Two-stage fluid filter

Abstract

Two-stage fluid filter (10), comprising: a first stage (12) spaced from and upstream of a second stage (14) with a gap therebetween; where the first stage (12) contains the following: pleated polymeric media (50) configured to coalesce water contained in a fluid, the pleated polymeric media having pleat valleys and downstream pleat ridges (60); non-pleated polymeric media (52) downstream of the pleated polymeric media (50); and Discharge points at or adjacent to the downstream pleat ridges (60); and the second stage (14) includes multilayer pleated polymeric media (56) and non-pleated polymeric media (54) upstream of the multilayer pleated polymeric media (56), the second stage being configured to separate coalesced water from the fluid and to remove solid contaminants from the fluid, the pleated polymeric media (50) of the first stage (12) comprising, from upstream to downstream, at least the following layers: (i) a layer 1 comprising a polymer nonwoven having a nominal mean fiber diameter of >10 µm and a basis weight of > 40±10 g / m 2 has; (ii) a layer 4 comprising a polymer fleece having a nominal mean fiber diameter of 0.1-1.0 µm, a mean pore size of < 8 µm, a maximum pore size between 5.0 and 15.0 µm, a permeability between 0.14 and 0.57 m3 / min, a thickness between 0.1 and 0.25 mm and a basis weight of > 20 g / m²; and (iii) a layer 6 comprising a polymer nonwoven having a nominal mean fiber diameter of >20 µm and a basis weight of 100 ± 20 g / m².

Description

Area

[0001] This disclosure relates to a fuel-water separator and a particulate filter designed for high water and particulate removal efficiency. State of the art

[0002] Fluid filters are well known and used in various filtration systems and applications, for example, when particulate and / or fluid separation from a working fluid in a protected system is necessary. As one example, fuel filtration systems for engines are well known and may use fluid filters designed to separate water and particulates from the fuel. Filter cartridges in some of these filters have one filter element with media designed to coalesce water and another filter element with media designed to further filter the fuel and separate the coalesced water from the fuel. In many cases, the filter elements are arranged in a concentric filter within a filter configuration, with an outer filter element surrounding an inner filter element.

[0003] GB 825 192 A discloses a single-element demulsifier filter assembly in which liquid to be filtered and dewatered first passes through a demulsifier element consisting of a resin-impregnated pleated fiber element, an onion-bag cloth, a layer of fiberglass or nylon, and a perforated metal core. The liquid then passes through a resin-impregnated pleated paper element and a perforated core, which together form a filter element.

[0004] US 2008 / 0 053 888 A1 discloses a pleated single-phase filter coalescer element comprising a rigid, porous support tube and a hydrophobic drainage layer covering its outer surface. A single-phase combination water coalescer with dual-function particulate filter pleat block is positioned within the support tube and consists of a multilayer material comprising a first porous support layer, a synthetic microfiber layer, a synthetic fiber media layer, and a second porous support layer. As the liquid passes through the pleat block, solid particles are physically filtered therefrom, and water is fused into droplets that pass from the pleats directly through the support tube and directly into the drainage layer, where the droplets grow to a size sufficient to fall under gravity to the bottom of the element.

[0005] US 2007 / 0 289 915 A1 discloses a filter element with an outer and an inner filter medium. The outer filter medium removes particles from a fluid stream and / or coalesces water contained therein. The inner filter medium removes particles from the fluid stream, separates water from the fluid stream, and removes particles from the fluid stream. Further embodiments include specific devices, apparatus, systems, and methods related to fuel filters and filtration. Brief description

[0006] A filter is described that exhibits improved fuel-water separation over the life of the filter. The filter has a two-stage configuration, for example, a concentric filter within a filter configuration, wherein the first or outer stage is designed primarily to coalesce water from the fuel or other fluid with which the filter is used, and the second or inner stage is designed to separate coalesced water from the fluid and also to remove fine solid contaminants from the fluid. The filter is preferably designed for use with fuel, such as ultra-low sulfur diesel (ULSD) or biodiesel, but the filter concepts described herein could be used with any type of fluid requiring water separation from the fluid, for example, hydraulic fluid, oil or lubricating fluid, air, and the like.When used with ULSD, biodiesel, or other fuels with low interfacial tensions (IFTs), for example, IFTs of less than about 15 dyne / cm, improved fuel-water separation is achieved.

[0007] In one embodiment, the filter may be constructed of purely polymeric materials. For example, the two stages of the filter, including the media and end caps, may be constructed of thermoplastic material(s) to facilitate disposal of the filter, such as through recycling or incineration. The use of purely polymeric (e.g., thermoplastic) media layers allows for better bonding of adjacent media layers. Additionally, polymeric media offers better chemical resistance / compatibility compared to media formed from other, non-polymeric materials. Furthermore, certain media properties, such as pore size and pore size distribution, are better controlled when using polymeric media.

[0008] Although the filter is primarily described as a two-stage configuration, the first stage itself could be used in a single-stage configuration, used in combination with various second-stage configurations, or used in combination with two or more additional stages. Likewise, the second stage itself could be used in a single-stage configuration, used in combination with various first-stage configurations, or used in combination with two or more additional stages.

