Abstract:
A device for gas analysis includes a detector tube ( 2 ) and can be used in the area of explosive or combustible gases. A filter material, which consists of a granular, porous material and has an impregnation for absorbing toxic gases, is provided between the detector tube ( 2 ) and a pump ( 6 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2009 039 886.4 filed Sep. 3, 2009, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a device for gas analysis with a detector tube. 
       BACKGROUND OF THE INVENTION 
       [0003]    A device for gas sampling with a detector tube is known from DE 733 715 B. A double-acting reciprocating pump, in which two pumps with hollow piston rods are arranged opposite each other, is provided for taking gas samples. A hollow housing with an insertion pipe is located between the free ends of the piston rods for receiving the detector tube. The interior space of the housing is provided with a filter mat, with which toxic substances, which have not been fully absorbed by the detector tube, are to be absorbed. Harmful gas shall be prevented with the filter mat from entering the pumps. Details of the properties of the filter mass cannot be found in DE 733 715 B. 
       SUMMARY OF THE INVENTION 
       [0004]    The basic object of the present invention is to improve a device of the said type such that it can be used in the area of explosive or combustible gases. 
         [0005]    According to the invention, a device is provided for gas analysis. The device comprises a detector tube connected to a pump for sampling gas. A filter material is provided through which flow can take place, between the detector tube and the pump. The filter material comprises a granular porous material with an impregnation for absorbing harmful gases. 
         [0006]    Provisions are made according to the present invention for using as the filter material in the gas analyzer the porous carrier material provided with such an impregnation. The porous material is mounted in a dense packing in a filter housing. Silica gel, aluminum oxide or aluminum silicate are suitable for use as porous materials. 
         [0007]    The carrier materials mentioned according to the present invention have the advantage, for example, over activated carbon that they cannot ignite at high toxic gas concentrations. Another advantage is that organic gases and vapors can be desorbed more rapidly in a rinsing cycle. 
         [0008]    The filter material is advantageously arranged between two plastic screens arranged opposite and two glass fabric mats. A particle filter arranged of the filter material is used to retain aerosols and dusts. 
         [0009]    The impregnation of the porous carrier is advantageously designed to adsorb acid gases, for example, H 2 S or SO 2 . The impregnating components are basic copper carbonate or basic zinc carbonate or a mixture of basic copper carbonate and basic zinc carbonate. The weight percentage of the impregnation relative to the porous carrier is up to 10%. 
         [0010]    A process of preparing a filter material for a device for gas analysis with a detector tube is characterized by the steps of dissolving 1,000 g of basic copper carbonate with 200 g of ammonium carbonate in 4,000 mL of ammonia solution and of subsequently impregnating 16 kg of silica gel with it. The silica gel thus impregnated is subsequently dried in a drying cabinet. 
         [0011]    An exemplary embodiment is shown in the figures and will be explained in more detail below. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    In the drawings: 
           [0013]      FIG. 1  is a schematic sectional view of a measuring device for gas analysis according to the invention; 
           [0014]      FIG. 2  is a perspective view of a filter cartridge according to the invention; 
           [0015]      FIG. 3  is a longitudinal sectional view of the filter cartridge according to  FIG. 2 ; and 
           [0016]      FIG. 4  is a detail view of the region labeled A of the filter cartridge according to  FIG. 3 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    Referring to the drawings in particular,  FIG. 1  schematically shows a measuring device  1  for gas analysis with a detector tube  2 . The measuring device  1  comprises a housing  3  with a bracket  4  for receiving the detector tube  2 , with a gas duct  5  between bracket  4  and a diaphragm pump  6  and with a filter cartridge  7  in the gas duct  5  between bracket  4  and diaphragm pump  6 . The diaphragm pump  6  is connected to a pump control unit  8  and a power source  9 . The measured gas, drawn through the detector tube along arrows  10 , leaves the diaphragm pump  6  at the measured gas outlet  11 . 
         [0018]      FIG. 2  shows a perspective view of the filter cartridge  7 . 
         [0019]      FIG. 3  shows the filter cartridge  7  according to  FIG. 2  in a longitudinal section. Filter cartridge  7  comprises a pot-shaped filter housing  12  with a gas inlet  13  and a filter cover  14  with a gas outlet  15 . Filter cover  14  is connected to the filter housing  12  in a gas- and liquid-tight manner. A first plastic screen  16  with a first glass fabric mat  17  placed on it, which are braced by means of a first snap ring  18 , is located at the bottom of filter housing  12 . This is topped by the filter material  19  consisting of a granular bulk material formed by impregnated silica gel. The filter material  19  is covered with a second glass fabric mat  20  and a second plastic screen  21 , which are braced by means of a second snap ring  22  in relation to the filter housing  12 , so that the filter material  19  is mounted in a dense packing in the filter housing  12 . A particle filter  23 , which is fixed to the filter housing  12  with the filter cover  14 , is located on the top side of filter housing  12 . 
         [0020]    Other porous carrier materials may be provided for the filter material  19 . In each case in the porous carrier is provided with an impregnation. According to other preferred embodiments, instead of the silica gel, aluminum oxide or aluminum silicate are used as porous materials. 
         [0021]    The carrier materials mentioned according to the present invention have the advantage, for example, over activated carbon that they cannot ignite at high toxic gas concentrations. Another advantage is that organic gases and vapors can be desorbed more rapidly in a rinsing cycle. 
         [0022]      FIG. 4  shows detail A according to  FIG. 3 . Identical components are designated by the same reference numbers as in  FIG. 3 . A particle seal  24  is located between the filter cover  14  and the filter housing  12  in the area of particle filter  23 , followed by an O-ring seal  25  as a gas seal and a closure  26 , which fills the free space between the filter cover  14  and the filter housing  12  and brings about a liquid-tight closure. 
         [0023]    The filter material  19  is impregnated such that 1,000 g of basic copper carbonate with 200 g of ammonium carbonate are dissolved in 4,000 mL of ammonia solution while gently heating. Then, 16 kg of granular silica gel are impregnated with the solution and subsequently dried in a drying cabinet. 
         [0024]    While specific embodiments of the invention have been described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles. 
       APPENDIX 
     List of Reference Numbers 
       [0000]    
       
           1  Measuring device 
           2  Detector tube 
           3  Housing 
           4  Bracket 
           5  Gas duct 
           6  Diaphragm pump 
           7  Filter cartridge 
           8  Pump control unit 
           9  Power source 
           10  Arrow 
           11  Measuring outlet 
           12  Filter housing 
           13  Gas inlet 
           14  Filter cover 
           15  Gas outlet 
           16  First plastic screen 
           17  First glass fabric mat 
           18  First snap ring 
           19  Filter material 
           20  Second glass fabric mat 
           21  Second plastic screen 
           22  Second snap ring 
           23  Particle filter 
           24  Particle seal 
           25  O-ring seal 
           26  Closure