Abstract:
A coupling device for connecting a filter element to a fluid conduit has a male coupling secured to either the fluid conduit or the filter element. The male coupling also has at least two radially projecting tabs. A polymeric female coupling engages with the male coupling for securing the filter element on the fluid conduit. The female coupling also has lands for receiving the tabs. The male and female couplings each have a passageway for fluid and that generally defines an axial direction. Each tab is configured for distributing an axial force generally throughout the tab and laterally relative the axial direction so that either the land being forced against the tab or the tab being forced against the land does not damage the female coupling and as long as the filter element remains secured to the fluid conduit.

Description:
TECHNICAL FIELD 
     The invention relates generally to filter cartridges for filter vessels in fluid purification systems, and more particularly to coupling devices that connect replaceable filter cartridges to outlet tubes in filter vessels for purification of radioactive or other hazardous fluids. 
     BACKGROUND OF THE INVENTION 
     Power plants and other facilities with fluid purification processes frequently have filter tanks or filter vessels to purify a variety of different liquids or gases, such as fluid fossil fuels, or radioactive steam or water at nuclear power plants. Known filter vessels have an inlet supplying a fluid to a main filtration chamber holding a number of tubular filters. Long tubes support and act as the core for the tubular filters. These long tubes extend from a tube sheet that separates the main chamber from a plenum for holding purified fluid. An outlet leads from the plenum to the exterior of the filter vessel. 
     In conventional practice, on the opposite end of the filters from the tube sheet, separate mount assemblies use compression to secure the filters to the tubes while sealing that end of the tube. Since the mount assemblies contain numerous parts, these parts frequently fall into the filter vessel while disassembling the mount assembly to replace the filters. Parts falling into the vessel must be removed to prevent damage to filter elements caused by motion of the loose parts during service flow, and in nuclear powered generating plants, Nuclear Regulatory Commission oversight mandates the retrieval of the loose parts. Regardless of the application, if loose parts cannot be located and removed with suitable “fishing” tools, filter elements must be removed to permit access to the vessel to retrieve the loose parts. U.S. Pat. No. 5,667,679 to Bozenmayer et al. attempts to solve this problem by providing a mount assembly that is removed quickly without losing parts. This design, however, is made of stainless steel parts that are difficult to dispose or recycle when radioactive. 
     Referring to FIG. 1, another conventional filter vessel  100  has an inlet  102  that delivers unpurified, typically pressurized, fluids to a main chamber  104 . The arrows F indicate direction of flow for the fluid during normal operations. 
     The fluid enters replaceable filter cartridges  106 , as known in the art, and through known tubular filters contained thereby that remove unwanted particulate or foreign matter. The purified fluid then flows downward through tubes or pipes  108  that open up into a plenum  110 . The plenum is separated from the main chamber  104  by a stainless steel false bottom or tube sheet  112  conventionally welded to the tubes  108 . The fluid then exits the filter vessel  100  through an outlet  114 . Conventional filter vessels  100  typically vary in diameter from six inches to seven feet (and three foot to eight foot heights) depending on the quantity and size of filter elements contained therein. Vessels are known to accommodate anywhere from two to over 1000 filter cartridges. 
     Some conventional filter cartridges  106  are held in place by a hold down plate  116  as known in the art. The filter cartridges  106  are single open-ended with a closed top and a protruding bolt, post, rod or other connector  118  to extend upward through a hole in the hold down plate  116  for lateral support and to maintain distances between adjacent filter cartridges. The hold down plates  116  are usually bolted to the perimeter of the vessel or secured to the bottom by long connecting rods (not shown). Either mechanism provides downward force to seal the cartridges  106  to the tube sheet  112 . Cartridges  106  that are held down by hold down plates  116  typically have a spigot that fits into holes in the tubesheet  112 , and is sealed with either a flat gasket or one or more O-rings (not shown). 
     Some filter cartridges  106  have threaded bottoms for securing the filter cartridge to the tubesheet  112  and affecting a liquid tight seal, which does not require a hold down plate. However, a steel threaded lower end (not shown) must be rotated numerous times by robot, hand, wrench, other special tool or automatic mechanism to thread each filter cartridge  106  onto one of the tubes  108 . 
