Patent Publication Number: US-2011068065-A1

Title: Filter assembly

Description:
TECHNICAL FIELD 
     The present disclosure relates to a filter assembly. More particularly, the present disclosure relates to a filter assembly for use with various fluid systems. 
     BACKGROUND 
     Modern fluid systems, such as common rail fuel systems and hydraulic systems, are increasingly becoming more precise and efficient. This is due in large part to the creation of systems that are able to reduce or minimize undesirable fluid leakage within these systems, such as leakage past seals, interfaces, valve elements, etc. One of the factors that is enabling this reduction in leakage is the manufacture and use of more precision parts and components that are manufactured to exacting tolerances. While these precision parts and components normally operate quite well, they tend to be more susceptible to damage from debris, such as the various types of debris that may be carried in the operating fluid (e.g., fine dust particles, sand, worn off material from other components within the system, etc.). Accordingly, including the appropriate filtration systems within these fluid systems can be very important. 
     Many modern fluid systems include a filtration system that includes a series of successively finer filtration elements through which the fluid passes as it travels through the system. These filtration systems may take a multitude of different configurations, depending on the application in which they are used. The objective of each filtration system is to ultimately filter out those particles from the fluid that can damage the components of the fluid system. However, like other components, the components within the filtration system are susceptible to failure due to manufacturing defects, misuse, damage, or other reasons. Depending on type of failure, the failure of one filtration element may lead to the failure of other filtration elements, and eventually, to the failure of the entire filtration system. Such a failure may occur slowly, in which case an operator may be able to remedy it before any damage to the fluid system results, or it may occur rapidly, in which case an operator may not be able to fix the filtration system before damage to the fluid system results. 
     Incorporating conventional backup filtration systems or elements that could at least prevent some of the larger and more harmful debris particles from making their way to the precision fluid system components before the primary filtration system can be repaired can add significant cost, complexity, and may require additional space that is often very limited. Similarly, for fluid systems with less demanding filtration requirements, the incorporation of many conventional filtration systems may add significant cost to the fluid system, introduce robustness or durability issues, and consume limited space. 
     It would be desirable to provide a filter assembly that is able to overcome one or more of the shortcomings described above and/or other shortcomings. 
     SUMMARY 
     According to one exemplary embodiment, a filter assembly for filtering particles from a fluid comprises a first plate, a second plate, and a channel. The first plate includes a first face, a second face, and a first set of apertures extending between the first face and the second face. The second plate includes a third face, a fourth face, and a second set of apertures extending between the third face and the fourth face. The second plate is coupled to the first plate such that the third face faces the second face. The channel is between at least a portion of the second face and at least a portion of the third face. The channel provides fluid communication between the first set of apertures and the second set of apertures and has a depth. The depth of the channel determines a filtration level. 
     According to another exemplary embodiment, a method of filtering particles from a fluid comprises the steps of directing the fluid through a first set of apertures provided in a first plate having a first face and a second face opposite the first face, directing the fluid through a second set of apertures provided in a second plate having a third face and a fourth face opposite the third face, directing the fluid through a channel formed between the second face of the first plate and the third face of the second plate, and stopping at least most of the particles having a size greater than a depth of the channel from going through the second set of apertures. 
     According to another exemplary embodiment, a filter assembly for filtering particles from a fluid comprises a first plate, a second plate, and a recessed region. The first plate includes a first face, a second face, and a first set of apertures extending between the first face and the second face. The second plate is coupled to the first plate and includes a third face, a fourth face, and a second set of apertures extending between the third face and the fourth face. The recessed region is defined by a recess extending into one of the second face of the first plate and the third face of the second plate. The recess has a depth. At least a portion of the second face of the first plate abuts at least a portion of the third face of the second plate. The recessed region fluidly couples the first set of apertures with the second set of apertures. The depth of the recess determines a filtration level. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a fuel system for an engine according to one exemplary embodiment. 
         FIG. 2  is a cross-sectional side view of a filter assembly according to one exemplary embodiment. 
         FIG. 3  is a top view of the upper plate of the filter assembly of  FIG. 2 . 
         FIG. 4  is a top view of the lower plate of the filter assembly of  FIG. 2 . 
         FIG. 5  is a cross-sectional side view of a filter assembly according to another exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Generally, the same or corresponding reference numbers will be used throughout the drawings to refer to the same or corresponding parts. 