[0009] In one embodiment, a coalescing fluid filter includes a pleated cylinder of polymeric media designed to coalesce water contained within the fluid. The pleated cylinder of polymeric media has pleat valleys and downstream pleat ridges, and discharge points at or adjacent to the downstream pleat ridges.

[0010] In one embodiment, the pleated cylinder of polymeric media has opposite ends attached to end caps, for example, using an adhesive. The ends are embedded in the end caps, which are preferably made of polymeric (e.g., thermoplastic) material, using mechanical fasteners or other fixation techniques. The pleated cylinder of polymeric media may have a single layer or multiple media layers.

[0011] The delivery points may, for example, be located at junctions of the downstream pleat spines and a non-pleated cylinder made of polymeric (e.g., thermoplastic) media, or at openings formed in the downstream pleat spines. When a non-pleated cylinder is used adjacent to the pleat spines, the spacing between the inner spines of the pleated cylinder and the non-pleated cylinder is such that there is no significant gap or separation between the two. The pleat spines of the pleated cylinder may or may not be attached to the outer surface of the non-pleated cylinder. Likewise, a support cylinder for carrying the media may be disposed between the pleat spines and the non-pleated cylinder, or may be disposed within and surrounded by the non-pleated cylinder.

[0012] In a two-stage configuration, a first stage is positioned upstream of a second stage with a gap therebetween. For example, the first and second stages may be in a filter assembly, with the first stage being an outer stage and the second stage being an inner stage. The outer stage contains a pleated cylinder of polymeric (e.g., thermoplastic) media designed to coalesce water contained within a fluid. The pleated cylinder has pleat valleys and downstream pleat ridges and discharge points at the downstream pleat ridges.The inner stage contains a non-pleated cylinder of polymeric (e.g., thermoplastic) media surrounding a multi-layer pleated cylinder of polymeric (e.g., thermoplastic) media, and the inner stage is designed to separate coalesced water from the fluid and to remove fine solid contaminants from the fluid.

[0013] The outer step and the inner step could be attached to end caps. The end caps could be separated such that the outer step includes end caps attached to its opposite ends, and the inner step includes end caps attached to its opposite ends. In another embodiment, the outer step and the inner step could share one or both end caps, with a single, common end cap attached to one end of each of the outer step and the inner step, and a single, common end cap attached to the opposite end of the outer step and the inner step. Short description of the drawings Fig. 1 is an exploded view of one embodiment of a two-stage filter described herein. Fig. Figure 2 is a cross-sectional view of the two-stage filter of Fig. 1 in an assembled state. Fig. 3 is an exploded view of another embodiment of a two-stage filter that may employ the concepts described herein. Fig. Figure 4 is an exploded view of the first or outer stage of the two-stage filter of the Fig. 1 and Fig. 2. Fig. Figure 5 is an exploded view of the second or inner stage of the two-stage filter of the Fig. 1 and Fig. 2. Fig. 6A- Fig. 6C show different configurations of the first stage media layers. Fig. Figure 7 shows an exemplary configuration of the media layers of the second stage. Fig. Figure 8 shows an example of an outer stage with slots, holes or openings formed in the downstream pleat ridges to form delivery points. Detailed description

[0014] A two-stage filter configuration having a first stage configured primarily for coalescing water from a fluid with which the filter is used, and a second stage configured to separate the coalesced water from the fluid and also to remove fine solid contaminants from the fluid. The fluid first flows through the first stage and then flows through the second stage. Although the filter is primarily described as having a two-stage configuration, the first stage could be used by itself in a single-stage configuration, used in combination with second-stage configurations other than those described herein, or used in combination with two or more additional stages.Likewise, the second stage could be used in a single-stage configuration, used in combination with first stage configurations other than those described herein, or used in combination with two or more additional stages.

[0015] The filter is preferably designed for use with fuel, preferably diesel fuel such as ULSD, biodiesel, or other fuels with low IFTs, to filter the fuel before it reaches an engine where the fuel is combusted. However, the filter concepts described herein could be used with any type of fluid requiring water separation from the fluid, for example, hydraulic fluid, oil or lubricating fluid, air, and the like.

[0016] Fig. 1 and Fig.2 show an example of a two-stage filter 10 having a first, upstream stage 12 designed primarily to coalesce water from the fluid, and a second stage 14 downstream of the first stage 12 designed to separate coalesced water from the fluid and also to remove fine solid contaminants from the fluid. In this example, the filter 10 is a filter in an outside-in flow filter construction, with the first stage 12 being an outer coalescing separator stage and the second stage 14 being an inner separator stage, the outer stage surrounding the inner stage with a gap 16 therebetween. The filter 10 is designed to be disposed within a filter housing, with the housing then being attached to a filter head. An example of this type of filter housing and attachment to a head in use with a single-stage filter is shown in U.S. Pat.See patent application publication no. US 2007 / 0 267 338 A1.