     Since a filter cartridge  106  that is threaded requires numerous turns, a worker or mechanism must use a relatively long amount of time to unscrew an old filter cartridge from the end of the tube  108  and then screw a new filter cartridge  106  back onto the tube. When radioactive or hazardous materials are being purified, the longer it takes to replace a filter cartridge, the longer a person or tool is exposed to the dangerous environment. Thus, when special tools are used, frequent replacement is required which is expensive. Alternatively, when a worker is required to replace a filter cartridge by placing his gloved hand in the vessel to turn the filter cartridge, the filter replacement may take a long period of time relative to a safe maximum exposure time available to a single worker. Limited by the maximum safe time periods, changing a filter either requires a number of workers taking turns, which raises labor costs, or requires a single worker to take breaks to reduce the exposure levels obtained in a single period, which is time consuming. Otherwise, the worker may feel encouraged to complete filter replacements within an unsafe period of time. 
     As shown in FIG. 2, an improvement over the threaded filter cartridge is a guide rod and hook design used to mount a filter cartridge  200  onto a tube  202  welded to a tube sheet  204  such as an Aegis™ Fossil Assembly as is known in the art. The filter cartridge  200  has a guide rod  206  welded to a plate  208  with an end with a hook (as disclosed in U.S. Pat. No. 3,279,608 to Soriente et al.), or in the illustrated case, a rivet  210 , to latch on the end of the tube  202 . A coil spring  212  and nut  214  are used to seal the top of the filter  216  while compressing the filter cartridge  216  against the tube  202  and to hold it in place against an adapter  218  threaded permanently to the tube  202 . 
     The upper end of the guide rod  206  is used to attach to a positioning lattice (not shown) for lateral stabilization. This design, however, still requires the unthreading of the nut  214  to remove the filter cartridge  200  from the tube  202 , and the rivet hook is not considered of adequate strength for high pressure and highly corrosive nuclear power plant applications. 
     Referring to FIG. 3, in a similar manner as filter cartridge  200 , filter cartridge  300  has a guide rod  302  welded to a plate  304 . However, the plate  304  has a tubular connector pipe  306  with two opposing holes  308  (only one is shown) that receives a pin (not shown). The pin is permanently press-fit into connector pipe  306  before the filter cartridge  300  is placed on a tubesheet tube  312  within the vessel. Connector pipe  306 , with the pin attached, is inserted downward through slots in adapter  310  which is previously attached to the tubesheet tube  312 . The connector pipe is pressed downward against tension from a top spring, and is rotated 60 to 90 degrees in either direction to engage cam slots (not shown) on the inside of the adapter  310 . The pin is not removed separately, but remains with connector pipe  306  and guide rod  302 , and the entire assembly is removed by pressing downward against spring compression and rotating until the pin ends pass upward through the slots in adapter  310 . 
     The top post  314  and mount assembly  316  are also similar to corresponding structures in filter cartridge  200 . While this design (named an Aegis™ Nuclear Assembly ) provides two places of contact (two holes) on the tube  312 , the pin blocks the interior of the tube  314  reducing the flow cross-section within the tube  312 . 
     Some of the problems of the threaded and guide rod filter cartridges have been addressed by the Ecolock™ system by Graver Technologies. Referring to FIG. 4, the filter cartridge  400  has an adapter  402  threaded to a filter vessel tube (not shown) on a tube sheet (not shown). Prior to placement of the cartridge  400  within the vessel, an extension pipe  404  has an upper end threaded to a filter  406 . To place the cartridge  400  within the vessel, a lower end of the extension pipe  404  is inserted over the adapter  402 . The extension pipe  404  has a snap ring  408  for securing to a groove on the adapter. The top of the filter  406  has a post  410  for attaching to a positioning lattice (not shown) and aiding in compressing the cartridge  400 . A spring assembly  412  is located within the extension pipe  404  for maintaining tension in the filter-to-extension pipe connection and adapter-to-extension pipe connection that further maintains the filter cartridge  400  in place. A passage  414  is provided from the center of the filter  406 , through the spring  412 , extension pipe  404  and adapter  402 , to the filter vessel tube (not shown). 
     For removal of the Ecolock™ filter cartridge  400 , the filter cartridge and associated hardware is rotated 90 degrees, which disengages the snap ring  408  from adapter  402 . The spring then assists in ejecting the filter cartridge and hardware assembly in a very expedient manner. However, the Ecolock™ hardware design is very expensive and assembly procedures should include extra measures to ensure that the assembly is in fact locked into place within the vessel since this can be difficult to determine sometimes. If the Ecolock™ assembly is not latched correctly during installation, premature unlatching can occur during operation of the vessel. 
