase a pressure within the backflush channels. 
     Turning now to  FIG. 11 , a method  200  of operating the filtering device  100  will now be discussed. With further reference to  FIGS. 5 to 7 , the method  200  comprises a step  202  of operating the filtering device  100  with the first and second filter elements  114 ( 1 ) and  114 ( 2 ), and the third and fourth filter elements  115 ( 1 ) and  115 ( 2 ) (if included) in the production mode and with each backflush valve  134 ( 1 ),  134 ( 2 ) in the closed position. For example, the first piston  106 ( 1 ) can be positioned within the first bore  104 ( 1 ) such that the first filter element  114 ( 1 ) of the first piston  106 ( 1 ) is in fluid communication with the at least one inlet channel  118 ( 1 ) and, if included, the second filter element  115 ( 1 ) of the first piston  106 ( 1 ) is in fluid communication with the at least one fluid channel  118 ( 3 ). Further, the first piston outlet  111 ( 1 ) of the first piston  106 ( 1 ) is aligned with the first outlet channel  120 ( 1 ) of the first piston  106 ( 1 ), and if included, the second piston outlet  112 ( 1 ) of the first piston  106 ( 1 ) is aligned with the third outlet channel  120 ( 3 ). 
     Similarly, the second piston  106 ( 2 ) can be positioned within the second bore  104 ( 2 ) such that the first filter element  114 ( 2 ) of the second piston  106 ( 2 ) is in fluid communication with the at least one inlet channel  118 ( 2 ) and, if included, the second filter element  114 ( 4 ) of the second piston  106 ( 2 ) is in fluid communication with the at least one fluid channel  118 ( 4 ). Further, the first piston outlet  111 ( 2 ) of the second piston  106 ( 2 ) is aligned with the second outlet channel  120 ( 2 ), and if included, the second piston outlet  112 ( 2 ) of the second piston  106 ( 2 ) is aligned with the fourth outlet channel  120 ( 4 ). 
     With the filter elements  114 ( 1 ),  114 ( 2 ),  115 ( 1 ),  115 ( 2 ) in the production mode, step  202  can comprise receiving the fluid to be filtered at the inlet opening  116 . Each filter element  114 ( 1 ),  114 ( 2 ),  115 ( 1 ),  115 ( 2 ) receives the fluid from the inlet opening  116  through a corresponding at least one inlet channel  118 ( 1 ),  118 ( 2 ),  118 ( 3 ),  118 ( 4 ). The fluid flows along a downstream direction through each filter element  114 ( 1 ),  114 ( 2 ),  115 ( 1 ),  115 ( 2 ) to a corresponding piston outlet  111 ( 1 ),  111 ( 2 ),  112 ( 1 ),  112 ( 2 ), and from each piston outlet to a corresponding outlet channel  120 ( 1 ),  120 ( 2 ),  120 ( 3 ),  120 ( 4 ). As the fluid flows through each filter element  114 ( 1 ),  114 ( 2 ),  115 ( 1 ),  115 ( 2 ), the filter element can restrict the fluid flow therethrough such that a pressure on an upstream side of the filter element is higher than a pressure on a downstream side of the filter element. 
     Referring now to  FIGS. 11 to 15 , after operating one or more of the filter elements in the production mode, the method  200  can comprise steps  204  to  212  to backflush a select cavity  109 ( 1 ),  109 ( 2 ),  110 ( 1 ),  110 ( 2 ), and consequently a select filter element  114 ( 1 ),  114 ( 2 ),  115 ( 1 ),  115 ( 2 ), of the filtering device  100 . For ease of description, the method will be described wherein the select cavity is the first cavity  109 ( 1 ) and the select filter element is the first filter element  114 ( 1 ) of the first piston  106 ( 1 ). However, it will be understood that steps  204  to  212  can be similarly performed to backflush any of the four filter elements  114 ( 1 ),  114 ( 2 ),  115 ( 1 ),  115 ( 2 ). 
