Patent Publication Number: US-7591278-B1

Title: Sewer system vent monitor

Description:
TECHNICAL FIELD 
     This invention relates to apparatus for controlling the flow of air into a sewer system and for controlling gaseous emissions from the sewer system. The invention has particular, but not exclusive, application to oil refinery sewer systems. 
     BACKGROUND OF THE INVENTION 
     Vent pipes employed in connection with refinery sewer systems must draw air easily to prevent vacuum lock. Increasingly stringent environmental regulations have created a need for vent pipes to be sealed against evaporative pollution of the outside atmosphere. Refinery sewer systems employ a variety of ordinary water seals, such as S-traps, P-traps and other water seals in various locations of the sewer system. These arrangements are not for the purpose of venting air into the sewer system and, in fact, it is imperative that the typical water traps remain full of water to effectively prevent emissions from the sewer system into the ambient atmosphere. In the absence of a vent pipe or vent pipes elsewhere in the system, low pressure episodes in the sewer system can suck the water from the water traps and destroy the effectiveness insofar as gaseous emission prevention is concerned. 
     DISCLOSURE OF INVENTION 
     The apparatus of the present invention controls the flow of air into a sewer system and controls gaseous emissions from the sewer system. As will be seen below, sealing is accomplished through a water seal forming a water barrier stopping sewer gas from migrating unimpeded out of the vent pipe. On the other hand, the vent pipe is allowed to draw air easily, thus preventing formation of a strong vacuum condition within the sewer system that would suck water out of the conventional water seals at other locations of the sewer system such as a ground drain. 
     Unlike other water seals, such as S-traps, P-traps and other conventional arrangements, none of the water creating the water seal in the present apparatus is sucked down the drain into the sewer system when the apparatus admits air. Instead, water continues to reside in a container of the apparatus. Air entering the apparatus merely “bubbles” up through this water. Upon pressure equalization, the water seal immediately reestablishes itself. 
     Other advantages of the apparatus reside in its incorporation of structure allowing for ready monitoring of water seal level and venting activity as well as structure for replenishing water in the container when lost by evaporation or other causes. 
     The apparatus includes a first fluid conduit and a second fluid conduit. 
     The apparatus also includes a container defining a container interior for accommodating water, the first and second conduits being operatively connected to the container and respectively in fluid-flow communication with the container interior through spaced first and second openings. 
     Trap structure is in operative association with the container to form a water seal employing the water in the container interior resisting air and gaseous emissions flow between the first opening and the second opening. 
     Monitoring structure is provided for observing the water in the container interior and any air drawn into the water by a pressure drop in the sewer system. 
     Water replenishment structure is provided for introducing supplemental water into the container interior responsive to a drop in water level within the container interior. 
     Also, the apparatus incorporates structure which ensures that air is easily introduced into the sewer system responsive to a low pressure event in the sewer system. In contrast, venting of gaseous emissions from the sewer system into the ambient atmosphere is deterred. 
     Other features, advantages and objects of the present invention will become apparent with reference to the following description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a frontal, perspective view of apparatus constructed in accordance with the teachings of the present invention; 
         FIG. 2  is a side, elevational view of the apparatus; 
         FIG. 3  is a front, elevational view of selected structure of the apparatus, a portion of which is designated in cross-section; 
         FIG. 4  is a side, elevational view of the structure illustrated in  FIG. 3 , a portion of which is in cross-section; 
         FIG. 5  is a diagrammatic presentation of the structure of  FIGS. 4 and 5  showing the interior of a container and associated water trap and the flow of venting air therethrough; and 
         FIG. 6  is a perspective view showing a housing of the invention in cross-section with an interiorly disposed baffle dividing the housing into a rising and descending fluid conduit portions. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Referring now to the drawings, apparatus constructed in accordance with the teachings of the present invention includes a fluid conduit  12  comprising the upper leg of a vent pipe having an upper end in communication with the ambient atmosphere. The apparatus also includes a fluid conduit  14  leading downwardly to a sewer system, such as a refinery sewer system (not shown), comprising the lower leg of the vent pipe. The lower end of the fluid conduit  12  is comprised of a portion  16  of a housing  18 . A solid baffle  20  (see  FIG. 6 ) divides the housing interior into portion  16  and a portion  22  which comprises the upper end of conduit pipe  14 , the separation between portions  16  and  22  being complete in housing  18 . 
