Abstract:
Vent filters for containers such as barrels which contain hazardous waste, such as transuranic (nuclear) waste, include a bore therethrough which does not intersect the material of carbon-to-carbon filter media inserts disposed within the vent filter. Each of the bores has a stainless steel tube disposed therein wherein the stainless steel tube has at an interior end a septa-type seal and at an outer end an impenetrable plug. In order to sample head gases, a syringe is used with a needle that penetrates the septa-type seal. After the needle is withdrawn, the septa-type seal closes and the impenetrable plug is replaced.

Description:
FIELD OF THE INVENTION 
     The present invention is directed to a vent filter with a direct sample capability, more particularly, the present invention is directed to a vent filter with a direct sample capability wherein the vent filter is installed in a container which contains material that may include or generate gasses. 
     BACKGROUND OF THE INVENTION 
     Material contained in containers frequently include or generate gasses or vapors need, for various reasons, to be vented from the container. It is frequently necessary or desirable to have knowledge of what these gasses or vapors are so that decisions can be in made with respect to the material within the container. This is especially the case if the material in the container is hazardous waste which generates or includes gasses which are, for one reason or another, also possibly hazardous. For example, transuranic waste stored in containers such as drums, convenience cans or bags wherein hydrogen gas as well as volatile organic compounds may be generated from the waste. If these gases or vapors are not vented, an explosion can occur within the container and the explosion can disperse radioactive materials into the surrounding environment. Accordingly, it is necessary to sample head gases which accumulate above the stored transuranic material in order to determine whether or not hazardous gases are being generated and if the vent filters are performing satisfactorily to let the gases escape. 
     The prior art approach has been to sample head space gas prior to installing the vent filter by sampling directly through a vent hole in the lid of a container. If it was necessary to sample head space gas after installation of the vent hole filter, the vent hole filter needed to be removed prior to sampling. This of course discourages sampling of head space gas because rather complex procedures must be followed in order to remove vent hole filters when a container contains hazardous waste such as transuranic waste or hazardous materials such as titanium oxides and salts. This of course discourages taking bead gas samples when perhaps the safest approach would be to take those samples in order to have a more reliable monitoring program. 
     SUMMARY OF THE INVENTION 
     In view of the aforementioned considerations, it is a feature of the present invention to incorporate a sampling facility with a vent filter in order to facilitate and make less complex sampling of materials in the containers. 
     In view of this feature and other features, the present invention is directed to an arrangement for sampling head space gas in a container having materials therein which include or generate gas accumulated in a head space above the materials. The arrangement comprises a vent insert having a filter element therein, the vent insert being disposed of a housing, the housing having a second portion which does not include the filter element. A bore through the second portion of the housing is adapted to receive a probe therethrough for withdrawing a sample of head space gas. Me bore contains a seal for sealing around the probe when the probe is inserted. 
     In more specific aspects of the invention, the seal is an elastic deformable material which allows the probe to be thrust therethrough and reseals behind the probe as the probe is withdrawn and the bore includes threads for receiving a threaded closure so as to impenetrably close the bore. 
     In still other aspects of the invention, the bore is coaxial with the axis of the vent if the filter element is annular and defines a hollow core through which the bore extends. In still other aspects of the invention, the bore is disposed obliquely with respect to the axis of the vent at an angle which does not intersect with the filter element whereby the probe may be inserted to pass beside the filter element into the head space. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation partially in section showing a container, such as a drum which includes a vent filter in accordance with the present invention; 
     FIG. 2 is a side elevation of a first embodiment of a vent filter configured in accordance with the principles of the present invention shown with a syringe used to withdraw a sample from the container with which the vent filter is used; 
     FIG. 3 is a side elevation similar to FIG. 2, but showing the syringe being inserted through the bore; 
     FIG. 4 is a top view of the first embodiment of the vent filter shown in FIGS. 2 and 3; 
     FIG. 5 is a side elevation of a second embodiment of a vent probe configured in accordance with the present invention; 
     FIG. 6 is a top view of the vent probe of FIG. 5; 
     FIG. 7 is a side elevation of a third embodiment of a vent probe configured in accordance with the present invention; 
     FIG. 8 is the top view of the vent probe of FIG.  7 ; 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, there is shown a container  10  which may, for example, be a drum or a convenience can for containing hazardous materials such as nuclear waste or other nuclear material that present a radiation hazard. Container  10  may also be a container for containing other types of materials which may or may not be waste materials, but which either have or generate a gaseous or fluid component which for one reason or another it is desirable to sample. 
