WO2008036898A1 - Pressure vessels and system for loading filter cartridges therein - Google Patents

Abstract

A system for filtering liquids using multiple cylindrical cartridges in a tubular pressure vessel (11) having a full-bore access at its upstream end and an end closure plug that seats in its counterbore wherein it is secured by a locking ring arrangement. Loading of cartridges into the pressure vessel is facilitated through a removable loading tool (51) which is supported in the entrance end via support structure (53) through engagement with, a circumferential groove (19) used to secure the said end closure plug. The tool provides a trough-like arcuate plate that leads to the circular cross-section interior bore (15) and extends rearward of the entrance end of the pressure vessel.

Description

PRESSURE VESSELS AND SYSTEM FOR LOADING FILTER CARTRIDGES THEREIN

This application claims priority from U.S. Provisional Patent Application Serial No. 60/846,781 , filed September 22, 2006, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to elongated pressure vessels designed to hold multiple cylindrical filtration cartridges, particularly cartridges of the crossflow filtration type, and to systems and methods for facilitating the loading of such cylindrical filtration cartridges.

BACKGROUND OF THE INVENTION With the growth of reverse osmosis, nanofiltration, ultrafiltration, and microfiltration as important commercial separation processes, there have been ever- increasing uses of elongated pressure vessels that will hold multiple such cartridges in end-to-end orientation. These pressure vessels are sometimes referred to as "full- bore-access" vessels because the entrance at at least one end, e.g. the upstream end, of the vessel must have an opening of a diameter such that a cartridge of a size close to the interior diameter of the interior bore can be supplied to and removed from the pressure vessel through such entrance. Likewise, the pressure vessel must have a removable end closure which can be used to seal this entrance to the pressure vessel during separation or filtration operation. U.S. Patent No. 6,632,356 is an example of a patent showing such a pressure vessel having a length such as to accommodate a multitude of cylindrical cartridges or elements of the spiral wound membrane design that are designed for use in separation or filtration processes. However, in this patent the end plate closure is only schematically shown. U.S. Patents Nos. 5,720,411; 5,866,001; 6,165,303; and 6,858,541; and published patent application WO88/03830 show end closures designed to provide full bore access to the interior of such an elongated tubular pressure vessel that will accommodate a plurality of such cylindrical filtration or separation cartridges. The disclosures of all these patents are expressly incorporated herein by reference. Although, heretofore, such filtration cartridges have been made with generally standard diameters (e.g., 4" and 8" diameters in the United States), a recent trend has been to produce larger diameter cartridges or elements, as well as some that are longer in length, which necessarily will have greater weight and thus pose potential handling difficulties. The size of some of the filtration cartridges that are presently being contemplated may even present some difficulty for two men to load and unload. Accordingly, solutions to this potential problem have been sought.

SUMMARY OF THE INVENTION It has been found that by designing the entrance or bell end of a fiber wound pressure vessel so as to have a counterbore of constant diameter that involves only a single step leading to the interior bore of the vessel, a loading tool can be designed that can interengage with a groove in the entrance bell end and thereby become mated with the entrance end section of the pressure vessel. Once secured in place, the tool will then support at least the leading end of a cylindrical cartridge being loaded into the vessel. Such cartridge can then be readily pushed or slid through the entrance guided by this loading tool, or a tool that supports the length of the cartridge may be automated to drive the cartridge into the interior bore of a pressure vessel.

More specifically, the invention provides a cartridge loading tool for combination with a pressure vessel at one end thereof where there is full bore access which is designed to be closed by a removable end closure. Such an end closure is generally secured in place through the use of a locking ring arrangement of some type that is received in a circumferential interior groove. Such a groove is commonly provided by a metal ring insert which is wound in a filament- wound, fiber-reinforced polymer (FRP) vessel) (see '303 patent), or a groove of suitable shape may be formed or machined in the interior surface. By providing a one-step counterbore at the pressure vessel entrance end wherein such a defined groove is located, the design of a loading tool that will support a cylindrical filtration cartridge in alignment with the elongated pressure vessel bore is facilitated. In one embodiment, a simple loading tool may incorporate a thin, half-tubular structure having a concave, arcuate upper surface that will lie in substantial axial alignment with a lower surface portion of the pressure vessel internal bore. The arcuate structure is accommodated in the annular void region in the bell end section in the space provided by the constant diameter counterbore. Attached to this support structure is a collapsible locking ring that is proportioned to be tightly received in the circumferential groove in the bell end section of the pressure vessel, e.g. that provided by a metal ring insert, where it can be locked in place so as to secure the tool mated to the pressure vessel. The support structure is dimensioned to extend outward through the pressure vessel entrance or bell end to an exterior location where it can receive at least the leading end of a cylindrical cartridge and thereby facilitate its loading into the pressure vessel.

