Liquid purification or separation – Filter – Within flow line or flow line connected close casing
Reexamination Certificate
1998-04-23
2001-08-07
Fortuna, Ana (Department: 1723)
Liquid purification or separation
Filter
Within flow line or flow line connected close casing
C210S457000, C210S484000, C210S497010
Reexamination Certificate
active
06269956
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates generally to filters and, more particularly, to a disposable filter for removing particulate matter from an aqueous flow, especially radioactive materials entrained in cooling water, which provides an improved cartridge-style filter for use in such installations to reduce the volume and weight of the hazardous waste resulting from the end of life of the filter.
(2) Description of the Prior Art
Nuclear reactors use water in primary and secondary support systems. Some of the particulate entrained in these systems are radioactive. These radioactive particles must be removed for safe and efficient system operational and maintenance. This is done conventionally by filter elements that are installed for a given period of time to remove the particulates. After a period of time, the filter becomes clogged with removed particulate and must be replaced.
Conventional filters for this purpose have a perforated, stainless steel outer cylinder and, in some cases, an inner stainless steel cylinder, and stainless steel end fittings, and a permanently installed interior filter medium. The filtrate flows from inside to outside through the filter medium and the pores of the stainless steel cylinder. The outer stainless steel cylinder and end fittings have been considered a necessity to give the filter the structural strength and integrity to withstand the temperature, pressure and dynamic filtration loads of the forces of the flowing liquid and avoid corrosion.
However, when the filter is spent, the outer and inner cylinders and end fittings become a large, strong, corrosion resistant, heavy piece of hazardous, radioactive waste. Requirements for disposal of this type of waste safely are very costly. The steel is difficult to compress to a reduced volume and does not easily shred to smaller pieces. Disposal of the filter, therefore, requires a great deal of cost.
One solution to this problem is disclosed in U.S. Pat. Nos. 5,478,469 and 5,678,230, issued to Bryan and Pop. These patents disclose a disposable filter for removing hazardous particulate matter from an aqueous flow. The filter includes a rigid support housing having an input port for the aqueous flow, an exit port for the aqueous flow, a brace to securingly engage a filter vessel for the aqueous flow, an internal seal and an external seal, and a disposable filter cartridge configured similarly to the housing and sized to be substantially entirely received within the housing and sealingly engage the internal seal and having a filter medium that extends across a path from the input port to the exit port when received in the housing, the cartridge having a terminal seal located to sealingly engage the cartridge to the aqueous flow filter vessel outside of the housing when the cartridge sealing engages with the internal seal. The rigid support housing may be installed in a filter vessel for an extended period and held in place by the brace, and repeatedly during the extended period, a disposable cartridge may be installed within the housing to seal the cartridge to the filter vessel, aqueous flow may be directed through the filter medium, and the cartridge may be removed and discarded. These patents are hereby incorporated by reference in their entirety.
For all of its advantages, the Bryan and Pop filter did have some drawbacks. Specifically, the brace arrangement was difficult to machine and install in the field. Furthermore, the disposable filter included some hard to dispose of metal parts. Finally, the porous outer sleeve used to add strength to the disposable filter took up critical space that limited the applications which could benefit from the filter.
Thus, there remains a need for a new and improved disposable filter which performs well in existing facilities, reduces the cost of disposal of spent filters contaminated with hazardous materials such as radioactive particulate matter while, at the same time, overcomes the problems associated with Bryan and Pop.
SUMMARY OF THE INVENTION
The present invention is directed to a filter for a filter vessel which converts the filter vessel to use disposable filters. The filter includes a rigid support housing having an input passage for the aqueous flow, an exit passage for the aqueous flow, an internal sealing surface and a locking seal located adjacent to the input passage to securingly engage the housing to the filter vessel for the aqueous flow.
The invention also includes a disposable filter cartridge. The cartridge includes a flexible filtering medium having first and second ends. A terminal seal is affixed to the first end of the filtering medium for sealing engagement with the filter vessel and filter vessel lid and a wall seal on the second end of the filtering medium for engagement with the internal sealing surface of the support housing. The filtering medium is sized to be substantially entirely received within the support housing and to sealingly engage the internal sealing surface in the support housing with the wall seal and the filter medium extends across a path from the input passages to the exit passages of the support housing when the terminal seal engages with the filter vessel and filter vessel lid.
In the preferred embodiment, a lifting point is formed in the disposable filter cartridge adjacent to the terminal seal to permit easy removal of the cartridge either by hand or tooling.
The support housing may be installed in a filter vessel for an extended period and held in place by the locking seal, and repeatedly during the extended period, the disposable filter cartridge may be installed within the support housing to seal the disposable filter cartridge to the filter vessel and the support housing, to direct aqueous flow through the filter medium, and the disposable filter cartridge may be removed and discarded.
In a preferred embodiment the housing has a cylindrical shape including two ends and inner and outer sidewalls, with an input port at one end of the cylindrical shape and a plurality of exit ports in the form of apertures in the outer sidewall. In the preferred embodiment the cartridge has a cylindrical shape including two ends and a sidewall, the terminal seal being located at one end, the sidewall extending across the path between inlet port and outlet ports of the housing, and the wall seal engaging the internal sealing surface of the housing.
Typically, the housing is made of stainless steel. In a preferred embodiment the cartridge includes ends containing seals and a flexible filtering medium. The flexible filtering medium may be of any suitable filtering medium such as polysulfone foam or polypropylene. The seals may be silicone rubber.
Accordingly, one aspect of the present invention is to provide a filter for removing particulate matter from an aqueous flow. The filter includes: (a) a rigid support housing having an input passage for the aqueous flow, an exit passage for the aqueous flow, an internal sealing surface and a locking seal located adjacent to the input passage to securingly engage the housing to a filter vessel for the aqueous flow; and (b) a disposable filter cartridge sized to be substantially entirely received within the housing and having a filter medium that extends across a path from the input passage to the exit passage when received in the housing, the cartridge having a terminal seal located to sealingly engage the cartridge to the filter vessel for aqueous flow outside of the filter vessel and the housing when the cartridge sealingly engages with the internal sealing surface of the housing, whereby the support housing may be installed in a filter vessel for an extended period and held in place by the locking seal, and repeatedly used during the extended period, the disposable filter cartridge may be installed within the support housing to seal the disposable filter cartridge to the filter vessel and the support housing, aqueous flow may be directed through the filter medium, and the disposable filter cartridge may be removed and discarded.
Anothe
Fortuna Ana
Framatome Technologies, Inc.
Rhodes & Mason PLLC
Ward Richard W.
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