     Referring generally to  FIG. 1 , a fuel system  10  is shown according to one exemplary embodiment. Fuel system  10  is a system of components that cooperate to deliver fuel (e.g., diesel fuel, gasoline, heavy fuel, etc.) from a location where fuel is stored to the combustion chamber(s) of an engine  12  where it will combust and where the energy released by the combustion process will be captured by engine  12  and used to generate a mechanical source of power. Although depicted in  FIG. 1  as a fuel system for a diesel engine, fuel system  10  may be the fuel system of any type of engine (e.g., an internal combustion engine such as a gaseous fuel or gasoline engine, a turbine, etc.). Also, although depicted as a common rail fuel system, the fuel system could take other configurations as well, such as a fuel system utilizing mechanically actuated unit injectors, hydraulically actuated unit injectors, mechanically or hydraulically intensified common rail injectors, and other types of fuel systems. According to one exemplary embodiment, fuel system  10  is a common rail fuel system and includes a tank  14 , a transfer pump  16 , a high-pressure pump  18 , a common rail  20 , fuel injectors  22 , an electronic control module (ECM)  23 , tubing  24 , a primary filter  26 , a secondary filter  28 , a tertiary filter  30 , and a filter assembly  32 . 
     Tank  14  is a storage container that stores the fuel that fuel system  10  will deliver. Transfer pump  16  pumps fuel from tank  14  and delivers it at a generally low pressure to high-pressure pump  18 . High-pressure pump  18 , in turn, pressurizes the fuel to a high pressure (suitable for injection) and delivers the fuel to common rail  20 . Common rail  20 , which is intended to be maintained at the high pressure generated by high-pressure pump  18 , serves as the source of high-pressure fuel for each of fuel injectors  22 . Fuel injectors  22  are located within engine  12  in a position that enables fuel injectors  22  to inject high-pressure fuel into the combustion chambers of engine  12  (or into pre-chambers or ports upstream of the combustion chambers in some cases) and generally serve as metering devices that control when fuel is injected into the combustion chamber, how much fuel is injected, and the manner in which the fuel is injected (e.g., the angle of the injected fuel, the spray pattern, etc.). Each fuel injector  22  is continuously fed fuel from common rail  20  such that any fuel injected by a fuel injector  22  is replaced by additional fuel supplied by common rail  20 . ECM  23  is a control module that receives multiple input signals from sensors associated with various systems of engine  12  (including fuel system  10 ) and indicative of the operating conditions of those various systems (e.g., common rail fuel pressure, fuel temperature, throttle position, engine speed, etc.). ECM  23  uses those inputs to control, among other engine components, the operation of high-pressure pump  18  and each of fuel injectors  22 . The purpose of fuel system  10  is to ensure that the fuel is constantly being fed to engine  12  in the appropriate amounts, at the right times, and in the right manner to support the operation of engine  12 . 
     Flow passages  24  generally serve as the structure used for conveying or transporting the fuel within fuel system  10 . According to various exemplary and alternative embodiments, flow passages  24  may be formed from any one or more of a variety of different structures and configurations, including tubes, pipes, conduits, ducts, hoses, etc. The flow passages within different fuel systems may be formed from one or more of these different structures or configurations, and flow passages at different locations within a fuel system may be formed from different structures or configurations. For example, flow passage  24  between tank  14  and transfer pump  16  may be formed from a different structure than that which is used between high-pressure pump  18  and common rail  20 , or between common rail  20  and each of fuel injectors  22 , due at least in part to the magnitude of the pressure flow passages  24  will be exposed to at different locations within fuel system  10 . According to other various exemplary and alternative embodiments, the flow passages may take any one of a variety of forms and configurations that are suitable for the particular fuel system in which they are used as well as the location in which the tubing or flow passages are used within the fuel system. For example, the tubing or flow passages may take the form of straight tubes, bent tubes, thin-walled tubes, thick-walled tubes, quill tubes, internal passages within other structures, and other forms and configurations. 
     Fuel system  10  may optionally include various filtration arrangements. For example, according to one exemplary embodiment, fuel system  10  includes a primary filter  26  (which may also serve as a water separator) located between tank  14  and transfer pump  16 , a secondary filter  28  located between transfer pump  16  and high-pressure pump  18 , and a tertiary filter  30  also located between transfer pump  16  and high-pressure pump  18 . According to various exemplary and alternative embodiments, the number of filters used in a particular fuel system, the location of the filters, and the filtration level (e.g., 2, micron, 4 micron, 10 micron, 30 micron, etc.) of each filter may be suitably adapted to a particular fuel system, based at least in part on the characteristics of the fuel systems (e.g., its tolerance to debris) and the environment in which it is likely to be used. 
