Radial split ring seal for filtration systems

A radial seal is described for use in a filtration system having annular elements. The rings or annuli fit in a groove in an outer surface of a seal plate. Each annulus has an outer diameter larger than the inner diameter of a cylindrical housing of the filtration system. A gap in the annulus has a width selected to enable the annular element to deform sufficiently to permit insertion of the at least one annulus into the cylindrical housing. Two or more annuli can be configured such that the gaps of the annuli are misaligned when both annuli are installed in the groove, thereby minimizing leakage in operation. A registration system includes a registration element that cooperates with a registration element of the other annulus to ensure misalignment of the gaps of the pair of annuli.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to membrane filtration systems and more particularly to seals used in spiral membrane elements of filtration systems.

2. Description of Related Art

Certain types of filtration systems used for removing chemical contaminants and organisms from water comprise one or more filtration elements that are sealed within an enclosure. The enclosure may comprise a canister, a drum and/or a pipe. In particular, filtration systems used for large-scale water treatment can include a series of elements that connect together within a pipe like structure and which direct an inflow of contaminated or impure water through a filter material and onto an outflow pipe or channel. In the example shown inFIG. 1, filtration element11in a spiral membrane filtration system comprises a membrane structure that is wound in a spiral. InFIG. 1, permeate carrier sheet18is laminated within an envelope of a membrane filtration sheet19and adjacent layers are separated by feed spacers101and typically enclosed within a hard shell or wrapping to prevent leakage of the inflow and to provide a degree of mechanical stability and strength to filtration element11. Filtration elements, such as spiral membrane filtration element11, are typically provided in a substantially cylindrical form and one or more filtration elements11can be installed end-on-end within a housing10(as shown inFIG. 1C). An inflow fluid140is introduced through an inlet under pressure into an end of the system, and enters filtration element11at one end140and, having passed through membrane19, exits either as a permeate stream143, typically through a center pipe or channel13, or as a concentrate stream144which exits from the membrane filtration device. The center pipe13is typically coaxial with the enclosure10and coupled or otherwise connected with the membrane19in a manner that permits collection of the permeate143. Permeate143can be drawn from the system in either direction.

These filtration elements function as membrane filters. Unlike conventional batch mode filtration systems, the described filtration system operates as continuous steady state process. As such the total of all material entering in the feed stream15is substantially equal to the summation of all material leaving the filtration device in the two exit streams143and144. Such systems may be used in applications that deliver drinking water, clean or treat wastewater and/or storm water, extract water from sludge, and/or desalinate water such as sea water; in these applications, the dilute permeate stream143is the principal product of the system. Conversely the concentrate stream144may provide the principal product where the objective is to recover or concentrate a valuable solute.

Spiral membrane elements11are used as a means of packaging flat sheet, reverse osmosis membrane19in useful separation applications. These elements are typically loaded end to end in a cylindrical housing10as shown inFIG. 1C. Process feed flow140is introduced at one end of the housing and flows axially141through the element11, with some portion142passing through the filter medium19to a center collection channel or pipe system13from which it is provided as an outflow143. The concentrated remnant144is drawn from a first element11into a second element11and so on. Concentrate144extracted from the system can be processed externally and/or recycled through the system based on system configuration and function. It is necessary to provide a sealing mechanism between successive spiral elements11that insures concentrate stream144from the first element11is passed as a feed stream140to the subsequent spiral membrane filtration element11.

This sealing mechanism can be accomplished using seal plates12(shown in more detail inFIG. 1B) that are attached to each end of each spiral element11. In conventional systems, elastomeric seals are placed in a groove16located on an external edge of seal plate12, in order to prevent escape of fluid into a space between element11and housing or vessel10. Couplings130connect successive center channels13are typically also sealed using elastomeric seals.

An additional seal120may be required between the spiral element11and the inner wall of the cylindrical housing10to direct the flow140into the element11itself rather than the annular space between the element11and the housing10. If the flow140were not directed primarily into the element structure the velocity of the feed flow over the membrane sheet would be reduced which would impact the separation performance of the membrane sheet. Conventional systems provide an elastomeric seal in a circumferential grooved depression16located on the outer surface of a seal plate12as shown in sectionalFIG. 2A. A commonly used elastomeric seal24is shaped in a cup form as shown inFIG. 2Bwhich creates an effective seal but requires that the element be inserted into the housing in one direction as the seal cannot be pushed a reverse direction. A symmetrical elastomeric seal such as an 0-ring26could be used within the element seal late groove as sown inFIG. 2C. This permits movement in either direction but relies on a greater amount of deformation of elastomeric seal in order to function as an effective seal. This results in greater force needed to insert the element into the cylindrical housing and is the principal reason for the preference for the cupped shaped elastomeric seal.