[0017] An end cap 18 is connected to a first or upper end of the first stage 12, and an end cap 20 is connected to a second or lower end of the first stage. The end caps 18, 20 are made of a polymeric material, for example, thermoplastic material, and the ends of the first stage media are conveniently attached to the end caps, for example, using an adhesive, with the ends of the media embedded in the end caps, or by other suitable fixation techniques. In another embodiment, the end caps 18, 20 may be made of a non-polymeric material, for example, metal, with the ends of the media being attached to the metal end caps using a potting material known in the art.

[0018] As in Fig.As shown in Figure 2, the end cap 18 includes a central opening 22 defined by a sleeve 23 that defines a fluid outlet passage for fluid filtered by the filter 10. An elastomeric seal 25 surrounds the sleeve 23 for sealing engagement with the filter head when the filter and filter housing are installed. The end cap 20 includes an opening 24 that allows insertion of the second stage 14 into the first stage 12 during filter assembly.

[0019] Additionally, an end cap 26 is connected to a first or upper end of the second stage 14, and an end cap 28 is connected to a second or lower end of the second stage. The end caps 26, 28 are also made of a polymeric material, for example, thermoplastic material, and the ends of the second stage media are conveniently attached to the end caps, for example, using an adhesive, with the ends of the media embedded in the end caps, or by other suitable fixation techniques. In another embodiment, the end caps 26, 28 are made of a non-polymeric material, for example, metal, with the ends of the media being attached to the metal end caps using a potting material known in the art.

[0020] The end cap 26 contains a central opening 30 (see Fig. 1, Fig. 2 and Fig.5), which allows the end cap 26 to be placed over and onto a cylindrical tube 32 (see Fig. 2) extending downwardly from the end cap 18 and forming part of the central opening 22. The end cap 28 is generally closed to prevent fuel flow through the end cap 28.

[0021] The first stage 12 and the second stage 14 can be connected together using any suitable connection technique. An example of a suitable connection technique is described in US Patent Application Publication No. 2009 / 0065425. Using the technique described in Publication No. 2009 / 0065425, the end caps 18, 26 can be connected using crimp ribs, while the end caps 20, 28 are connected using resilient arms 34 that provide a snap fit to the end cap 20.

[0022] Fig. 1 and Fig.2 show that the end caps 18, 20 of the first stage 12 are separate from the end caps 26, 28 of the second stage 14. However, in another embodiment, the first stage 12 and the second stage 14 could share common end caps, with a single common end cap attached to the first or upper ends of the first stage and the second stage, and a single common end cap attached to the second or lower ends of the first stage and the second stage. An example of a first stage and a second stage sharing common end caps can be found in US Patent Application Publication No. 2007 / 0289915.

[0023] Fig.Figure 3 is an exploded view of another embodiment of a two-stage filter 40 configured as a filter in an outside-to-inside flow filter design that can employ the inventive concepts described herein, having a first stage 42 that is an outer coalescing stage and a second stage 44 that is an inner separating stage, the outer stage surrounding the inner stage with a gap therebetween. The first stage 42 filter media and the second stage 44 filter media are connected to end caps 46, 48 and 51, 53, respectively, in the same manner as described above for end caps 18, 20, 26, 28, although a common end cap may also be used at each end. The filter 40 is configured to be installed over a standpipe in a filter housing. Further details of this general type of two-stage filter design are described in U.S.Patent application publication no. 2009 / 0065425 disclosed.

[0024] Fig. 4 and Fig. 5 show details of the first or outer coalescing separator stage 12 and the second or inner separator stage 14 of the filter 10, respectively. The stages 42, 44 of the filter 40 are essentially the same as the stages 12, 14, except for the end caps, and are not described separately.

[0025] As in Fig. 2 and Fig. 4, the first or outer coalescing separator stage 12 includes a pleated cylinder 50 of polymeric media which, when assembled, surrounds a non-pleated cylinder 52 of polymeric media. As shown in Fig. 2 and Fig. 5, the second or inner separator stage 14 includes a non-pleated cylinder 54 of polymeric media which, when assembled, surrounds a pleated cylinder 56 of polymeric media.

[0026] With reference to Fig. 2 and Fig. 4, the pleated media 50 includes inner (i.e., downstream) pleat ridges 60 that, in use, are positioned immediately adjacent to the outer surface of the cylinder 52 such that there is no significant gap or separation between the two. In one embodiment, the inner pleat ridges 60 are in close contact with the outer surface of the cylinder 52. The inner pleat ridges 60 may or may not be attached or fixed to the outer surface of the cylinder 52, but are positioned immediately adjacent to, for example, in contact with, the cylinder.

[0027] Fig. Figure 6A shows a cross-sectional view of an embodiment of the first stage 12, with the thickness of the layers exaggerated for clarity. In Fig.6A, the downstream pleat ridges 60 of the pleated media 50 are in direct, intimate contact with the outer surface of the non-pleated media 52, with the ridges 60 optionally being fixed or unfixed to the outer surface. Thus, in the embodiment in Fig. 6A, no central tube, screen, basket, or other support structure is used for the first stage media 12. In this case, the non-pleated media 52 and / or the pleated media 50 would be rigid enough to serve as a support structure itself.

