Abstract:
A pneumatic sensor/indicator device includes a sensor assembly having a bellows receiving chamber and sensor housing. An elastic bellows is in the bellows receiving chamber. A shaft connects to the bellows so bellows extension/retraction causes shaft axial movement. A magnet connected to the shaft generates a field moving an indicator ring. An indicator dome connects to the sensor body. The indicator ring is in the sensor housing in a non-indicating condition and displaces into the indicator dome providing a visible indicating condition. A flexible sensor tube connected to the sensor/indicator device extends into a well tube having a level sensing tube extending therefrom. A well fluid level rising above a level sensing tube inlet end increases inlet pressure port pressure inducing bellows axial displacement causing indicator device movement toward the indicating condition. The dome and indicating ring are isolated from the well preventing well contents entering and fogging the dome.

Description:
FIELD 
       [0001]    The present disclosure relates to fluid level sensing devices. 
       BACKGROUND 
       [0002]    This section provides background information related to the present disclosure which is not necessarily prior art. 
         [0003]    In groundwater wells, landfill gas, landfill leachate recovery wells and condensate recovery wells, hereinafter generally referred to as “wells”, there is a need to monitor liquid level in the well. If liquid level exceeds a preset level, action may be required to lower the liquid level so that methane recovery is not impacted. This may involve installing a pump, repairing an existing pump, adjusting vacuum levels, adjusting gas flow, and the like. Well liquid level status should be measurable without impacting the well environment. Well environments may be hazardous because of flammable gasses such as methane in the well, or chemicals in the leachate that corrode or damage test equipment, therefore use of electronic measurement devices directly in the well may be precluded. Measurement systems that require the well to be opened for manual liquid level measurement are also undesirable, particularly in wells operating under a vacuum to prevent outside air entering the well during a liquid level monitoring event. In addition, opening the well for liquid measurement can by itself affect the liquid level, and can further adversely impact methane recovery in methane recovery wells. 
       SUMMARY 
       [0004]    This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
         [0005]    According to several embodiments, a pneumatic sensor/indicator device includes a sensor assembly having a bellows receiving chamber created in a sensor housing, an inlet pressure port, and a reference port. An elastic bellows is positioned in the bellows receiving chamber. The bellows has an inner chamber isolated from the bellows receiving chamber and in communication with the inlet pressure port. The bellows receiving chamber external to the bellows is in communication with the reference port. An indicator dome connected to the sensor body. An indicator member is positioned in the sensor housing in a non-indicating condition and is axially displaced by an extension of the bellows into the indicator dome in an indicating condition where the indicator member is visible through the indicator dome. 
         [0006]    According to other embodiments, a pneumatic sensor/indicator device includes a sensor assembly having a bellows receiving chamber created in a sensor housing. An elastic bellows is positioned in the bellows receiving chamber. A shaft is connected to the bellows such that extension or retraction of the bellows causes axial movement of the shaft. A magnet is connected to a connecting end of the shaft. An indicator dome is connected to the sensor body. An indicator member is positioned in the sensor housing in a non-indicating condition and is axially displaced into the indicator dome in an indicating condition where the indicator member is visible through the indicator dome. 
         [0007]    According to additional embodiments, a flexible sensor tube connected to the sensor/indicator device extends into a well tube. A level sensing tube extends from the flexible sensor tube. A well fluid level rising above an inlet end of the level sensing tube thereafter increases inlet pressure port pressure inducing bellows axial displacement, causing the indicator member to reposition from the non-indicating condition toward the indicating condition. The indicating member is moved by a magnet so the indicating member can be isolated from the environment in the well to prevent contents of the well from condensing in and/or fogging the indicator dome. A reference port is provided so that the sensor/indicator device functions at atmospheric pressure, at vacuum pressure, or at pressures above atmospheric pressure. 