     Referring now to  FIGS. 2 through 4 , filter assembly  32  serves as a mechanism for stopping (or substantially stopping) particles larger than a particular size that are within a fuel stream (or other fluid) from passing beyond filter assembly  32 . As illustrated in  FIG. 1 , and according to various exemplary and alternative embodiments, one or more filter assemblies  32  may be used in one or more locations within fuel system  10 . According to one exemplary embodiment, filter assembly  32  includes a plate  34 , a plate  36 , and a retention assembly  38 . 
     According to one exemplary embodiment, plate  34  (e.g., panel, disc, member, etc.) is a generally flat, circular element that includes a face  40 , an opposing face  42 , an outer edge  44 , and a hole or aperture pattern  46  made up of one or more apertures or holes  48 . Faces  40  and  42  are generally parallel to one another and are spaced apart to define a thickness of plate  34 . Face  42  is defined by a substantially planar surface. Face  40  includes a circular recess  50 , which creates within face  40  a nonrecessed surface  54 , a recessed surface  56 , and an edge  58  that extends between nonrecessed surface  54  and recessed surface  56  and that defines the shape of recess  50 . A depth  59  of recess  50  determines the distance the plane defined by recessed surface  56  is spaced apart from the plane defined by nonrecessed surface  54 . Outer edge  44  of plate  34  extends generally perpendicularly between the outer periphery of faces  40  and  42 . Hole pattern  46  is illustrated in  FIG. 3  as eight holes  48  arranged in a circular pattern in which the center of each hole  48  is located on a circle  52  and uniformly spaced around circle  52 . In this arrangement, each of holes  48  are provided within a ring or band defined by the area between an inner circle  60  and an outer circle  62 . To position each of holes  48  within recess  50 , the diameter of outer circle  62  is less than the diameter of recess  50 . 
     According to one exemplary embodiment, plate  36  (e.g., panel, disc, member, etc.) is a generally flat, circular element that includes a face  70 , an opposing face  72 , an outer edge  74 , and a hole or aperture pattern  76  made up of one or more holes or apertures  78 . Faces  70  and  72  are generally parallel to one another and are spaced apart to define a thickness of plate  36 . Face  72  is defined by a substantially planar surface. Face  70  includes a circular recess  80 , which creates within face  70  a nonrecessed surface  84 , a recessed surface  86 , and an edge  88  that extends between nonrecessed surface  84  and recessed surface  86  and that defines the shape of recess  80 . A depth  89  of recess  80  determines the distance the plane defined by recessed surface  86  is spaced apart from the plane defined by nonrecessed surface  84 . Outer edge  74  of plate  36  extends generally perpendicularly between the outer periphery of faces  70  and  72 . Hole pattern  76  is illustrated in  FIG. 3  as nine holes  78 , eight of which are arranged in a circular pattern in which the center of each hole  78  is located on a circle  82  and uniformly spaced around circle  82 , and one of which is located in the center of circle  82 . In this arrangement, all but one of holes  78  are provided within a ring or band defined by the area between an inner circle  90  and an outer circle  92 . To position each of holes  78  within recess  80 , the diameter of outer circle  92  is less than the diameter of recess  80 . Relative to hole pattern  46  of plate  34 , the diameter of outer circle  92  of plate  36  is less than the diameter of inner circle  60  of plate  34 . As a result, none of the individual areas consumed by the individual holes  78  of plate  36  overlap any of the individual areas consumed by the individual holes  48  of plate  34 . 
     Plates  34  and  36  are located relative to one another such that they share a common axis  94  and face  42  of plate  34  abuts or rests against nonrecessed surface  84  of face  70  of plate  36 . In this position, a channel or gap  96  is formed between plate  34  and plate  36  that is defined by recess  80  within plate  36 . Channel  96  provides a restricted flow path (e.g., fluid communication) between holes  48  and holes  78 , the depth of which can be altered by altering the depth of recess  80 . 