     Another known filter cartridge and filter vessel eliminates the need for threading the filter cartridge to a tube on a tube sheet. As shown on FIGS. 5A-5D, a filter cartridge  500  has a steel adapter  502  that connects a filter  504  to a stainless steel filter vessel tube  506 . As shown in FIGS. 5C-5D, a spring  508  applying forces of 50-60pounds is located between a support ring  510  welded to the exterior of the tube  506  and two pins  512  also welded to the exterior of the tube  506 . Referring to FIGS. 5B and 5C, the adapter  502  has two opposing slots  514  (only one shown) for receiving the pins  512  and has an annular groove  516  that slides over the pins as the adapter is rotated about the tube  506 . Once the adapter is rotated 90° as shown in FIG. 5D, the pins  512  are positioned in two opposing locking apertures  518 . 
     In order to position a filter cartridge  500  on the tube  506 , the filter cartridge must be pushed downward (axially) to engage the pins  512  and spring  508 , and then rotated a full ninety degrees to place the pins in the locking apertures  518 . The spring  508  biases the adapter  502  upward to hold the pins  512  against the bottoms  520  of the locking apertures  518 , which further stabilizes and secures the filter cartridge  500  on the tube  506 . 
     In some nuclear power plant filter vessel applications, during backwashing (fluid flow in the upward direction on FIGS. 5A-5D) the spring and fluid can combine to form an axial force of approximately 100 pounds that impacts the filter cartridge  500 . The adapter  502  must be made of steel to withstand this force, which is transmitted through the circular pins  512 . Otherwise, the high axial forces will cause the pins  512  to rip through an adapter  502  made of a weaker material such as plastic and disengage the filter cartridge  500  during backwashing operations. 
     Radioactive steel hardware, however, is dangerous, difficult and expensive to handle when replacing filter cartridges. Steel hardware cannot be recycled or incinerated using present technology. If hardware is to be separated and re-used with new filter cartridges, significant operator exposure to radiation occurs during disassembly and re-assembly. For this reason alone, the hardware is often replaced rather than re-used. The discarded hardware that is disposed of as radioactive waste will incur a disposal cost ten times or more its initial cost. Even though certain steels might be reusable after 18 months to six years, usually hardware that is “buried” as radioactive waste remains buried forever. 
     SUMMARY OF THE INVENTION 
     In keeping with one aspect of the present invention, a coupling device is able to provide a recyclable thermoplastic female coupling on a filter element for engaging a steel male coupling on a fluid conduit by using tabs on the steel male coupling that reduce the impact of forces on the thermoplastic coupling. This is accomplished by spreading out an axial force laterally along flat surface areas of the tabs that engage lands on the female coupling. With this configuration, the tabs impact the lands along a flat surface rather than merely at a single point, which occurs when a cylindrical pin is used as in the known filter adapters. 
     More specifically, a coupling device for connecting a filter element to a fluid conduit has a male coupling secured to either the fluid conduit or the filter element. The male coupling also has at least two radially projecting tabs. A polymeric female coupling engages with the male coupling for securing the filter element on the fluid conduit. The female coupling also has lands for receiving the tabs. The male and female couplings each have a passageway for fluid that generally defines an axial direction. Each tab is configured for distributing an axial force generally throughout the tab and laterally relative the axial direction so that either the land being forced against the tab or the tab being forced against the land does not damage the female coupling and the filter element remains secured to the fluid conduit 
     In another aspect of the present invention, a coupling device for connecting a filter element to a fluid conduit has a male coupling with at least two radially extending tabs, and a substantially polymeric female coupling with a land for engaging each tab. The female coupling defines an axis, a circumference and an axially extending access channel continuous with a circumferentially extending land channel receiving one of the tabs. Each land defines a surface of the land channel, and the access channel is configured and disposed on the female coupling so that each access channel receives one tab. Either the access channels are moved axially over the tabs or the tabs are moved axially through the access channels in order to place the tabs within the land channels. 