     The method  200  can optionally comprise step  204  to clean at least one backflush channel, such as the first backflush channel  132 ( 1 ) corresponding to the first cavity  109 ( 1 ) and first filter element  114 ( 1 ) of the first piston  106 ( 1 ) by flushing the first backflush channel  132 ( 1 ) out the outlet  134   b  of the first backflush valve  134 ( 1 ) to discharge any degraded material disposed in the first backflush channel  132 ( 1 ) to the atmosphere outside of the filtering device  100 . Step  204  can additionally clean the second backflush channel  132 ( 2 ) corresponding to the first cavity  109 ( 2 ) and first filter element  114 ( 2 ) of the second piston  106 ( 2 ). The degraded material may be amounts of the fluid that stagnates under temperature. For example, if the fluid is a plastic melt, then the fluid can become discolored (e.g., brown) and carbonize over time as it stagnates in the select backflush channel  132 ( 1 ). Therefore, it may be beneficial to clean the first backflush channel  132 ( 1 ) to evacuate any degraded fluid therein. 
     Step  204  can comprise a step of moving the first piston  106 ( 1 ) within the first bore  104 ( 1 ) until the first backflush channel  132 ( 1 ) is in fluid communication with a groove  107 ( 1 ) of the first cavity  109 ( 1 ). In this position, the first piston  106 ( 1 ) is still in a production mode, and fluid can continue to flow through the select filter element  114 ( 1 ) to the first outlet channel  120 ( 1 ), and through the second filter  115 ( 1 ) (if implemented) to the third outlet channel  120 ( 3 ). As shown in  FIG. 15 , the first and second piston outlets  111 ( 1 ) and  112 ( 1 ) of the first piston  106 ( 1 ) still have some overlap with, and thus are in fluid communication with, the outlet channels  120 ( 1 ) and  120 ( 3 ) of the housing  102 . Further, step  204  can comprise a step moving the second piston  106 ( 2 ) within the second bore  104 ( 2 ) until the second backflush channel  132 ( 2 ) is in fluid communication with a groove  107 ( 2 ) of the first cavity  109 ( 2 ) of the second piston  106 ( 2 ). In this position, the second piston  106 ( 2 ) is still in a production mode, and fluid can continue to flow through the first filter  114 ( 2 ) of the second piston  106 ( 2 ) to the second outlet channel  120 ( 2 ), and through the second filter  115 ( 2 ) (if implemented) to the fourth outlet channel  120 ( 4 ). As shown in  FIG. 15 , the first and second piston outlets  111 ( 2 ) and  112 ( 2 ) of the second piston  106 ( 2 ) still have some overlap with, and thus are still in fluid communication with, the outlet channels  120 ( 2 ) and  120 ( 4 ) of the housing  102 . Step  204  can comprise a step of moving the first backflush valve  134 ( 1 ) to the open position (e.g., as shown in  FIG. 9 ) such that fluid received by the first cavities  109 ( 1 ) and  109 ( 2 ) of the first and second pistons  106 ( 1 ) and  106 ( 2 ) is dispensed through the first and second backflush channels  132 ( 1 ) and  132 ( 2 ), respectively, and out of the first backflush valve  134 ( 1 ) to the atmosphere. 
     The method  200  can optionally comprise a step  206  of moving the first backflush valve  134 ( 1 ) to the closed position (e.g., as shown in  FIG. 10 ) after a predetermined period of time. In examples in which the first backflush valve  134 ( 1 ) is a pressure-boosting backflush valve, step  206  can comprise filling the chamber  134   k  of the backflush valve  134 ( 1 ) with the fluid. In particular, the chamber  134   k  can be filled with the fluid as the valve seat  134   f  moves past the valve inlet  134   a  along a direction that extends from the first end of the valve chamber to the second end of the valve chamber  134   d.  In step  206 , the pistons  106 ( 1 ) and  106 ( 2 ) do not move relative to their positions in step  204 , and the filter elements  114 ( 1 ),  114 ( 2 ),  115 ( 1 ), and  115 ( 2 ) can remain in production mode. 