A mechanized loading tool may alternatively be provided which employs an arcuate support ring structure that is supported by abutting the end surface of the bell end section of the pressure vessel and secured in place by four axially extending shafts that are journalled therein and that have transverse fingers at the ends that can be rotated into engagement with the near wall of the groove in the bell end section interior surface. An arcuate plate extends from the entrance end of the pressure vessel to a transition section to the interior bore, and its upper surface is substantially aligned with the interior of the bore. This plate and the four rotatable shafts are accommodated in the annular void region provided by this single step counterbore of constant diameter, with space left over for accommodating the flange of a side port fitting if desired. A motor-powered drive mechanism is provided wherein a pusher plate is driven toward the entrance end of the pressure vessel along a cradle that supports a cylindrical filtration cartridge.

In one particular aspect, the invention provides a system for filtering liquids that employs a plurality of cylindrical filtration cartridges, which system comprises a generally tubular pressure vessel having an interior bore of circular cross-section, and having a length sufficient to hold a plurality of the filtration cartridges, a removable end closure for closing at least an upstream end of said vessel, said vessel having a counterbore at said end in which said removable end closure is seated, means defining a circumferential groove formed in an interior wall of said counterbore for receiving circular locking means to secure said removable end closure in a closed position, and a loading tool for use in sliding said cartridges through said upstream end and into said bore of said vessel, said loading tool having (i) structure that will support at least the forward end of a cylindrical cartridge at a location exterior of said upstream end of said vessel and aligned with said bore, and (ii) means attached to said support structure for engagement with said circumferential groove defining means in a manner that secures said support structure in a cartridge-loading orientation in said upstream end of said pressure vessel.

In another particular aspect, the invention provides a method for supplying cylindrical filtration cartridges to a generally tubular pressure vessel, which pressure vessel has a circular interior bore and full-bore access at at least an upstream end thereof, said method comprising the steps of providing a loading tool for mating with the upstream end portion of the pressure vessel so that a portion of said tool will be located within the confines of said pressure vessel and an exterior portion of said tool will extend rearward from the upstream end of the pressure vessel, which tool has structure for supporting at least the forward end of a filtration cartridge, positioning said loading tool in loading orientation at the entrance to the upstream end of the pressure vessel, securing said loading tool in place by interengaging said tool with means defining an internal circumferential groove provided near the entrance to the pressure vessel, and disposing a cylindrical filtration cartridge on said loading tool and sliding said cartridge into the bore of the pressure vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a fragmentary cross-sectional view of the bell-end region of a pressure vessel which is designed to hold a plurality of cylindrical crossflow filtration cartridges.

FIGURE 2 is a perspective view of the pressure vessel of FIG. 1, shown in cross-section, wherein the end closure and two diametrically opposed side port fittings are installed. FIGURE 3 is a perspective view of a cartridge loading tool embodying various features of the present invention that is designed to mate with the pressure vessel illustrated in FIGS. 1 and 2.

FIGURE 4 is a schematic perspective view showing the loading tool of FIG. 3 mated to the end of the pressure vessel shown in FIG. 1, with a cylindrical separation cartridge being loaded on the tool for insertion into the pressure vessel.

FIGURE 5 is a perspective view of another cartridge loading tool embodying various features of the present invention that is motor driven and is likewise designed to mate with the pressure vessel illustrated in FIGS. 1 and 2. FIGURE 6 is another perspective view of the loading tool of FIG. 5 taken from a different angle.

FIGURE 7 is an enlarged fragmentary view showing additional detail of the support and latching portion of the cartridge loading tool of FIG. 5, with the slide plate omitted.