BRIEF SUMMARY OF THE INVENTION

A radial seal for a filtration system comprises one or more annulus having an outer circumference and an inner circumference and a thickness. Each annulus may have a diameter of the inner circumference that fits in a groove in an outer surface of a seal plate and each annulus has a diameter of the outer circumference selected to be larger than the diameter of an inner surface of a cylindrical housing that receives the seal plate. A gap in the annulus of the ring centered along a radius of the at least one annulus has a width selected to enable the annular element to deform sufficiently to permit insertion of the at least one annulus into the cylindrical housing.

The inner and outer diameters of the annuli and the width of the gap may be selected to obtain a tight fit between the outer circumference of the at least one annulus and the inner surface of the cylindrical housing. The tight fit is maintained by a restoring force reactive to compression of the annular element, the magnitude of the restoring force being related to the width of the gap and the materials used to fabricate the at least one annulus. The width of the gap can be selected to permit a controlled degree of leakage when an annulus is installed in the groove and the seal plate is inserted in the cylindrical housing.

In some embodiments, the seal comprises two or more annuli configured such that the gaps of the annuli are misaligned when the annuli are installed in the groove, thereby minimizing leakage in operation. A registration system includes a registration element that cooperates with a registration element of the other annulus to ensure misalignment of the gaps of the pair of annuli. The registration system can comprise a raised element provided on a surface of one of pair of annuli that fits in the gap of an adjacent annulus and/or a raised element provided on a surface of one of pair of annuli that fits in a groove provided on a surface of an adjacent annulus.

Methods for sealing a spiral membrane element inserted into a cylindrical housing of a filtration system are provided. A method according to certain aspects of the invention includes steps of providing at least one split ring seal in a groove located on an outer surface of a seal plate of the spiral membrane element, inserting the seal ring into the cylindrical housing, including inserting the seal ring includes a step of compressing the at least one split ring seal.

DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the invention provide a seal element for filtration systems. The presently disclosed seal can be constructed with dimensions that allow it to serve as a substitute for conventional elastomeric seals, including 0-ring, chevron and U cup seals and the like. With reference again toFIGS. 1A-1C, certain embodiments of the invention comprise a split-ring seal that may be fitted to a conventional seal plate12, in a radial groove16that would otherwise receive a compressible elastomeric seal. As will be described in more detail below, the presently disclosed split ring seal is typically constructed using materials selected for rigidity, elasticity, inertness, ability to withstand operational temperature ranges, ability to withstand operational pressures and coefficient of friction with materials used in construction of a filtration system (e.g. inner surface of housing10). Materials can be selected according to the application and, for example, seals constructed according to certain aspects of the invention can be used in 8-inch or 16-inch filtration systems in which conventional elastomeric seals are unable to withstand the water pressures involved.

In one example described herein, an annular seal30(seeFIGS. 3A and 3B), formed from a substantially non-compressible polymer, can be placed in a groove16of an outer surface of a seal plate12. The seal30has a gap32in its annulus and the annular shape can be deformed under pressure by applying a force that closes gap32. Such force is applied when seal plate12, with seal30installed, is inserted into a housing10. Seal30acts as a spring, causing an outer surface of ring30to create a tight interface with an inner surface of the housing10. Some portion of gap32in ring seal30may remain open when seal plate12is located within housing10. In some embodiments, such gap is desirable because, if sized appropriately, gap32can limit and/or equalize pressure differences on either side of seal30. In certain embodiments however, a more watertight seal is desired and a second split-ring seal30may be placed in groove16such that the gaps32in seals30are offset. Other variations on the latter theme will be described in more detail herein.

