FLUID TREATMENT ARRANGEMENT

Abstract: A fluid treatment arrangement includes a tube sheet (30) and a plurality of fluid treatment elements (60) sealed to the tube sheet (30). The fluid treatment arrangement is designed so that the fluid treatment elements (60) can be easily unsealed and removed from the tube sheet (30). According to one form of the invention, the arrangement includes an ejector mechanism (90) movable with respect to the tube sheet (30) into and out of contact with the fluid treatment elements (60). When the ejector mechanism (90) contacts the fluid treatment elements (60), it exerts an axial force on the fluid treatment elements to produce relative movement between the fluid treatment elements (60) and the tube sheet (30) by a sufficient distance to unseal the fluid treatment elements (60) from the tube sheet (30), making it easy to remove the fluid treatment elements from the tube sheet. In preferred embodiments, the fluid treatment elements comprise filter elements.

Description: FLUID TREATMENT ARRANGEMENT Background of the Invention 1. Field of the Invention This invention relates to a fluid treatment arrangement having a plurality of fluid treatment elements. In particular, but not exclusively, it relates to a filter arrangement having a plurality of filter elements which can be readily detached from a tube sheet. 2. Description of the Related Art Many fluid treatment arrangements include a plurality of fluid treatment elements, such as filter elements, disposed in a housing. Frequently, the fluid treatment elements are mounted on a plate, referred to as a tube sheet, which partitions the interior of the housing into an inlet chamber containing fluid which has yet to be treated and an outlet chamber containing fluid which has passed through the fluid treatment elements. The number of fluid treatment elements in a fluid treatment arrangement may be quite large, and it is not unusual to have hundreds of fluid treatment elements mounted on a single tube sheet. Therefore, it is highly desirable to be able to rapidly detach the fluid treatment elements from the tube sheet to minimize the time required to replace all of the elements. This is particularly the case when the fluid treatment elements have been used to treat hazardous materials. Since some of the materials may remain in the fluid treatment elements being replaced, it is desirable to minimize the exposure time of workers performing the replacement. Summary of the Invention The present invention provides a fluid treatment arrangement having fluid treatment elements which can be easily and quickly replaced. The present invention also provides a tube sheet for use with a fluid treatment arrangement. The present invention also provides a method of removing fluid treatment elements from a tube sheet in a fluid treatment arrangement. According to one form of the present invention, a fluid treatment arrangement comprises a tube sheet and a plurality of fluid treatment elements, each sealed to the tube sheet. The tube sheet supports the fluid treatment elements such that the distances of the lower ends of the fluid treatment elements vary among the fluid treatment elements. According to another form of the present invention, a fluid treatment arrangement comprises a tube sheet for supporting a plurality of fluid treatment elements and an ejector mechanism for unsealing the upper ends of fluid treatment elements from the tube sheet. In a preferred embodiment, the ejector mechanism includes an ejector plate spaced from the tube sheet and movable toward and away from the tube sheet and a plurality of projections mounted on the ejector plate for engagement with the lower ends of fluid treatment elements supported by the tube sheet. When the fluid treatment elements are brought into contact with the projections and the tube sheet is moved toward the ejector plate, the projections can exert an axial force on the fluid treatment elements to produce relative movement between the fluid treatment elements and the tube sheet by a sufficient distance to unseal the fluid treatment elements from the tube sheet. According to another form of the present invention, a tube sheet for a fluid treatment arrangement comprises a plate having first and second surfaces and an outer periphery shaped for sealing to a housing. A plurality of holes extend between the first and second surfaces of the plate, with each hole having a ledge formed therein for supporting a fluid treatment element. The depth of the ledges from the first side of the tube sheet varies among the holes. With this structure, a plurality of fluid treatment elements can be supported by the tube sheet with the ends of the fluid treatment elements at varying distances from the tube sheet, making it easy to unseal and remove the fluid treatment elements from the tube sheet. A method of removing fluid treatment elements from a tube sheet according to one form of the present invention includes placing a plurality of fluid treatment elements having upper ends sealed to a tube sheet on a support surface with lower ends of the fluid treatment elements contacting the surface to cause relative movement between the upper ends of the fluid treatment elements and the tube sheet by a sufficient amount to unseal the upper ends from the tube sheet. The fluid treatment elements are then removed from the tube sheet. The fluid treatment elements may contact the surface at different times so that the upper ends of the fluid treatment elements are unsealed from the tube sheet at different times rather than simultaneously. The support surface against which the fluid treatment elements are contacted need not be of any particular structure. For example, it may be the ground, a floor, or a raised support member such as a frame or a base. According to yet another form of the present invention, a method of removing fluid treatment elements from a tube sheet comprises supporting a plurality of fluid treatment elements having first and second ends with a tube sheet sealed to the first ends. The second ends of the fluid treatment elements are made to contact a plurality of projections to produce relative movement between the first ends of the fluid treatment elements and the tube sheet by a sufficient amount to unseal the first ends from the tube sheet, after which the fluid treatment elements are removed from the tube sheet. The fluid treatment elements need not be of any one type or for any one function. For example, the fluid treatment elements can perform filtration, coalescing, or other types of fluid treatment. In preferred embodiments of the present invention, the fluid treatment elements comprise filter elements for filtering fluids, and the fluid treatment arrangement comprises a filter arrangement capable of employing filter elements. The fluid to be treated by the fluid treatment arrangement is also not restricted to any particular type and may be a liquid, a gas, or a mixture of several different phases, for example. Brief Description of the Drawings Figure 1 is a cross-sectional elevation of an embodiment of a fluid treatment arrangement according to the present invention in the form of a filter arrangement. Figure 2 is a cross-sectional elevation of the filter assembly of the filter arrangement of Figure 1. Figure 3 is an enlarged cross-sectional view of a portion of a tube sheet of the filter assembly of Figure 2. Figure 4 is an enlarged plan view of one of the filter elements of the filter assembly of Figure 2. Figure 5 is a bottom view of the retaining plate of the filter assembly of Figure 2. Figure 6 is a cross-sectional elevation of the filter assembly disposed on a support surface when the filter elements are being detached from the tube sheet. Figure 7 is a cross-sectional elevation of one half of another embodiment of a filter assembly in which the heights of the upper ends of the filter elements are staggered. Figure 8 is an enlarged cross-sectional view of the circled region in Figure 7. Figure 9 is a cross-sectional elevation of the other half of the embodiment of Figure 7 when placed on a support surface in order to detach the filter elements from the tube sheet. Figure 10 is a cross-sectional elevation of the lower portion of another embodiment of a filter assembly according to the present invention in which the lower ends of the filter elements are retained by individual retaining members. Figure 11 is a cross-sectional elevation of the lower end of another embodiment of a filter assembly in which the lower ends of the filter elements can directly contact a surface on which the assembly is supported when the filter elements are being detached from a tube sheet of the filter assembly. Figure 12 is a cross-sectional elevation of the lower end of another embodiment of a filter assembly in which the filter elements are detached from a tube sheet by placing the filter assembly on a surface with height variations. Figure 13 is a partially cross-sectional elevation of another embodiment of a filter assembly according to the present invention partially withdrawn from a housing. Figure 14 illustrates the filter assembly of Figure 13 with the filter elements of the filter assembly unsealed from a tube sheet. Figure 15 is a plan view of an ejector plate of the embodiment of Figure 13. Figures 16 is a partially cross-sectional elevation showing the manner in which one of the legs of the filter assembly of Figure 13 is connected to the tube sheet and an ejector mechanism. Figure 17 is an end view of a lifting beam for use in lifting the filter assembly of Figure 13. Figures 18 and 19 are a side elevation and a front elevation, respectively, of a portion of one of the legs of the filter assembly of Figure 13. Figure 20 is a horizontal cross-sectional view taken along line 20-20 of Figure 18. Figure 21 is an enlarged cross-sectional elevation of a portion of the filter assembly of Figure 13 as it would appear during filtering operation. Figure 22 is an enlarged cross-sectional elevation of the portion shown in Figure 21 when the legs of the filter assembly are in a raised state with respect to the tube sheet. Figure 23 is a cross-sectional elevation of a portion of another embodiment of a filter assembly according to the present invention having legs slidably connected to a tube sheet by pins. Description of Preferred Embodiments Figure 1 is a cross-sectional elevation of an embodiment of a fluid treatment arrangement according to the present invention. The illustrated embodiment is a filter arrangement for filtering fluids, although as stated above, a fluid treatment arrangement according to the present invention may be used for performing fluid treatment other than filtration. The illustrated filter arrangement includes a housing 10 and a filter assembly 20 removably disposed in the housing 10 and including a plurality of filter elements 60 for filtering a fluid passing through the housing 10. The housing 10 may have any structure which enables it to guide fluid through the filter elements 60 in a desired direction. The housing 10 will typically comprise a plurality of sections which can be detached from each other when desired to enable the filter assembly 20 to be removed from the housing 10. The illustrated housing 10 includes a bottom 11 and a cover 13 which can be detachably secured to the bottom 11 by any suitable means, such as by bolts. The housing 10 also includes an inlet 15 through which fluid to be filtered can be introduced into the housing 10 and an outlet 16 through which fluid which has been filtered can exit from the housing 10. The inlet 15 and outlet 16 are not restricted to any particular location. In the illustrated embodiment, the inlet 15 is formed in the lower portion of the bottom 11 of the housing 10, while the outlet 16 is formed in an upper portion of the cover 13 of the housing 10. The housing 10 may include fluid