FIGURE 8 is a schematic perspective view showing the loading tool of FIG. 5 mated to the end of the pressure vessel shown in FIG. 1, with the side port fitting omitted, with a cylindrical separation cartridge loaded on the tool and beginning its insertion into the pressure vessel. FIGURE 9 is a schematic view similar to FIG. 8 shown with the pressure vessel removed except for the metal ring insert, to illustrate the interengagement of the transverse fingers at the ends of the four rotatable shafts with the grooved ring insert.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Very generally, pressure vessels for crossflow filtration can be made from any suitable material that has the strength and stability to withstand the superatmospheric pressure which the pressure vessel will be designed to accommodate during a filtration or separation operation. Although stainless steel and other corrosion- resistant alloys may be used to construct such a pressure vessel shell, the most popular construction for pressure vessel shells of this type today is that of fiber-reinforced polymeric (FRP) resin material, e.g., fiberglass-reinforced epoxy or polyurethane resins. For example, a pressure vessel that is designed to accommodate six spiral wound cylindrical cartridges, each having an individual length of about 40 inches, might have a shell or casing with an overall length of about 260 inches, which would include bell-end portions at the respective ends that might each be about 10 inches in length. For the past two or more decades, such 40-inch cartridges have been commonly constructed with 4-inch and 8-inch diameters; however, at the present time, there is interest in employing spiral wound, semipermeable membrane filtration cartridges having diameters of both 12 inches and 16 inches, which cartridge would very likely be about 40 inches in length, but might be even longer.

FIG. 1 illustrates a pressure vessel 11 having a full bore opening suitable for crossflow filtration or separation. The pressure vessel 11 is designed so it can be produced by conventional filament-winding about a mandrel, as generally described with respect to FIG. 2 in the '303 patent. As such, the vessel will have a central casing section 13 that has a cylindrical interior bore 15 of circular cross-section that is sized to be just slightly greater than the diameter of the cylindrical filtration cartridges that will be accommodated therewithin, e.g. 8 in. or 16 in. Each end of the pressure vessel 11 is preferably formed as a bell end section 17 of greater interior and exterior diameter than the central casing section 13.

In the fabrication of such a pressure vessel, a suitable spacer is positioned on a mandrel which is shaped to provide an interior sidewall in the bell end of greater diameter and a short frustoconical transition section between the bell end and the central bore 15. An annular insert 19 that is either shaped to define an interior groove 21, or which itself is formed with a central groove, is slidably located on the spacer. In the latter situation, the insert remains as an integral part of the pressure vessel 11, whereas it is removed in the former after removal of the spacer. Following its fabrication and removal from the mandrel, the pressure vessel is trimmed so that bell end section 17 has a flat end surface 22; its interior cylindrical entrance wall 23 of constant diameter extends from this flat end surface to a short, frustoconical, transition surface 25 that leads to the interior bore 15 of the pressure vessel. The pressure vessel may be provided with two side ports by simply cutting two diametrically opposed circular passageways through the sidewall of the bell end section 17 in the region between the annular groove and the transition surface 25; two side port fittings 27 are then installed within such radial passageways, generally at each end of the vessel. The fittings may have peripheral flanges 27a at their inward ends that are accommodated in the annular void region of the bell end section. Alternatively, the diametrically opposed circular passageways in the bell end may be counterbored to receive the peripheral flanges of side port fittings.

FIG. 2 illustrates an end plug 31 that is used to effectively seal the upstream bell end of the pressure vessel 11. The end plug 31 is circular in shape, having a peripheral surface 33 that is a section of a right circular cylindrical surface. Its diameter is such that it is slidably received in the bell end of the vessel, being just slightly less than the diameter of the entrance surface 23, which is of constant diameter extending to the transition section 25. The plug's outer surface 33 has a recess wherein an annular seal 35 is carried. An axial passageway extends centrally through the core portion of the end plug 31 which accommodates a narrow diameter section of a tubular connector 41, the inward end section of which serves as a female connector that accepts the permeate discharge conduit extending from a cylindrical filtration cartridge, as well known in this art and shown, e.g., in U.S. Patent No. 6,632,356. A locking ring arrangement in the form of a segmented ring 43 is shown; it is received in the groove 21 provided in the metal ring insert 19 and secures the end plug 31 in its closed position in the bell end section 17, as well known in this art. Alternatively, the groove to receive the locking ring segments could be formed in the FRP structure and could have a different cross-sectional shape if desired. The removable end plug 31 may also instead be secured in place by a helical locking ring, e.g. as illustrated in U.S. Design Patent No. D468,392, or by a snap ring (e.g., U.S. Patent No. 5,866,001) or by some other suitable type of a locking arrangement used in this art.