     Turning now to  FIGS. 11 and 16 to 19 , the method can comprise a step  208  of isolating and pressurizing the first cavity  109 ( 1 ) and first filter element  114 ( 1 ). In particular, step  208  can comprise a step of moving the first piston  106 ( 1 ) to a first isolated position, in which the first cavity  109 ( 1 ) and first filter element  114 ( 1 ) are isolated from the at least one first inlet channel  118 ( 1 ) and the first outlet channel  120 ( 1 ) so that fluid cannot flow through the first filter element  114 ( 1 ) and out of the housing  102 . Thus, as shown in  FIG. 18 , the first cavity  109 ( 1 ) and first filter element  114 ( 1 ) are not in fluid communication with any of the inlet channels  118 ( 1 ),  118 ( 2 ),  118 ( 3 ),  118 ( 4 ). Further, as shown in  FIG. 19 , the first piston outlet  111 ( 1 ) corresponding to the first cavity  109 ( 1 ) and first filter element  114 ( 1 ) does not overlap with, and thus is not in fluid communication with, any of the outlet channels  120 ( 1 ),  120 ( 2 ),  120 ( 3 ),  120 ( 4 ). The second cavity  110 ( 1 ) (if implemented) of the first piston  106 ( 1 ) can remain in production mode. Thus, as shown in  FIGS. 18 and 19 , the second cavity  110 ( 1 ) can have some overlap with, and thus in fluid communication with, the at least first one channel  118 ( 1 ), and the second piston outlet  112 ( 1 ) of the first piston  106 ( 1 ) can have some overlap with, and thus in fluid communication with, the first outlet channel  120 ( 1 ) of the housing  102 . The first backflush valve  134 ( 1 ) can remain in the closed position, and the second piston  106 ( 2 ) does not move relative to its position at the end of step  206 . Thus, the cavity  109 ( 2 ), the cavity  110 ( 1 ) (if implemented), and the cavity  110 ( 2 ) (if implemented) can remain in the production mode. 
     In the first isolated position, the first cavity  109 ( 1 ) and first filter element  114 ( 1 ) can be in fluid communication with the first cavity  109 ( 2 ) of the second piston  106 ( 2 ). With the first cavity  109 ( 1 ) and first filter element  114 ( 1 ) in the first isolated position, step  208  can comprise pressurizing the first cavity  109 ( 1 ) of the first piston  106 ( 1 ) by flowing fluid to the first filter element  114 ( 1 ). In particular, step  208  can comprise flowing the fluid from the first cavity  109 ( 2 ) of the second piston  106 ( 2 ), such as from the groove  107 ( 2 ) of the first cavity  109 ( 2 ), and through the second and first backflush channels  132 ( 2 ) and  132 ( 1 ) to the upstream side of the first filter element  114 ( 1 ). As the fluid flows into the first cavity  109 ( 1 ), the first cavity  109 ( 1 ) pressurizes such that a pressure on both the upstream side and downstream side of the first filter element  114 ( 1 ) is substantially equal. In the example shown, the fluid is flowed to the upstream side of the first filter element  114 ( 1 ). However, it will be understood that the first backflush valve  134 ( 1 ) and the backflush channels  132 ( 1 ) and  132 ( 2 ) can be configured to flow fluid to the downstream side of the first filter element  114 ( 1 ). 
     With reference to  FIGS. 20 to 23 , once the first cavity  109 ( 1 ) has been pressurized to a desired pressure or for a desired time, step  208  can comprise a step of isolating the first cavity  109 ( 1 ) of the first piston  106 ( 1 ) from the first cavity  109 ( 2 ) of the second piston  106 ( 2 ). In particular, step  208  can comprise a step of moving the second piston  106 ( 2 ) such that first cavity  109 ( 2 ) of the second piston  106 ( 2 ) is no longer in fluid communication with the second backflush channel  132 ( 2 ). 
     As shown in  FIGS. 22 and 23 , the first cavity  109 ( 2 ) of the second piston  106 ( 2 ) can have some overlap with, and thus in fluid communication with, the second at least one channel  118 ( 2 ), and the first piston outlet  111 ( 2 ) of the second piston  106 ( 2 ) can have some overlap with, and thus in fluid communication with, the second outlet channel  120 ( 2 ) of the housing  102 . The first backflush valve  134 ( 1 ) can remain in the closed position, and the first piston  106 ( 1 ) does not move relative to its isolated position. Thus, the filter element  114 ( 2 ), the filter element  115 ( 2 ) (if implemented), and the filter element  115 ( 1 ) (if implemented) can remain in the production mode. 