ports in addition to the illustrated ones, such as drains, other inlets or outlets, or vents. The housing 10 is shown with the cover 13 disposed above the bottom 11 of the housing 10 and with the filter elements 60 extending vertically. However, the housing 10 and filter elements 60 may have any orientation with respect to the vertical, such as horizontal or at any angle between horizontal and vertical. The filter assembly 20 is a removable unit including a tube sheet 30 and a plurality of filter elements 60 sealed to the tube sheet 30. As described below, the filter assembly 20 is preferably designed so that the filter elements 60 can be unsealed from the tube sheet 30 simply by placing the entire filter assembly 20 on a floor or other support surface outside of the housing 10. The tube sheet 30 is disposed between the inlet 15 and outlet 16 of the housing 10 and partitions the interior of the housing 10 into an inlet chamber 17 communicating with the inlet 15 and an outlet chamber 18 communicating with the outlet 16. The tube sheet 30 may be supported by the housing 10 in any manner which prevents fluid to be filtered from unintentionally bypassing the filter elements 60 by flowing between the tube sheet 30 and the housing 10. In the illustrated embodiment, the tube sheet 30 is sandwiched between a mounting flange 14 formed on the cover 13 and another mounting flange 12 formed on the bottom 11 of the housing 10, with the periphery of the tube sheet 30 exposed to the exterior of the housing 10. However, it is also possible for the tube sheet 30 to be located entirely within the housing 10 and not be exposed to the exterior. When a portion of the tube sheet 30 is exposed to the housing 10 exterior, a fluid port may be formed in the tube sheet 30 for communication between the interior and exterior of the housing 10. For example, as shown in Figure 2, in the present embodiment, a passage 36 is formed in the tube sheet 30 between its outer periphery and its bottom surface to vent air or other gas from the interior of the housing 10 to the exterior. The tube sheet 30 is sealed to the housing 10 by suitable sealing members 34, such as gaskets or O-rings, disposed between the upper surface of the tube sheet 30 and the cover 13 and between the lower surface of the tube sheet 30 and the bottom 11 of the housing 10. The illustrated tube sheet 30 is a substantially flat member having substantially planar upper and lower surfaces and a substantially constant thickness, but the tube sheet 30 may have other shapes. For example, it may have a curved or stepped profile, and its thickness may vary over its diameter. The tube sheet 30 is formed with a plurality of holes 31 extending between its upper and lower surfaces for receiving the upper ends of the filter elements 60. The number of holes 31 is not restricted, and they may be arranged in any desired geometric pattern. Each of the holes 31 is large enough for one of the filter elements 60 to pass through the hole 31 until the upper end of the filter element 60 is sealed against the tube sheet 30. In the present embodiment, each of the holes 31 has a ledge 32 extending around its inner periphery for supporting one of the filter elements 60. The ledges 32 in this embodiment are at a constant depth with respect to the top surface of the tube sheet 30, but as described below, it is possible for the depths of the ledges to vary from hole to hole. The tube sheet 30 may be made of any material which is impervious to the substance which is to be removed by the filter elements 60. For example, if the filter elements 60 are used to remove particles from a fluid, the tube sheet 30 is preferably impervious to particles of the size which are to be removed, but the tube sheet 30 need not be completely fluid tight. In many applications, a corrosion resistant metal, such as stainless steel, is suitable for forming the tube sheet 30. The filter elements 60 may have any shape or structure and be formed of any materials suited to the filtering conditions and the fluid to be filtered, including but not limited to metals, polymers, ceramics, and composites of different materials. Frequently the filter elements 60 will be generally cylindrical members of substantially constant cross section over their lengths, but they need not be cylindrical, and the transverse cross section of the filter elements 60 may vary over their lengths. A few examples of possible structures for the filter elements 60 are a pleated structure with lengthwise or accordion pleats, or a nonpleated structure, such as a fibrous tube, a bag, or a stack of filtering plates. Each filter element 60 includes a filter medium for removing a selected substance or substances from the fluid being filtered. The filter medium may be in a variety of forms, including but not limited to a mass of fibers, fibrous mats, woven or nonwoven fibrous sheets, porous membranes such as supported or unsupported microporous membranes, porous foam, and porous metals or ceramics. In addition to a filter medium, the filter element 60 may include a variety of conventional components, such as a perforated inner core, one or more end caps, drainage layers, cushioning layers for reducing abrasion of the filter medium, diffusion layers, and an outer protective member such as an external cage or a wrap member. Each filter element 60 may comprise a single section, or it may comprise a plurality of sections joined end-to-end in series. Flow through the filter elements 60 may be in any desired direction, such as in a radial direction of the filter element 60 (either radially inwardly or outwardly), in an axial direction, or both radially and axially. The filter elements 60 in this embodiment are located in the inlet chamber 17 so that all fluid which passes through the tube sheet 30 has already been filtered by the filter elements 60. Alternatively, the filter elements 60 may be installed in the outlet chamber 18 so that fluid is filtered after it passes through the tube sheet 30 and enters the filter elements 60. Figure 4 illustrates an example of a filter element 60 which can be employed in the present embodiment. The right end of the filter element 60 in the figure is the upper end which is sealed to the tube sheet 30, and the left end of the filter element 60 in the figure is the lower end which is remote from the tube sheet 30, although the terms "upper" and "lower" are used merely for reference purposes, and the filter element 60 need not be vertical and can be employed in any orientation to the vertical. The filter element 60 may extend continuously from its upper to its lower end, but in the present embodiment, the filter element 60 is divided into a plurality of sections 61 which are joined to each other end-to-end in series. Each section 61 has a polymeric end cap at its upper and lower ends and a filter body extending between the end caps. Each filter body comprises a composite of one or more layers of a polymeric filter medium, an upstream polymeric drainage mesh disposed on a first side of the filter medium layer, and a downstream polymeric drainage mesh disposed on a second side of the filter medium layer. The composite is pleated with conventional pleating equipment to form parallel, axially extending pleats, and the pleated composite is then formed into a tubular shape and sealed along the edges of the composite to form a side seal. The end caps are then melt sealed to the lengthwise end surfaces of the filter body. The pleats of the filter body may extend substantially radially with respect to the longitudinal axis of the filter body, or they may in a laid over state in which the radially outer end of each pleat of the filter body is displaced in a circumferential direction of the filter body with respect to the radially inner end of the pleat. Prior to the end caps being sealed to the filter body, a strip of a metallic mesh is helically wrapped around the outside of the filter body in a plurality of overlapping turns to form a wrap member 62 to protect the pleats from abrasion and to prevent them from ballooning outward when subjected to radially outward forces. The overlapping turns of the wrap member 62 may be secured to each other at intervals along the length of the wrap member 62 by spot welding, for example. The hollow center of each filter body is supported by an unillustrated perforated polymeric core which extends between and is secured to both end caps of the section 61. The core gives the filter rigidity and supports the pleats of the filter body against radially inward forces. However, if the filter body has sufficient strength and rigidity by itself, the core may be omitted. Each section 61 of the filter element 60 has an open polymeric end cap 63 which is joined to a similar end cap 63 of the adjoining section 61 by melting the two end caps 63 together, although they may be joined by other means, such as by a mechanical connector. The end cap 65 at the upper end of the filter element 60 is an open end cap which can be sealed to the tube sheet 30, while the end cap 70 at the lower end of the filter element 60 is a blind end cap which seals the lower end against the fluid being filtered. The open end cap 65 at the upper end of the filter element 60 has a generally cylindrical outer shape with a bore extending through its length. At its upper end, it is formed with a flange 66 which has an outer diameter larger than the rest of the end cap 65 and which is dimensioned so as to rest on the ledge 32 in any one of the holes 31 in the tube sheet 30 and thereby prevent the end cap 65 from passing entirely through the tube sheet 30. The blind lower end cap 70 at the lower end of the filter element 60 is formed with an axial projection 71 against which an axial force can be applied to unseal the filter element 60 from the tube sheet 30. In this embodiment, all of the filter elements 60 are identical in structure and of the same length so that the lower ends of the filter elements 60 are at a uniform distance from the tube sheet 30. However, the filter elements 60 may vary in structure or in length. Each filter element 60 may be sealed to the tube sheet 30 in any manner which can prevent the material being removed by the filter element 60 from passing between the filter element 60 and the tube sheet 30. A so-called face seal between an axially facing surface of the filter element 60 and an axially facing surface of the tube sheet 30 may be employed, but generally a radial seal, such as a piston seal, between the outer periphery of the filter element 60 and the inner periphery of one of the holes 31 in the tube sheet 30 is preferable because a face seal usually requires that the filter element 60 be loaded in the axial direction, so it is more complicated in terms of hardware and places greater stresses on the filter element 60. Furthermore, a radial seal can permit thermal expansion and makes it easier to remove the filter element 60 from the tube sheet 30. In the present embodiment, a radial seal on each filter element 60 is formed by a sealing member in the form of an O-ring 67 mounted in a groove 68 formed in the exterior surface of the upper end cap 65 of the filter element 60 and in sealing contact with the inner periphery of one of the holes 31 in the tube sheet 30. The weight of the filter elements 60 may be supported partially or entirely by the tube sheet 30. In the present embodiment, substantially the entire weight of the filter elements 60 is supported by the ledges 32 formed in the holes 31 in the tube sheet 30. Alternatively, if the filter elements 60 are sufficiently strong in compression to support their own weight, the lower ends of the filter elements 60 may rest on a support member located beneath them. In the present embodiment, the upper end of each filter element 60 is recessed within the corresponding hole 31 in the tube sheet 30 and is supported