The entrance interior surface 23 of the pressure vessel is of constant internal diameter (ID) all the way to the short transition surface 25, and the exterior surface of the bell end section 17 is generally constant in diameter except for being slightly larger in the region where the grooved ring insert 19 is located. It can be seen that this constant ID design construction facilitates fabrication of pressure vessels by filament winding on a mandrel in a straightforward manner; moreover, it readily provides an annular void space of sufficient depth in the bell-end of the vessel (axially between the groove 21 and the transition surface 25) wherein a flange 27a at the inward end of a side port fitting 27 can reside. This can be of value to avoid the need to wind the bell-end sections to have a sidewall of increased wall thickness to permit the subsequent creation of interior counterbores in the radial passageways to accommodate flanges of side port fittings.

With the growing increase in size and weight of separation/filtration cylindrical cartridges, it has become more of a chore to load such cartridges into pressure vessels and unload them without occasionally damaging the leading end of the cartridge and/or the interior of the entrance end of the pressure vessel as a worker often wrestles such a heavyweight cartridge into position. In one aspect, the present invention proposes to solve this problem by providing a cartridge-loading tool 51 that mates with pressure vessel 11 at its entrance end and provides a support structure or slide which greatly facilitates installing cylindrical cartridges. One embodiment of such a tool 51 is shown in FIG. 4 which includes an elongated main body support structure 53 having a concave arcuate upper surface 55 that is preferably a section of the surface of a cylinder that essentially matches the interior bore 13 of the pressure vessel. The support structure 53 has a support ring segment 57 rigidly affixed to its outer surface which is aligned so as to be perpendicular to the center line of the arcuate surface 55. The ring segment 57 preferably has a thickness, a shape and a size such that it will be snugly received within the circumferential groove 21 that is provided in the entrance surface 23 of the counterbore that receives the segmented locking ring 43; as a result, the seated support ring segment 57 provides stable support for the concave support structure 53 when the tool is disposed in the upstream entrance end section of the pressure vessel, where it extends past the side ports to the transition surface 25 that leads into the bore 13 of the pressure vessel, as seen in FIG. 4.

The illustrated arcuate segment 57 is slightly less than a semicircular segment, (e.g. about a 120° to a 170° segment and preferably about 140° to 150°), and it is interconnected at its ends with a complementary arcuate segment 61 of about the same size and shape. Interconnection of the two support ring segments is via a suitable mechanism that permits transformation of the combined support segments back and forth between a collapsed orientation and an expanded circular orientation. Illustrated are pairs of links 63 that are arranged as toggle mechanisms such that, when both pairs are moved radially outward over center while the support segments 57, 61 are received in the circumferential groove 21, such action locks the expanded support ring assembly tightly within the groove 21.

The support ring arrangement is also stable in its collapsed orientation because the arcuate segments 57 and 61 preferably have flat, facing end surfaces 65 which abut each other; this allows the movable upper arcuate segment 61 to rest on the lower fixed ring segment 57, forming a flattened circle. The links 63 are preferably proportioned to have a radial dimension just less than one-half the radial dimension of the ring segments 57, 61, and about equal to the depth of the groove 21. They are pivotally pinned to opposite surfaces of the ring segments at locations near the radially interior edges thereof, so that, in their expanded, locking orientation, the links 63 will lie just radially inward of the groove 21 and adjacent the interior surface 23 of the counterbore in the void annular space provided. When collapsed, each pair of links 63 is displaced generally radially inward, reducing the effective diameter of the collapsed ring assembly such that it can be easily inserted axially through the entrance into the bell end section 17 of the vessel to the region of the groove 21. Then, with the lower arcuate segment 57 seated in the groove 21, the upper segment 61 is moved upward and away from it until the upper segment also seats in the groove 21. First one toggle mechanism and then the other is manually moved over center to reach the expanded circular orientation, as shown in FIG. 3. The tolerances are such that over center movement of the latter toggle snaps it in place and secures the support ring assembly snugly within the circumferential groove 21.