[0028] Fig.Figure 6B shows another embodiment of the first stage where a central tube, screen, basket, spring, or other support cylinder structure 70 for the first stage 12 media is located downstream and adjacent to the non-pleated media cylinder 52. The support structure 70, if used, may be formed of a polymeric material, for example, thermoplastic material, and is provided with openings so that fluid can flow through the first stage to the second stage. The optional support structure 70 is used to prevent the inner non-pleated media 52 from collapsing under the flow and pressure drop of the fluid. Ideally, however, the pleated 50 and non-pleated media 52 together provide sufficient strength and rigidity that make the use of the support structure 70 unnecessary. In the embodiment in Fig.6B, the non-pleated media 52 could be attached to the support structure 70 only at the end caps, since there is no need to attach it elsewhere due to fluid pressure during use. Nevertheless, the non-pleated media 52 could be attached to the support structure 70 at any location deemed suitable.

[0029] Fig. Figure 6C shows another embodiment of the first stage where the support structure 70 is located between, adjacent to, and in contact with both the upstream pleated media 50 and the downstream non-pleated media 52. In Fig.6C, the support structure 70 provides support for the pleated media 50, whose inner pleat ridges 60 are in close contact with it, while the non-pleated media 52 lies inside and downstream of and in close contact with the support structure 70. The non-pleated media 52 could be heat-welded or injection-molded to the polymeric support structure 70 to secure it to the support structure.

[0030] In Fig. 6A- Fig. 6C, reference numerals 1-5 indicate, in order from upstream to downstream in the direction of fluid flow, the various media layers of an example of pleated media 50. In the examples described herein, the media layers of pleated media 50 are composed of polymeric materials, for example, thermoplastic materials.

[0031] In one embodiment, the pleated media 50 may include three layers of polymeric fibrous filter media (1-3), one layer of polymeric nanofiber media (4), and a final layer (5) of polymeric fibrous media. In this example, the non-pleated media 52 consists of a single layer of polymeric fibrous media formed as a tube and disposed within the pleated media 50, with the upstream surface either in direct contact with the pleated media via the pleat ridges 60 or in indirect contact with the pleated media 50 via the intermediate support structure 70.

[0032] Usually, the axial lengths L1 (see Fig.2) the layers of pleated media 50, non-pleated media 52, and support structure (if used) are the same, with the ends each embedded in the end caps 18, 20 or potted in an adhesive, e.g., polyurethane, or otherwise secured to the end caps such that bypassing of unfiltered fluid around the media is prevented.

[0033] While Fig. 6A- Fig. 6C shows five layers for the pleated media 50 and one layer for the non-pleated media 52, more or fewer layers for the pleated media 50 and the non-pleated media 52 may be used depending, for example, on the application requirements and the coalescer design.

[0034] The functional and design constraints for each layer of the first or coalescer stage 12, and how and when they are applied, will now be described. For illustrative purposes, examples of each layer are provided in Table 1 for three different media combinations, designated Coalescers X, Y, and Z. It should be noted that these three media combinations demonstrate design possibilities based on the recognition that for low interfacial tension fuels, such as ULSD and biodiesel, there is a relatively low thermodynamic drive for coalescence and coalescing kinetics tend to be slow. The examples described herein are designed to physically slow the passage of water droplets through the media and locally increase their concentration within the coalescer.

[0035] The media combinations, materials, and properties listed in Table 1 are exemplary only and represent combinations, materials, and properties that the inventors, at the time of filing this application, believe provide adequate performance results for high-pressure common rail diesel fuel systems running on ULSD or biodiesel. Further research may reveal suitable media combinations, materials, and material properties other than those listed in Table 1, both for high-pressure common rail diesel fuel systems running on ULSD or biodiesel, as well as for other types of fluids in other types of systems.