     Referring to  FIGS. 9, 10, and 11 , once the first cavity  109 ( 1 ) has been pressurized to a desired pressure or for a desired time, the method can comprise a step  210  of moving the first backflush valve  134 ( 1 ) to the open position as shown in  FIG. 9  so as to discharge fluid in the first cavity  109 ( 1 ) to the atmosphere, thereby relieving the pressure in the first cavity  109 ( 1 ). Thus, step  210  can comprise causing fluid to flow from the first cavity  109 ( 1 ), through the first backflush channel  132 ( 1 ), and out the valve outlet  134 ( b ). 
     In examples in which the backflush valve  134 ( 1 ) is a pressure-boosting backflush valve, the step  210  of opening the first backflush valve  134 ( 1 ) can comprise a step of increasing a pressure in the first backflush channel  132 ( 1 ), and consequently in the first cavity  109 ( 1 ), to a third pressure as the first backflush valve  134  is opened. The third pressure can be higher than the first pressure (i.e., the upstream pressure at the first filter element  114 ( 1 ) when the first filter element  114 ( 1 ) is in production mode). Sealing between the piston  106 ( 1 ) and the housing  102  should be sufficient to maintain the pressure in the first cavity  109 ( 1 ) at the third pressure. In particular, the step of increasing the pressure can comprise moving the valve seat  134   f  along a select direction towards the first end of the chamber  134   k,  and hence towards the valve inlet  134   a,  such that the fluid in the valve chamber  134   d  is compressed through the valve inlet  134   a  to the first backflush channel  132 ( 1 ), and consequently in the first cavity  109 ( 1 ). Step  210  can comprise further moving the valve seat  134   f  along the select direction towards the first end of the valve chamber  134   d  such that the valve seat  134   f,  and in particular the valve seat outer surface  134   h,  moves past at least a portion of the valve inlet  134   a,  thereby opening the first backflush valve  134 ( 1 ) so as to place the valve inlet  134   a  and valve outlet  134   b  in fluid communication. As the outer surface  134   h  of the valve seat  134   f  moves past at least a portion of the valve inlet  134   a  along a direction that extends from the second end of the valve chamber to the first end of the valve chamber, the fluid in the first cavity  109 ( 1 ) is discharged through the valve outlet  134   b  to the atmosphere, thereby relieving the pressure in the first cavity  109 ( 1 ). Increasing the pressure in the first cavity  109 ( 1 ) above the first pressure, and then rapidly decreasing the pressure, can cause the fluid to exert a greater force on the first filter element  114 ( 1 ) in the upstream direction to break impurities and agglomerations free from the first filter element  114 ( 1 ). This increase and rapid decrease of pressure can create a powerful, explosion-like impact on the filter element  114 ( 1 ), thereby breaking free any impurities or agglomerations that are embedded in the filter element  114 ( 1 ). 
     Turning now to  FIGS. 11, 24, and 25 , the method  200  can comprise a step  212  of backflushing the first filter element  114 ( 1 ) with the fluid. The step  212  can comprise a step of moving the first piston  106 ( 1 ) to a second isolated position, in which the first cavity  109 ( 1 ) is in fluid communication with the first outlet channel  120 ( 1 ) of the housing  102 , while maintaining the first cavity  109 ( 1 ) in fluid communication with the first backflush channel  132 ( 1 ) and isolated from the first inlet channel  118 ( 1 ). As shown in  FIG. 24 , the first cavity  109 ( 1 ) is not in fluid communication with any of the input channels. Further, as shown in  FIG. 25 , the first piston outlet  111 ( 1 ) overlaps with, and this is in fluid communication with, the first outlet channel  120 ( 1 ) of the housing  102 . Step  212  comprises causing fluid to flow from the first outlet channel  120 ( 1 ) through the first filter element  114 ( 1 ) along the upstream direction, through the first backflush channel  132 ( 1 ), and out the valve outlet  134   b  of the first backflush valve  134 ( 1 ) to the atmosphere. The pressure of the fluid at the outlet  126   c  (labeled in  FIG. 6 ) of the filtering device  100  can cause the fluid to reverse flow from the outlet  126   c  to the first outlet channel  120 ( 1 ). As shown in  FIGS. 24 and 25 , the second filter element  115 ( 1 ) (if implemented) of the first piston  106 ( 1 ), the first filter element  114 ( 2 ) of the second piston  106 ( 2 ), and the second filter element  115 ( 2 ) (if implemented) of the second piston  106 ( 2 ) can remain in the production mode. 