on the ledge 32 in the hole 31. However, the filter elements 60 may extend to above the upper surface of the tube sheet 30 into the outlet chamber 18, and they may be supported in a different manner. For example, the upper end cap 65 of each filter element 60 may be equipped with a flange or other portion which rests atop the upper surface of the tube sheet 30 to support the weight of the filter element 60. To prevent the lower ends of the filter elements 60 from moving in the lateral direction and to maintain a desired spacing between adjoining filter elements 60, a retaining plate 80 for engagement with a portion of each filter element 60 may be disposed beneath the tube sheet 30. The retaining plate 80 can have any structure which enables it to restrict or prevent lateral movement of the filter elements 60 yet allow the filter elements 60 to move with respect to the retaining plate 80 in the lengthwise direction of the filter elements 60 when the filter elements 60 are to be removed from the tube sheet 30. The retaining plate 80 may be attached to the housing 10, but in the present embodiment, it is part of the filter assembly 20 and serves to stabilize the filter elements 60 when they are being removed from the tube sheet 30. When the housing inlet 15 is located beneath the retaining plate 80, the retaining plate 80 preferably has as large an open area as possible to permit the fluid to be filtered to easily pass through the retaining plate 80 and reach the filter elements 60. In the present embodiment, the retaining plate 80 is formed by plasma cutting a circular metal plate to form a plurality of generally circular lands 81 connected with each other by narrow strips 82 of metal and largely surrounded by openings 83 through which fluid can pass. A circular bore 84 is cut through each land 81, and a metal tube 85 large enough to slidably receive the lower end cap 70 of any one of the filter elements 60 is inserted into the bore 84 and welded or otherwise secured to the land 81. The retaining plate 80 is supported at its outer periphery by a plurality of vertical legs 50 disposed at intervals around the periphery of the tube sheet 30 and secured at their upper ends to the tube sheet 30 by threaded engagement, welding, or other suitable method. The illustrated filter assembly 20 is equipped with an ejector mechanism 90 for automatically breaking the seals between the upper ends of the filter elements 60 and the tube sheet 30 when the filter assembly 20 is set on a floor or other surface so that the filter elements 60 can be easily removed from the tube sheet 30. The ejector mechanism 90 comprises an ejector plate 91 movably supported with respect to the tube sheet 30 and a plurality of projections in the form of eject pins 92 extending from the ejector plate 91 toward the lower ends of the filter elements 60. The ejector plate 91 can move with respect to the tube sheet 30 in the direction normal to the surface of the tube sheet 30 between a lowered position shown in Figure 2 and a raised position shown in Figure 6. In the lowered position, the upper ends of the eject pins 92 may be spaced from the lower ends of the filter elements 60 or otherwise disposed such that the upper ends of the filter elements 60 can remain sealed to the tube sheet 30. When the ejector plate 91 is in its raised position, each of the eject pins 92 is in contact with the lower end of one of the filter elements 60, and the upper ends of the filter elements 60 are raised with respect to the tube sheet 30 by a sufficient distance that the filter elements 60 are no longer sealed to the tube sheet 30 and can be easily removed from the tube sheet 30. The ejector plate 91 can be moved from its lowered to its raised position by placing the filter assembly 20 on a floor or other support surface so that the weight of the filter assembly 20 can press the filter elements 60 downward into contact with the eject pins 92 of the ejector plate 91. The ejector plate 91 can be supported for movement relative to the tube sheet 30 in any desired manner. In the illustrated embodiment, a plurality of rods 94 are secured to the ejector plate 91 at intervals along its outer periphery, and each of the rods 94 is telescopically received in the lower end of one of the legs 50 of the filter assembly 20. A locking mechanism may be provided to lock the ejector plate 91 with respect to the legs 50. As shown in Figure 2, in the present embodiment, each leg 50 is provided with a locking mechanism in the form of a quick release pin 52 which can be passed through a pair of opposing holes 51 formed in the leg 50 and a corresponding hole 95 formed in each rod 94 of the ejector plate 91. When the quick release pins 52 are engaged with the holes 51 in the legs 50 and the rods 94, the ejector plate 91 is incapable of movement with respect to the legs 50, so the ejector plate 91 can be placed on a floor or other support surface and support the entire weight of the filter assembly 20. A compression spring 96 may be disposed around each of the rods 94 between the top surface of the ejector plate 91 and the bottom surface of each leg 50. The springs 96 provide a cushioning effect when the ejector plate 91 is moving between its lowered and raised portions, and they also urge the ejector plate 91 to return to its lowered position when the filter assembly 20 is suspended above a surface and no upward force is acting on the ejector plate 91. To prevent the ejector plate 91 from being inadvertently detached from the legs 50, each rod 94 may be equipped with an unillustrated, removable, radially extending pin slidably engaged in an unillustrated longitudinally extending slot formed in the corresponding leg 50. When the ejector plate 91 is in its raised position, the pins contact the upper ends of the slots and prevent further upward movement of the ejector plate 91, and when the ejector plate 91 is in its lowered position, the pins contact the lower ends of the slots and prevent further downward movement of the ejector plate 91. When the pins abut the lower ends of the slots, the holes 51 in the legs 50 will be aligned with the holes 95 in the corresponding rods 94 of the ejector plates 91 to enable the quick release pins 52 to be inserted through the holes 51 and 95 to lock the rods 94 with respect to the legs 50. The ejector plate 91 is preferably sufficiently strong to support the entire weight of the filter assembly 20 when set upon a floor or other support surface. When the inlet 15 of the housing 10 is located beneath the ejector plate 91, the ejector plate 91 preferably has a highly open structure to permit the fluid to be filtered to easily pass through it. In the present embodiment, the ejector plate 91 has a structure similar to that of the retaining plate 80, being formed by plasma cutting a circular metal plate to form lands interconnected by narrow strips and largely surrounded by openings through which fluid can flow. The eject pins 92 are then secured to the lands in any suitable manner, such as by welding or threaded engagement. One or more stiffeners 93 may be secured to the bottom surface, for example, of the ejector plate 91 to increase its bending stiffness. The lengths of the eject pins 92 are selected so that when the ejector plate 91 is in its raised position, each of the filter elements 60 will be contacted by the upper end of one of the eject pins 92, and the upper end of the filter element 60 will be pushed upward with respect to the tube sheet 30 far enough to release the seal between the O-ring 67 at the upper end of the filter element 60 and the inner surface of the corresponding hole 31 in the tube sheet 30 so that the filter element 60 can be readily detached from the tube sheet 30. Generally, it is sufficient if each filter element 60 is moved upward far enough that the O-ring 67 is no longer in sealing contact with the inner surface of the corresponding hole 31 in the tube sheet 30, such as if the O-ring 67 is raised to above the ledge 32 in the corresponding hole 31 in the tube sheet 30. However, the filter elements 60 may be raised by a greater distance with respect to the tube sheet 30, such as far enough that the upper end caps 65 at least partially protrude from the tube sheet 30, enabling the end caps 65 to be easily grasped by a worker. When the O-rings 67 are in sealing contact with the holes 31 in the tube sheet 30, the friction between the O-rings 67 and the tube sheet 30 produces significant resistance to movement of the filter elements 60 with respect to the tube sheet 30 in their lengthwise directions. For example, for a tube sheet 30 equipped with four hundred filter elements 60 and with the O-ring 67 of each filter element 60 producing a resistance to movement of approximately ten pounds force, the total force required to release the seals of all the filter elements 60 simultaneously would be on the order of four thousand pounds. However, if the filter elements 60 can be made to contact the eject pins 92 at different times so as to be pushed upward with respect to the tube sheet 30 at different times, such as in groups, the total force required at any time to release the seals of the filter elements 60 can be significantly reduced. The filter elements 60 can be made to contact the eject pins 92 at different times in a variety of manners, such as by making the filter elements 60 of varying lengths, or by supporting filter elements 60 of the same length in a tube sheet 30 such that the lower ends of different filter elements 60 are at different heights. In the present embodiment, the filter elements 60 are all of the same length and are supported by the tube sheet 30 so that their lower ends are at a uniform distance from the tube sheet 30, so the filter elements 60 are made to contact the eject pins 92 at different times by making the eject pins 92 of varying lengths. When the filter assembly 20 is set on a floor or other surface, the filter elements 60 will come into contact with the eject pins 92 at different times, with the longest eject pins 92 contacting the corresponding filter elements 60 before the other eject pins 92. Each of the filter elements 60 may contact the corresponding eject pin 92 at a different time from all of the other filter elements 60, or the eject pins 92 may be arranged in a plurality of groups with the eject pins 92 in the same group having a constant length but differing in length from the eject pins 92 of a different group, so that the filter elements 60 will be pushed upward from the tube sheet 30 in groups. In the present embodiment, the height of the eject pins 92 decreases from the outer periphery toward the center of the ejector plate 91 so that the outer filter elements 60 are pushed upward with respect to the tube sheet 30 before the inner ones, but the heights of the eject pins 92 may vary in a different manner. If the eject pins 92 are arranged in groups, the number of eject pins 92 in a group of the same height is preferably selected so that the weight of the tube sheet 30 and of those filter elements 60 exerting a downward force on the tube sheet 30 is sufficient to release the seals of the filter elements 60 being contacted by the eject pins 92 in the group without the need for application of any external force. The eject pins 92 need not have any particular shape. The illustrated eject pins 92 are rods of a uniform cross section and have a rounded upper end for engagement with a recess in the lower end cap 70 of each filter element 60. The resistance to movement by an O-ring 67 on a filter element 60 is greatest when the O-ring 67 is stationary with respect to the tube sheet 30 but rapidly decreases once starting friction has been overcome and the O-ring 67 has begun to slide with respect to the tube sheet 30. The height difference between any different eject pins 92 of different length is preferably at least long enough that one eject pin 92 comes into contact with the corresponding filter element 60 only after the filter element 60 previously contacted by another eject pin 92 of different length has started to move upward with respect to the tube sheet 30. There is no upper limit on the height difference between different eject pins 92. For example, one eject pin 92 may contact the corresponding filter element 60 after the seal of the O-rings 67 on a filter element 60 to be contacted by a different eject pin 92 has been released. During operation of the filter arrangement, the fluid pressure will tend to be higher in the inlet chamber 17 of the housing 10 than in the outlet chamber 18. This pressure difference can exert an upward force on the filter elements 60. Therefore, the filter arrangement may be equipped with a mechanism for preventing the upward force from pushing the filter elements 60 upward with respect to the tube sheet 30 far enough to release the seals between the filter elements 60 and the mbe sheet 30. In the present embodiment, a mechanism for limiting the upward movement of the filter elements 60 comprises a hold-down plate 40 disposed atop the mbe sheet 30. The hold-down plate 40 comprises a flat disc 41 having a plurality of perforations 42 in locations corresponding to the locations of the bores in the upper end caps 65 of the filter elements 60. The perforations 42 are small enough that the upper ends of the filter elements 60 cannot pass through the perforations 42 but large enough not to produce any significant impediment to fluid flow. The hold-down plate 40 may include stiffeners 43 on its upper surface to give it rigidity, and it may include a lifting ring 44 or similar member for use in lifting the hold-down plate 40 off the mbe sheet 30. It is not necessary for the hold-down plate 40 to prevent all axial movement of the filter elements 60. Rather, it is sufficient for it to limit any upward axial movement of the filter elements 60 relative to the mbe sheet 30 to a level which will not release the seals between the filter elements 60 and the mbe sheet 30. Therefore, it is not necessary to tightly clamp the hold-down plate 40 to the mbe sheet 30 or to seal the hold-down plate 40 to the tube sheet 30. In the present embodiment, the hold-down plate 40 rests atop the mbe sheet 30 and is prevented from upward movement by a step formed on the interior of the cover 13 of the housing 10. However, it is also possible for the hold-down plate 40 to be secured to the cover 13 of the housing 10. Mechanisms other than a hold-down plate 40 can also be employed to limit the upward movement of the filter elements 60, such as retaining rings, retaining pins, or a grid placed atop the mbe sheet 30. Furthermore, if the differential pressure across the tube sheet 30 is sufficiently low to be unable to release the seals between the filter elements 60 and the mbe sheet 30, a hold-down plate 40 or other mechanism for limiting movement of the filter elements 60 may be omitted. During operation of the filter arrangement of Figure 1 , fluid to be filtered enters the inlet chamber 17 of the housing 10 though the inlet 15, passes through the filter elements 60, and is discharged from the upper ends of the filter elements 60 into the outlet chamber 18, from which the filtered fluid exits the housing 10 via the outlet 16. When it is desired to replace the filter elements 60, the cover 13 of the housing 10 and the hold-down plate 40 are removed, and then the entire filter assembly 20 is lifted out of the housing 10 by means of lifting lugs 35 attached to the mbe sheet 30. With the filter assembly 20 suspended from the lifting lugs 35, the quick release pins 52, if installed, are removed from the legs 50 of the filter assembly 20 to enable the ejector plate 91 to move with respect to the mbe sheet 30, and the filter assembly 20 is lowered to set the bottom of the ejector plate 91 on a floor or other support surface 100. The support surface 100 may but need not be level and can have any shape which enables it to stably support the filter assembly 20. For example, it may be the ground, a floor, a support frame, a raised base, or blocks. The weight of the mbe sheet 30 and the filter elements 60 pressing downward on the mbe sheet 30 causes the mbe sheet 30 and the filter elements 60 to move downward toward the ejector plate 91. When the tallest eject pins 92 contact the corresponding filter elements 60, the downward movement of the filter elements 60 which are contacted will be prevented so as the mbe sheet 30 continues to move downward, the seal between the filter elements 60 contacting the eject pins 92 and the mbe sheet 30 is released. As the mbe sheet 30 continues its downward movement, more and more of the seals are released, so that by the time the mbe sheet 30 reaches the bottom of its travel, i.e., when the ejector plate 91 reaches its raised position with respect to the tube sheet 30, all of the seals for the filter elements 60 will have been released, i.e., the upper ends of all the filter elements 60 will have been unsealed from the tube sheet 30. Once the filter elements 60 have been unsealed, they can then be easily removed from the mbe sheet 30, either by hand, or by a tool such as a manipulator or a robot. In order to insert new filter elements 60 into the tube sheet 30, the filter assembly 20 can be lifted into the air far enough for the springs 96 to push the ejector plate 91 to its lowered position. The quick release pins 52 can then be inserted into the aligned holes 51, 95 in the legs 50 and the rods 94 of the ejector plate 91, and the filter assembly 20 can be lowered back onto the support surface 100. The new filter elements 60 can then be inserted into the mbe sheet 30 from above until their lower ends engage the retaining plate 80. Once the upper ends of the filter elements 60 have been automatically unsealed with respect to the mbe sheet 30 by the operation of the ejector plate 91, it requires very little force for a worker to withdraw the filter elements 60 from the mbe sheet 30. Therefore, the removal of the filter elements 60 can be performed quickly and easily, resulting in fewer hours of labor and less exposure of workers to potentially harmful substances in the filter elements 60. Furthermore, because the ejector plate 91 releases the seals of different ones of the filter elements 60 at different times, the weight of the filter assembly 20 is sufficient to release the seals, and it is unnecessary to employ any other equipment to release the seals, such as a press for applying a downward force on the mbe sheet 30 or a device for pulling the filter elements 60 upward. In the embodiment of Figure 2, the lower ends of all the filter elements 60 are at the same height, and the heights of the eject pins 92 vary so that the filter elements 60 are contacted at different times by the eject pins 92. Alternatively, the heights of the lower ends of the filter elements 60 can vary, and the eject pins 92 can have the same length. Figures 7 through 9 illustrate an embodiment of a filter assembly 110 according to the present invention having a mbe sheet 120 which supports a plurality of identical filter elements 60 so that the bottom ends of the filter elements 60 are at different heights. Figure 7 is a cross-sectional elevation of one half of the filter assembly 110 when installed in a housing 10 like the one shown in Figure 1, Figure 8 is an enlarged cross-sectional view of the circled region in Figure 7, and Figure 9 is a cross-sectional elevation of the other half of the filter assembly 110 when removed from the housing 10 and sitting on a floor or other support surface 100. In each of Figures 7 and 9, the unillustrated half of the filter assembly 110 is the mirror image of the illustrated half. The mbe sheet 120 is generally similar in structure to the mbe sheet 30 of the embodiment of Figure 2 and includes a plurality of through holes 121 each having a ledge 122 for supporting a flange 66 of an upper end cap 65 of a filter element 60. However, whereas in the mbe sheet 30 of Figure 2 the ledges 32 are at a constant depth with respect to the top surface of the mbe sheet 30, in the mbe sheet 120 of the present embodiment, the depths of the ledges 122 vary so that the heights of the upper and lower ends of the filter elements 60 also vary from element to element. All of the ledges 122 may be at different depths, or the holes 121 may be divided into a plurality of groups, with the holes 121 in each group having ledges 122 at a different depth from the ledges 122 in the holes 121 in the other groups but with the holes 121 of a single group having ledges 122 at the same depth. The filter assembly 110 includes an ejector mechanism 90, which may be similar in strucmre to that of the previous embodiment except that all of the eject pins 92 have the same length, although it is possible for the lengths to vary. The illustrated ejector mechanism 90 does not include a biasing spring 96 for urging the ejector plate 91 to its lowered position with respect to the mbe sheet 120, but such a spring may be added if desired. In this embodiment, the upper ends of the filter elements 60 are recessed with respect to the upper surface of the mbe sheet 120 and are at various heights, so the filter assembly 110 is equipped with a hold-down plate 130 of somewhat different strucmre from the hold-down plate 40 shown in Figure 2. This hold-down plate 130 includes a flat metal plate 131 having a plurality of openings 132 in locations corresponding to the bores of the upper end caps 65 of the filter elements 60. A mbe 133 is secured to the plate 131 at each opening 132 and extends downward from the plate 131 into one of the holes 121 in the mbe sheet 120 to the vicinity of the upper end cap 65 of one of the filter elements 60. Since the upper end caps 65 are at different depths in the mbe sheet 120, the lengths of the tubes 133 vary so that each mbe 133 is close enough to the upper end cap 65 of the corresponding filter element 60 to restrain the upward movement of the end cap 65 to an amount such that the upper end cap 65 will not become unsealed from the tube sheet 120. The hold-down plate 130 may be restrained from upward movement in the same manner as the hold- down plate 40 of the embodiment of Figure 2, for example. The hold-down plate 130 may also include a lift ring 134 or similar member for use in raising the hold- down plate 130 off the mbe sheet 120. The strucmre of this embodiment is otherwise the same as that of the previous embodiment. The operation of this filter assembly 110 is similar to that of the filter assembly 20 of Figure 2. The two filter assemblies perform filtration in the same manner. When it is desired to replace the filter elements 60, the filter assembly 110 is removed from the housing 10 in which it is used and placed on a floor or other surface 100 capable of supporting the weight of the filter assembly 110. If the quick release pins 52 have been removed from the legs 50 of the filter assembly 110, the tube sheet 120 will move downward under its own weight and under the weight of the filter elements 60 to bring the lower ends of the filter elements 60 into contact with the eject pins 92 of the ejector plate 91. The filter element 60 or group of filter elements 60 having lower ends furthest from the tube sheet 120 will contact the eject pins 92 first and be lifted upward with respect to the mbe sheet 120 to release the seal between the upper ends of these filter elements 60 and the mbe sheet 120. After the first group of filter elements 60 have contacted the eject pins 92 and have begun to move with respect to the mbe sheet 120, the group of filter elements 60 having lower ends next furthest from the mbe sheet 120 will contact the eject pins 92, and so forth until all the filter elements 60 have contacted the eject pins 92 and the seals of all the filter elements 60 have been released, i.e., the upper ends of all the filter elements 60 have been unsealed from the mbe sheet 120. As in the previous embodiment, because different filter elements 60 contact the eject pins 92 at different times, the total force required at any given time to release the seals is lower than if all the filter elements 60 contacted the eject pins 92 simultaneously. Thus, the required force can be kept to a level sufficiently low that the weight of the mbe sheet 120 and the filter elements 60 supported by the mbe sheet 120 at any given moment is sufficient to release the seals. Figure 10 is a cross-sectional elevation of a portion of the lower end of another embodiment of a filter assembly according to the present invention. The overall strucmre of this embodiment is similar to that of the embodiment of Figure 2, and the strucmre of the unillustrated portions may be the same as in that embodiment. In contrast to Figure 2, the retaining plate 80 has been replaced by a plurality of retaining tubes 140, each slidably mounted on one of the eject pins 92 of the ejector mechanism 90. Each retaining mbe 140 has an inner diameter large enough to loosely receive the lower end cap 70 of one of the filter elements 60 and the upper end of one of the eject pins 92. At its upper end, each retaining mbe 140 has a flange 141, a cup, or other shape which is capable of supporting the lower end of one of the filter elements 60. Each retaining mbe 140 is urged into contact with the corresponding filter element 60 by a compression spring 142 having an upper end pressed against the lower surface of the flange 141 and a lower end pressed against the top of the ejector plate 91. The spring 142 is not intended to exert any substantial upward force on the filter element 60 and merely serves to maintain contact between the retaining tube 140 and the filter element 60. Thus, the force exerted by the spring 142 by itself is preferably unable to overcome the frictional force between the sealing member at the upper end of the filter element 60 and the unillustrated mbe sheet. At the maximum extension of the spring 142, the retaining tubes 140 and the eject pins 92 overlap each other in the lengthwise direction. Therefore, the retaining tubes 140 are prevented from lateral movement by the eject pins 92, and when one of the retaining tubes 140 is engaged with one of the filter elements 60, the retaining mbe 140 can restrain the filter element 60 from lateral movement and thus perform a function similar to that performed by the retaining plate 80 of the embodiment of Figure 2. As in the embodiment of Figure 2, the lower ends of the filter elements 60 are at a constant height, while the lengths of the eject pins 92 vary. The filter assembly of Figure 10 may be installed and used in a housing 10 in the same manner as the embodiment of Figure 2. During filtration, the upper end of each filter element 60 is sealed to the unillustrated mbe sheet of the filter assembly, while the lower end of each filter element 60 is engaged with one of the retaining tubes 140 in the manner shown in Figure 10, with the lower ends of the filter elements 60 spaced from the eject pins 92. In order to remove the filter elements 60 from the tube sheet, the entire filter assembly is removed from the housing 10 and placed on a floor or other support surface 100, with the quick release pins 52 which lock the ejector plate 91 to the legs 50 of the filter assembly removed so that the ejector plate 91 is free to move with respect to the tube sheet. Under the weight of the mbe sheet and the filter elements 60, the tube sheet moves downward to bring the lower ends of the filter elements 60 into contact with the eject pins 92. In the same manner as in the embodiment of Figure 2, the seals between the upper ends of the filter elements 60 and the mbe sheet are released a group at a time by the axial forces exerted on the filter elements 60 by the eject pins 92, with the seals of the filter elements 60 contacted by the longest eject pins 92 being released first and the seals of the filter elements 60 contacted by the shortest eject pins 92 being released last. When the ejector plate 91 reaches its raised position with respect to the mbe sheet, all the seals will have been released, i.e., all the filter elements 60 will have been unsealed from the mbe sheet, so the filter elements 60 can be easily removed from the mbe sheet. In the present embodiment, the length of the retaining mbes 140 is such that they do not contact the ejector plate 91 when the ejector plate 91 is in its raised position, so except for the relatively small upward force produced by the springs 142, the retaining mbes 140 do not apply an upward force on the filter elements 60 tending to dislodge the filter elements 60 from the mbe sheet. However, if the retaining mbes 140 are sufficiently long, the lower ends of the retaining mbes 140 can be made to abut against the ejector plate 91 as the mbe sheet and filter elements 60 are moving downward, in which case the upper ends of the retaining tubes 140 can exert an upward force on the filter elements 60 to urge the filter elements 60 to move upwards with respect to the mbe sheet and unseal the filter elements 60 from the mbe sheet. If each retaining mbe 140 is sized to abut against the ejector plate 91 at the same time that the corresponding eject pin 92 contacts the filter element 60, each retaining mbe 140 and the corresponding eject pin 92 can together urge a filter element 60 upward with respect to the mbe sheet to release the seal between the filter element 60 and the mbe sheet. On the other hand, if each retaining mbe 140 is sufficiently long, the retaining mbe 140 can abut against the ejector plate 91 before the eject pin 92 contacts the corresponding filter element 60, so the filter element 60 can be urged upward with respect to the mbe sheet by the retaimng mbe 140 rather than by the eject pin 92, and the eject pin 92 can function as a guide for the retaining mbe 140. In the embodiment of Figure 10, the lower ends of the filter elements 60 are at the same height as each other and the eject pins 92 have varying lengths. Alternatively, as in the embodiment of Figure 8, the eject pins 92 may have a constant length, and the mbe sheet can be constructed so that the heights of the lower ends of the filter elements 60 vary. Figure 11 illustrates the lower portion of another embodiment of a filter assembly according to the present invention. In this embodiment, an ejector mechanism has been omitted, and the seal between the upper ends of the filter elements 60 and an unillustrated mbe sheet is released by direct contact between the lower ends of the filter elements 60 and a floor or other surface 100. Except for the lower end portion, the strucmre of the filter assembly and of a filter arrangement employing the assembly may be the same as that of any of the preceding embodiments. The unillustrated upper ends of the filter elements 60 are sealed to the unillustrated mbe sheet in the same manner as in the preceding embodiments, while the lower ends of the filter elements 60 are retained by a retaining plate 150 secured to the legs 50 of the filter assembly. Each filter element 60 has a lower end cap 70 with a projection 71 which extends downward through a corresponding opening 151 in the retaining plate 150 to below the bottom of the retaining plate 150. When the filter assembly is installed in a housing, there is no significant upward axial force acting on the lower ends of the projections 71, so the weight of the filter elements 60 is supported substantially entirely by the mbe sheet. When it is desired to remove the filter elements 60 from the tube sheet, the entire filter assembly is removed from the housing 10 and set on a floor or other support surface 100, with the lower ends of the projections 71 contacting the support surface 100. The weight of the mbe sheet and the filter elements 60 forces the mbe sheet downward with respect to the filter elements 60, thereby releasing the seals between the upper ends of the filter elements 60 and the mbe sheet. It is preferable if different filter elements 60 or different groups of filter elements 60 are urged upward with respect to the mbe sheet by contact with the surface 100 at different times so as to reduce the total force required at any time to release the seals between the filter elements 60 and the mbe sheets. The filter elements 60 can be made to contact the surface 100 at different times in various manners. For example, the filter elements 60 may all have the same length, but they may be supported by a mbe sheet like that shown in Figure 8 so that the lower ends of the filter elements 60 will be at different heights. Alternatively, the upper ends of the filter elements 60 can be supported at a constant height, as in the embodiment of Figure 2, but the lengths of the projections 71 on the lower ends caps 70 of the filter elements 60 can be varied among the filter elements 60 so that the lower ends of the projections 71 will extend from the retaining plate 150 by different amounts. The projections 71 on the lower end caps 70 need not be integral with the other portions of the lower ends caps 70, and may be separately formed members which can be attached to any one of the lower end caps 70 to adjust the overall length of the filter elements 60 to a desired level. Figure 12 illustrates a variation of the embodiment of Figure 11 in which the lower ends of the projections 71 of all of the lower end caps 70 of a plurality of identical filter elements 60 are at a constant height, and the support surface 100 on which the filter assembly is placed when the filter elements 60 are to be removed from the mbe sheet has height variations such as steps, holes, or sloping portions. Due to the height variations of the surface 100, when the filter assembly is lowered onto the surface 100, the projections 71 of different end caps 70 will contact the surface 100 at different times, so that the seals of different filter elements 60 will be released at different times. The unillustrated portions of this embodiment may be otherwise the same as any one of the previous embodiments, and it may be installed in a filter housing in the same manner as those embodiments. Figures 13 - 22 illustrate another embodiment of a filter assembly 200 according to the present invention which has a strucmre such that filter elements 60 can be readily unsealed and removed from a mbe sheet of the filter assembly while the filter assembly is still at least partially disposed in a housing. Figure 13 is a partially cross-sectional elevation of this embodiment while supported from above with the lower portion of the filter assembly 200 disposed in the bottom 11 of a housing 10 like the one shown in Figure 1, and Figure 14 shows the filter assembly 200 supported atop a body flange 12 of the bottom 11 of the housing. The overall strucmre of the filter assembly 200 is similar to that of the filter assembly 20 of Figure 2. It includes a mbe sheet 210 for supporting a plurality of filter elements 60, an ejector mechanism 240 capable of movement relative to the mbe sheet 210 to unseal the filter elements 60 from the mbe sheet 210, and a plurality of legs 220 extending between the mbe sheet 210 and the ejector mechanism 240. In contrast to the legs 50 of the filter assembly 20 of Figure 2, which remain stationary with respect to mbe sheet 30, the upper ends of the legs 220 of this embodiment are movable with respect to the mbe sheet 210, thereby enabling the mbe sheet 210 and the ejector mechanism 240 connected to the legs 220 to undergo relative movement to unseal the filter elements 60 from mbe sheet 210 while the filter elements 60 are at least partially inside the bottom 11 of the housing. The mbe sheet 210 may be similar in strucmre to the mbe sheet 30 of Figure 3. It is a disc-shaped member which can be sandwiched between the body flange 12 of the bottom 11 of the housing and the body flange 14 of a cover 13 for the housing. It includes a plurality of holes 211 each shaped to support and seal against the upper end cap 65 of a filter element 60 like the one shown in Figure 4. On its outer periphery, the mbe sheet 210 includes a plurality of lifting lugs 213 which can be secured to a beam 170 when the filter assembly 200 needs to be lifted. The mbe sheet 210 also includes a plurality of holes 216, each of which rotatably receives a jack screw 230 associated with one of the legs 220. As in the embodiment of Figure 2, the upper end caps 65 of all the filter elements 60 are at the same height as each other when sealed to the mbe sheet 210, but it is instead possible for the height of the upper end caps 65 to vary among the filter elements 60 as in the embodiment of Figure 7. The ejector mechanism 240 includes an ejector plate 241 supporting a plurality of ejector mbes 246 for use in ejecting the filter elements 60 from the mbe sheet 210. The ejector plate 241, shown in plan in Figure 15, may be similar in strucmre to the retaining plate 80 of Figure 5. It is formed by plasma cutting a circular metal plate to form a plurality of generally circular lands 242 connected with each other by strips of metal and largely surrounded by openings 243 through which fluid can pass. The ejector plate 241 may be reinforced by various stiffeners. For example, in the present embodiment, a ring-shaped stiffener 244 is welded to the bottom surface of the ejector plate 241 along its outer periphery, and a plurality of radial stiffeners 245 extending radially inwards from the ring-shaped stiffener 244 are also welded to the bottom surface of the ejector plate 241. Each of the ejector mbes 246 is secured to the top of one of the lands 242 in a suitable manner, such as by welding. Each ejector mbe 246 can slidably receive the projection 71 on the lower end cap 70 of one of the filter elements 60 but is longer than the projection 71 so that when the full length of the projection 71 has entered the ejector mbe 246, the upper end of the ejector mbe 246 will abut against the lower end cap 70. Like the ejector pins 92 of the embodiment of Figure 2, the ejector mbes 246 have varying lengths so that when the ejector mechanism 240 undergoes relative movement with respect to the mbe sheet 220, different ejector mbes 246 will abut against and exert an axial force on the corresponding filter elements 60 at different times. Each of the ejector mbes 246 may have a different length from any of the other ejector mbes 246, or the ejector mbes 246 may be arranged in a plurality of groups, with the ejector tubes 246 in the same group having the same length but differing in length from the ejector mbes 246 of a different group so that the filter elements 60 will be moved by the ejector mechanism 240 with respect to the mbe sheet 210 in groups. Each leg 220 has an upper end movably connected to the tube sheet 210 and a lower end connected to the ejector mechanism 240 so that the legs 220 and the ejector mechanism 240 can undergo axial movement relative to the mbe sheet 210 as a unit. There is no restriction on the number of legs 220, and a single leg or a plurality of legs may be employed. The present embodiment includes six legs 220 spaced at equal intervals around the periphery of the filter assembly 200 and a seventh leg 220 disposed at the radial center of the filter assembly 200. In this embodiment, it is unnecessary for the legs 220 to be capable of movement with respect to the ejector mechanism 240, so the legs 220 and the ejector mechanism 240 are rigidly secured to each other, but they may instead be capable of axial movement with respect to each other, as in the embodiment of Figure 10, for example. At its upper and lower ends, each leg 220 is equipped with internally threaded portions in the form of nuts 221 and 222, respectively, which are welded or otherwise secured to the tubular portion of the leg 220. Each upper nut 221 engages with threads of one of the jack screws 230, while each lower nut 222 is connected with the ejector mechanism 240 by a threaded stud 247. The stud 247 passes through a mbe 249 and is prevented from axial movement with respect to the ejector mechanism 240 by one or more nuts 248 mounted on its lower end. The tube 249 is immobilized with respect to the ejector plate 241 in any suitable manner, such as by being welded to the ring-shaped stiffener 244. Each jack screw 230 is rotatably mounted in one of the holes 216 in the mbe sheet 210. At its lower end, it has threads 232 for engagement with the upper nut 221, and at its upper end, it has a head 231 which rests on a ledge 217 of the hole 216 and prevents downward movement of the jack screw 230. A fluid-tight seal is formed between the jack screw 230 and the hole 216 by one or more suitable sealing members, such as one or more O-rings 233 which are mounted in grooves in the jack screw 230 and enable the jack screw 230 to rotate while preventing fluid from flowing between the wall of the hole 216 and the jack screw 230. A flange 234 is formed on the jack screw 230 above its threads 232. The jack screw is prevented from moving upwards into the hole 216 by a removable split-type locking collar 236 which is clamped sufficiently loosely around the jack screw 230 between the flange 234 and the bottom surface of the mbe sheet 210 so that the jack screw 230 can rotate with respect to the collar 236. To prevent the jack screws 230 from inadvertently being unscrewed from the legs 220, a pin 235 is inserted into the bottom end of each jack screw 230 through a hole 223 in the corresponding leg 220. The pin 235 is longer than the diameter of the threaded hole in the upper nut 221 engaging the jack screw 230 so that the jack screw 230 cannot be disengaged from the upper nut 221 when the pin 235 is in place. When it is desired to detach the jack screw 230 from the nut 221, the pin 235 can be removed from the jack screw 230 through the holes 223 in the leg 220. Figure 18 is a side elevation of one of the legs 220 with its brackets 224 in the extended position, Figure 19 is a front elevation of the same leg, and Figure 20 is a horizontal cross-sectional view along line 20-20 of Figure 18. As shown in these figures, each leg 220 is equipped with a support member in the form of a support bracket 224 which can rest atop the body flange 12 of the bottom 11 of the housing to transmit the weight of the filter assembly 200 to the body flange 12. Each bracket 224 includes a sleeve 225 which is pivotably mounted on one of the legs 220 for movement about the axis of the leg 220 between a retracted position shown by dashed lines in Figure 20 and an extended position shown by solid lines in the same figure. In the retracted position of the bracket 224, the radially outer end of each bracket 224 is located within the inner periphery of the bottom 11 of the housing such that the filter assembly 200 can be inserted into or removed from the housing without interference by the bracket 224. In the extended position, the bracket 224 overlaps the body flange 12 of the bottom 11 of the housing in the radial direction of the housing to enable the bracket 224 to rest upon the body flange 12 and transmit the weight of the filter assembly 200 to the body flange 12. When all of the brackets 224 are in their extended positions, the entire weight of the filter assembly 200 can be supported by the body flange 12 through the brackets 224. Two pins 228 are inserted into each leg 220 above and below the sleeve 225 of the corresponding bracket 224. When the brackets 224 are in their extended positions and sitting atop the body flange 12 of the bottom 11 of the housing, the upper pins 228 rest atop the sleeves 225 of the brackets 224 and transmit the weight of the filter assembly 200 to the brackets 224. When the brackets 224 are in their retracted positions, they rest atop the lower pins 228. Each bracket 224 includes two diametrically opposed recesses 226 in the lower end of its sleeve 225 which fit over one of the lower pins 228 when the bracket 224 is in its retracted position to limit or prevent the rotation of the bracket 224 on the leg 220. Similarly, two diametrically opposed elongated recesses 227, each extending approximately 90 degrees around the circumference of the sleeve 225, are formed in the upper end of the sleeve 225 of each bracket 224 for engagement with one of the upper pins 228 when the bracket 224 is in its extended position to limit rotation of the bracket 224. Other structures can be used to limit or prevent the rotation of the brackets 224, such as various detent mechanisms. Other types of support members can be used to transmit the weight of the filter assembly 200 to body flange 12. For example, instead of being rotatable about the axes of the legs 220, they could be rotatable on the legs about a horizontal axis between a vertical (retracted) and a horizontal (extended) position. In addition, instead of being attached to the legs 220 at all times, the support members could be detachable members, such as pins, collars, or detachable brackets, which are secured to the legs 220 when the filter assembly 200 is to be supported atop the body flange 12 and detached at other times. Figure 17 is an end view of the beam 170 for use in lifting the filter assembly 200. At each end, it includes two lugs 171 each having a hole formed in it. The two lugs 171 are spaced from each other by a sufficient distance for one of the lifting lugs 213 on the mbe sheet 210 to fit between them. When each lug 213 of the mbe sheet 210 is disposed between two of the lugs 171 on the beam 170 and the hole in lug 213 is aligned with the holes in lugs 171, a quick release pin 172 can be inserted into the aligned holes of lugs 171 and 213 to secure the beam 170 to the tube sheet 210. The beam 170 also includes a suitable fitting 173 by means of which the beam 170 can be connected to a crane or other device for lifting the filter assembly 200. The filter assembly 220 will typically include a hold down plate 45 for restraining the filter element 60 against upward movement relative to the mbe sheet 210 during operation of the filter assembly 200. The illustrated hold down plate 45 includes a plurality of openings 46 through which fluid can flow through the hold down plate 45 into or out of the filter element 60. In the present embodiment, the hold down plate 45 is secured to the cover 13 of the housing by bolts so that the cover 13 and the hold down plate 45 can be removed from the bottom 11 of the housing at the same time, but the hold down plate 45 may instead be separate from the cover 13. During operation of the filter assembly 200, it is disposed inside a housing in substantially the same manner as shown in Figure 1, with the mbe sheet 210 resting atop the body flange 12 of the bottom 11 of the housing and being sealed against body flange 12 and against body flange 14 of the cover 13 of the housing by suitable sealing members sandwiched between the mbe sheet 210 and body flange 12 and between the tube sheet 210 and body flange 14. The filter elements 60 can be removed from the mbe sheet 210 of the filter assembly 200 in a variety of manners. A first method will be described while referring to Figures 13 and 14. The cover 13 of the filter housing and the hold down plate 45 are first removed from atop the mbe sheet 210, and then the lifting beam 170 is attached to the lifting lugs 213 of the mbe sheet 210 with the quick release pins 172. The beam 170 and the filter assembly 200 are then lifted upwards by a crane or other suitable mechanism until the brackets 224 on the legs 220 are located high enough (such as above the body flange 12 of the bottom 11 of the housing) to enable them to be pivoted to their extended positions). The brackets 224 are then swung outwards to their extended positions, and the filter assembly 200 is then lowered by the crane until the brackets 224 sit atop the body flange 12 and the entire weight of the filter assembly 200 is supported by the body flange 12, as shown in Figure 13. The lifting beam 170 is then detached from the mbe sheet 210 and removed. The jack screws 230 are then turned by wrenches or other suitable means to screw the jack screws 230 into the legs 220. As the jack screws 230 advance into the legs 220, the mbe sheet 210 gradually moves downwards under its own weight, under the weight of the filter elements 60 suspended from it, and under any downward force applied to it by the jack screws 220. The jack screws 230 may be turned one at a time, or a plurality of the jack screws 230 may be turned simultaneously by any suitable method. As the mbe sheet 210 moves downwards, each of the filter elements 60 will move downwards with the mbe sheet 210 until the lower end cap 70 of the filter element 60 abuts against a corresponding one of the ejector tubes 246 of the ejector mechanism 240. Once abutment takes place, the filter element 60 is incapable of further downward movement, so as the mbe sheet 210 continues to move downwards due to the mπύng of the jack screws 230, the upper end cap 65 of the filter element 60 will begin to slide axially with respect to the corresponding hole 211 in the mbe sheet 210. After a certain amount of relative movement of the upper end cap 65 and the mbe sheet 210, the upper end cap 65 will become unsealed from the mbe sheet 210. As the upper end cap 65 of a filter element 60 is sliding with respect to the mbe sheet 210, the friction between the sealing rings of the upper end cap 65 of the filter element 60 and the hole 211 receiving the upper end cap 65 will produce an axial force acting in a direction resisting the further downward movement of the tube sheet 210. The number of filter elements 60 which at a given time exert a frictional force on the tube sheet 210 resisting its downwards movement may be selected so that the total frictional force is less than the dead weight acting downwards on the mbe sheet 210 (the weight of the mbe sheet 210 and of the filter elements 60 supported by it) so that the filter elements 60 can be automatically unsealed from the mbe sheet 210 simply by lowering the mbe sheet 210 with the jack screws 230. Alternatively, the dead weight acting on the mbe sheet 210 may be supplemented by the downward force which the heads 231 of the jack screws 230 exert on the tube sheet 210 as the jack screws 230 are advanced into the legs 220. When the mbe sheet 210 has been lowered by a certain distance with respect to the body flange 12 of the bottom 11 of the housing, the lower end caps 70 of all of the filter elements 60 will have come into abutment with one of the eject mbes 246 and will have been unsealed from the mbe sheet 210 by relative movement of the tube sheet 210 and the filter elements 60. The state in which all of the filter elements 60 are unsealed from the mbe sheet 210 is illustrated in Figure 14. In this state, the filter elements 60 can be easily lifted out of the mbe sheet 210 with minimal effort, since after the seals are broken, there is little friction between the filter elements 60 and the mbe sheet 210. After the old filter elements 60 are withdrawn from the mbe sheet 210 but before new filter elements 60 are inserted into it, the jack screws 230 are turned in the opposite direction from before to raise the mbe sheet 210 with respect to the ejector mechanism 240 to increase the separation between the mbe sheet 210 and the ejector tubes 246 so that the new filter elements 60 can be inserted into the mbe sheet 210 to a depth sufficient to create a seal between the upper end caps 65 of the filter elements 60 and the mbe sheet 210. Alternatively, instead of mrning the jack screws 230 to raise the mbe sheet 210, the entire filter assembly 200 can be raised by a crane, a jack, or other mechanism to lift the brackets 224 above the body flange 12 of the bottom 11 of the housing, and then the jack screws 230 can be turned to lower the legs 220 with respect to the mbe sheet 210 and increase the spacing between the mbe sheet 210 and the ejector mbes 246, after which the brackets 224 are lowered back onto body flange 12 and the new filter elements 60 are inserted into the mbe sheet 210. When the new filter elements 60 have been installed in the mbe sheet 210, the lifting beam 170 is reattached to the mbe sheet 210 and the entire filter assembly 200 is lifted by the crane with respect to the bottom 11 of the housing 10 to raise the brackets 224 above the body flange 12 until they can be rotated to their retracted positions. The filter assembly 200 is then lowered into the bottom 11 of the housing 10 until the mbe sheet 210 rests on the body flange 12 of the bottom 11 of the housing 10. The hold down plate 45 and the cover 13 of the housing 10 are then sealed atop the mbe sheet 210, and the filter assembly 200 can be restored to operation. Another method of removing the filter elements from the mbe sheet 210 will be described while referring to Figures 21 and 22. Figure 21 illustrates a portion of the filter assembly 200 as it would appear during filtering operation, and Figure 22 illustrates the same portion of the filter assembly 200 with a filter element 60 unsealed from the tube sheet 210 of the filter assembly 200. In this method, the filter elements 60 are unsealed from the mbe sheet 210 by raising the ejector mechanism 240 while the mbe sheet 210 remains stationary atop the body flange 12 of the bottom 11 of the housing 10. To remove the filter elements 60, the cover 13 and the hold down plate 45 are first lifted off the mbe sheet 210. Then, with the mbe sheet 210 resting on the body flange 12 of the bottom 11 of the housing 10, the jack screws 230 are turned to advance them into the legs 220, causing the legs 220 and the ejector mechanism 240 to be raised with respect to the tube sheet 210. As the ejector mechanism 240 rises, the ejector mbes 246 come into abutment with the lower end caps 75 of the filter elements 60 and force the filter elements 60 upwards to unseal them from the mbe sheet 210. Figure 21 shows a portion of the filter assembly 200 when the legs 220 are in a fully raised state and all the filter elements 60 (only one of which is shown in this figure) are unsealed from the tube sheet 210. The cover 13 is shown suspended above the mbe sheet 210, but at this time, it will usually be moved to a location in which it does not interfere with access to the jack screws 230 or the filter elements 60. In this state, the filter elements 60 can be easily removed from the mbe sheet 210, since all of the filter elements 60 will have been unsealed from the mbe sheet 210. When it is desired to insert new filter elements 60 into the mbe sheet 210, after the old filter elements 60 have been removed, the jack screws 230 are turned to lower the legs 220 and the ejector mechanism 240 relative to the mbe sheet 210 to enable the new elements 60 to be fully inserted into the corresponding holes 211 in the mbe sheet 210. After the ejector mechanism 240 has been lowered, the new filter elements 60 can be inserted. This second method of removing the filter elements 60 provides the advantage that it is unnecessary to partially remove the filter assembly 200 from the housing in order to remove the filter elements 60. Therefore, a crane or other lifting equipment is not required to raise the tube sheet 210, wear and tear on the filter assembly 200 are reduced as well as the likelihood of the filter assembly 200 being damaged, and it is unnecessary to break a seal between the mbe sheet 210 and the bottom 11 of the housing 10. Furthermore, since the filter elements 60 remain within the bottom 11 of the housing during the unsealing process, there is less exposure of the filter elements 60 to the environment than in the first method. This feature is particularly advantageous when the filter elements 60 are used to handle toxic or radioactive materials, such as when the filter assembly is installed in a nuclear power plant. Maintaining the filter elements 60 within the bottom 11 of the housing during the unsealing process provides better shielding against radioactivity and increases the safety of the procedure of replacing the filter elements 60. On the other hand, in this second method, the weight of the tube sheet 210 and of any members suspended from it does not exert a force helping to unseal the filter elements 60 from the mbe sheet 210 and the force for unsealing the filter elements 60 must be exerted by the jack screws 230. Therefore, a greater effort may be required to turn the jack screws 230 to unseal the filter elements 60 from the mbe sheet 210 than is required with the first method. Instead of the jack screws 230 being rotatably connected to the mbe sheet 210 and being threaded into the upper ends of the legs 220, they may be rotatably connected to the upper ends of the legs 220 and threaded into holes in the mbe sheet 210 so that as the jack screws 230 are rotated, they translate with respect to the mbe sheet 210. Mechanisms other than jack screws 230 can be used to connect the legs 220 to the mbe sheet 210. For example, as shown in Figure 23, which is a vertical cross- sectional view of a portion of another embodiment, the jack screws 230 may be replaced by unthreaded pins 237, each having an upper end connected to the mbe sheet 210 in a manner preventing translation of the pin 237 relative to the mbe sheet 210 and a lower end slidably connected to one of the legs 220. The illustrated pin 237 is similar in strucmre to the jack screw 230 shown in Figure 16 and is connected at its upper end to the mbe sheet 210 in a similar manner, but it does not have a threaded portion. When the filter assembly 200 is lifted partway out of the housing 10 and the brackets 224 on the legs 220 are pivoted to their extended positions atop the flange 12 of the bottom 11 of the housing 10, if the mbe sheet 210 is released, it can slide downwards under its own weight with respect to the flange 12 and in the process unseal the filter elements 60 from the mbe sheet 210 in the same manner as described with respect to the embodiment of Figure 13. If desired, hydraulic cylinders or other devices may be temporarily connected to the mbe sheet 210 as it is being lowered so as to control the downwards movement of the mbe sheet 210. For example, as shown in Figure 23, a plurality of hydraulic cylinders 250 can be disposed between the body flange 12 of the bottom 11 of the housing 10 and mbe sheet 210 for supporting the mbe sheet 210. The cylinders 250 may be controlled individually, or they may be controlled simultaneously by a common controller. When the mbe sheet 210 is to be placed back upon the body flange 12 of the bottom 11 of the housing 10, the cylinders 250 are removed, and the mbe sheet 210 is lowered onto the body flange 12 with lifting beam 170 or other suitable mechanism. The pins 237 need not be prevented from axial movement with respect to the mbe sheet 210. For example, they may be axially slidable with respect to the mbe sheet 210 and fixed to the legs 220, or they may be slidable with respect to both the mbe sheet 210 and the legs 220. Thus, if the collars 236 are removed from the jack screws 230, the jack screws 230 can slide upwards with respect to the mbe sheet 210 and function as sliding pins. Although the present invention has been described with respect to a number of preferred embodiments, the present invention is not limited to the features shown in the individual embodiments. The features of different ones of the embodiments may be combined with one another to result in arrangements according to the present invention other than those specifically illustrated.