FIGS. 3A-3Band4A-4B relate to a simple example of a seal according to certain aspects of the invention. The annular seal ofFIGS. 3A-3Band4A-4B can be fitted to an outer portion40of a seal plate12and/or can be used to create a seal between concentric elements, typically between substantially cylindrical surfaces of the elements. Seal30can be used as a replacement for conventional elastomeric seals. For example, the dimensions of rigid ring30can be configured to permit ring30to replace conventional 0-ring or U-cup seals commonly installed in radial grooves16in seal plates12of spiral membrane filtration elements. Width38of the ring seal30may be selected to permit a desired number of seals30to be placed in groove16of existing seal plates12.FIG. 4Ashows an embodiment in which a single seal420is disposed in groove42, whileFIG. 4Brelates to an embodiment in which two rings421and422are provided within groove42. Split ring seal30can also be used in more demanding applications where, for example, the seal30will be subjected to high temperatures and/or high pressures, or where the presence of caustic agents requires the use of a non-reactive sealing material. In one example, pressures within a spiral membrane filtration system may preclude the use of certain conventional elastomeric seals. Elastomeric seals commonly used in four-inch diameter spiral membrane systems typically cannot be scaled to operate in 8-inch or 16-inch systems because of the increase operational pressures and because of the increased difficulty of installation and removal of sealed elements caused by exponentially increased frictional forces attributable to the increase in contact area of the conventional elastomeric seal with a housing10.

Certain embodiments of the invention comprise a rigid split-ring seal30suitable for use in filtration systems. Seal plates12are generally circular in shape, somewhat resembling a wheel, and are configured for insertion into a cylindrical housing10. A portion40of seal plate12has an externally, facing radial surface46proximate to, and interfacing with an inner surface of enclosure44. Currently-produced seal plates40typically include a groove42in externally-facing surface46of seal plate40. A rigid ring30,420-422constructed according to certain aspects of the invention may be installed in such seal plate groove42. Prior to insertion, the rigid ring30can typically be rotated in either direction about the axis14of the seal plate12(see FIGS.1A-1C) and gap32can be oriented and/or aligned with a feature of the seal plate12or housing10, as desired. The seal plate12with seal30may be inserted into either end of a cylindrical housing10and can be moved along the axis of the cylindrical housing10in either direction. It will be appreciated that seal30may have a coating or other surface treatment that provides a desired coefficient of friction. Seal30can be configured to fit a seal plate12that has a non-circular shape and some seals30may be used with different shaped seal plates including, for example, circular and oval seal plates, or a somewhat asymmetrical seal plate. In one example, seal30may be installed in a groove16on a declining radius surface (not shown) and seal ring30may have a cross-section that follows the shape of a surface of the seal plate12and/or the housing10.

Seal ring30is typically constructed from a non-elastomeric material that substantially maintains its cross-sectional shape (e.g.FIG. 3B) under pressure and when a compression force as radially applied to the annulus30. Under compression, gap32in seal ring30is reduced when a radial compression force is applied to the seal ring and seal ring30is typically configured and constructed with sufficient elasticity to resist closure of gap32and to restore its original at-rest annular shape when compression forces are removed. For example, hard and/or hardened polymers, metals, ceramics and other such materials can be used to construct seal ring30. It will be appreciated that conventional elastomeric seals maximize sealing capabilities by deforming under compression such that the cross-sectional area of the elastomeric seal changes. However, the deformation of conventional elastomeric seals under pressure can limit motion of the seal plate12and seal assembly within housing10to a single direction. Cross section20of seal plate12is shown inFIG. 2A-2C. Deformation of a conventional elastomeric cup seal24(seeFIG. 2B) during insertion typically creates very high resistance to movement in a reverse direction because of the orientation of the U cup legs. The force required to overcome the resistance of conventional elastomeric seals is often insurmountable without causing destruction of these seals. Therefore, a filtration element11in an assembled multi-element filtration system (seeFIGS. 1A-1C), when fitted with conventional cup seals24and inserted into a housing10in one direction, can be practicably removed only by forcing the elements completely through the housing in the same direction as used for insertion. Deformation of an O-ring seal26typically increases the surface area of seal26in contact with the enclosure10. Therefore, an assembled multi-element structure (seeFIGS. 1A-1C), when fitted with 0-ring seals26and inserted into a housing, require significant force to insert and remove the elements into the housing.