     After the first filter element  114 ( 1 ) is backflushed, the method  200  can comprise a step  214  of returning the first filter element  114 ( 1 ) to the production mode as shown in  FIGS. 5 to 7 . Alternatively, the method  200  can perform steps  208  to  212 , and optionally steps  204  and  206 , for another filter element of the filtering device  100 . 
     Although  FIGS. 1 and 2  show an example of a filtering device  100  having at least one backflush valve  134 ( 1 ) and  134 ( 2 ) disposed at an upstream side  102   a  of the housing  102 , examples of the disclosure are not so limited. In alternative examples, the at least one backflush valve can be disposed at the downstream side  102   b  of the housing  102 . For example, the first and second backflush valves  134 ( 1 ) and  134 ( 2 ) can be disposed at the downstream side  102   b  of the housing  102 . In such examples, the at least one backflush channel  132 ( 1 ) and  132 ( 2 ) corresponding to the first backflush valve  134 ( 1 ) and the at least one backflush channel  132 ( 3 ) and  132 ( 4 ) corresponding to the second backflush valve  134 ( 2 ) can each be disposed at the downstream side  102   b  of the housing  102 . 
     In yet other examples, the filtering device can have at least one backflush valve at the upstream side  102   a  and at least one backflush valve at the downstream side  102   b.  For example, and with reference to  FIGS. 26 and 27 , the filtering device  300  can have first and second backflush valves  134 ( 1 ) and  134 ( 2 ) disposed at the upstream side  102   a  of the housing  102  and third and fourth backflush valves  134 ( 3 ) and  134 ( 4 ) disposed at the downstream side  102   b  of the housing  102 . One or more, up to all of the backflush valves  134 ( 1 ),  134 ( 2 ),  134 ( 3 ), and  134 ( 4 ) can be a pressure-boosting shutoff valve as described above. Additionally, or alternatively, one or more of the backflush valves  134 ( 1 ),  134 ( 2 ),  134 ( 3 ), and  134 ( 4 ) can be a standard shutoff valve. In some examples, the filtering device can have one or more pressure-boosting valves and one or more standard shutoff valves. 
       FIGS. 28 to 30  show an example in which the filtering device  300  comprises at least one standard shutoff valve, such as first and second standard shutoff valves  134 ( 1 ) and  134 ( 2 ), disposed at the upstream side  102   a  of the housing  102  and at least one pressure-boosting valve, such as first and second pressure-boosting valves  134 ( 3 ) and  134 ( 4 ), disposed at the downstream side  102   b  of the housing  102 . It will be understood that, in other examples, the at least one standard shutoff valve  134 ( 1 ) can alternatively be disposed at the downstream side  102   b  of the housing  102  and the at least one pressure-boosting valve  134 ( 3 ) can alternatively be disposed at the upstream side  102   a.    
     In one example, the standard shutoff valve  134 ( 1 ) can be implemented as shown in  FIGS. 28 to 30 , although the standard shutoff valve can be implemented as any other suitable backflush valve. The standard shutoff valve  134 ( 1 ) has a valve inlet  134   a  and a valve outlet  134   b.  The valve inlet  134   a  can be in fluid communication with at least one backflush channel, such as backflush channels  132 ( 1 ) and  132 ( 2 ). The backflush channels  132 ( 1 ) and  132 ( 2 ) extend from the upstream side  102   a  of the housing  102 , and therefore, can be considered upstream backflush channels. 