Claims: What is claimed is: 1. A mbe sheet for a fluid treatment arrangement comprising: a plate having first and second surfaces, an outer periphery shaped for sealing to a housing, and a plurality of holes extending between the first and second surfaces, each hole having a ledge formed therein for supporting a fluid treatment element, a depth of the ledge from the first side varying among the holes. 2. A mbe sheet as claimed in claim 1 wherein each hole comprises first and second adjoining sections of differing diameters, the ledge being formed where the sections adjoin one another. 3. A mbe sheet as claimed in claim 1 wherein the plate is substantially flat. 4. A fluid treatment arrangement comprising: a mbe sheet comprising a plate having first and second surfaces, an outer periphery shaped for sealing to a housing, and a plurality of holes extending between the first and second surfaces; and a plurality of fluid treatment elements of equal length each disposed in one of the holes of the mbe sheet, distances of the lower ends of the fluid treatment elements from the mbe sheet varying among the fluid treatment elements. 5. An arrangement as claimed in claim 4 wherein each hole has a ledge formed therein, and an upper end of each fluid treatment element rests on one of the ledges. 6. An arrangement as claimed in claim 4 wherein an upper end of each fluid treatment element is sealed to an inner surface of one of the holes. 7. An arrangement as claimed in claim 6 including a sealing member surrounding the upper end of each fluid treatment element and forming a seal between the upper end and the inner surface of one of the holes. 8. An arrangement as claimed in claim 6 wherein the upper end of each fluid treatment element is sealed to the inner surface of one of the holes by a piston seal. 9. An arrangement as claimed in claim 4 including a hold-down plate adjoining the mbe sheet and opposing an upper end of each fluid treatment element to limit movement of the fluid treatment elements in a lengthwise direction of the fluid treatment elements. 10. A fluid treatment arrangement comprising: a mbe sheet comprising a plate having a plurality of holes formed therein for receiving fluid treatment elements; and an ejector mechanism for unsealing the upper ends of fluid treatment elements with respect to the mbe sheet and comprising an ejector plate spaced from the mbe sheet and movable towards and away from the mbe sheet, and a plurality of projections mounted on the ejector plate for engagement with the lower ends of fluid treatment elements mounted on the mbe sheet. 11. An arrangement as claimed in claim 10 including a retaining mechanism disposed between the mbe sheet and the ejector plate for restricting lateral movement of fluid treatment elements mounted on the mbe sheet. 12. An arrangement as claimed in claim 11 wherein the retaining mechanism comprises a retaining plate having a plurality of openings formed therein through which the projections on the ejector plate can pass to contact the lower ends of fluid treatment elements mounted on the mbe sheet. 13. An arrangement as claimed in claim 12 wherein the retaining mechanism includes a plurality of tubular members secured to the retaining plate at the openings and each sized to receive the lower end of a fluid treatment element mounted on the tube sheet. 14. An arrangement as claimed in claim 10 wherein all of the projections have the same length. 15. An arrangement as claimed in claim 10 wherein the projections having varying lengths. 16. An arrangement as claimed in claim 10 including at least one leg connecting the mbe sheet to the ejector plate. 17. An arrangement as claimed in claim 16, wherein the ejector plate is movably connected to the leg to enable the ejector plate to move with respect to the mbe sheet in a lengthwise direction of the leg. 18. An arrangement as claimed in claim 16, wherein the leg has an end movably connected to the tube sheet for movement relative to the mbe sheet in a lengthwise direction of the leg. 19. An arrangement as claimed in claim 18, including a screw connecting the mbe sheet to the leg, the leg moving with respect to the mbe sheet when the screw is rotated. 20. An arrangement as claimed in claim 19, wherein the screw is rotatably connected to the mbe sheet in a manner preventing lengthwise movement of the screw relative to the mbe sheet. 21. An arrangement as claimed in claim 18 including a support member mounted on the leg for supporting the leg on a flange of a housing for the fluid treatment arrangement. 22. An arrangement as claimed in claim 21 wherein the support member is rotatable about an axis of the leg. 23. An arrangement as claimed in claim 11 wherein the retaining mechanism comprises a plurality of hollow retainers each slidably mounted on one of the projections of the ejector mechanism and having an upper end shaped for engagement with the lower end of a fluid treatment element mounted on the mbe sheet. 24. An arrangement as claimed in claim 23 wherein each retainer is substantially tubular and fits over one of the projections. 25. An arrangement as claimed in claim 23 including a spring acting on each retainer to urge the retainer away from the ejector plate. 26. An arrangement as claimed in claim 10 wherein each projection comprises a mbe mounted on the ejector plate and sized to receive the lower end of one of the fluid treatment elements. 27. A fluid treatment arrangement comprising: a mbe sheet comprising a plate having a plurality of holes formed therein for receiving fluid treatment elements; a plurality of fluid treatment elements each having a first end disposed in and sealed to one of the holes in the mbe sheet and a second end; and an ejector mechanism for unsealing the first ends of the fluid treatment elements with respect to the mbe sheet and comprising an ejector plate spaced from the mbe sheet and movable towards and away from the mbe sheet, and a plurality of projections mounted on the ejector plate for engagement with second ends of the fluid treatment elements. 28. A fluid treatment arrangement comprising: a housing having an inlet and an outlet; a mbe sheet disposed in the housing between the inlet and the outlet and partitioning the housing into an inlet chamber communicating with the inlet and an outlet chamber communicating with the outlet, the mbe sheet having a plurality of holes formed therein; a plurality of fluid treatment elements each having a first end disposed in and sealed to one of the holes in the mbe sheet and a second end disposed in the inlet chamber; and an ejector mechanism disposed in the inlet chamber opposing the second ends of the fluid treatment elements and movable into and out of contact with the second ends of the fluid treatment elements to produce relative movement of the fluid treatment elements and the mbe sheet to unseal the first ends of the fluid treatment elements from the mbe sheet. 29. An arrangement as claimed in claim 28 wherein the ejector mechanism comprises an ejector plate movable towards and away from the mbe sheet, and a plurality of projections mounted on the ejector plate for engagement with second ends of the fluid treatment elements. 30. A fluid treatment arrangement comprising: a housing having an inlet and an outlet; a flat mbe sheet disposed in the housing between the inlet and the outlet and partitioning the housing into an inlet chamber communicating with the inlet and an outlet chamber communicating with the outlet, the mbe sheet having a plurality of holes formed therein; and a plurality of fluid treatment elements of equal length each having a first end disposed in and sealed to one of the holes in the tube sheet and a second end disposed in the inlet chamber, wherein the mbe sheet supports the first ends of the fluid treatment elements such that the distance of the second ends of the fluid treatment elements from the mbe sheet varies among the fluid treatment elements. 31. An arrangement as claimed in claim 30 wherein each of the holes in the mbe sheet has a ledge formed therein for supporting the first end of one of the fluid treatment elements, depths of the ledges with respect to a surface of the mbe sheet varying among the holes. 32. A method of removing fluid treatment elements from a mbe sheet comprising: placing a plurality of fluid treatment elements having first ends sealed to a tube sheet against a surface with second ends of the fluid treatment elements contacting the surface to cause relative movement between the first ends of the fluid treatment elements and the mbe sheet by a sufficient amount to unseal the first ends from the mbe sheet; and removing the fluid treatment elements from the mbe sheet after unsealing the first ends. 33. A method as claimed in claim 32 including contacting the second ends of the fluid treatment elements against the surface at different times so that different fluid treatment elements are unsealed at different times. 34. A method as claimed in claim 33 including contacting the second ends of the fluid treatment elements against the surface in groups. 35. A method as claimed in claim 33 including sealing the fluid treatment elements to the mbe sheet with the second ends of the fluid treatment elements at varying distances from the mbe sheet. 36. A method as claimed in claim 33 wherein the surface varies in distance from the fluid treatment elements. 37. A method as claimed in claim 36 wherein the surface is stepped. 38. A method as claimed in claim 33 including sealing the fluid treatment elements to the mbe sheet such that second ends of the fluid treatment elements lie in a single plane, wherein the surface varies in distance from the plane. 39. A method of removing fluid treatment elements from a mbe sheet comprising: supporting a plurality of fluid treatment elements having first and second ends with a mbe sheet sealed to the first ends; producing relative movement of the mbe sheet and a plurality of projections to contact the second ends of the fluid treatment elements against the projections to produce relative movement between the first ends of the fluid treatment elements and the mbe sheet by a sufficient amount to unseal the first ends from the mbe sheet; and removing the fluid treatment elements from the mbe sheet after unsealing the first ends. 40. A method as claimed in claim 39 including contacting the second ends of different ones of the fluid treatment elements against the projections at different times to unseal the first ends of the fluid treatment elements from the mbe sheet at different times. 41. A method as claimed in claim 40 including increasing the number of fluid treatment elements contacted by the projections as a distance between the mbe sheet and the projections decreases. 42. A method as claimed in claim 40 including supporting the fluid treatment elements on the mbe sheet with the second ends of the fluid treatment elements at varying distances from the mbe sheet. 43. A method as claimed in claim 39 including disposing the fluid treatment elements vertically when producing relative movement of the mbe sheet and the projections. 44. A method as claimed in claim 39 wherein producing relative movement of the mbe sheet and the projections comprises maintaining the projections stationary and moving the mbe sheet towards the projections. 45. A method as claimed in claim 39 wherein producing relative movement of the mbe sheet and the projections comprises maintaining the mbe sheet stationary and moving the projections towards the mbe sheet. 46. A method as claimed in claim 39 wherein producing relative movement of the mbe sheet and the projections comprises turning a screw connected between the mbe sheet and a leg extending between the mbe sheet and an ejector plate on which the projections are mounted. 47. A method as claimed in claim 39 including producing relative movement of the mbe sheet and the projections with the fluid treatment elements at least partially disposed in a housing. 48. A method as claimed in claim 39 including producing relative movement of the mbe sheet and the projections with the mbe sheet resting on a portion of the housing.

Inventors: PRESTON TERRY, SIMONSON ERIC H, SOBEL NELSON J, PRESTON, TERRY, SIMONSON, ERIC, H., SOBEL, NELSON, J.
Applicants: PALL CORP, PRESTON TERRY, SIMONSON ERIC H, SOBEL NELSON J, PALL CORPORATION, PRESTON, TERRY, SIMONSON, ERIC, H., SOBEL, NELSON, J.
Application year: 1998
Main classification: B01D29
IPC codes: B01D29, B01D46, B01D63, B01D65