         [0008]    Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0009]    The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
           [0010]      FIG. 1  is a partial cross sectional front elevational view of a pneumatic level sensor assembly of the present disclosure mounted to a methane recovery well assembly; 
           [0011]      FIG. 2  is a partial cross sectional front elevational view of the level sensor assembly of  FIG. 1  further connected to a control/measurement device; 
           [0012]      FIG. 3  is a top front perspective view of the level sensor assembly of  FIG. 1 ; 
           [0013]      FIG. 4  is a front elevational view of the level sensor assembly of  FIG. 3  in a normal non-indicating condition; 
           [0014]      FIG. 5  is a front elevational view of the level sensor assembly of  FIG. 3  in an indicating condition; 
           [0015]      FIG. 6  is an assembly view of the level sensor assembly of  FIG. 3 ; 
           [0016]      FIG. 7  is a cross sectional elevational view at section  7  of  FIG. 1 ; 
           [0017]      FIG. 8  is a top front perspective view of another embodiment of a level sensor assembly of the present disclosure; 
           [0018]      FIG. 9  is a front elevational view of the level sensor assembly of  FIG. 8  in a normal non-indicating condition; 
           [0019]      FIG. 10  is a front elevational view of the level sensor assembly of  FIG. 8  in an indicating condition; 
           [0020]      FIG. 11  is a cross sectional elevational view similar to section  7  of  FIG. 1  showing a further embodiment of the level sensor; and 
           [0021]      FIG. 12  is a partial cross sectional front elevational view of a level sensor assembly adapted for use in a tank; 
           [0022]      FIG. 13  is a front elevational view of another embodiment of a pneumatic level sensor assembly having an attached reed switch; 
           [0023]      FIG. 14  is a top plan view of the level sensor assembly of  FIG. 13   
           [0024]      FIG. 15  is a cross sectional front elevational view taken at section  15  of  FIG. 14 ; and 
           [0025]      FIG. 16  is schematic for a control system using the level sensor assembly of  FIG. 13 . 
           [0026]    Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    Example embodiments will now be described more fully with reference to the accompanying drawings. 
         [0028]    Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
         [0029]    The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
         [0030]    When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0031]    Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
         [0032]    Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
         [0033]    Referring to  FIG. 1 , a sensor system  10  includes a pneumatic level sensor assembly  12  which is either directly or indirectly connected to a well assembly  14 . Level sensor assembly  12  is provided to indicate the presence of an undesirable level of fluid  16 , such as leachate present in the well assembly  14 . Well assembly  14  can include a well tube  18  commonly made of a metal, such as steel, or a plastic material, such as PVC. Well tube  18  commonly has an exposed well portion  20  positioned above a ground surface  22  and a buried well portion  24  positioned below the ground surface  22 . Buried well portion  24  can extend from tens of feet to more than one hundred feet below ground surface  22 . 
         [0034]    Level sensor assembly  12  includes a sensor/indicator device  26  which can be directly or indirectly connected to a well top  28  of well tube  18 . According to several embodiments, an inlet portion  30  of level sensor assembly  12  can be positioned at least partially within a well cavity  32  of well tube  18 . A sensor tube  34 , made for example of a thin-walled polymeric material, is connected to inlet portion  30  and extends for a predominant length of well tube  18  within both the exposed well portion  20  and the buried well portion  24 . A level sensing tube  36 , commonly made of a metal material such as stainless steel, is connected at a lower end of sensor tube  34 . A length of level sensing tube  36  is predetermined such that fluid  16  within well cavity  32 , which substantially fills level sensing tube  36 , provides a visual indication or alarm in an indicator portion  38  of level sensor assembly  12 . 
         [0035]    Level sensing tube  36  is positioned within buried well portion  24  such that a tube inlet end  40  is positioned above a well tube lower end  41  at a distance from well tube lower end  41  that permits fluid  16  entering through a plurality of fluid inlet apertures  42  created through buried well portion  24  to reach an anticipated or normal liquid high level  43  which does not contact the tube inlet end  40 . When fluid  16  in well cavity  32  is at or below the normal liquid high level  43 , no visual indication is provided by indicator portion  38  of level sensor assembly  12 . When fluid  16  rises within well cavity  32  and contacts tube inlet end  40  or rises above tube inlet end  40 , for example to a sensed liquid level  44 , the air/gas mixture contained within liquid level sensing tube  36  and sensor tube  34  is compressed, which causes a visual indication of this level change to be visible at indicator portion  38 . As the level of fluid  16  in well cavity  32  rises toward a tube upper end  45  of level sensing tube  36 , indicator portion  38  of level sensor assembly  12  visually indicates an increasing level alarm condition by further visual exposure of indicator portion  38 . The indication point is a function of a length of sensor tube  34  and a length of liquid level sensing tube  36 . According to several embodiments, the length of liquid level sensing tube  36  is approximately 45.7 cm (18 inches). The full or any intermediate level alarm condition can be seen by an operator monitoring sensor system  10  and provides a visual indication that the level of fluid  16  within well cavity  32  is above a desired level. The operator can then take remedial measures, such as operating a fluid pump, to reduce the level of fluid  16  within well cavity  32  back to the normal liquid high level  43  or below. The pump (not shown) can be operated until all visual indication of the fluid level indicated at indicator portion  38  is removed. 