     A container in the form of a water box  26  is attached to the housing  18  and defines a container interior for accommodating water. The conduits  12  and  14  are in fluid-flow communication with the interior of the container  26  through slot-like openings  28 ,  30 , respectively, providing communication between the housing and container interiors. Opening  28  is in communication with conduit  12  through portion  16  thereof defined by the housing  18  and baffle  20 . The portion  22  of descending conduit  14  is in communication with the interior of the container  26  through opening  30 . 
     The structure just recited constitutes a trap structure in operative association with the container to form a water seal employing the water in the container interior resisting air and gaseous emissions flow between openings  28  and  30 . When a low pressure event takes place in the sewer system, air will be drawn downwardly through the conduit  12  through opening  28  (which is below the surface level of the water  32  in the water box) and thence will proceed through opening  30  and downwardly into the sewer system through conduit  14 . This is shown in diagrammatic fashion by the flow line incorporating the arrows in  FIG. 5 . 
     On the other hand, pressurized gas emissions produced by the sewer system will flow in the opposite direction along the flow path; that is, the gaseous emissions will flow upwardly through conduit  14  into container  26  through opening  30 , and upon downward displacement of the water through opening  28  and thence upwardly through the conduit  12 . 
     Water replenishment structure is provided for introducing supplemental water into the interior of the water box responsive to a drop in water level within the container interior. As seen in the drawings, the water level is normally positioned between the two openings  28  and  30  to ensure proper operation of the water trap, the top of opening  28  being below the level of the bottom of opening  30 . 
     The water replenishment structure includes a water inlet  36  communicating with the interior of the water box  26 . A hose or other form of conduit  38  leads to a water vessel  40  used to hold a supply of replenishment water. The water vessel  40  in this embodiment of the invention is connected to conduit  12  by brackets or U-bolts  42  and disposed above the container  26  so that water will flow from the water vessel to the interior of the container under the influence of gravity. A shut off valve  46  is preferably incorporated in the structure to allow manual shut off of the replenishment water supply if desired. A supplemental water level indicator  44  is utilized to observe the level of supplemental water in the water vessel  40 . A displaceable top lid is provided to allow the water box to be filled. 
     A float valve  48  is operatively associated with the inlet  36  to establish fluid-flow communication between the water inlet and the interior of the container when the water level in the container drops below a predetermined level. The float valve also operates to terminate fluid-flow communication between the water inlet and the container interior when the water level in the container interior rises to or above the predetermined level. An observation or sight window  50  is formed in the container to monitor or observe the water in the container interior as well as any air drawn into the water  32  due to a pressure drop in the sewer system. 
     It is to be noted that the opening  28  includes an upwardly projecting notch  52  at an upper corner thereof. This notch may be readily observed through the observation window  50 . Air entering the container interior from the vent pipe  12  as a result of a low pressure event in the sewer system will pass through notch  52  and form a readily observable air bubble stream rising upwardly from the notch through water  32 . 
     In the arrangement illustrated, regulatory testing of the air above the water seal, if necessary, can be accomplished by removal of a testing plug  60 . A drain plug  62  may be employed if desired. 
     For proper operation of the apparatus, it is important that the lower end of fluid conduit  12  have an interior cross-section substantially smaller than the cross-section of the water box interior. This provides a hydraulic advantage to the apparatus whereby any water in the vent pipe pushed a distance down in the vent pipe by atmospheric pressure due to a low pressure event in the sewer system will cause the level of water in the water box interior to rise just a fraction of that distance. Furthermore, the water in the container interior when pushed downwardly by a high pressure event in the sewer system will escape into the lower end of the fluid conduit  12  and rise at a higher rate in the vent pipe than the rate of lowering of water in the container interior caused by the high pressure event. This structure results in a greater pressure deferential being required to allow air and gaseous emissions to escape from the container interior than to draw atmospheric air into the container interior from the vent pipe  12 . The apparatus provides an effective emission gas seal while allowing air to be drawn easily into the sewer system. This prevents formation in the sewer system of a strong vacuum condition which would suck water out of the water seals in ground drains and the like. 
     Unlike ordinary water seals, none of the water creating the water seal drains to the sewer when atmospheric air is admitted to the sewer. Instead the water continues to reside in the water containment box. Air entering the system merely “bubbles” up through the water. Upon pressure equalization, the water seal immediately reestablishes itself. 
     If air bubbles can be seen rising through the observation window or sight glass, air is entering the sewer system. The bubbles are not indicative of air escaping from the system into the outside atmosphere. The bubbles are merely being formed as air is being sucked down the vent pipe, bubbling up through the internal water seal of the apparatus and continuing on down into the sewer system.