In contrast, annular seals30constructed according to certain aspects of the invention typically do not restrict motion in any direction parallel to axis14of seal plate12. Furthermore, seal30can be constructed from a low-friction material and/or the surfaces of seal30can be coated or treated in order to reduce frictional forces experienced during insertion and removal of the element. Consequently, a multi-element component may be inserted and extracted with greater ease through the same end of a housing when rigid ring seals30according to certain aspects of the invention are used. Moreover, rigid seal rings30according to certain aspects of the invention resist deformation under axial pressure from either direction. Accordingly, filtration elements employing the split ring seals30disclosed herein can receive and resist bidirectional flows, including reverse flows provided for flushing, cleaning and for other reasons. Conventional seals, including U-cup and chevron seals (seeFIG. 2B) often cannot resist reverse flows and must be replaced or reoriented for flushing.

Seal plates10that use conventional elastomeric seals require significantly greater force for insertion of the seal plate because of the deformation of the seal material required to form a seal, the angle of engagement of the elastomeric seal, the significant contact pressure required to maintain a seal using elastomeric seals and/or increased contact area of the elastomeric seals. In one example, a seven element component equipped with conventional seal U-cup brine seals24(with lubrication) can require the equivalent of 45 pounds of force or more to insert the elements into a housing. It can be shown that an equivalent seven element component fitted with the presently disclosed rigid ring seals30can be inserted into a housing using 20 pounds or less of force.

In certain embodiments, dimensions of rigid ring30are selected to obtain an efficient seal. The outer diameter34of rigid ring30is typically selected to be slightly larger than the internal diameter of the cylindrical housing10, while inner diameter36of the annulus30is selected to provide a good fit within the groove42of seal plate40. Thickness38of annulus30may be selected according to application and to fit a desired number of ring seals30in the groove42to obtain a desired level of tightness of seal. In certain embodiments, more than one ring seal421and422can be provided in groove42for sealing seal plate40. Multiple ring configurations (FIG. 4B) may be used with gaps in rings421and422offset from one another to minimize leakage through the seal structure. Multiple ring configurations (FIG. 4B) may be used such that rings421and422have different thicknesses. In some embodiments, multiple ring configurations comprise different rings421and422manufactured from different materials.

As seen inFIG. 3, a small portion is removed from the annulus ring30to leave a gap32in the annulus30. Gap32in rigid split ring30tends to close when the ring30is compressed to enable insertion into the cylindrical housing10. The size and shape of the gap32can be selected to allow the ring to minimize the gap32when the ring is compressed to fit into the cylindrical housing10. Factors affecting the selection of the size of gap32include specified or expected operational temperature swings and coefficients of expansion of materials used to construct the ring30. Typically, the cross-section300of ring30does not deform significantly under compression and the force of compression is accommodated by a change in diameter of the ring30. It is contemplated that, in certain embodiments, it can be desirable to have at least one ring420,421or422constructed from materials that include a portion of a deformable material where, for example, it is necessary to accommodate shrinkage and expansion under temperature or pressure and a softer, more deformable ring421or422can be coupled with a stronger, more rigid ring422or421to provide a combination of pressure resistance and malleability under operational conditions.

Compression of the rigid ring30creates a reactive radial force that causes the ring30to maintain contact of the ring with the outer wall of the cylindrical housing10, thereby creating a seal. This reactive force can create a resistive drag force that resists movement of the seal plate along the axis of the cylindrical housing10. The amount of reactive force can be controlled by selection of the materials used to construct the rigid ring and by dimensioning the rigid ring. For example, the thickness of the ring30and the outer34and inner36diameters of the annulus30can be selected to obtain a desired reactive force. The reactive force and resistivity of material of ring30may be selected to permit a certain amount of movement of seal and/or seal plate in order to adjust to expansion and/or compression, of cylindrical housing10or the sealed spiral element.

Gap Profiles

The profile of gap32may be selected to control flow of fluids past the ring seal30. Leakage through ring seal30typically results in a portion of the unfiltered or contaminated inflow fluid (process feed) passing through the space between successive filtration elements11and the system housing10. Some systems comprise a radial seal installed only on the seal plate12of the first filtration element11in a series of filtration elements in order to direct the inflow through the filtration elements11. Downstream seal plates12of adjacent filtration elements prevent leakage from the filtration elements11into the space between filtration elements11and the system housing10. Unfiltered fluid in the space can be removed and recycled through the system as desired. It can be desirable to allow a degree of leakage through the radial seal30into the space to reduce stress on wrapping or shell of the filtration elements caused by a difference in pressure between the space and the interior of the filtration elements11. Therefore, the profile of gap32may be selected to obtain and control a level of leakage that operates to equalize pressure within the system.