         [0036]    It is desirable to maintain the level of fluid  16  within well cavity  32  at or below the normal liquid high level  43  such that fluid and gas can enter the plurality of fluid inlet apertures  42  for subsequent removal of the gas, such as methane for methane recovery, from well cavity  32 . High levels of fluid  16  within well cavity  32  can block the plurality of fluid inlet apertures  42  and can also be an indication of high water levels in the ground area surrounding well assembly  14 , which can lead to erosion or well collapse. Level sensor assembly  12  operates entirely from a differential pressure sensed between fluid  16  within level sensing tube  36  and the pressure (normally a vacuum pressure) maintained within well cavity  32 . Level sensor assembly  12  requires no outside power and provides a visual indication of an alarming condition. 
         [0037]    Referring to  FIG. 2 , if the operator monitoring well assembly  14  sees a visual indication of a high liquid level by displacement at the indicator portion  38 , the operator can take further remedial steps to determine the actual fluid level within well cavity  32 . For example, the operator can connect a control/measurement device  46  to well assembly  14  via connections provided with level sensor assembly  12 . Control/measurement device  46 , according to several embodiments, can include a compressor assembly  48  which provides a source of pressurized air to a pressure regulator unit  50 . Compressor assembly  48  is commonly provided with its own power source, such as a battery (not shown) and a compressor (not shown), which is operated by an on/off switch  52 . A pressure indication meter  54  can be provided to provide visual indication to the operator of the compressor pressure. Compressed air is supplied by compressor assembly  48  via an air supply line  56  and a tubing connector  58  to pressure regulator unit  50 . The pressurized air received in pressure regulator unit  50  is reduced to a desirable pressure (e.g., approximately  30  psi or another predetermined pressure) which is provided via an air bubbler sensing line  60  to a differential pressure measurement device  62 , such as a manometer. Differential pressure measurement device  62  can be connected and portably released from pressure regulator unit  50  and can be releasably stored using a storage housing  64  connected to pressure regulator unit  50 . The regulated pressurized air is also provided from pressure regulator unit  50  via an air bubbler line  66  to an air bubbler connection port  68  of level sensor assembly  12 . A well atmosphere reference line  70 , connected between a reference port  72  of level sensor assembly  12  and differential pressure measurement device  62 , provides a reference pressure of well cavity  32 . A differential pressure measured using differential pressure measurement device  62  between air bubbler connection port  68  and well atmosphere reference line  70 , given the known pressurized air pressure provided by pressure regulator unit  50 , provides an accurate indication of the actual level of fluid  16  above tube inlet end  40 . The connection of air bubbler line  66  to air bubbler connection port  68  and the connection of well atmosphere reference line  70  to reference port  72  is by quick connect minimally invasive connectors such that the vacuum normally present in well cavity  32  is minimally affected by the connection of these tubes. This reduces the possibility that connection of control/measurement device  46  to well assembly  14  will itself significantly alter the level of fluid  16  within well cavity  32 . 
         [0038]    Referring to  FIG. 3 , sensor/indicator device  26  includes a sensor housing  74  having a housing flange  76  which is mechanically and releasably connected to an inlet portion flange  78  of inlet portion  30 . The releasable connection between housing flange  76  and inlet portion flange  78  allows for disassembly of sensor/indicator device  26  for maintenance, or to replace sensor/indicator device  26 . Sensor housing  74 , according to several embodiments, is made of a molded polymeric material and can further include a housing extension  80  integrally molded with sensor housing  74 . Indicator portion  38  can include a transparent or semi-transparent indicator dome  82  releasably connected to housing extension  80 . A sensor tube connector  84  is connected to inlet portion  30  and is provided for mechanical connection to sensor tube  34  shown in  FIG. 1 . Air bubbler connection port  68  is provided with inlet portion  30 . 