     According to various exemplary and alternative embodiments, each of plates  34  and  36  may take one of a multitude of different configurations that may be selected based at least in part on the characteristics of the fluid system in which filter assembly  32  is used (e.g., flow rates, desired filtration levels, type of fluid, fluid temperatures, etc.). For example, the apertures in each plate may be provided in one or more of a variety of different shapes and may, for example, be circular, oval, or rectangular, or be slots or slits, or may take one of a variety of other shapes. Similarly, the hole pattern of each plate may take one of a variety of different configurations by varying the locations of the holes (e.g., the hole pattern), the size and/or shape of one or more of the holes, and/or the number of holes in the pattern. Similarly, each of the plates may take one of a variety of different shapes, and both plates may have the same shape or they may have different shapes. For example, one or both of the plates may be flat and have a square, oval, triangular, rectangular, trapezoidal, or any other shape, or one or both of the plates may be contoured in some way. For example, one or both of the plates may be concave, convex, conical, domed, pointed, etc. Furthermore, the shape, size, and depth of the recess in each plate may be altered to tailor the level of filtration to be suitable for a particular application. Moreover, the filter assembly may include more than two plates (e.g., more than one filtration level or more than one pass at the same filtration level). For example, the filter assembly may include three plates stacked together to form two channels (one between the first and second plate, and one between the second and third plate). The channels may be the same size, shape, and depth, or they may be different sizes, shapes, and/or depths to accomplish different filtration levels. Further, only one of the two plates may include a recess, or each plate may include more than one recess (e.g., a recess on each face). Moreover, the channel between the two plates may be formed by a recess in one plate or by the recesses in two plates. According to other exemplary and alternative embodiments, the plates may take any one of a variety of other configurations and may be selectively combined to tailor the characteristics of the filter assembly. 
     Retention assembly  38  serves as the structure or mechanism that holds plates  34  and  36  in position relative to one another and that may facilitate the mounting of filter assembly  32  within a flow passage  24 . According to one exemplary embodiment, retention assembly  38  includes a receiver  98  that is configured to receive plates  34  and  36  and a retainer  100  that is configured to retain plates  34  and  36  within receiver  98 . 
     According to one exemplary embodiment, receiver  98  (e.g., body, receptacle, container, etc.) is a rigid, tube-shaped member that includes an outer surface  102  and an inner surface  104 . Outer surface  102  has a generally cylindrical shape that is configured to facilitate the coupling of filter assembly  32  within a portion of a flow passage  24  (e.g., pipe, tube, etc.), various fittings, or other portions of a fluid system. According to various exemplary and alternative embodiments, the outer surface of receiver  98  may be smooth, rough, tapered, notched, grooved, threaded, or may include any one or more of a variety of engagement structures (e.g., groove, projection, etc.) that facilitate the coupling of filter assembly  32  within a fluid system. Inner surface  104  includes a first portion  106  that extends axially inwardly from an end  108 , a second portion  110  having a diameter smaller than that of first portion  106  and extending axially inwardly from an opposite end  112 , and a radially extending shoulder  114  that extends between first portion  106  and second portion  110 . In such a configuration, first portion  106  receives plates  34  and  36  and shoulder  114  serves as a stop that cooperates with retainer  100  to hold plates  34  and  36  together. According to various exemplary and alternative embodiments, the first portion may be configured in one of a variety of different ways to receive plates  34  and  36  and cooperate with retainer  100  to retain plates  34  and  36 . For example, the first portion may be sized to freely receive plate  34  and  36 , it may be sized to receive either or both of plates  34  and  36  and/or retainer  100  as a press-fit, it may be at least partially threaded to receive cooperating threads provided on retainer  100  or on one or both of plates  34  and  36 , it may include a groove configured to receive a snap ring, it may include structure that can be crimped or rolled to retain plates  34  and  36  in place, or in may be configured in one of a plurality of different ways to cooperate with retainer  100 , plate  34 , plate  36 , and/or another member to retain plates  34  and  36  in position relative to one another. 