     The standard shutoff valve  134 ( 1 ) can have an inner surface  134   c  that defines a valve chamber  134   d  therein. The valve chamber  134   d  can have a first end and a second end that are offset from one another along a valve axis A. In one example, the valve axis A can extend along the transverse direction T. The valve inlet  134   a  can extend through the inner surface  134   c  such that the valve inlet  134   a  is open to the valve chamber  134   d  at a position that is between the first and second ends of the valve chamber  134   d.  The valve outlet  124   b  can be defined at the second end of the valve chamber  134   d.  The valve outlet  124   b  can be positioned such that the valve axis A extends through the valve outlet  124   b.    
     The standard shutoff valve  134 ( 1 ) can have a valve stem  134   m  that is configured to translate within the valve chamber  134   d.  The valve stem  134   m  can be configured to translate along the valve axis A. The valve stem  134   m  can have a sealing surface that is configured to seal against the inner surface  134   c  of the valve chamber  134 . The valve stem  134   m  can have a cross-sectional dimension in a plane that is perpendicular to the valve axis A that is sized to seal against the inner surface  134   c.  Unlike the pressure-boosting valve of  FIGS. 9 and 10 , the standard shutoff valve  134 ( 1 ) can be devoid of the space that is configured to receive the fluid therein. 
     The pressure-boosting valve  134 ( 3 ) can be configured as described above in relation to  FIGS. 9 and 10 , or can be implemented in any other suitable manner. The housing  102  can define at least one backflush channel therein corresponding to the backflush valve  134 ( 3 ), such as first and second backflush channels  133 ( 1 ) and  132 ( 3 ). Although not shown, the housing  102  can define least one backflush channel therein corresponding to the backflush valve  134 ( 4 ), such as first and second backflush channels. Each backflush channel  133 ( 1 ),  132 ( 2 ) extends from the downstream side  102   b  of the housing  102  to a respective one of the bores  104 ( 1 ),  104 ( 2 ). Thus, each backflush channel  133 ( 1 ) and  132 ( 2 ) can be considered to be a downstream backflush channel. The housing  102  can define a downstream backflush channel for each cavity  109 ( 1 ),  110 ( 1 ),  109 ( 2 ),  110 ( 2 ). Each downstream backflush channel  132 ( 1 ),  132 ( 2 ) can be outwardly offset from the at least one outlet of the filtering device  300  along the lateral direction A. Each downstream backflush channel  132 ( 1 ),  132 ( 2 ) can be spaced entirely from the at least one outlet and from the outlet channels  120 ( 1 ),  120 ( 2 ),  120 ( 3 ),  120 ( 4 ). 
     The housing  102  can define a first downstream backflush channel  133 ( 1 ) and a second downstream backflush channel  133 ( 2 ) for the backflush valve  134 ( 3 ). The first and second downstream backflush channels  133 ( 1 ) and  133 ( 2 ) can be offset from one another along the transverse direction T. The first downstream backflush channel  133 ( 1 ) extends between an inlet of the backflush valve  134 ( 3 ) and the first bore  104 ( 1 ). Thus, the first downstream backflush channel  133 ( 1 ) is in fluid communication with the backflush valve  134 ( 3 ) and the first bore  104 ( 1 ). The first downstream backflush channel  133 ( 1 ) is configured to be in fluid communication with the first cavity  109 ( 1 ) of the first piston  106 ( 1 ) when the first piston  106 ( 1 ) is in the backflushing mode. The second downstream backflush channel  133 ( 2 ) extends between the inlet of the backflush valve  134 ( 3 ) and the second bore  104 ( 2 ). Thus, the second downstream backflush channel  133 ( 2 ) is in fluid communication with the backflush valve  134 ( 3 ) and the second bore  104 ( 2 ). The second downstream backflush channel  133 ( 2 ) is configured to be in fluid communication with the first cavity  109 ( 2 ) of the second piston  106 ( 2 ) when the second piston  106 ( 2 ) is in the backflushing mode. The second downstream backflush channel  133 ( 3 ) can also be in fluid communication with the first downstream backflush channel  133 ( 1 ). 