     In yet another aspect, a coupling device for connecting a filter element to a fluid conduit has a first coupling with an exterior surface of rotation and at least two tabs projecting generally radially from the exterior surface. The first coupling also defines a passageway for fluid and an axial direction. Each tab has a flat mating surface with a predetermined surface area for distributing an axial force generally throughout the mating surface and laterally relative to the axial direction. 
     In a further part of the present invention, a female coupling for connecting a fluid element to a fluid conduit has a polymeric body with a land for receiving a projection at a fully secured position. The female coupling defines an axis, a circumference and an axially extending access channel continuous with a circumferentially extending land channel. The land defines a surface of the land channel. 
     The present invention is also directed to a coupling device for connecting a filter element to a fluid conduit that has a polymeric filter-side coupling attached to the filter element, and a conduit-side coupling attached to the fluid conduit and engaging the filter-side coupling. A selected one of the filter-side coupling and the conduit-side coupling has at least two radially projecting tabs, and the corresponding other coupling has lands for receiving the tabs. The filter-side coupling receives an axial force causing the lands and the tabs to press against each other. The filter-side coupling also has either the lands or the tabs configured for generally distributing the axial force throughout the land or the tab laterally relative to the axial direction so that the filter-side coupling is not damaged by the axial force. 
     In similar terms, the present invention has a quick-connect coupling device for connecting a filter element to a fluid conduit. The device has a male coupling with generally radially projecting tabs, and a polymeric female coupling with lands for mating with the tabs. One of the couplings is part of the filter element, and the couplings are configured so that they are fully engaged with each other with at most a single twist of a gripping mechanism (robotic mechanism or the like) or human hand grasping the filter element. 
     The flat tabs also allow for quick placement or removal of the filter element because the tabs merely require a twist of one-sixth of a full 360 degree turn or about 60 degrees, in order to fully secure the couplings or to completely disconnect the couplings. In more detail, a method of rapid installment of a filter element on a fluid conduit has the steps of, with a gripping mechanism or human hand grasping the end of a filter element, moving the filter element axially for engaging a polymeric female coupling on a selected one of the filter element and the fluid conduit with a male coupling on the corresponding opposite one of the filter element and the fluid conduit. One of the couplings is a part of the filter element. Twisting a selected one of the female coupling and the male coupling on the filter element fully engages the fluid conduit coupling without releasing and re-grasping the filter element. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above mentioned and other features of this invention and the manner of obtaining them will be apparent, and the invention itself will be best understood, by reference to the following description of illustrated embodiments of the invention in conjunction with the drawings, in which like characters identify like parts and in which: 
     FIG. 1 is a cross-sectional side view showing components of a filter vessel as known in the prior art; 
     FIG. 2 is a cross-sectional side view of a first filter cartridge to outlet tube connection as known in the art; 
     FIG. 3 is a cross-sectional side view of a second filter cartridge to outlet tube connection as known in the art; 
     FIG. 4 is a part-elevational, part cross-sectional side view of a third filter cartridge to outlet tube connection as known in the art; 
     FIG. 5A is a cross-sectional side view of a fourth filter cartridge to outlet tube connection as known in the art; 
     FIG. 5B is an exploded side view of a coupling device for the fourth filter cartridge as known in the art; 
     FIG. 5C is an assembled side view of the coupling device known in the art; 
     FIG. 5D is another assembled side view of the coupling device known in the art with an upper portion of the coupling turned ninety degrees; 
     FIG. 6 is a cross-sectional side view showing components of a filter vessel in accordance with the present invention; 
     FIG. 7 is an elevational view of the coupling device in accordance with the present invention; 
     FIG. 8 is a top and side isometric view of an adapter portion of the coupling device in accordance with the present invention; 
     FIG. 9 is a top and side cross-sectional isometric view taken substantially along line  9 — 9  in FIG. 8 of the adapter portion in accordance with the present invention; 
     FIG. 10 is an exploded side view of the coupling device in accordance with the present invention, certain interior structure being shown in hidden line; 
     FIG. 11 is an assembled, top cross-sectional view taken substantially along the line  11 — 11  in FIG. 7; 
     FIG. 12 is an assembled, top cross-sectional view taken substantially along the line  12 — 12  in FIG. 7 showing a socket twisted sixty degrees clockwise upon the adapter; 
     FIG. 13 is a top and side cross-sectional perspective view taken along the line  13 — 13  in FIG. 11 of a female coupling in accordance with the present invention; and 
     FIG. 14 is a cross-sectional side view along the line  14 — 14  in FIG. 11 of the female coupling in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 6, a filter vessel  12  has a fluid inlet  14 , an outlet  16 , a main filtration chamber  18  and a plenum  20  separated from the main chamber by a tube sheet or false bottom  22 . While the filter vessel  12  is shown holding three filter elements or cartridges  24 , it will be appreciated that filter vessels are designed to hold anywhere from a single filter cartridge to thousands of filter cartridges depending on the particular filtration requirements of the fluid system. 