     According to one exemplary embodiment, retainer  100  is a ring-shaped member that engages receiver  98  to retain plates  34  and  36  in position relative to one another and includes an outer surface  115  and an inner surface  116 . Outer surface  115  engages first portion  106  of receiver  98  to retain retainer  100  at an axial position within receiver  98  that is sufficient to hold plates  34  and  36  together. According to various exemplary and alternative embodiments, outer surface  115  may be configured in one of a variety of different ways to couple retainer  100  to receiver  98  in such a way that plates  34  and  36  are held within receiver  98 . For example, the outer surface may include threads that engage corresponding threads on first portion  106  of receiver  98 , it may be sized to be received within receiver  98  through a press-fit, or it may be configured in one of a plurality of different ways to cooperate with receiver  98 , plate  34 , plate  36 , and/or another member to retain plates  34  and  36  in position relative to one another. Inner surface  116  generally defines an opening in retainer  100  that allows fluid passing through plates  34  and  36  to pass through retainer  100 . According to other exemplary and alternative embodiments, retainer  100  may take one of a variety of different forms and configurations. For example, retainer  100  may be provided in the form of a snap ring that is configured to fit within a cooperating groove provided in receiver  98 , it may be integrally formed with receiver  98  and may take the form of a structure that can be crimped or rolled to retain plates  34  and  36  in place. According to another alternative embodiment, the retainer may be excluded and plates  34  and  36  may be held in place by other means, such as through welding, the use of adhesives, brazing, crimping, cooperating threads, or other means. 
     According to various alternative and exemplary embodiments, retention assembly  38  may be replaced by any suitable structure, device, or element that can hold plates  34  and  36  together. For example, plates  34  and  36  may be held together by fasteners (e.g., screws or bolts), springs, various collars, slots or grooves in other elements within the fluid system that receives plates  34  and  36 . According to still other various alternative and exemplary embodiments, any structure serving to hold plates  34  and  36  together may be formed separately from plates  34  and  36  or may be integrally formed as part of either or both of plates  34  and  36 . 
     Referring now to  FIG. 5 , a filter assembly  132  is shown according to another exemplary embodiment. Filter assembly  132  is similar to filter assembly  32 , in that it includes a plate  134 , a plate  136 , and a retention assembly  138 . However, instead of utilizing a recess in plate  36  to create channel  96 , as is done with filter assembly  32 , filter assembly  132  utilizes a ring-shaped spacer  139  (e.g., washer, disk, etc.) located between two flat plates  134  and  136  to create a channel  196  between plates  134  and  136 . With such a configuration, the shape of channel  196  is defined by an inner surface  188  of spacer  139  and the depth of channel  196  is defined by a height  189  of spacer  139 . Thus, the desired filtration level of filter assembly  132  can be easily selected by using a spacer having a height approximately equal to the desired filtration level. 
     According to various exemplary and alternative embodiments, plates  34  and  36 , receiver  98  and retainer  100  may each be made from any one or more of a variety of different materials, including various elastomers, polymers, metals, composites, etc, depending on the environment in which the filter assembly is used (e.g., fluid pressure, flow rate, the nature of the fluid, temperature of the fluid, etc.) and the required performance characteristics of the filter assembly components. For example, if the filter assembly is used in a low-pressure, low flow fluid system, one or more of plates  34  and  36 , receiver  98 , and retainer  100  may be constructed from a polymer. However, if the filter assembly is used in a high-pressure, high flow fluid system, one or more of plates  34  and  36 , receive  98 , and retainer  100  may be constructed from more durable materials such as metal. 
     Although filter assembly  32  is described above primarily in connection with fuel system  10 , filter assembly  32  may be adapted for use in any one of a variety of different fluid systems, such as high-pressure and low-pressure systems, systems using one or more of a variety of different fluids (e.g., fuel, oil, water, urea, coolant, solvent, etc.), systems with different fluid temperatures, systems in different operating environments, etc. Filter assembly  32  may also be used within the fluid systems of many different devices such as, for example, engines, pumps, transmissions, aftertreatment systems, etc. Filter assembly  32  may also be used at one or more different positions within a fluid system. For example, it may be placed within a tube, it may be integrated into a fitting or other component of the fluid system, it may placed at an inlet or an outlet, or it can be placed in other positions or locations. 
     Although filter assemblies  32  and  132  are each illustrated as having generally flat plates that are arranged perpendicular to the flow of the fluid as it enters the filter assembly, each filter assembly may, according to various alternative embodiments, include one or more plates that are oriented non-perpendicularly relative to the input flow of fluid, or one or more plates may include portions that are oriented non-perpendicularly to the input flow of fluid. For example, both plates could be flat and be oriented 45 degrees relative to the direction of the input flow of fluid. Similarly, both plates could be cone-shaped (e.g., in a cone within a cone configuration) such that the surface into which the fluid enters is not perpendicular to the direction of flow of the input fluid. 
     INDUSTRIAL APPLICABILITY 
     In many modern fluid systems where the size of components and the tolerances between interacting components are being reduced, keeping potentially harmful particles from passing through the sensitive components of the fluid system is becoming increasingly important. Although there are different ways to accomplish this, the use of one or more filtration apparatuses is one of the most common and practical. Filter assemblies  32  and  132  are two such filtration apparatuses that may be useful to filter out particles larger than a particular, predetermined size to prevent most, if not all, of those particles from passing beyond the filter assembly and possibly causing damage to one or more of the components of the fluid system that are susceptible to being damaged by those particles. 
     The operation of filter assembly  32  will now be described. It should be noted, however, that the operation of filter assembly  132  will not be described, it being understood that its operation is substantially similar to that of filter assembly  32 . Referring to  FIG. 2 , filter assembly  32  is positioned within a portion of flow passage  24  such that fluid flowing within flow passage  24  flows toward plate  34 . Because most of plate  34  is a solid, nonpermeable structure, the only place for the fluid to continue to flow is through holes  48 . Thus, as indicated by arrows  120 , the fluid flows through holes  48 . Once the fluid passes through holes  48 , it enters gap  96  (as indicated by arrows  122 ) and is then forced to flow laterally between plate  34  and plate  36  within gap  96  until the fluid reaches one of holes  78 . Then, as indicated by arrows  124 , the fluid is permitted to flow out of filter assembly  32  through holes  78 . When the fluid is forced to flow laterally within gap  96  between plates  34  and  36 , only those particles in the fluid that are able to fit into gap  96  will be able to continue to travel along with the flow of fluid and ultimately exit filter assembly  32  through holes  78 . Those particles in the fluid that are not able to fit into gap  96  will either become trapped or will otherwise not be permitted to exit filter assembly  32 . In this way, filter assembly  32  functions to filter out of the fluid stream those particles that are not able to fit within or pass through gap  96 . 
     The level of filtration of filter assembly  32  is determined by the size of gap  96 . The size of gap  96  is determined by the size, or more specifically the height or depth, of recess  80  of plate  36 . Thus, altering the depth of recess  80  in plate  36  has the effect of altering the level of filtration of filter assembly  32 . 
     Unlike many screen type filters, where the filtration is accomplished by simply passing fluid through a series of holes or openings having a certain size and then filtering out particles that are larger than the hole size, the level of filtration of filter assembly  32  is not dependent on the ability to manufacture holes or openings that are small enough to achieve the desired filtration level. Utilizing common manufacturing techniques, a very shallow recess can be machined into a plate more easily and consistently than a similarly sized holed can be machined (e.g., drilled) in the plate. Thus, by utilizing a recess to provide the filtration level rather than a hole, finer levels of filtration may be more easily achieved. 
     Although the fluid path illustrated in  FIG. 2  is shown flowing from plate  34  to plate  36  (with the fluid flowing radially inwardly between the plates), filter assembly  32  is also capable of providing the same level of filtration when the fluid is moving in the opposite direction (e.g., from plate  36  to plate  34 ). Thus, the bi-directional nature of filter assembly  32  may help to alleviate assembly errors that could otherwise occur with a unidirectional filter that is assembled into the system in the wrong direction or orientation. Similarly, the addition of a recess to both plate  34  and  36 , although not necessary, may help to alleviate or reduce assembly errors by making the positions of plates  34  and  36  interchangeable. 
     According to various alternative and exemplary embodiments, the filter assembly may be used within a fluid system for different purposes, including as the sole means of filtration, a first level of filtration, a second, third, or larger level of filtration, or as a backup filter that can help protect the fluid system if the other levels of filtration fail. 
     It is important to note that the construction and arrangement of the elements of the filter assembly as shown in the exemplary and alternative embodiments are illustrative only. Although only a few embodiments of the filter assembly have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited. For example, elements shown as integrally formed may be constructed of multiple parts or elements shown as multiple parts may be integrally formed, the operation and relative orientations of the interfaces (e.g., recesses, holes, etc.) may be reversed or otherwise varied, the length, width, diameter, or shape of the structures and/or members or connectors or other elements of the system may be varied, and/or the nature or number of different relative positions of the components may be varied (e.g., by variations in the locations, lengths, depths, or angles of the recesses, spacers, retainer, receiver, etc.). It should be noted that the elements and/or assemblies of the filter assembly may be constructed from any of a wide variety of materials that provide sufficient strength or durability, and in any of a wide variety of textures and combinations. It should also be noted that the filter assembly may be used in association with any of a wide variety of different fluid systems or fluid subsystems and in any of a wide variety of applications. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary and alternative embodiments without departing from the spirit of the present disclosure.