     Similarly, in examples in which the first and second pistons  106 ( 1 ) and  106 ( 2 ) each have first and second cavities, the housing  102  can define a third downstream backflush channel and a fourth downstream backflush channel (not shown). The third and fourth downstream backflush channels can be offset from one another along the transverse direction T. The third downstream backflush channel can extend between an inlet of the backflush valve  134 ( 4 ) and the first bore  104 ( 1 ). Thus, the third downstream backflush channel  133 ( 3 ) can be in fluid communication with the backflush valve  134 ( 4 ) and the first bore  104 ( 1 ). The third downstream backflush channel  133 ( 3 ) can be configured to be in fluid communication with the second cavity  110 ( 1 ) of the first piston  106 ( 1 ) when the first piston  106 ( 1 ) is in the backflushing mode. The fourth downstream backflush channel can extend between an inlet of the backflush valve  134 ( 4 ) and the second bore  104 ( 2 ). Thus, the fourth downstream backflush channel  133 ( 4 ) is configured to be in fluid communication with the backflush valve  134 ( 4 ) and the second bore  104 ( 2 ). The fourth downstream backflush channel can be configured to be in fluid communication with the second cavity  110 ( 2 ) of the second piston  106 ( 2 ) when the second piston  106 ( 2 ) is in the backflushing mode. 
     The backflush valve  134 ( 3 ) can be configured to selectively moved between an open position ( FIG. 29 ) and a closed position ( FIG. 28 ). In the open position, the backflush valve  134 ( 3 ) places the first and second downstream backflush channels  133 ( 1 ) and  133 ( 2 ) in fluid communication with the atmosphere outside of the filtering device  300 . In the closed position, the backflush valve  134 ( 3 ) closes such that the first and second downstream backflush channels  133 ( 1 ) and  133 ( 2 ) are not in fluid communication with the atmosphere outside of the filtering device  100 . Similarly, the backflush valve  134 ( 4 ) can be configured to selectively moved between an open position and a closed position. In the open position, the backflush valve  134 ( 4 ) places the third and fourth downstream backflush channels in fluid communication with the atmosphere outside of the filtering device  300 . In the closed position, the backflush valve  134 ( 4 ) closes such that the third and fourth downstream backflush channels are not in fluid communication with the atmosphere outside of the filtering device  300 . 
     With reference to  FIGS. 11 and 28 to 30 , the filtering device  300  can be operated in a manner similar to that of the filtering device  100  with a few notable exceptions. For example, in addition, or alternatively, to cleaning the first and second upstream backflush channels  132 ( 1 ) and  132 ( 2 ), step  204  can comprise cleaning at least one downstream backflush channel, such as the first downstream backflush channel  133 ( 1 ) corresponding to the first cavity  109 ( 1 ) and first filter element  114 ( 1 ) of the first piston  106 ( 1 ) by flushing the first downstream backflush channel  133 ( 1 ) out the outlet  134   b  of the backflush valve  134 ( 3 ) to discharge any degraded material disposed in the first downstream backflush channel  133 ( 1 ) to the atmosphere outside of the filtering device  300 . Step  204  can additionally clean the second downstream backflush channel  133 ( 2 ) corresponding to the first cavity  109 ( 2 ) and first filter element  114 ( 2 ) of the second piston  106 ( 2 ). To clean the first and second downstream backflush channels  133 ( 1 ) and  133 ( 2 ), the backflush valve  134 ( 3 ) can be moved to the opened position in a manner similar to that shown by valve  134 ( 1 ) in  FIG. 9 . 
     As another example, step  210  can comprise opening the pressure-boosting backflush valve  134 ( 3 ) disposed at the downstream side  102   b  of the housing  102  as shown in  FIG. 29  so as to increase a pressure in the first downstream backflush channel  133 ( 1 ), and consequently in the first cavity  109 ( 1 ), to a third pressure as the backflush valve  134 ( 3 ) is opened. As discussed above, the third pressure can be higher than the first pressure (i.e., the upstream pressure at the first filter element  114 ( 1 ) when the first filter element  114 ( 1 ) is in production mode). The step of increasing the pressure can comprise moving the valve seat  134   f  of the pressure-boosting backflush valve  134 ( 3 ) along a select direction towards the first end of the chamber  134   k,  and hence towards the valve inlet  134   a,  such that the fluid in the valve chamber  134   d  is compressed through the valve inlet  134   a  to the first downstream backflush channel  133 ( 1 ), and consequently in the first cavity  109 ( 1 ). 