As shown inFIG. 5A, some embodiments provide a square gap50in annulus30. The shape of square gap50is obtained by providing squared ends500and501of annulus30. Square gap50is aligned with a direction of flow (illustrated as arrowed line58) of fluids through a filtration system. It will be appreciated that the square gap is also perpendicular to the radius of the seal plate and parallel to an axis14(FIGS. 1A-1C) of the seal plate12.FIG. 5Billustrates an angled gap52in which the ends520and521of annulus30are cut at an angle selected to provide an overlap of the ends. The angle of cut used for ends520and521may be selected to accommodate the expected level of expansion/compression of seal ring30under operational temperature ranges.FIG. 5Cshows a simplified compound gap54. Annulus30has overlapping step-shaped ends540and541that are typically configured to provide an overlap regardless of whether the annulus30is under compression or at rest. Accordingly, compound gap54provides at least two gaps542and544that are offset along the circumference of annulus30. Gaps542and544may be connected by a channel543. Under typical operating pressures, gap provided by channel543is typically negligible, because ends540and541are typically forced into contact and consequently the width of channel543may be defined by the texture and planarity of the surfaces of ends540and541and the presence of discontinuities, grease, dirt or other particles on those surfaces. Accordingly, a configuration such as those shown inFIGS. 5B-5Dmay be referred to as discontinuities in the annulus because a gap may be effectively closed in these configurations under operating conditions.FIG. 6, which will be described in more detail below, depicts an embodiment of the invention comprising an annular seal60with a compound gap/discontinuity62in the shape of a step. As discussed below, the performance of annular seal60has been shown to meet or surpass the performance of an equivalent elastomeric seal under the same conditions.FIG. 5Dshows a dual ring seal configuration56that can be used to minimize leakage. As shown, the annular seals of the dual ring configuration56have angular gaps52, but square gap50and step gap54profiles can also be used as desired or required by the application.

From the perspective of process feed flow, gap50,52or54presents a discontinuity in a seal ring30that can give rise to leakage, allowing process feed to flow “through” the seal ring30. Accordingly, certain embodiments of the invention employ a plurality of seal rings46, as shown inFIG. 4B(see alsoFIG. 5D), which are assembled to obtain a more complete seal. Various schemes for overlapping the seal ring may be used to ensure that gap size is minimized and/or maximizes resistance to flow of the process feed. For example, seal rings421and422may be angularly offset to eliminate or minimize respective gaps32in the seal rings421and422. Offset in a multiple ring seal configuration may be maintained using registration elements such as a protrusion in a first seal ring421that mates with corresponding indentations in an adjacent seal ring422. Other registration elements may engage with gaps32in the seal rings421and422. In certain embodiments, an offset in the relative locations of gaps32in seal rings421and422may be maintained by permanently or temporarily bonding seal rings421and422.

FIG. 6depicts an embodiment of the present invention that can be configured for use in spiral membrane filtration systems. A substantially rigid annular seal60is fabricated from a hard polymer selected to withstand temperatures and pressures associated with filtration systems having 4, 8 or 16 inch filtration elements. The annulus600of seal60has a discontinuity62formed at the intersection of two overlapping step-shaped ends64and65of annulus600, as depicted in detail63. Before compression of annular seal60, the steps of ends64and65partially overlap, leaving gaps66and67in surfaces (only surface630shown) on opposite sides of annulus61. The distance of overlap68is selected to minimize leakage while maintain mechanical strength of annulus61. Upon compression, gaps66and67tend to close, allowing the diameter of annular seal60to be reduced. For the purposes of this discussion, each end64and65is shown to have a single step. However, certain embodiments of the invention comprise an annulus that has multi-stepped ends64and65. Annular seal60can be placed in a groove16in a seal plate12prior to insertion of the seal plate12into a housing10. The step shaped discontinuity62in annular seal60allows reconfiguration of the annular geometry measurable as changes in radius and circumference of annular seal60when the annular seal60is compressed after the seal plate12is inserted into the housing. In certain embodiments, step profile discontinuity62may have a channel between gaps66and67prior to operation. When seal ring60is fitted to an groove16of a seal plate10and inserted within a housing10, one or both of gaps66and67are reduced in size and when pressurized fluid flows through the filtration element, steps of ends64and65are pressed together closing any channel, with a net impact of improved sealing when under pressure.