     Each filter cartridge  24  has a top portion  26 , preferably designed to be free standing, but alternatively supported laterally and/or vertically by a hold down plate or positioning lattice  28  (shown in dashed line) as known in the art. This may include a hold down plate or positioning lattice  28  with spaced dimples (not shown) to mate with indents (not shown) on the top portion  26  of the filter cartridges  24 , or posts or bolts (not shown) may extend from the top portion  26  to be inserted through holes in the hold down plate or positioning lattice  28  as known in the art. 
     Each filter cartridge  24  holds a tubular filter  30 , as known in the art, that includes yarn and/or pleated non-woven membrane surrounding a perforated core. The filters  30  also have thermoplastic, preferably polypropylene, parts to hold the top and bottom ends of the filter  30 . 
     Referring now to FIG. 7, a coupling device  10  according to the invention mounts each filter cartridge  24  onto a steel filter conduit or tube  32  integrally formed with, or welded to, the tube sheet  22 . Each coupling device  10  includes a preferably stainless steel adapter or male coupling  34  and a polymeric socket or female coupling  36  which is a part of the filter cartridge  24 . The adapter  34  is permanently attached to the tube  32 , as explained below. It will be appreciated that the adapter  34  may be made of any corrosion-resistant material of suitable strength as long as it is compatible with the hazardous or radioactive environment of the fluid process. Polymeric materials suitable for forming the female coupling  36  include thermoplastic and thermosetting plastics, polymers and resins that have sufficient structural strength to withstand, in the structures shown, at least 70 to 100 pounds in axial force without shearing, tearing or otherwise failing. A particularly preferred material includes injection molded polypropylene. 
     Referring to FIGS. 8-10, in the preferred embodiment, the male coupling  34  has a generally cylindrical shape  38  defining a hollow core  40  to be used as a fluid passageway and defining an axial direction or axis ‘a’. The coupling  34  also includes a cylindrical first upper portion  42  that connects to the socket  36 , and a second lower portion  44  that connects to the tube  32 , preferably by welding or threaded connection (best seen in FIG.  10 ). The lower portion  44  has an inner cylindrical surface  46  and an outer hexagonal surface  48 . The top portion  42  has an outer cylindrical surface or exterior side wall  50  with a diameter d1 smaller than the outer diameter d2 of the hexagonal surface  48  (shown in FIG.  10 ). The lower portion  44  has a ledge  52  extending from the outer surface  48  to the outer surface  50 . 
     The inner diameters of the upper and lower portions are also different lengths to accommodate the sizes of the filter cartridge  24  and the fluid conduit  32 . The fluid conduit  32  comes in a range of sizes from 1″ to 6″ outer diameter, but typically is provided with approximately 1½″ outer diameter for both nuclear and fossil fuel applications, while the filter cartridges themselves are provided in the 2—2½″ outer diameter range for all applications. The upper portion  42  of the adapter  34  typically has inner diameter of 1¼ to 1½″ for filter cartridges  24  spaced within the filter vessel  12  at 3 to 3½″ centers. 
     Referring to FIGS. 8,  10  and  11 , the adapter  34  has two diametrically opposed, radially extending tabs  54 . The tabs  54  also extend laterally relative to the axial direction ‘a’ and are elongated circumferentially relative to the circumference of the outer surface  50 . Each tab  54  has a lower flat engaging surface  56  and a corresponding opposing upper surface  58 , both with nonzero widths  60  at an angle to the axial direction or axis ‘a’ while subtending a nonzero arc  62  about the axis ‘a’. The engaging surface  56  also faces the end  64  of the adapter  34  attached to the fluid conduit  32  while the upper surface  58  faces the free end  66  of the adapter  34 , both facing generally normal to the axis and preferably extending in planes perpendicular to the axial direction ‘a’. In the preferred configuration, tabs  54  are welded to, or integrally formed with, the exterior  50  of the adapter  34  so that the core  40  is not blocked by any support mechanism for the tabs  54 . 