     In some examples, the pressure in the first cavity  109 ( 1 ) can be discharged through the first backflush valve  134 ( 1 ). In particular, movement of the valve seat  134   f  of the backflush valve  134 ( 3 ) can be stopped before placing the valve inlet  134   a  and valve outlet  134   b  of the backflush valve  134 ( 3 ) in fluid communication with one another as shown in  FIG. 29 . Then, step  210  can comprise a step of opening the first backflush valve  134 ( 1 ) as shown in  FIG. 30  so as to place the so as to place the valve inlet  134   a  and valve outlet  134   b  of the backflush valve  134 ( 1 ) in fluid communication with one another, thereby allowing the fluid in the first cavity  109 ( 1 ) to be discharged through the valve outlet  134   b  of backflush valve  134 ( 1 ) to the atmosphere, thereby relieving the pressure in the first cavity  109 ( 1 ). 
     In an alternative example, step  210  can comprise discharging the fluid through the backflush valve  134 ( 3 ), rather than through the first backflush valve  134 ( 1 ). In particular, step  210  can comprise further moving the valve seat  134   f  of the backflush valve  134 ( 3 ) along the select direction towards the first end of the valve chamber  134   d  such that the valve seat  134   f,  and in particular the valve seat outer surface, moves past at least a portion of the valve inlet  134   a  in a manner similar to that shown in  FIG. 9 , thereby opening the backflush valve  134 ( 3 ) so as to place the valve inlet  134   a  and valve outlet  134   b  in fluid communication. As the outer surface of the valve seat  134   f  of the backflush valve  134 ( 3 ) moves past at least a portion of the valve inlet  134   a  along a direction that extends from the second end of the valve chamber to the first end of the valve chamber, the fluid in the first cavity  109 ( 1 ) can be discharged through the valve outlet  134   b  of backflush valve  134 ( 3 ) to the atmosphere, thereby relieving the pressure in the first cavity  109 ( 1 ). 
     It should be noted that the illustrations and descriptions of the examples shown in the figures are for exemplary purposes only and should not be construed limiting the disclosure. One skilled in the art will appreciate that the present disclosure contemplates various examples. Additionally, it should be understood that the concepts described above with the above-described examples may be employed alone or in combination with any of the other examples described above. It should further be appreciated that the various alternative examples described above with respect to one illustrated example can apply to all examples as described herein, unless otherwise indicated. 
     Unless explicitly stated otherwise, each numerical value and range should be interpreted as being approximate as if the word “about,” “approximately,” or “substantially” preceded the value or range. 
     Conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain examples include, while other examples do not include, certain features, elements, and/or steps. Thus, such conditional language is not generally intended to imply that features, elements, and/or steps are in any way required for one or more examples or that one or more examples necessarily include these features, elements and/or steps. The terms “comprising,” “including,” “having,” and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. 
     While certain examples have been described, these examples have been presented by way of example only and are not intended to limit the scope of the inventions disclosed herein. Thus, nothing in the foregoing description is intended to imply that any particular feature, characteristic, step, module, or block is necessary or indispensable. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions, and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions disclosed herein. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of certain of the inventions disclosed herein. 
     It should be understood that the steps of the exemplary methods set forth herein are not necessarily required to be performed in the order described, and the order of the steps of such methods should be understood to be merely exemplary. Likewise, additional steps may be included in such methods, and certain steps may be omitted or combined, in methods consistent with various examples of the present invention. 
     Although the elements in the following method claims, if any, are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence. 
     It will be understood that reference herein to “a” or “one” to describe a feature such as a component or step does not foreclose additional features or multiples of the feature. For instance, reference to a device having or defining “one” of a feature does not preclude the device from having or defining more than one of the feature, as long as the device has or defines at least one of the feature. Similarly, reference herein to “one of” a plurality of features does not foreclose the invention from including two or more, up to all, of the features. For instance, reference to a device having or defining “one of a X and Y” does not foreclose the device from having both the X and Y.