When the loading tool 51 is so installed, the interior end portion of the support structure 53 extends to the transition section 25 where it leads directly to the internal bore 13 of the pressure vessel. To facilitate sliding of a cylindrical cartridge, the arcuate plate-like support structure 53 is at least about a 120° arcuate sector of a cylinder; it commonly constitutes an arc between about 120° and about 170° to provide a desired smooth slide path for a cartridge into the bore 13. With the tool 51 seated, the overall length of the support structure 53 is such that it extends rearward out of the end of the pressure vessel a distance sufficient to facilitate loading of at least the front end portion of a cylindrical filtration cartridge onto the arcuate surface 55 as depicted in FIG. 4, but preferably not so far as to create a potential obstacle. In a loading operation using the tool 51 , a cylindrical cartridge is placed so that its leading end rests in the trough that is provided by the concave slide section of the loading tool as seen in FIG. 4. It can then be slid smoothly through the entrance end of the pressure vessel and all the way into the closely fitting interior bore 13 wherein it will be automatically joined in end-to-end relationship with other such cartridges already loaded. Once the entire loading operation is complete, the pair of toggle mechanisms 63 are manually moved over center, radially inward to unlatch the support ring assembly and collapse it. The tool 51 is then manually raised to lift the lower arcuate segment 57 out of the circumferential groove 21 and withdrawn to allow the installation of the end closure.

Illustrated from different perspectives in FIGS. 5 and 6 are two views of an alternative embodiment of a loading tool 71 that is motor-driven. Basically, the loading tool 71 includes an annular support structure 73 that mates with the flat entrance or bell end of a pressure vessel 11. A cartridge-loading cradle assembly 75 is supported from the annular support structure 73, and an arcuate slide plate 77 extends forward therefrom through the arcuate support structure and for the length of the bell end section 17 of the pressure vessel. The annular support structure 73 functions as a hollow plug; it has the shape of a stepped ring with a flat, radially outer surface 79 that abuts the flat end surface 22 of the pressure vessel, and a short, radially inner, tubular extension 81 protrudes therefrom and is received snugly within the entrance to the counterbore of the pressure vessel, to assure proper alignment of the loading tool. If desired for operation with a pressure vessel having a short upper flange that extends from the upper region of the entrance, an optional clamping device 83 can be included, having a thumb screw mechanism or the like, that would allow it to be tightened so as to clamp the support structure 73 securely to the end of the pressure vessel 11.

To latch the support structure 73 in place, there are four shafts 85 that are positioned at 90° increments; they are journalled in the support structure and extend completely therethrough. As best seen in FIG. 7, transverse fingers 87 at the ends of the shafts 85 extend radially therefrom and terminate at pointed ends. These fingers are shaped and oriented to cam against and engage the front wall of the locking ring groove 21 that is provided in the counterbore, e.g. in the metal insert 19. Pivotal control arms 89 are attached to the opposite, outward ends of the shafts 85; after the annular support 73 is in position in the bell end section, these control arms are turned to rotate the shafts to align the fingers radially outward where they engage and cam against the near wall of the circumferential groove 21 at four equiangularly spaced points, i.e. 90° apart. If the rear wall of the groove 21 is not perpendicular to the pressure vessel centerline, the transverse fingers are similarly offset from perpendicular.

With the support structure 73 latched in place, the arcuate slide plate 77 is aligned so its concave upper surface extends from the annular support 73 through the bell end section 17 in axial alignment with the interior surface of the interior bore 13 of the pressure vessel. The length of the slide plate 77 is such that it extends to the transition section 25 of the pressure vessel bell end; thus, it provides a smooth pathway along which a cylindrical cartridge can be slid through the bell end of the pressure vessel and past the locking ring groove 21 and any flange 27a of a side port fitting, which is accommodated in the void region provided by the counterbore. The thickness of the annular slide plate 77 is such that it would be juxtaposed upon or just above the surface of any side port fitting flange 27a that was included within the lower region of the pressure vessel, as depicted in FIGS. 1 and 2.

The cradle assembly 75 which extends axially outward from the support structure 73 includes three rods or tubes 91 that are supported at one end in the support structure 77 and at the opposite end in a plate portion 93 of a drive mechanism 95 schematically shown in FIGS. 5, 8 and 9. The three rods 91 are parallel to one another and are placed at about 60° angular increments about the circular opening through the annular support 73; they are positioned so that their cylindrical surfaces are essentially tangent to the interior cylindrical surface of the annular support 73. The three parallel rods 91 thus serve to cradle a cylindrical filtration cartridge 109 and support it in axial alignment with the aperture through the support structure 75. The cradle assembly additionally includes two elongated, parallel, threaded shafts 97, which are cut to have worm screw threads in helical fashion along their surfaces. The threaded shafts 97 are journalled to rotate in the annular support structure 73 at two diametrically opposed locations therein. The opposite ends of the shafts 97 pass through the drive plate 93, where they have a pair of sheaves 99 affixed thereto. The sheaves 99 are driven by a drive belt 101 so as to rotate in the same direction when powered by a motor (not shown).

A pusher plate 103 is slidingly supported on the three rods 91 so it can move axially therealong to push a cartridge 109 through the annular support structure 73 and into the bore of the pressure vessel. A pair of nuts 105, mounted in the pusher plate 103, ride along the worm screw threads and drive the pusher plate 103 in either direction depending upon whether the worm shafts 97 are being turned clockwise or counterclockwise. The pusher plate 103 has a central cutout 107 which accommodates the spigot end of the permeate tube 111 that traditionally extends from one end of a cylindrical filtration cartridge 109, as seen in FIGS. 8 and 9; this tube 111 is received within the female coupling 41 associated with an end closure.

FIG. 8 shows the loading tool 71 latched in place at the entrance end to a pressure vessel 11 , with the side port fitting omitted simply for purposes of clarity. A cylindrical filtration cartridge 109 has been loaded in the cradle portion of the tool, and it is shown as it is beginning to be slid into the annular support structure 73. The pusher plate 103 abuts the end of the cylindrical cartridge 109, and the permeate discharge tube 111 extends through the cut out opening 107 provided in the plate. In this position, the cartridge 109 would have become axially interconnected with the permeate tube of the next cartridge 109a (FIG. 8) in the pressure vessel bore.

FIG. 9 is provided simply as a schematic representation as to better show the engagement between the loading tool 71 and the bell end section 17 of the pressure vessel. The pressure vessel tubular body is omitted except for the metal ring insert 19 that provides the locking ring groove 21 in the bell end. It can be seen that the four rotatable shafts 85 have their control arms 89 turned to radially outward orientations where the transverse fingers 87 are likewise aligned radially outward, in which orientation, they cam and seat against the near wall of the groove 21; thus, the four fingers hook into this groove and tightly support the loading tool 71 at four 90° spaced apart locations in the bell end section 17 of the pressure vessel. This same orientation of shafts 85 is illustrated in the enlarged FIG. 7 view of the loading tool 71 where the tool is shown apart from the pressure vessel.

The length of the cradle portion 75 of the tool should be sufficient to accommodate at least one filtration cartridge 109, and should some manual interconnection between adjacent cartridges be desired, a slightly longer cradle may be preferred to afford such manual interconnection between a cartridge 109a previously slid some distance into the bell end section and the next cartridge 109 being loaded. Depending upon the overall length of the pressure vessel 11 and the diameter of the filtration cartridges 109, it may be preferred to utilize such a motor- driven pusher plate 103 in order to push the entire group of such cartridges along in the interior bore 15, particularly when the last one or two cartridges are being loaded. Moreover, to finally position the entire line of now interconnected cartridges in the pressure vessel bore, it may be desirable to back off the pusher plate 103 and place a short solid cylinder in the cradle having a length just longer than the concave support plate 77 and an opening to receive the conduit 111. Then, when this cylinder is inserted by pushing it to the annular support 73, the group of filtration cylinders will be correctly positioned in the bore.

Once the line of cartridges are in position in the vessel, the control arms 89 are turned to disengage the four fingers 87 from contact with the wall of the groove 21, and the loading tool 71 is withdrawn. An end plug 31, having an elastomeric seal 35 installed in its peripheral recess, would then be slidably inserted. A lead-in chamfer on the tubular connector 41 would guide the entry of the end of the permeate discharge conduit 111 into the female connector portion of the tubular connector 41. With the end plug 31 in place, locking ring segments 43 or some other suitable locking device would be installed.

Although the invention has been described with regard to certain preferred embodiments which constitute the best mode presently known for carrying out the invention, it should be understood that various changes and modifications as would be obvious to one having ordinary skill in this art may be made without departing from the scope of the invention which is set forth in the claims that are appended hereto. For example, although only one end of the pressure vessel has been discussed, and although it is usually desired to load and/or unload cartridges from only one end of a pressure vessel, pressure vessels are usually constructed with both ends similar, and a similar end closure arrangement would thus generally be provided at both ends.

Particular features of the invention are emphasized in the claims that follow.