     It will be appreciated that while tabs  54  are shown at diametrically opposite positions, many positions at angles to the axis ‘a’ are possible. Additionally, three, four or more tabs can be used rather than just the two tabs shown. For example, the use of more tabs may be indicated where greater axial force is to be withstood. 
     Referring again to FIG. 9, the exterior side wall  50  has a portion  68  that defines a first surface of rotation that fits within the socket  36 . The surface of rotation  68  is provided with a smooth finish for slidably engaging a sealing member  92  as discussed below. Surface of rotation  68  is, in the illustrated embodiment, cylindrical, but could otherwise conform to conical, spherical, ellipsoidal or paraboloidal shapes, or other forms. 
     Referring now to FIGS. 10-14, the female coupling or socket  36  has a preferably cylindrical body  70  with an interior cylindrical surface or side wall  72  defining a hollow core  74  that provides a passageway for fluid and defines an axial direction or second axis ‘a’ in the general direction of flow through the socket  36 . 
     In order to engage the tabs  54 , the socket  36  has two opposing axially extending access channels  76  respectively continuous with two opposing, radially extending land channels  78 , each of which has an opening  80  on the interior cylindrical surface  72  of the socket  36  for receiving the tabs  54 . 
     The tabs  54  are received first by the access channels  76 , which have a cross-section corresponding to, and slightly larger than, a periphery of each tab  54  so that the tab can slide axially through the access channel  76 . The bottom surface of the land channel  78  is also a land  82  for mating with the engaging surface  56  of the tab  54 . The land  82  has a predetermined, preferably flat, surface area and shape corresponding to the shape and size of the surface  56 . The juncture of the access channel  76  and land channel  78  includes a raised triangular pad  84  to secure the tab  54  on the land  82  and from preventing the tab from sliding radially or counter-rotating off of the land  82 . The top surface  86  of the land channel  78  may also act as a land when fluid forces the filter cartridge  24  toward the adapter  34 . 
     The plastic material of the socket  36  is preferably made similar to other plastic parts of the filter cartridge  24  or other substantially nonmetallic material that can be shredded or incinerated along with the filter cartridge  24  when the filter cartridge purifies hazardous or radioactive material. It will be appreciated, however, when recycling or handling is not a concern, the socket could be made of metal, such as stainless steel, as long as it is strong enough to withstand the impact of axial forces distributed by the tabs  54 . 
     While the upper end  88  (shown in FIG. 7) of the socket  36  is attached to the remainder of the filter cartridge  24  preferably by thermo-bonding, it may be attached by welding, chemical bonding, threading, pinning, or any other mechanical mechanism that provides an adequate seal between the remainder of the filter cartridge  24  and the socket  36  while permitting the core of the filter to communicate with the core  74  of the socket. 
     Referring to FIGS. 13-14, the socket  36  also has an annular groove  90  opening on the interior side wall or second surface of rotation  72 . Second surface of rotation  72  matches first surface of rotation  68 . A sealing member, such as an O-ring  92 , fits snugly in the groove  90 . When the coupling device  10  is assembled, the sealing member  92  engages the first surface of rotation  68  on the adapter  34 , forming a tight seal that prevents unpurified material entering the core of the filter cartridge  24  and device coupling cores  40 ,  74 . 
     Referring to FIGS. 7 and 10, the coupling device  10  includes a biasing or elastic member such as a wavy washer  94 . The biasing member  94  creates an axial force that biases the socket  36 , and in turn the filter cartridge  24 , up and away from the adapter  34  and fluid conduit  32 . The axial force is distributed on the areas of the lands  82  and the engaging faces  56  of the tabs  54 . This configuration maintains the tabs  54  against the lands  82  for locking the filter cartridge  24  in place. However, a coil spring, leaf spring or any other biasing device that biases the socket  36  upward and away from the adapter  34  can be used. 
     The wavy washer  94  is mounted around the upper portion  42  and disposed between the ledge  52  and a bottom edge  96  of the socket  36  so that when assembled a top side or surface  98  of the washer  94  abuts the bottom edge  96  and a bottom side or surface  100  of the washer abuts the ledge  52 . The use of the ledge  52  eliminates the need for an additional piece to mount the biasing member  94  on the adapter  34 . 