[0036] Therefore, although Table 1 lists various specific thermoplastic materials, such as polyamide, polybutylene terephthalate, and polyethylene terephthalate, the media layers are not limited to these specific thermoplastic materials. Other thermoplastic materials could be used. Furthermore, the media layers are not limited to thermoplastic materials. Other polymeric materials could be used for the media layers, including, but not limited to, thermosetting plastics. Table 1 Example media layers and properties for the outer stage Coalescing separator X - Coalescing separator for speed change layer material Nominal mean fiber diameter (µm) Average pore size (µm) Max pore size (µm) Permeability (m 3 / min(cfm)) Thickness (mm) Basis weight (g / m 2 ) 1 Polybutylene terephthalate fleece > 10 > 50 > 100 >7,08(> 250) > 0.3 > 40±10 2 Polybutylene terephthalate fleece 1,0-4,0 5,0-15,0 10,0-20,0 0,99-1,56(35-55) 0,7-0,15 27±5 3 Polybutylene terephthalate fleece 1,0-5,0 15,0-30,0 25,0-40,0 2,12-2,83(75-100) 0,15-0,3 33±5 4 polyamide fleece 0,1-1,0 < 8,0 5,0-15,0 0,14-0,57(5,0-20,0) 0,1-0,25 > 20 5 Polyethylene terephthalate fleece > 40 20,0-40,0 40-60 1,42-2,12(50-75) 0,4-0,7 198±20 6 Polyethylene terephthalate fleece > 20 25-45 40-60 4,25-5,66(150-200) 0.8-1,2 100±20 Coalescing separator Y - Single layer surface coalescing separator layer material Nominal mean fiber diameter (µm) Average pore size (µm) Max pore size (µm) Permeability (m 3 / min(cfm)) Thickness (mm) Basis weight (g / m 2 ) 4 polyamide fleece 0,1-1,0 <8,0 5,0-15,0 0,14-0,57(5,0-20,0) 0,1-0,25 >20 5 Polyethylene terephthalate fleece (optional) >40 20,0-40,0 40-60 1,42-2,12(50-75) 0,4-0,7 198±20 6 Polyethylene terephthalate fleece >20 25-45 40-60 4,25-5,66(150-200) 0,8-1,2 100±20 Coalescence separator Z - Surface coalescence separator layer material Nominal mean fiber diameter (µm) Average pore size (µm) Max pore size (µm) Permeability (m 3 / min Thickness (mm) Basis weight (g / m 2 ) 3 Polybutylene terephthalate fleece 1,0-5,0 15,0-30,0 25-40 2,12-2,83(75-100) 0,15-0,3 33±5 4 polyamide fleece 0,1-1,0 <8,0 5,0-15,0 0,14-0,57(5,0-20,0) 0,1-0,25 >20 5 Polyethylene terephthalate fleece (optional) >40 20-40 40-60 1,42-2,12(50-75) 0,4-0,7 198±20 6 Polyethylene terephthalate fleece >20 25-45 40-60 4,25-5,66(150-200) 0,8-1,2 100±20

[0037] In Table 1 (and following Table 2): gsm is defined as grams per square meter and cfm is defined as cubic feet per minute, the thickness is measured from upstream to downstream relative to the primary fluid flow direction through the media layers. Coalescing separator X

[0038] The example coalescer X contains at least 6 media layers, and a support structure can optionally be used. Layers 1-5 form the pleated media 50, and layer 6 forms the non-pleated cylinder 52. The coalescer X could be referred to as a variable-velocity coalescer (see, for example, PCT Publication No. WO 2010 / 042706) for use in a filter-in-filter design.

[0039] Layer 1 serves as a pre-filter and reduces the pressure drop across the outer stage 12. Layer 1 is more open (e.g., has higher porosity, larger pore size, larger mean fiber diameter, higher Frasier permeability, and / or lower contaminant removal efficiency) than Layer 2.

[0040] Layer 2 serves to capture fine emulsified droplets, such as water droplets in ULSD fuel. Layer 2 is denser (e.g., has lower porosity, smaller pore size, smaller mean fiber diameter, lower Frasier permeability, and / or higher contaminant removal efficiency) than Layer 3.

[0041] Layer 3 serves to reduce the fluid velocity within the layer and provides space for droplets trapped in Layer 2 to drain, collect, and coalesce. The physical properties of Layer 3 are such that the fluid velocity in this layer is lower than in Layer 4. Layer 3 is more open (e.g., has higher porosity, larger pore size, larger mean fiber diameter, higher Frasier permeability, and / or lower contaminant removal efficiency) than Layer 4.

[0042] Layer 4 serves to capture droplets not captured by the preceding layers, especially the finer droplets, and acts as a semipermeable barrier to the passage of the captured droplets. The function of the semipermeable barrier causes droplets to concentrate and collect in Layer 3, providing more time and a higher probability for coalescence to occur. Layer 4 also leads to a locally increased fluid velocity and a temporary increase in the droplet surface area, further increasing coalescence. The fluid velocity in Layer 4 is higher than in Layer 5. Layer 4 is denser (e.g., has lower porosity, smaller pore size, smaller mean fiber diameter, lower Frasier permeability, and / or higher contaminant removal efficiency) than Layer 5.

[0043] Layer 4, for example, may consist of thermoplastic nanofiber filter media with fibers having a diameter of less than about 1 µm, which helps achieve the very high water removal efficiency requirements for modern high-pressure common rail diesel fuel systems running on ULSD or biodiesel. Layer 4 may be formed using an electroblowing process, but may also be manufactured using other suitable methods. In addition to the properties listed in Table 1 for Layer 4, Layer 4 may also have a maximum-to-average pore size ratio of less than about 3, and more preferably less than about 2.

[0044] Layer 5 serves to create a lower-velocity environment for the coalesced droplets formed in the preceding layers to collect and pass through prior to dispensing. Layer 5 is more open (e.g., has higher porosity, larger pore size, larger mean fiber diameter, higher Frasier permeability, and / or lower contaminant removal efficiency) than Layer 4.

[0045] Layer 6 (i.e., the non-pleated cylinder 52) serves to provide delivery points for coalesced droplets. As such, layer 6 is more open (e.g., has a higher porosity, a larger pore size, a larger average fiber diameter, a higher Frasier permeability, and / or a lower contaminant removal efficiency) than layer 5. In one embodiment, layer 6 also provides a structural support for the first stage 12, as described above for Fig.6A, eliminating the need for a separate support structure. Coalescence separator Y

[0046] In the example of coalescer Y, two to three media layers are used, with or without an optional support structure. Coalescer Y could be described as a single-layer surface coalescer (see U.S. Patent Application Serial No. 61 / 178,738, filed May 15, 2009, and U.S. Patent Application Serial No. 12 / 780,392, filed May 14, 2010) for use in a filter-in-filter design.

[0047] The first layer, Layer 4, serves to provide a semi-permeable barrier to the passage of finely emulsified droplets, causing them to concentrate at their upstream surface. This allows the droplets time and a suitable environment to coalesce and grow. Layer 4 is a relatively dense layer with properties comparable to or even denser than Layer 4 in Coalescer X. Layer 4 relies on screening to prevent the passage of fine droplets and, in this example, may be composed of thermoplastic nanofiber filter media having fibers with a diameter of less than about 1 µm, a mean pore size smaller than the mean droplet size of the incoming droplets, and a maximum-to-mean pore size ratio of less than about 3, and preferably less than about 2.The layer 4 may be formed using an electroblowing process, but may also be formed using other suitable processes.

[0048] Layer 5 is optional and, if required, provides structural support for layer 4 and serves as an outlet channel for coalesced droplets forced through layer 4. Layer 5 also connects layer 4 to discharge layer 6 (i.e., non-pleated cylinder 52). Layer 5 creates a lower velocity environment for the coalesced droplets to collect and pass through prior to discharge. Layer 5 (if used) is more open than layer 4 and is structurally stronger to provide support for layer 4 and facilitate processing of the filter media.

[0049] Coalescing separator Y has an additional non-pleated layer 6 (i.e., a non-pleated cylinder 52) downstream of layer 4 and the optional layer 5, which provides discharge points for coalesced droplets. Layer 6 is more open than the optional layer 5. Coalescence separator Z

[0050] In the example of coalescer Z, three or more media layers with an optional support structure are used (see US patent application Serial No. 61 / 179,170, filed May 18, 2009; US patent application Serial No. 61 / 179,939, filed May 20, 2009; and US patent application Serial No. 12 / 780,392, filed May 14, 2010). Coalescer Z is a more complex surface coalescer than coalescer Y for use in a filter-in-filter construction.

[0051] Layer 3 serves to reduce the pressure drop across the coalescing separator and acts as a particulate pre-filter for the coalescing separator, extending its operating life. Layer 3 is more open than layer 4 and has a higher capillary pressure (i.e., a more positive capillary pressure) than layer 4.

[0052] The functions and properties of layer 4, layer 5 (optional) and layer 6 are as described for coalescing separator Y.

[0053] In all three coalescers X, Y, and Z, the nature of the transition from layer 5 to layer 6 is of interest. In the illustrated and described embodiments, layers 1-5 are pleated. As such, the fluid flow profile within the pleats and the resistance to trapped droplets cause them to accumulate in the valleys 62 (downstream direction) of the pleats. This results in a concentration of droplets in this localized region, increasing coalescence because a longer time is allowed for the droplets to coalesce before they are discharged. The inventors have observed that coalesced droplets tend to be discharged from the same active regions or areas of the downstream surface of the coalescers, while little droplet discharge occurs at other locations. This suggests that once an outlet path through the media is established, it is used repeatedly.

[0054] In the described first stage, preferred outlet paths leading into large pores are created by the close contact of the inner pleat ridges of layer 4 (for coalescers Y and Z) or layer 5 (for coalescer X, as well as coalescers Y and Z if layer 5 is included) with the upstream surface of the unpleated layer 6. At the point of contact between the pleated media and the non-pleated media, there is a local disruption of the media pore structure, leading to these preferred outlet paths. The result is that larger droplets are released. Furthermore, these outlet paths occur at the bottoms 64 of the pleat valleys 62 (see Fig. 6A, Fig. 6B and Fig.6C), where coalesced droplets tend to concentrate and the effect is greatest. The contact between layers 4 or 5 and layer 6 need not be direct. Instead, the same benefits can be achieved indirectly by having the inner or downstream pleat ridges 60 of the pleated media 50 in direct contact with the porous support structure 70, which in turn is in direct contact with layer 6 (i.e., the non-pleated cylinder 52) on its downstream side, as in Fig. 6C.

[0055] In an additional embodiment, the pleated media 50 could be as described in the exemplary coalescers X, Y, or Z described above, except that layer 6, i.e., the non-pleated cylinder 52, would be omitted. This additional embodiment achieves the same fluid flow profile within the pleat and the same drag effect on trapped droplets as coalescers X, Y, or Z to cause droplets and coalesced droplets to concentrate in the valleys 62 of the pleats to increase coalescence. However, instead of the coalesced droplets draining to layer 6, the droplets are released from small slits or holes (i.e., orifices) in the inner pleat ridges 60. These orifices could be created by needle punching or other means and may be on the order of 30-300 µm. The orifices serve as delivery points for the coalesced droplets.

