Apparatus for measuring the differential pressure of dissolved gases in a fluid medium
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the field of gas pressure measurement, and in particular the measurement of the differential pressure of dissolved gases in fluids. 
     2. Description of the Prior Art 
     Prior art have used a semipermeable membrane enclosure inserted in the fluid to allow the gas to migrate through the membrane and reach equilibrium with the pressure of the dissolved gases in the fluid. The pressure in the interior of membrane enclosure is then measured. One problem with a number of the previous devices has been inaccurate readings due to the formation of bubbles on the membrane when the fluid is supersaturated with dissolved gases. A second problem has been leaks developing within the system causing the devices to malfunction. A third problem has been that prior devices have required continuous monitoring by a technician to insure that the system functions properly and to dislodge accumulated bubbles. The disclosed invention solves these problems by pressurizing the chamber where the measurements are taken, thus inhibiting the formation of bubbles. The second problem is solved by having the fluid being measured separated from the pressure measuring means in a sealed chamber. In regard to the third problem, this disclosed invention is an improvement over the prior art in that since the subject invention is installed as a part of the fluid transport system, reduces the formation of bubbles, and operates continuously and automatically, no technician is required to be on constant standby during the operation of the invention. 
     BRIEF SUMMARY OF THE INVENTION 
     The disclosed invention, a gasometer, provides a device for continuously and automatically measuring the dissolved gas pressure in a fluid transport system. The gasometer has a pressurizable chamber which can be installed in a fluid transport system, such as in the piping in the system. Inside the chamber is a tubular-shaped semipermeable membrane which is in contact with the pressurized fluid. This membrane allows the passage of dissolved gases, but prohibits the passage of the fluid, to the interior of the tubing where equilibrium is attained between the gases in the fluid and in the tubing. The pressurizable chamber can be variable pressurized by inlet and outlet valves to prevent the formation of bubbles on the semipermeable membrane, thus making the results more accurate. The tubing is connected to the exterior of the chamber by an impermeable means where the pressure can be measured on a device such as a manometer, or recording pressure guage. 
     It is an object of this invention to provide an accurate means of determining the differential dissolved gas pressure of a gas in a fluid medium. 
     It is a further object of the invention to provide a means of continuous measurement of the differential dissolved gas pressure of a gas in a fluid medium. 
     It is yet a further object of this invention to provide an automatically operated means of measuring the differential dissolved gas pressure of a gas in a fluid medium. 
     It is yet a further object of this invention to provide a low maintenance apparatus for measuring the differential dissolved gas pressure of a gas in a fluid medium. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic front view of the completely assembled and installed gasometer. 
     FIG. 2 is a schematic front view of the internal components of the gasometer. 
     FIG. 3 is a cross section A--A view of FIG. 2 showing the base plate and the location of the three support members and a portion of the semipermeable tubing wrapped around the support members. 
     FIG. 4 is a top schematic view of FIG. 2 showing the internal components of the gasometer. 
     FIG. 5 is a fragmentary cross section C--C view of FIG. 4 showing the preferred embodiment of the cap with the support members and the passage detailed therein. 
     FIG. 6 is a fragmentary cross section B--B view of FIG. 3 showing the preferred method of attaching the support members to the base plate. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows the front view of the completely assembled and installed gasometer 1, installed between pipes 3 and 5 in a fluid transport system. Connected to inflow pipe 3 is an inflow valve 7, and to outflow pipe 5, an outflow valve 9, so that when said valves are operated in combination, the pressure inside the gasometer can be regulated. The selective pressurization of the gasometer by valves 7 and 9 prevents the formation of bubbles on semipermeable tubing 33. The bottom portion of the gasometer chamber consists of a Tee joint conduit connector 11. The first opening is connected to inflow pipe 3. The second opening is adopted for connection of a pressure gauge 13 and optional temperature gauge 15. The third opening communicates with the interior of the gasometer 1 and is attached, such as with a solvent weld, to a translucent tubular sleeve 17. This translucent tubular sleeve 17, which is of sufficient size and diameter to accept the interior assembly of the gasometer and forms the middle portion of the chamber, is clear so that direct observation can be made of the interior of the chamber to monitor the formation of bubbles. The upper portion of the gasometer chamber consists of a tubular adapter 19, the lower portion of which is connected to the translucent sleeve 17, such as with a second solvent weld, and the upper portion of which has internal threads to accept the cap 21. The cap 21 in turn has external threads and is secured into the adapter 19. As shown in FIG. 5, the cap 21 has a concentric threaded passage 37 to which the outlet pipe 5 is connected, and a second threaded passage 39 through which a threaded center bore coupling 23 is sealably inserted to provide communication between the interior and exterior of the chamber. As shown in FIG. 1, the exterior end of the coupling communicates with a differential pressure measuring means 25 such as a manometer or a recording pressure gauge by means of an impermeable flexible hose 27. 
     FIGS. 2-6 show the internal assembly of the gasometer. The internal assembly is mounted on the underside of the cap 21 and consists of a plurality of support members 29, base plate 31, semipermeable tubing 33, and impermeable tubing 35. As shown in FIG. 5, The upper ends support members 29 are threadably mounted in underside of the cap 21. As shown in FIGS. 3 and 4, the support members 29 are equidistantly spaced and project downward, parallel to each other, and as shown in FIG. 6, are threadably mounted to the base plate 31 which has openings adopted to allow passage and mixing of entering fluids. FIGS. 2 and 3 show the semipermeable tubing 33 spirally wrapped around the support members 29, with the bottom end of the tubing 33 sealed and attached to one of the support members 29 near the base plate 31. FIGS. 2 and 5 show the upper end of the semipermeable tubing 33 sealably attached to the impermeable tubing 35 such that their respective interior passages are in communication. 
     As shown in FIG. 5, the impermeable tubing 35 is sealably mounted onto the coupling 23 such that their interior passages are in communication, thus allowing the gases that migrate through to the interior of the semipermeable tubing 33 to ultimately be in communication with the differential pressure measuring means 25 located exterior to the chamber.