     In the illustrated embodiment, the material needing immediate consideration is a transuranic material  10  which is generally a solid material and which may include or generate a gas  11  which it is necessary or desirable to vent. The gas  11  accumulates in a head space  14  above the material  12 , underneath the lid  16  of the drum  10 . The lid  16  has a vent hole  18  therethrough which communicates the space  14  with the surrounding atmosphere  20 . In accordance with the present invention, vent hole  18  is plugged with a vent filter  22 , the vent filter  22  including a filter media  24  and a bore  26 . The bore  26  includes at least a sealing material  27  which keeps the bore  26  closed unless a needle  30  of a syringe  32  is pushed therethrough to withdraw a sample of the gas in the head space  14 . Normally, all of the gas  11  in the head space  14  can vent through the filter media  24  so that particulate matter and compounds in the gas are trapped or adsorbed before the gas enters the surrounding atmosphere  20 . 
     Generally, the filter media is a carbon composite filter media such as that disclosed in U.S. Pat. No. 4,500,328, incorporated herein in its entirety by reference. while a carbon composite filter media  24  is specifically disclosed, the filter element  24  may be of any suitable material which keeps harmful materials out of the atmosphere  20 . 
     Turning now to FIGS. 2-4, there is shown a first embodiment of a vent filter  30  configured in accordance with the principles of the present invention, wherein the vent filter comprises a housing  32  having first portion  34  and a second portion  36 . First portion  34  is hexagonal in shape so that it may be readily gripped by a wrench (not shown) has a cavity  38  therein which receives a carbon-carbon filter media insert  40 . Both the cavity and insert are preferably cylindrical but may be other shapes if necessary or desired. The filter media insert  40  is retained in place with a layer of RTV silicon adhesive  42 . spaced inwardly from the cavity  38  that holds the carbon-carbon filter media insert  40  is a cylindrical opening  43  that provides a hollow core to the second portion  36  of the housing  30 , which second portion  36  has exterior threads  46  for threading into the vent opening  18  in the lid  16  oft he container  10  (see FIG.  1 ). Since the second portion  36  has a diameter less than the diameter of the first portion  34 , a shoulder  48  is provided at their juncture, which shoulder is abutted by a gasket  50 . A lid  52  is welded to the top surface of the first portion  34  of the housing  34  at weld points  54 . The weld points  54  are at the bottom of projecting spacers or feet  56  which project from the lid  52  to define a gap  58 . 
     In operation, gases such as hydrogen which have accumulated in the head space  14  of the container  10  (see FIG. 1) pass through the hollow core  44  and are filtered by the filter element  40  before entering the gap  58  and venting to the surrounding atmosphere  20 . 
     In accordance with the present invention, the vent filter  30  is provided with a bore  60  which is oblique with respect to the axis  62  of the vent filter so that it does not intersect the filter media  40 . The bore  60  is closed with two plugs, the first plug being a resilient plug  62  made of a silicon septa-type material and the first plug being a nylon tipped set screw  64 . The first plug  62  is penetrable and self-sealing, while the second plug  64  is impenetrable. 
     In order to sample gas in the head space  14  of the container  10  (see FIG.  1 ), a syringe  68  which has a needle  69  is used. The impenetrable plug  64  is unscrewed and removed and the needle  69  is inserted through the sealing plug  62 . Head space gas  11  is then withdrawn into the barrel  70  of the syringe  68  by pulling a plunger  72  in the barrel with a knob  73 . The head space is then stored in the barrel  70  for analysis. The needle  69  is then withdrawn from the self-sealing first plug  62  and the bore  60 . The bore  60  is then further sealed with the nylon tipped second plug  64  which is preferably in the form of a set screw that is threaded back into the bore  60 , which bore has internal threads complementing those of the set screw. Consequently, gas  11  in the head space  14  may be conveniently and safely sampled whenever the vent filter  30  is accessible. Accordingly, it is not necessary to place the top of the container  10  in a glove box environment in order to analyze head space gases. 