[0056] Fig. Figure 8 shows an example of openings 80 formed in the inner pleat ridges of the pleated media 50. An optional layer 82 with a relatively large pore size (compared to the media 50), which may be equivalent to the non-pleated cylinder 52 or the support structure 70, may also be present. As in Fig.8, during flow, an emulsion containing water droplets flows into the pleat at (1). At (2), water droplets unable to penetrate the barrier formed by the media flow along the media surface to the valley of the pleat. At (3), water droplets collect in the valley and coalesce into droplets. At (4), the pressure drop forces coalesced droplets through an opening 80 in the pleat back. At (5), droplets are ejected through layer 82, if present. At (6), coalesced water droplets precipitate and / or are carried downstream to the outer, non-pleated cylinder 54 of the second stage 14, where they are separated and drain.

[0057] Fig.Figure 7 and Table 2 show an exemplary configuration of the second or inner separation stage 14. The second stage 14 serves to separate coalesced water droplets from the fluid and to remove fine solid contaminants from the fluid. The second stage 14 contains the outer, non-pleated cylinder 54 in close contact with the outer pleat ridges of the inner multi-layer pleated cylinder 56.

[0058] As in Fig. 2, the axial lengths L2 of the non-pleated cylinder 54 and the pleated cylinder 56 are substantially the same, with the ends of the cylinders being embedded in the end caps 26, 28 or encapsulated in an adhesive, for example, polyurethane, or otherwise secured to the end caps in a manner that prevents bypassing of unfiltered fluid around the media.

[0059] The media combinations, materials, and properties listed in Table 2 are exemplary only and reflect combinations, materials, and properties that the inventors, at the time of filing this application, believe provide adequate performance results for high-pressure common rail diesel fuel systems running on ULSD or biodiesel. Further research may reveal suitable media combinations, materials, and material properties other than those listed in Table 2, both for high-pressure common rail diesel fuel systems running on ULSD or biodiesel, and for other types of fluids in other types of systems.

[0060] While Table 2 lists various specific thermoplastic materials such as polyamide, polybutylene terephthalate, and polyethylene terephthalate, the media layers are not limited to these specific thermoplastic materials. Other thermoplastic materials could be used. Furthermore, the media layers are not limited to thermoplastic materials. Other polymeric materials could be used for the media layers, including, but not limited to, thermosetting plastics. Table 2 Example media layers and properties of the inner stage layer material Nominal mean fiber diameter (µm) Average pore size (µm) Max pore size (µm) Permeability (m 3 / min(cfm)) Thickness (mm) Basis weight (g / m 2 )(gsm) A Polyethylene terephthalate mesh * 30 - 50 30 - 50 11,33 - 17,00(400-600) 0.03 - 0,1 37±10 B Polybutylene terephthalate fleece > 10 > 50 > 100 6.37 - 9.20(225 - 325) 0,3 - 0,5 48±10 C Polybutylene terephthalate fleece 1,0-5,0 5,0 - 15,0 10,0-25,0 1,00 - 1,56(35 - 55) 0,1 - 0,3 38±5 D polyamide fleece 0,1-0,8 1,0 - 8,0 1,0 - 10,0 0,08-0,57(3,0-20,0) 0,1 - 0,3 > 20 E Polyethylene terephthalate fleece > 40 20 - 35 40-65 1,42-2,12(50-75) 0,45 - 0,65 198±20 *It is currently believed that the nominal mean fiber diameter for layer A is irrelevant for functionality.

[0061] In the Fig.7 and in the example shown in Table 2 above, the second stage contains at least five layers. Layer A (i.e., the non-pleated cylinder 54) serves to separate coalesced water droplets from the fuel. Layer A can, for example, be a woven polymer mesh in the shape of a tube that repels the coalesced water droplets and allows them to drain freely from the surface.

[0062] Layer A lies outside and in close contact with the outer pleat ridges 90 of the inner multilayer pleated cylinder 56. The inventors currently believe that the mesh opening of Layer A should be less than 100 µm, and preferably less than 50 µm for ULSD and biodiesel applications. However, further research may reveal other suitable mesh opening sizes.

[0063] The pleated layers (layers BE, i.e., the pleated cylinder 56) serve to capture solid contaminants and droplets that have not been removed by upstream layers. The first of these pleated layers, layers B and C in Fig. 7 and Table 2 are transition layers that reduce pressure drop, provide further removal of drops and droplets, and reduce solids accumulating at the following nanofiber filtration layer, Layer D. Layers B and C have properties similar to Layers 1 and 2 in the outer stage 12. Layer B also facilitates manufacturing and processing.

[0064] The next pleated layer, Layer D, serves as a high-efficiency filter for fine particles, 4 µm(c) and smaller. For high-pressure common rail applications, very high removal efficiencies for particles as small as 4 µm(c) are required to protect fuel injectors. The layers upstream of Layer D primarily serve to remove and trap water droplets. Layer D serves to protect a downstream system, such as a high-pressure common rail fuel injection system, from fine solids. Layer D also removes droplets that may have passed through the preceding layers. Preferably, Layer D is denser than any of the other layers of the outer stage 12 or the inner stage 14 and, in one exemplary embodiment, comprises thermoplastic nanofiber filter media with fibers less than 1 µm in diameter. Layer D should be at least as dense as Layer 4 of the outer stage 12.

[0065] The final layer, Layer E, serves as a support for the preceding layers without significantly increasing the pressure drop. Layer E is a relatively open media with sufficient strength and stiffness to support upstream layers of the inner stage 14 under service conditions and to improve the processability of the inner stage 14 media.

[0066] The examples in Tables 1 and 2 above indicate that the various media layers are made of specific thermoplastic materials. The end caps and support structure 70 are also described as being made of thermoplastic materials. However, the performance benefits of the filter described herein may be achieved if some of these components are not thermoplastic, but are made of other polymeric materials or, under certain circumstances, non-polymeric materials. For example, one or more of the media layers of the outer stage 12 and / or the inner stage 14 may be made of polymeric materials that are not thermoplastic. In another embodiment, the end caps may be formed of a material that is not thermoplastic, for example, metal or another polymeric material such as thermosetting plastics.In addition, the support structure 70 may be made of materials that are not thermoplastic, for example, other polymeric materials, metal, or other materials known in the art.

[0067] Suitable polymeric materials that may be used for the various elements of the filter described herein may include, but are not limited to, polyamide material, polyalkylene terephthalate material (e.g., polyethylene terephthalate material or polybutylene terephthalate material), another polyester material, halocarbon material (e.g., Halar® brand ethylene chlorotrifluoroethylene (ECTFE)), and polyurethane material.

[0068] The pleated media 50 and pleated media 56 may be manufactured using any suitable technique known in the art, including, but not limited to, meltblowing two different superimposed media layers, by a wet-lay process, electrospinning, electroblowing, melt spinning, ultrasonic bonding, co-pleating, or by other chemical or physical bonding of two or more different layers, or using other techniques or combinations of techniques.

[0069] The invention may be embodied in other forms without departing from its spirit or novel features. The embodiments disclosed in this application are to be considered in all respects as illustrative and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalents of the claims are intended to be embraced therein. List of reference symbols: 1 - 6, 82 layers 10, 40 filters 12, 42 first stage 14, 44 second stage 16 gap 18, 20, 26, 28, 46, 48, 51, 53 end cap 22, 24, 30, 80 opening 23 sleeve 25 elastomer seal 34 elastic arms 50, 56 pleated cylinders, pleated media 52 non-pleated cylinders, non-pleated media 60 pleated spines 70 support structure 62 fold valleys 64 Floors of the Fold Valleys

Claims

[1] Two-stage fluid filter (10), comprising: a first stage (12) spaced from and upstream of a second stage (14) with a gap therebetween; where the first stage (12) contains the following: pleated polymeric media (50) configured to coalesce water contained in a fluid, the pleated polymeric media having pleat valleys and downstream pleat ridges (60); non-pleated polymeric media (52) downstream of the pleated polymeric media (50); and Discharge points at or adjacent to the downstream pleat ridges (60); and the second stage (14) includes multilayer pleated polymeric media (56) and non-pleated polymeric media (54) upstream of the multilayer pleated polymeric media (56), the second stage being configured to separate coalesced water from the fluid and to remove solid contaminants from the fluid, the pleated polymeric media (50) of the first stage (12) comprising, from upstream to downstream, at least the following layers: (i) a layer 1 comprising a polymer nonwoven having a nominal mean fiber diameter of >10 µm and a basis weight of > 40±10 g / m 2 has; (ii) a layer 4 comprising a polymer fleece having a nominal mean fiber diameter of 0.1-1.0 µm, a mean pore size of < 8 µm, a maximum pore size between 5.0 and 15.0 µm, a permeability between 0.14 and 0.57 m3 / min, a thickness between 0.1 and 0.25 mm and a basis weight of > 20 g / m²; and (iii) a layer 6 comprising a polymer nonwoven having a nominal mean fiber diameter of >20 µm and a basis weight of 100 ± 20 g / m². [2] A two-stage fluid filter according to claim 1, wherein the polymeric media of the first stage (12) and the second stage (14) comprise thermoplastic material. [3] A two-stage fluid filter according to claim 1, further comprising a support structure (70) disposed between the downstream pleat ridges (60) and the non-pleated polymeric media (52) of the first stage (12), or the non-pleated polymeric media (52) of the first stage (12) are disposed between the pleat ridges (60) and the support structure (70). [4] A two-stage fluid filter according to claim 1, wherein the layers of pleated polymeric media are bonded by ultrasonic bonding. [5] A two-stage fluid filter according to claim 1, wherein layer 1 has a higher porosity, a larger maximum pore size, a larger average fiber diameter, a higher Frasier permeability, and a lower contaminant removal efficiency than a layer immediately downstream of layer 1. [6] Two-stage fluid filter according to claim 1, wherein the layer 4 has a maximum to average pore size ratio of less than 3 and a basis weight of more than 20 g / m 2 has. [7] A two-stage fluid filter according to claim 1, wherein layer 6 has a higher porosity, a larger pore size, a larger average fiber diameter, a higher frasier permeability and a lower contaminant removal efficiency than a layer immediately upstream.

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