With reference also toFIGS. 7A and 7B, certain embodiments comprise an offset step gap configuration, where each side of the gap has a compound and/or complex stepped configuration as shown generally at70. Step configuration70can be constructed using two identical annular seals72and73that have a step gap54(seeFIG. 5C). One of the two annular rings72flipped relative to the other seal ring73and the step gaps54are aligned.FIG. 7Billustrates one side72and73of each annular seal step gap54in detail. If not a single molded piece, the two annular seals can be bonded or glued to obtain the complex step configuration70. As depicted, two different vertical risers74and75are used in the step. Accordingly, when flipped and bonded, overlaps are provided within the gap and a tortuous path is presented to fluid attempting to flow through the gap. This tortuous path can significantly reduce leakage through the gap. In some embodiments, an annular seal having the complex step gap ofFIG. 7Acan be provided in a molded ring or by machining and/or cutting a single ring71formed by extrusion, stamping or by other suitable means known to those with skill in the art.

FIG. 7Cdepicts, generally at76, a variation of the stepped configuration by providing a step in both radial and axial directions. In the depicted example, one end761has a post78that is configured to fit a mating indentation or tunnel77in a second end760Typically, the post78rests within tunnel77andFIG. 7Cshows ends760and761in a pulled-apart configuration. It will be appreciated that such “post-and-hole” and/or “pin-and-hole” configuration may provide improved axial and radial strength to the split ring seal, but may be susceptible to greater leakage or bypass flow.

In certain embodiments, a degree of bypass flow may be desirable to relieve and/or equalize pressure, particularly during system startup. It will be appreciated that certain conventional spiral elements are supplied with weep/bleed holes or grooves located within seal plate to create a controlled amount of flow past the conventional elastomeric seals. It will be appreciated that certain aspects of the invention remove the need for such holes and grooves because the described novel seals can be structured to obtained a desired degree of leakage within the seal itself. For this purpose the separation performance of the membrane element is used as the primary criterion. Therefore if two radial seals give substantially the same separation performance the amount of bypass flow can be assumed to be insignificant.

A plurality of seal rings may be mounted in the same groove42to minimize or eliminate leakage. Multiple split ring seals46can be included within the grooved depression42of the seal plate40as shown in detail inFIG. 4B, in which two adjacent rings46reside within the groove42of the seal plate40. As shown inFIG. 5D, the gaps54and56of adjacent rings can be oriented in opposite directions. The combination of multiple rings30and the design of gap overlap can provide an effective measure of control over amount of flow that can pass through combinations of ring gaps32. Overlap can be maintained using registration methods that serve to lock two or more rings30with respect to one another and/or with respect to the groove42of the seal plate40. Registration may be used to ensure that gaps42do not line up through the depth of the entire seal. Registration may be maintained using hydrodynamic surfaces, pins and holes, bumps and dents, friction, slots, grooves and other such methods. In one example, a raised surface, pin or tab may be provided on a surface of one ring that can engage the gap of a neighboring ring such that the gaps of the two rings are misaligned and have no overlap.

Additional Descriptions of Certain Aspects of the Invention

The foregoing descriptions of the invention are intended to be illustrative and not limiting. For example, those skilled in the art will appreciate that the invention can be practiced with various combinations of the functionalities and capabilities described above, and can include fewer or additional components than described above. Certain additional aspects and features of the invention are further set forth below, and can be obtained using the functionalities and components described in more detail above, as will be appreciated by those skilled in the art after being taught by this disclosure.

Certain embodiments of the invention provide a radial seal for a filtration system. Some of these embodiments comprise one or more annulus having an outer circumference and an inner circumference and a thickness. In some of these embodiments, each annulus has a diameter of the inner circumference selected to fit in a groove in an outer surface of a seal plate. In some of these embodiments, each annulus has a diameter of the outer circumference selected to be larger than the diameter of an inner surface of a cylindrical housing that receives the seal plate. In some of these embodiments, each annulus has a gap in the annulus of the ring centered along a radius of the at least one annulus. In some of these embodiments, this gap has a width selected to enable the annular element to deform sufficiently to permit insertion of the at least one annulus into the cylindrical housing.

In some of these embodiments, the inner and outer diameters of the annuli and the width of the gap are selected to obtain a tight fit between the outer circumference of the at least one annulus and the inner surface of the cylindrical housing. In some of these embodiments, a tight fit is maintained by a restoring force reactive to compression of the annular element. In some of these embodiments, the magnitude of the restoring force is related to the width of the gap and the materials used to fabricate the at least one annulus. In some of these embodiments, the width of the gap is selected to permit a maximum degree of leakage when an annulus is installed in the groove and the seal plate is inserted in the cylindrical housing.