Claims

1. A system for filtering liquids that employs a plurality of cylindrical filtration cartridges, which system comprises: a generally tubular pressure vessel having an interior bore of circular cross- section, and having a length sufficient to hold a plurality of the filtration cartridges, a removable end closure for closing at least an upstream end of said vessel, said vessel having a counterbore at said end in which said removable end closure is seated, means defining a circumferential groove formed in an interior wall of said counterbore for receiving circular locking means to secure said removable end closure in a closed position, and a loading tool for use in sliding said cartridges through said upstream end and into said bore of said vessel, said loading tool having (i) structure that will support at least the forward end of a cylindrical cartridge at a location exterior of said upstream end of said vessel and aligned with said bore, and (ii) means attached to said support structure for engagement with said circumferential groove defining means in a manner that secures said support structure in a cartridge- loading orientation in said upstream end of said pressure vessel.

2. The system according to claim 1 wherein said support surface includes an upwardly concave arcuate plate that extends past said groove-defining means toward said bore.

3. The system according to claim 2 wherein the loading tool arcuate plate has a surface which is a section of a right circular cylindrical surface.

4. The system according to any one of claims 1 to 3 wherein said pressure vessel counterbore has a cylindrical surface in which said circumferential groove is located, wherein a fitting for a side port having a flange at its inner end is located between said groove and said interior bore, and wherein said arcuate plate is of a thickness less than the radial depth of said counterbore so that it provides clearance for the flange at the inward end of said fitting which is juxtaposed with the interior surface of said counterbore.

5. The system according to claim 3 wherein said loading tool arcuate plate extends through the upstream axial end of said pressure vessel when said loading tool is secured in place.

6. The system according to any one of claims 1, 2, 3 and 5 wherein said engagement means (ii) includes collapsible support means comprising two circular segments, one of which is affixed to said support structure, and link means for permitting movement of said two arcuate segments between expanded and collapsed orientations while remaining interconnected.

7. The system according to claim 6 wherein said link means includes two pairs of pivotally interconnected links that respectively interconnect adjacent ends of said arcuate segments to form a circle.

8. The system according to any one of claims 1 to 3 wherein a support structure is proportioned to be seated against the entrance end surface of said pressure vessel and has a plurality of shafts that extend through the entrance end to said groove defining means, which shafts have transverse fingers at their ends extending radially therefrom, and wherein means located exterior of said pressure vessel is provided to rotate said shafts so that said fingers engage with or disengage from said groove-defining means.

9. The system according to claim 8 wherein said loading tool includes a cradle extending axially rearward from said annular support and said pressure vessel, which cradle is proportioned to receive and support a cylindrical filtration cartridge.

10. The system according to claim 9 wherein there is included a motor driven pusher plate for sliding a filtration cartridge from said cradle, through said support structure, and into the pressure vessel.

11. The system according to claim 10 wherein said cradle includes a plurality of tubular supports for the cylindrical cartridge to rest upon and wherein said pusher plate is supported on said tubular supports and slides therealong.

12. A method for supplying cylindrical filtration cartridges to a generally tubular pressure vessel, which pressure vessel has a circular interior bore and full-bore access at at least an upstream end thereof, said method comprising the steps of: providing a loading tool for mating with the upstream end portion of the pressure vessel so that a portion of said tool will be located within the confines of said pressure vessel and an exterior portion of said tool will extend rearward from the upstream end of the pressure vessel, which tool has structure for supporting at least the forward end of a filtration cartridge, positioning said loading tool in loading orientation at the entrance to the upstream end of the pressure vessel, securing said loading tool in place by interengaging said tool with means defining an internal circumferential groove provided near the entrance to the pressure vessel, and disposing a cylindrical filtration cartridge on said loading tool and sliding said cartridge into the bore of the pressure vessel.

13. The method according to claim 12 wherein said tool includes a cradle that extends exterior of the pressure vessel and a motor-driven plate for sliding the cartridge into said pressure vessel from said cradle.

14. The method according to either claim 12 or 13 wherein, after a plurality of cylindrical filtration elements have been sequentially loaded into said bore of the pressure vessel in end-to-end relation, (a) said loading tool is removed by disengaging it from said groove-defining means and withdrawing it from said pressure vessel upstream end, and (b) a removable end closure is installed in said pressure vessel upstream end and secured in place by installing a locking ring arrangement in said circumferential groove.