     Referring now to FIGS. 5 and 6, there is shown a second detailed embodiment of the invention wherein the filter media insert  40 ′ has an axial length which is longer than the axial thickness of the filter media  40  shown in FIGS. 2 and 3 and wherein the filter media insert is annular defining a hollow core  81 . As with the first embodiment, the housing  72 ′ has first portion  34 ′ and a second portion  36 ′, the second portion  36 ′ being externally threaded for threading into the vent opening  18  in a lid  16  of a container  10 . The vent filter  80  further includes a lid  52 ′ which is welded to the first portion  34 ′ of the housing  32 ′, the lid  52 ′ having a central opening  83  therethrough aligned with a hollow core  81  of the filter media  40 ′. 
     Disposed within hollow core  81  and the central opening  83  through the lid  52 ′ there is a stainless steel tube  85 . The stainless steel tube  85  includes a first plug  86  of a septa-type silicon material which is self-sealing and a second plug  87  which is an impenetrable material, the second plug preferably being in the form of a set screw which is nylon tipped at its inner end and screws into threaded end portion  88  of the tube  85 . The second embodiment  80  of the vent filter functions substantially the same as the first embodiment  30  and receives the needle  69  of a syringe  68  in the same way with the first plug  86  allowing passage therethrough of the needle  69  and then sealing the tube  85  when the needle  69  is withdrawn (see FIG.  3 ). The second plug  87  is then screwed into the threaded end of the tube  85  to securely seal the tube  85 . 
     Referring now to FIGS. 7 and 8 where a third detailed embodiment  90  of the vent filter is shown, the third embodiment is integrated with a filter cutter assembly  92  such as the filter cutter assembly disclosed in U.S. Pat. No. 6,041,669 issued Mar. 28, 2000 incorporated herein by reference. The filter cutter assembly  92  includes a housing  93  which has a cylindrical central cavity  94  which receives therein a carbon-to-carbon filter media insert  40 ″. The filter media insert  40 ″ rests on a shelf  86  within the cylindrical cavity  94  in spaced relation to the bottom  97  of the cavity so as to define a space  99 . Preferably, the carbon-to-carbon filter media insert  40 ″ is held within the cavity  94  by RTV silicon sealing adhesive  100 . 
     Disposed within the normally hollow core of the annular filter media insert  40 ″ is a stainless steel tube  104  which is secured coaxially with the annular filter media insert by a layer of RTV silicon  105 . The stainless steel tube  104  has a septa-type seal  108  at the lower end thereof and an impenetrable plug  110  at the upper end thereof, the impenetrable plug being in the form of a nylon tipped set screw which is threaded into the threaded upper end of the stainless steel tube  104 . 
     The diameter of the stainless steel tube  104  is less than the diameter of a bore  112  extending from the space  99  down through a tubular portion  116  of the housing  93 . The tubular portion  116  has an insertion portion  118  which is received within the head space  14  of the barrel (see FIG. 1) and has an open end  120 , as well as side ports  122 ,  124  and  126  that enable gas to enter the tubular portion  102 . The head space gas then flows through these openings in the tube  116  so as to be conveyed by the bore  102  to the space  99 . Since the space  99  communicates directly through the filter media insert  40 ′, the gas passes through the filter media insert  40 ′ and into the atmosphere through holes  130  in a lid  132  which is fixed to the upper surface  134  of the housing  93  by welding or by adhesive. A gasket  136  seals with the top surface oft he lid  16  of barrel  10  (see FIG.  1 ). 
     When it is necessary or desirable to sample the head space gas, the impenetrable plug  110  is removed and the needle  69  of the syringe  68  (see FIG. 2) is inserted through the stainless steel tube  104  and through the septa-type seal  108  to withdraw the gas into the syringe. After the sample has been taken, the needle is withdrawn so that the septa-type seal  108  closes and thereafter the impenetrable plug  110  is threaded back into the threaded end of the stainless steel tube  104 . 
     From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.