In some of these embodiments, the seal comprises two or more annuli. In some of these embodiments, the annuli are configured such that the gaps of the annuli are misaligned when the annuli are installed in the groove, thereby minimizing leakage in operation. Some of these embodiments comprise a registration system. In some of these embodiments, each annulus in a pair of adjacent annuli includes a registration element that cooperates with a registration element of the other annulus to ensure misalignment of the gaps of the pair of annuli. In some of these embodiments, the registration system comprises a raised element provided on a surface of one of pair of annuli that fits in the gap of an adjacent annulus. In some of these embodiments, the registration system comprises a raised element provided on a surface of one of pair of annuli that fits in a groove provided on a surface of an adjacent annulus. In some of these embodiments, an annulus is fabricated from a metal. In some of these embodiments, at least one annulus is fabricated from a polymer.

Certain embodiments of the invention provide systems and methods for sealing a spiral membrane element inserted into a cylindrical housing of a filtration system. Some of these embodiments comprise a step of providing at least one split ring seal in a groove located on an outer surface of a seal plate of the spiral membrane element. In some of these embodiments, the split ring seal has an outer diameter exceeding the diameter of an inner surface of the cylindrical housing. Some of these embodiments comprise the step of inserting the seal ring into the cylindrical housing. In some of these embodiments, inserting the seal ring includes a step of compressing the at least one split ring seal.

In some of these embodiments, a gap in the split ring has a width selected to enable the annular element to deform in response to the compressing step sufficient to enable the at least one split ring seal to fit within the cylindrical housing. In some of these embodiments, the width of the gap is selected to permit a maximum degree of leakage when the at least one annulus is installed in the groove and the seal plate is inserted in the cylindrical housing. In some of these embodiments, the at least one split ring seal comprises a plurality of split ring seals. Some of these embodiments comprise the step of aligning each of the plurality of split ring seals to avoid an overlap of gaps of adjacent split rings, thereby minimizing leakage in operation. In some of these embodiments, the step of aligning includes using registration elements provided on each split ring seal to configure the alignment of adjacent pairs of spilt ring seals. In some of these embodiments, the registration elements include one or more of a groove, a pin, a hole and a slot.

Certain embodiments of the invention provide a split-ring seal for maintaining a seal between a filtration element and a housing of a filtration system. Certain of these embodiments comprise a rigid annulus having a discontinuity therein. In certain embodiments, the annulus has an inner diameter selected to allow the annulus to fit a groove provided in an outer surface of the filtration element. In certain embodiments, the annulus has an outer diameter is selected to be larger than the diameter of an inner surface of the housing. In certain embodiments, the discontinuity accommodates a reduction of inner and outer diameters of the annulus in response to a compressive force received during insertion of the filtration element into the housing. In certain embodiments, the annulus is configured to resist changes in its cross-sectional profile in response to the compressive force. In certain embodiments, the discontinuity comprises a step shaped channel in the annulus wherein the step shaped channel is substantially closed under pressure of an axial flow of fluid through the filtration system. In certain embodiments, the discontinuity is formed by the overlap of two step shaped ends formed in the annulus. In certain embodiments, the annulus is configured to maintain the seal between the filtration element and the housing and to resist an axial flow of fluid through the filtration system regardless of direction of the axial flow. In certain embodiments, the seal operates to resist bypass of a fluid around the filtration element and into a space between the filtration element and the housing during filtration. In certain embodiments, the seal operates to resist bypass of a flushing fluid around the filtration element and into the space between the filtration element and the housing during cleaning.

Certain embodiments of the invention comprise a seal ring having some combination of the above-described elements. The seal ring may be deployed within a filtration element in a filtration system used to filter and/or treat water, waste water, storm water, potable and non-potable water, and juices. Filtration system may comprise a spiral membrane filtration system, a reverse osmosis system for home or commercial use and or other filtration system that houses a filtration element in a pipe, canister, or other vessel or conduit. In some embodiments, the filtration system may be used for filtering and treating other fluids in chemical and industrial applications.

Although the present invention has been described with reference to specific exemplary embodiments, it will be evident to one of ordinary skill in the art that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.