     Referring to FIGS. 6,  10  and  11 , to mount the filter cartridges  24  on the fluid conduits  32 , the adapters  34  are preferably previously and permanently attached to the fluid conduits during the construction of the tube sheet  22  and filter vessel  12 . From a top opening in the tank (not shown), the filter cartridges  24  are inserted into the filter vessel by grasping the top ends of the filter cartridges opposite the ends with the sockets  36 , lining up the access channels  76  on the socket  36  with the tabs  54  on the adapters  34 , and then axially engaging the socket with the adapter  36  by lowering the filter cartridge and socket. 
     The filter cartridge  24  and socket  36  are lowered so that the tabs  54  slide axially through the access channels  76  in the socket (best seen in FIG.  11 ). Pressure is applied to overcome the force of the wavy washer  74  until the socket  36  will not downwardly displace any farther. In this position, the tab  54  is in line with the land channel  78  and clear of the pad  84 . To place the tabs  54  on the corresponding lands  82 , the filter cartridge  24  is preferably rotated only ⅙ a full rotation as shown in FIG.  12 . It will be appreciated, however, that the design can accommodate up to a maximum of ¼ turn for full engagement or disengagement. The filter cartridge  24  is grasped by hand, robotic mechanism, wrench or other device as known in the art for twisting or turning the filter cartridge  24  and engaging the couplings. 
     Releasing the hold on the cartridge  24  allows the wavy washer  94  to push the filter cartridge  24  upward, which locks each tab  54  on a corresponding land  82 . In the preferred embodiment, at rest the washer  94  exerts an axial force of approximately 20 pounds, which is distributed by the tabs  54 . 
     Referring again to FIGS. 6-7, during normal operation, fluid flowing into the filter vessel  12  from the inlet  14  flows through filter  30  purifying the fluid. The fluid then flows through the core of the filter cartridge  24 , down through the socket  36  and adapter  34 , into the fluid conduit or tube  32  and the plenum  20 , and finally out of the filter vessel  12  through outlet  16 . 
     During backwashing operations, the fluid flows in the reverse of the normal operation, which causes the filter cartridge  24  and socket  36  to be pulled upward by the fluid. This causes the axial forces from the fluid to add to the axial force generated by the wavy washer  94  so that the lands  82  in the socket  36  can press against the tabs  54  with strengths totaling approximately 70 pounds. Since the tabs  54  spread this axial force laterally throughout the flat mating surface  56  or  58  of the tab  54 , the force is distributed so that the thermoplastic material of the socket  36  is not ripped through or sheared off. 
     It will be appreciated that many alternative configurations fall within the scope of the present invention contemplated by the inventors. For instance, the filter cartridges  24  may hang down from an upper tube sheet  32 . Additionally, a filter-side coupling may be a polymeric adapter or male coupling instead of the female coupling while a steel socket may be permanently attached to the fluid conduit as the conduit-side coupling. 
     Both incineration and shredding are used in processing radioactive waste for purposes of volume reduction. Incineration provides the maximum volume reduction, but requires the added expense of containment of combustion products. Landfilling of radioactive waste is not permitted under present laws. Consequently, radioactive waste must be contained in secure containers in a monitored storage facility for the foreseeable future, which is extremely expensive. 
     The many advantages of this invention are now apparent. A coupling device  10  has a polymeric socket  36  that can be incinerated or shredded along with other parts of the filter cartridge  24  for recycling after the socket  36  is used in hazardous or radioactive material processes. Incineration and shredding reduces volume of radioactive material which must be contained in secure containers at monitored storage facilities because landfilling of radioactive material is not permitted under current law. In addition, this type of recyclable and shreddable material is safer to the environment than landfill operations which require long periods of time to reuse radioactive material and large land areas where radiation can escape from. 
     Also, an adapter  34  has tabs  54  designed to spread an axial force laterally, by providing a generally flat predetermined surface area  56  or  58  on the tabs  54  for impacting a land  82  on the socket  36  so the full force is not directed to a single point on the socket  36 . The tabs  54  and channels  76 ,  78  are configured so that only a single twist of ¼ to ⅙ a rotation is needed to fully engage the socket  36  on the adapter  34 . 
     While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims.