阅读说明：本技术 核发电中过滤流体的方法和装置 (Method and apparatus for filtering fluid in nuclear power generation ) 是由 理查德·达姆 弗朗索瓦·库萨克 徐坚 王玮炎 林颖辉 于 2018-10-05 设计创作，主要内容包括：一种用于核发电设施的流体进口的过滤装置,包含一级和二级框架。一级框架界定围闭体积,围闭体积具有至少一个入口开口和与流体进口流体连通的至少一个出口开口。一级过滤器支撑在一级框架上,一级过滤器覆盖入口开口,使得流体通过一级过滤器进入围闭体积。二级框架位于一级框架围闭的体积内。二级过滤器支撑在二级框架上,二级过滤器界定与出口开口连通的围闭流道,使得流体通过二级过滤器和围闭流道进入至少一个出口开口。(A filter arrangement for a fluid inlet of a nuclear power generating facility includes primary and secondary frames. The primary frame defines an enclosed volume having at least one inlet opening and at least one outlet opening in fluid communication with the fluid inlet. A primary filter is supported on the primary frame, the primary filter covering the inlet opening such that fluid passes through the primary filter into the enclosed volume. The secondary frame is located within the volume enclosed by the primary frame. A secondary filter is supported on the secondary frame, the secondary filter defining an enclosed flow passage in communication with the outlet opening such that fluid passes through the secondary filter and the enclosed flow passage into the at least one outlet opening.)

1. A fluid inlet filter arrangement for a nuclear power generating facility, comprising:

a primary frame defining a primary enclosed volume, at least one inlet opening in fluid communication with the enclosed volume, and at least one outlet opening in fluid communication with the fluid inlet;

a primary filter supported on the frame, the primary filter covering the at least one inlet opening such that fluid enters the enclosed volume through the primary filter;

a secondary frame within the primary enclosed volume;

a secondary filter supported on the secondary frame, the secondary frame defining an enclosed flow passage in communication with the at least one outlet opening such that fluid enters the at least one outlet opening through the secondary filter and the enclosed flow passage.

2. The filtration device of claim 1, wherein the secondary filter is wrapped around the secondary frame to enclose the enclosed flow path.

3. The filtration apparatus of claim 1, wherein the secondary filter defines the enclosed flow path.

4. The filtration apparatus of claim 1, wherein the secondary filter defines a cylindrical filtration surface.

5. The filtration apparatus of claim 1, wherein the secondary filter defines a filter surface having a plurality of polygonal sides.

6. The filtration apparatus of claim 5, wherein the secondary frame supports the plurality of polygonal sides around the edges of each side.

7. The filtration device of claim 1, wherein the secondary filter is welded to the secondary frame.

8. The filter apparatus of claim 1, comprising a plurality of said secondary frames forming corrugations having a plurality of peaks to support said primary filters, said secondary filters being supported by each of said secondary frames, each secondary filter defining an enclosed flow passage in communication with a respective outlet opening.

9. The filtration device of claim 8, wherein the secondary frame is inclined relative to fluid flowing through the secondary filter such that the fluid forces the secondary frames adjacent each peak to move toward each other to bias the peaks toward the secondary filter frames.

10. The filtration device of claim 1, wherein the total surface area of the secondary filter is at least 5% of the surface area of the primary filter.

11. The filtration device of claim 1, wherein said total surface area of said secondary filter is at least 10% of said surface area of said primary filter.

12. The filtration device of claim 1, wherein the total surface area of the secondary filter is at least 20% of the surface area of the primary filter.

13. The filtration apparatus of claim 1, wherein the total surface area of the secondary filter is at least 40% of the surface area of the primary filter.

14. The filtration device of claim 1, wherein the primary filter has a pore size greater than the pore size of the secondary filter.

15. A fluid filtration device for a nuclear power generation facility, comprising:

a fluid conduit;

a plurality of filter modules, each of said filter modules being in communication with said fluid conduit for drawing fluid into said fluid conduit through said filter module, each filter module comprising:

a primary frame defining a primary enclosed volume, at least one inlet opening in fluid communication with the enclosed volume, and at least one outlet opening in fluid communication with the fluid conduit;

a primary filter supported on the frame, the primary filter covering the at least one inlet opening such that fluid enters the enclosed volume through the primary filter;

a secondary frame within the primary enclosed volume;

a secondary filter supported on the secondary frame, the secondary frame defining an enclosed flow passage in communication with the at least one outlet opening such that fluid enters the at least one outlet opening through the secondary filter and the enclosed flow passage.

16. The filtration device of claim 15, wherein the secondary filter is wrapped around the secondary frame to enclose the enclosed flow path.

17. The filter apparatus of claim 15, wherein the secondary filter defines the enclosed flow path.

18. The filtration apparatus of claim 15, wherein the secondary filter defines a cylindrical filtration surface.

19. The filter apparatus of claim 15, wherein the secondary filter defines a filter surface having a plurality of polygonal sides.

20. The filter apparatus of claim 19, wherein the secondary frame supports the plurality of polygonal sides around the edges of each side.

21. The filtration device of claim 15, wherein the secondary filter is welded to the secondary frame.

22. The filter apparatus of claim 15, comprising a plurality of said secondary frames forming corrugations having a plurality of peaks to support said primary filters, said secondary filters being supported by each of said secondary frames, each secondary filter defining an enclosed flow passage in communication with a respective outlet opening.

23. The filtration device of claim 22, wherein the secondary frame is inclined relative to the fluid flowing through the primary and secondary filter such that the fluid forces the secondary frames adjacent each peak to move toward each other to bias the peaks toward the primary and secondary filter.

24. The filtration apparatus of claim 15, wherein the total surface area of the secondary filter is at least 5% of the surface area of the primary filter.

25. The filtration apparatus of claim 15, wherein the total surface area of the secondary filter is at least 10% of the surface area of the primary filter.

26. The filtration apparatus of claim 15, wherein the total surface area of the secondary filter is at least 20% of the surface area of the primary filter.

27. The filtration apparatus of claim 15, wherein the total surface area of the secondary filter is at least 40% of the surface area of the primary filter.

28. The filtration apparatus of claim 15, wherein the primary filter has a pore size greater than the pore size of the secondary filter.

29. The filtration apparatus of claim 15, wherein the fluid conduit is in communication with a fluid recirculation pump.

30. The filtration apparatus of claim 15, wherein the fluid conduit comprises a sump.

31. The filtration apparatus of claim 15, wherein the fluid conduit comprises a manifold.

Technical Field

The present invention relates to fluid filtration, particularly to filtering substances from cooling water in nuclear power plants.

Background

Nuclear power plants use large volumes of water that is circulated through one or more loops for purposes such as cooling system components. The water collects, for example, in a sump and is recirculated.

As the water circulates through the system components, debris such as particulate and fibrous matter may be entrained in the water. Such substances may risk contaminating system components. The water may be filtered before being recirculated.

Filtration performance can be affected by parameters such as filter surface area and pore size. Performance requirements may include fluid throughput or debris removal, and head loss. Very fine filters can remove small debris, albeit at the expense of a large pressure loss. In contrast, a coarse filter can remove larger debris, but at the expense of passing smaller particles or fibers. The filter surface area may be constrained by the available physical space.

Disclosure of Invention

An example filtration device for a fluid inlet of a nuclear power generation facility, comprising: a primary frame defining a primary enclosed volume, at least one inlet opening in fluid communication with the enclosed volume, and at least one outlet opening in fluid communication with the fluid inlet; a primary filter supported on the frame, the primary filter covering the at least one inlet opening such that fluid passes through the primary filter into the enclosed volume; a secondary frame within the primary enclosure volume; a secondary filter supported on the secondary frame, the secondary frame defining an enclosed flow passage in communication with the at least one outlet opening such that fluid passes through the secondary filter and the enclosed flow passage into the at least one outlet opening.

In some embodiments, the secondary filter may be wrapped around the secondary frame to enclose the enclosed flow path.

In some embodiments, the secondary filter may define an enclosed flow path.

In some embodiments, the secondary filter may define a cylindrical filtering surface.

In some embodiments, the secondary filter may define a filter surface having a plurality of polygonal sides.

In some embodiments, the secondary frame supports a plurality of polygonal sides of the second filter around the edges of each side.

In some embodiments, the secondary filter may be welded to the secondary frame.

In some embodiments, the filter device may include a plurality of secondary frames forming corrugations having a plurality of peaks to support a primary filter and a secondary filter, the secondary filter being supported by each secondary frame, each secondary filter defining an enclosed flow passage in communication with a respective outlet opening.

In some embodiments, the secondary frame is inclined relative to the fluid flowing through the secondary filter such that the fluid forces the secondary frames adjacent each peak to move toward each other to bias the peaks toward the secondary filter.

In some embodiments, the total surface area of the secondary filter may be at least 5% of the surface area of the primary filter.

In some embodiments, the total surface area of the secondary filter may be at least 10% of the surface area of the primary filter.

In some embodiments, the total surface area of the secondary filter may be at least 20% of the surface area of the primary filter.

In some embodiments, the total surface area of the secondary filter may be at least 40% of the surface area of the primary filter.

In some embodiments, the pore size of the primary filter is greater than the pore size of the secondary filter.

An example fluid filtration device for a nuclear power generation facility, comprising: a fluid conduit; a plurality of filter modules, each filter module in communication with the fluid conduit for drawing fluid through the filter module into the fluid conduit. Each filter module comprises: a primary frame defining a primary enclosed volume, at least one inlet opening in fluid communication with the enclosed volume, and at least one outlet opening in fluid communication with the fluid conduit; a primary filter supported on the frame, the primary filter covering the at least one inlet opening such that fluid passes through the primary filter into the enclosed volume; a secondary frame within the primary enclosure volume; a secondary filter supported on the secondary frame, the secondary frame defining an enclosed flow passage in communication with the at least one outlet opening such that fluid passes through the secondary filter and the enclosed flow passage into the at least one outlet opening.

In some embodiments, the secondary filter is wrapped around the secondary frame to enclose the enclosed flow path.

In some embodiments, the secondary filter defines an enclosed flow path.

In some embodiments, the secondary filter defines a cylindrical filtering surface.

In some embodiments, the secondary filter defines a filter surface having a plurality of polygonal sides.

In some embodiments, the secondary frame supports a plurality of polygonal sides of the second filter around the edges of each side.

In some embodiments, the secondary filter is welded to the secondary frame.

In some embodiments, the filter device comprises a plurality of secondary frames forming corrugations having a plurality of peaks to support a primary filter and a secondary filter, the secondary filter supported by each secondary frame, each secondary filter defining an enclosed flow passage in communication with a respective outlet opening.

In some embodiments, the secondary frame is inclined relative to the fluid flowing through the secondary filter such that the fluid forces the secondary frames adjacent each peak to move toward each other to bias the peaks toward the secondary frames.

In some embodiments, the total surface area of the secondary filter is at least 5% of the surface area of the primary filter.

In some embodiments, the total surface area of the secondary filter is at least 10% of the surface area of the primary filter.

In some embodiments, the total surface area of the secondary filter is at least 20% of the surface area of the primary filter.

In some embodiments, the total surface area of the secondary filter is at least 40% of the surface area of the primary filter.

In some embodiments, the pore size of the primary filter is greater than the pore size of the secondary filter.

In some embodiments, the fluid conduit is in communication with a fluid recirculation pump.

In some embodiments, the fluid conduit comprises a sump.

In some embodiments, the fluid conduit comprises a manifold.

Embodiments in accordance with the present disclosure may include a combination of the above features.

Drawings

In the drawings which illustrate example embodiments:

FIG. 1 is an isometric view of a fluid recirculation inlet system;

FIG. 2 is a top view of the fluid recirculation inlet system of FIG. 1;

FIG. 3 is a side cross-sectional view of the fluid recirculation inlet system of FIG. 1 taken along line III-III of FIG. 2;

FIG. 4 is an isometric partial cross-sectional view of a filter element of the fluid recirculation inlet system of FIG. 1;

FIG. 5 is an isometric partial cross-sectional view of another cartridge;

FIG. 6 is an isometric partial cross-sectional view of another cartridge; and

fig. 7 is an isometric view of another fluid recirculation inlet system with a filter cartridge mounted to an inlet manifold.

Detailed Description

FIG. 1 illustrates an example recirculation inlet system 100 of a nuclear power plant. After a fluid, such as cooling water, is circulated through the system of the nuclear power plant, the recirculation inlet system 100 gathers the fluid, such as cooling water, for subsequent recirculation.

Particulate and fibrous matter may be entrained in the fluid during circulation of the fluid. For example, the cooling fluid may accumulate fibers, paint chips, dust, sludge, and other debris such as insulation displacement material. The recirculation inlet system 100 is designed to filter such debris prior to fluid recirculation.

The facility design specifications or regulatory requirements may define performance criteria for the recycle inlet system 100. For example, such criteria may define a minimum fluid throughput rate, a maximum acceptable screening rate of particulate matter, and a maximum particle size that can pass through the recirculation inlet system 100. Such criteria may conflict with design constraints, including physical space limitations and maximum flow limitations of the sump system 100, such as the maximum allowable pressure drop across the recirculation inlet system 100 at a particular flow rate or range of flow rates.

The recirculation inlet system 100 forms part of a cooling subsystem of a nuclear power plant and therefore may be critical to safety. For example, if the recirculation inlet system 100 is blocked or otherwise excessively restricts fluid flow, a failure of the recirculation inlet system 100 may result in a loss of cooling.

The recirculation inlet system 100 may be further subject to structural performance standards. For example, the recirculation inlet system 100 may be designed to have sufficient strength to withstand physical shock or seismic events.

The recirculation inlet system 100 may include a sump 102. Fluid collects in sump 102 and is drawn in by suction through one or more suction ports 114 for recirculation.

In the illustrated embodiment, suction inlet 114 is positioned within sump 102. Suction port 114 communicates with a pumping apparatus that draws fluid from sump 102 into suction port 114 for recirculation. Such communication may be accomplished, for example, by a catheter. Suction inlet 114 is enclosed such that fluid passes through filter assembly 110 before entering suction inlet 114. In the illustrated embodiment, suction inlet 114 is enclosed by sump 102 and filter assembly 110. That is, fluid drawn into suction inlet 114 passes through filter assembly 110, into sump 102, and then into suction inlet 114. The filter assembly 110 includes a plurality of filter elements 112, the filter elements 112 being in communication with the sump 102 via an inlet plate 115. Each filter element 112 mates with a corresponding inlet aperture (not shown) in the inlet plate 115.

The filter assembly 110 may be designed to provide a large filtering surface area within a confined enclosure. For example, in the illustrated embodiment, filter assembly 110 is configured to be positioned within an area overlying sump 102. In some embodiments, the filter assembly 110 may be subject to other spatial constraints, such as height and volume limitations.

Fig. 2 illustrates a top view of the filter assembly 110. As shown, the filter elements 112 are arranged in parallel rows. Adjacent filter elements 112 are closely spaced together to achieve a high packing density while allowing sufficient space for fluid flow. As previously described, the filter element 112 is located within the area a defining the sump 102.

Fig. 3 illustrates a cross-sectional view of an example recirculation inlet system 100, showing filter element 112, sump 102, and suction inlet 114. As shown, the design may specify a maximum height h of the filter assembly 110. As shown, the maximum height h is defined with reference to the top of sump 102. Additionally or alternatively, the maximum height h may be defined relative to other components. A maximum height may be defined, for example, to avoid interference with other system components.

One or more reserved areas R may be defined within sump 102 or outside sump 102. The retention zone R can be designated as having no components such as a filter element 112. For example, the reserved area R may provide a workspace for maintenance purposes or provide clearance for system components.

The spatial constraints shown and described with reference to fig. 2-3 are merely examples. The specific constraints applicable to any given power generation facility may vary. However, the space available to accommodate the filter assembly 110 is often severely constrained, which requires a high ratio of the filter area of the filter element 112 to its external dimensions. Thereby providing a sufficient ratio of filter surface area for the filter element 112.

Fig. 4 illustrates an example filter cartridge 112. The cartridge 112 has a frame 120, the frame 120 having a plurality of walls 122. The frame 120 defines an enclosed volume V, i.e., the volume defined by the members of the frame 120. In the illustrated embodiment, the frame 120 includes upper and lower walls 122 and an end wall 122.

One of the end walls 122 of the frame 120 is configured to mate with an inlet aperture of the inlet plate 115 and has one or more outlets (not shown) through which the enclosed volume V is in fluid communication with the sump 102.

The primary filter 124 is supported on the frame 120. As shown, a primary filter 124 occupies each side of the filter element 112. In the illustrated embodiment, the primary filter 124 is pleated to define a plurality of corrugations or ridges. Each ridge extends generally transversely of the filter element 112 and has opposing side surfaces and end surfaces, each of which may include perforations for passage of fluid. Thus, the ridges provide a greater fluid filtration area relative to a flat filter. The ridges may also increase the stiffness of the primary filter 124. That is, the ridges may increase the degree of bending resistance about a direction oriented perpendicular to the ridges.

Fluid may be drawn into the enclosed volume V through the primary filter 124. The primary filter 124 may be formed from, for example, a perforated metal plate or mesh. As the fluid passes through the primary filter 124, the filter removes at least some of the debris entrained in the fluid. Some debris (hereinafter referred to as bypass debris) passes through the filter 124 with the fluid. The size and amount of the diverted debris depends on the pore size of the primary filter 124, the area of the primary filter 124, and the spacing between the pores, i.e., the proportion of the filter area occupied by the open pores. As used herein, the term "pores" includes perforations in thin plate filters and open slots in screen filters.

In general, a filter 124 having a smaller pore size and a smaller total pore area (e.g., less pores) allows less debris to pass through. For example, the pore size defines the maximum debris that can pass through the filter 124. In other words, a finer screen allows only smaller debris to pass through. However, smaller pore sizes and smaller total pore areas also generally impose greater flow restrictions, resulting in greater pressure losses (i.e., head loss) throughout the filter. Therefore, filtration performance must be balanced against flow restrictions.

In the embodiment of fig. 4, the primary filter 124 is also supported by an internal secondary frame 126. As shown, the secondary frame 126 comprises a series of triangular supports that form a wave having a plurality of peaks 129. The support extends longitudinally of the filter element 112 and provides physical reinforcement to the primary filter 124.

The filter cartridge 112 also includes a secondary filter 128 supported by the inner secondary frame 126. As illustrated in fig. 4, the secondary filter 128 is a flat sheet that is placed on the secondary frame 126. The secondary filter 128 may be formed from, for example, a perforated metal sheet or mesh. The plurality of peaks 129 of the secondary frame 126 support the secondary filter 128 and possibly also the primary filter 124. That is, the secondary frame 126 is angled relative to the secondary filter 128 such that fluid (shown as W) flowing through the secondary filter 128 forces the frames adjacent each peak to move toward each other to bias the peaks 129 toward the secondary filter 128 to support the secondary filter 128, and in a certain embodiment the primary filter 124. As shown in fig. 4, the peaks of the secondary frame 126 may extend substantially perpendicular to the ridges of the primary filter 124.

The secondary filter 128 and the secondary frame 126 cooperate to define an enclosed fluid passage 130. Each fluid passage 130 communicates with a respective outlet into sump 102. Thus, to enter sump 102, fluid must pass through primary filter 124, into enclosed volume V, then through secondary filter 128, into fluid passageway 130, and finally into sump 102. Specifically, fluid enters the filter element 112 through a primary filter 124 located on the side of the filter element, then passes through a secondary filter 128 and flows in a generally longitudinal direction along a flow path 130 and through an outlet into the sump 102.

The filter element 112 allows little debris to pass through, but also imposes a relatively small flow restriction. For example, as the cooling fluid passes through the primary filter 124, a portion of the entrained debris is separated from the cooling fluid. Debris that passes through the primary filter 124 is at least partially separated from the cooling fluid as it passes through the secondary filter 128.

In the design of the filter element 112, very fine filter sizes can be used to achieve high filtration performance while maintaining acceptable head loss due to filtration flow restrictions.

In some examples, the particulate diversion limit is defined in terms of a maximum acceptable amount of diverted material that can reach the core. Such limits may be defined by regulations, operational considerations, or a combination thereof. In some examples, the limit may be as low as a few grams per fuel assembly of the power plant. In other examples, the target split requires 15 grams per fuel assembly for the power plant.

Filtration performance can be significantly improved as the filtration pore size is reduced. Specifically, the amount of diverter material for a fine (e.g., 80 mesh) screen tends to be reduced relative to a coarser filter (e.g., 1/16 "perforations). Unfortunately, fine filters are prone to clogging. For example, the filtered material may build up on the filter element, partially or completely blocking its pores. Plugging due to the thin layer of debris can result in a sharp rise in head loss across the filter.

The debris sheet blockage is related to the debris loading of the fluid passing through the filter (i.e., the amount of debris entrained in the fluid flow). A large amount of debris is more likely to accumulate on the filter and cause clogging. Filter pore size also affects the likelihood of clogging. Filters with smaller pore sizes are generally more likely to clog.

The debris loading in some power generation facilities is such that clogging of fine filters (e.g., 80 mesh screens) with a thin layer of debris is likely to occur.

In some embodiments, the filter element 112 may have a primary filter 124 and a secondary filter 128 with different pore sizes. Specifically, the pore size of the primary filter 124 may be larger than the pore size of the secondary filter 128. Such a configuration may achieve low flow diversion performance associated with fine filters while reducing head loss and reducing the risk of clogging of a thin layer of debris. Generally, the primary filter 124 may be designed to remove larger debris to minimize clogging of the secondary filter 128 so that the secondary filter can maintain the designed bypass requirements.

In a particular example, the primary filter 124 may be formed from a perforated plate, e.g., 1/16 "perforated. The secondary filter 128 may be formed of an 80 mesh metal screen. As fluid is drawn through filter element 112 toward suction inlet 114, the fluid passes through primary filter 124 and secondary filter 128 in sequence. The fluid passes through the primary filter 124 relatively easily, i.e., with relatively little flow restriction. The primary filter 124 removes some debris, particularly large debris, from the fluid, but allows a relatively large amount of debris to pass through. Thus, the amount of fluid-borne debris passing through the secondary filter 128 is less than the amount of fluid-borne debris passing through the primary filter 124. In addition, the debris removed by the secondary filter 128 is often smaller in size than the debris removed by the primary filter 124. In other words, the removal of debris is in two stages. Such two-stage filtration tends to provide some protection against clogging and tends to impose lower head losses relative to a single stage filter having equivalent passage performance.

In another example, fluid passing through the primary filter 124 will deposit debris on the primary filter 124. Debris, such as fibers, may stack and reduce the effective pore size of the primary filter 124 over time, thereby enabling smaller sized debris to accumulate on the primary filter 124.

In other embodiments, the primary filter 124 and the secondary filter 128 may have the same pore size. Two-stage filtration can provide reduced passage of debris compared to a single stage filter of the same pore size. Debris passing through the first filter may be further reduced at the second filter. Thus, passage can be reduced without imposing head losses associated with finer filters.

Furthermore, the arrangement of the filter 112 is particularly space-saving. Specifically, the two filtration stages fit within the periphery of the primary frame 120. Thus, a second stage of filtration is provided without affecting the spacing density of the filter element 112.

As shown in fig. 4, the secondary filter 128 of the filter element 112 is a plate or screen. In some embodiments, the secondary filter may have a three-dimensional structure.

Fig. 5-6 illustrate an example filter element 212, 312 having such a secondary filter 228, 328. The filter elements 212, 312 are substantially similar to the filter element 112. Like parts thereof are denoted by like numerals and will not be described in detail for the sake of simplicity. In some embodiments, the filter elements 212, 312 are interchangeable with the filter element 112.

As shown in fig. 5, the filter element 212 has a plurality of secondary frames 226. Each secondary frame 226 extends longitudinally within the volume enclosed by the filter element 212 and defines a generally cylindrical shape. In the illustrated embodiment, each frame 226 includes one or more stringers 226 a and one or more loops 226 b. As shown, the ring 226 b extends helically. Alternatively, the ring 226 b may be a cylindrical ring. The beam 226 a and the ring 226 b may be attached to each other, for example, using suitable fasteners or by welding. In some embodiments, the frame 226 may include various combinations of beams, rings, or other support structures.

A secondary filter 228 is supported on each secondary frame 226. Specifically, each secondary filter 228 is wrapped around a respective secondary frame 226, defining a cylindrical filtering surface that defines and encloses a respective flow passage 130. The secondary filter 228 may be attached to the secondary frame 226, for example, using suitable fasteners or by welding.

The secondary filter 228 may be formed from a perforated metal sheet or mesh. In some embodiments, the pore size of the secondary filter 228 is smaller than the pore size of the primary filter 124. For example, the primary filter 124 may be an 1/16 "perforated plate, while the secondary filter 228 may be a fine mesh screen, such as an 80 mesh screen. Alternatively, the secondary filter 228 may have the same pore size as the primary filter 224.

The primary filter 124 and the secondary filter 228 may perform two-stage filtration as described above with reference to the filter element 112, and thus may provide a balance between filtration performance (e.g., low particulate passage), flow resistance (e.g., low head loss), and anti-debris sheet clogging.

The total surface area of the secondary filter 228 can be greater than the total surface area of the secondary filter 128 within a cartridge of the same external dimensions.

Accordingly, the configuration of the filter element 212 may provide greater space efficiency. For example, the total filtering surface area of the primary filter 124 and the secondary filter 228 may be increased while still fitting within the periphery of the first frame 120 of the same size.

Increased filter area may provide improved filtration performance, e.g., less debris passing; lower head loss for a given fluid flow; and the anti-debris thin layer is more clogged because the filtered particles may spread over a larger area.

In some applications, a secondary filter that is at least 10% of the primary filter surface area may provide the preferred performance. In other applications, a secondary filter that is at least 20% of the surface area of the primary filter may provide the preferred performance. In other applications, a secondary filter that occupies 25% to 30% of the primary filter surface area may provide the preferred performance. In other applications, a secondary filter having a surface area of at least 5% of the area of the primary filter, or a secondary filter having a surface area greater than 40% of the area of the primary filter, may be suitable.

As previously mentioned, the filter element may be subject to stringent strength specifications. For example, the filter element may need to withstand suction, shock, and seismic events. Thus, the secondary frame 226 reinforces the secondary filter 228. The beam 226 a provides longitudinal strength. The ring 226 b provides radial strength. In addition, the beam 226 a and the ring 226 b reinforce each other.

The filter element 212 may also include one or more reinforcement plates 232 for further supporting the secondary frame 226, the secondary filter 228, and the primary filter 124. The reinforcement plate 232 may be attached to the primary frame 120, for example, using suitable fasteners or by welding. The reinforcement plate 232 has a plurality of openings through which the secondary frame 226 and the secondary filter 228 are received. Alternatively, the secondary frame 226 and secondary filter 228 may be attached to the reinforcement plate 232, such as by welding.

The secondary frame and secondary filter may be configured in other three-dimensional shapes, such as prisms having polygonal cross-sections. For example, fig. 6 illustrates a filter element 312 in which an inner secondary frame 326 and a secondary filter 328 define a diamond-shaped cross-section.

Each secondary frame 326 has one or more stringers 326a and one or more cross beams 326 b. The stringers 326a and cross beams 326 b may be attached to one another, for example, using suitable fasteners or by welding.

A secondary filter 328 is wrapped around each secondary frame 326 to define and enclose a respective flow passage 130. Secondary filter 328 may be formed from a perforated plate or screen. Each secondary filter 328 may be a single unitary piece that is bent to define the desired cross-sectional shape. Alternatively, secondary filter 328 may be formed from multiple pieces.

In some embodiments, the pore size of the secondary filter 328 is smaller than the pore size of the primary filter 124. For example, the primary filter 124 may be an 1/16 "perforated plate, while the secondary filter 328 may be a fine mesh screen, such as 80 mesh. Alternatively, the secondary filter 328 may have the same pore size as the primary filter 224.

The primary filter 124 and the secondary filter 328 may perform two-stage filtration as described above with reference to the filter element 112, and thus may provide a balance between filtration performance (e.g., low debris passage), flow resistance (e.g., low head loss), and anti-debris sheet clogging.

The total surface area of the secondary filter 328 may be greater than the total surface area of the secondary filter 128 within a cartridge of the same external dimensions. In some embodiments, the total surface area of secondary filter 328 may be at least 20% of the surface area of primary filter 124.

Accordingly, the configuration of the filter element 312 may provide greater space efficiency. For example, the total filtering surface area of the primary filter 124 and the secondary filter 328 may be increased while still fitting within the periphery of the same size first frame 120.

Secondary frame 326 reinforces secondary filter 328. The beam 326a provides longitudinal strength. The ring 326 b provides radial strength. In addition, beam 326a and ring 326 b reinforce one another.

The filter element 312 may also include one or more reinforcement plates 332 for further supporting the secondary frame 326 and the secondary filter 328. The reinforcement plate 332 may be attached to the primary frame 120, for example, using suitable fasteners or by spot welding. The reinforcement plate 332 has a plurality of openings through which the secondary frame 326 and the secondary filter 328 are received. Alternatively, secondary frame 326 and secondary filter 328 may be attached to reinforcement plate 332, such as by welding.

The secondary frame and filter having a polygonal cross-section as shown in fig. 6 may be less expensive to manufacture and may have a reduced weight as compared to a similarly sized cylindrical secondary frame and filter as shown in fig. 5. A secondary filter having a polygonal cross-section may also require less support structure than a circular (i.e., cylindrical) shape because the sides of the polygon are flat and may be supported around the edges of each side of the polygon. In contrast, filters having a cylindrical cross-section may require intermediate supports, such as the supports 226 a, 226 b shown in fig. 6, to maintain the cylindrical shape when the filter is in use. However, using a cylindrical secondary filter may result in a larger secondary filter area, e.g., a larger ratio of secondary filter area to primary filter area. Accordingly, in some applications, a cylindrical secondary filter may be used to provide a large secondary filter area, albeit at a slightly higher cost. In other applications, a secondary filter having a polygonal cross-section may be used to reduce cost. In some applications, different shapes of secondary filters may be used in combination.

As described above, filter elements 112, 212, 312 communicate with suction inlet 114 through sump 102. However, in some embodiments, the filter element may be mounted to one or more fluid conduits (e.g., a manifold), and fluid may pass from the filter element through the fluid conduits to suction inlet 114. Fig. 7 illustrates an example of a recirculation inlet system 100 'in which a filter cartridge 112 is mounted on a manifold 102'.

The physical layout of sump 102 and filter assembly 110 described above and shown in the figures is merely an example. It may vary, which may depend on the location of other components in a particular facility.

Although the embodiments have been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereto.

Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

It is to be understood that the detailed description and drawings described above are exemplary only. The invention is defined by the appended claims.