         [0039]    Referring to  FIG. 4 , reference port  72  is oriented approximately 90° with respect to bubbler connection port  68 . A first plug  86  is shown threadably connected to reference port  72  to provide an atmospheric seal at reference port  72 . First plug  86  can be removed and replaced by a quick release fitting (not shown) when actual pressure measurements are taken via sensor/indicator device  26 . 
         [0040]    Sensor/indicator device  26  further includes an indicator member  87  includes an indicator ring  88  made, for example, of a magnetically permeable material, such as steel, which is normally slidably disposed within housing extension  80  in a non-indicating condition shown. Indicator member  87  further includes an indicator label  90  affixed to an outer perimeter of indicator ring  88 . According to several embodiments, indicator label  90  is adhesively applied to indicator ring  88  and is orange or red in color to be readily visible when indicator label  90  is positioned within indicator dome  82 . Both indicator ring  88  and indicator label  90  attached to indicator ring  88  are slidably disposed within housing extension  80  and are axially movable with respect to a sensor longitudinal axis  92 . The non-indicating condition of sensor/indicator device  26  shown is provided when indicator member  87  has indicator label  90  and indicator ring  88  retracted within the housing extension  80  such that indicator label  90  is not visible to a user or operator from the outside of sensor/indicator device  26 . 
         [0041]    Referring to  FIG. 5  and again to  FIGS. 1 and 4 , an alarm or indicating condition of sensor/indicator device  26  is shown. In the sensor indicating condition of indicator member  87 , indicator ring  88  and indicator label  90  axially displace in an indicator extending direction “A” such that indicator label  90  is visible through indicator dome  82 . This condition occurs when a high fluid level is present in the well assembly  14 . When the fluid level within the well assembly  14  decreases below the sensing capability of sensor/indicator device  26 , indicator ring  88  and indicator label  90  return in an indicator retracting direction “B” to the non-indicating condition shown in  FIG. 4  where no visual indication of indicator label  90  is present through indicator dome  82 . 
         [0042]    Referring to  FIG. 6 , inlet portion flange  78  of inlet portion  30  has a flange face  94  into which a counter-bore  96  is created. Counter-bore  96  is sized to receive a seating flange  98  of a bellows  100  made from an elastic material such as a resilient polymeric material. Bellows  100  further includes a mounting ring  102  positioned at an opposite end with respect to seating flange  98 . A washer  104  and a clamp  106  can be slidably received over an outer diameter of mounting ring  102  and used to releasably fix mounting ring  102  about a perimeter of a mounting portion  110  of a sliding shaft  108 . Sensor housing  74  further includes a construction port  111  which can be sealed using a second plug  86 ″. The purpose for construction port  111  will be described in greater detail in reference to  FIG. 7 . 
         [0043]    With continuing reference to  FIG. 6  and again to  FIG. 1 , sliding shaft  108  is slidably disposed within sensor housing  74  and extends through housing extension  80 . According to several embodiments a first magnet  112  can be releasably fixed to a magnet end  114  of sliding shaft  108  using a fastener  116  connected in an installation direction “C” to magnet end  114 . According to further embodiments first magnet  112  is not used and the magnet end  114  of sliding shaft  110  can be itself magnetized. A stop member  118  made for example of a metal material includes a receiving aperture  120  which is sized to be slidably received over a mounting portion diameter  122  of sliding shaft  108 . A set screw  124 , threadably inserted through a threaded bore  126  of stop member  118  is inserted to releasably fix stop member  118  at a desired axial position along sliding shaft  108 . Stop member  118  is slidably positioned in housing extension  80  and provides a sliding stop for axial outward motion of sliding shaft  108  as best shown in reference to  FIG. 7 . An O-ring  128  is positioned in an O-ring groove  130  created in sliding shaft  108  at an approximate mid-point of sliding shaft  108 . One purpose of O-ring  128  is to create a fluid seal at the junction of sliding shaft  108  at its connection with bellows  100  to prevent gas or liquid entering bellows  100  from flowing into a tubular post  132  or indicator dome  82 . Tubular post  132  is externally disposed over a portion of sliding shaft  108  with respect to sensor longitudinal axis  92  and is threadably engaged at a post threaded end  134  to a female threaded portion of a housing extension inner wall  161  in housing extension  80  shown and described in reference to  FIG. 7 . Sliding shaft  108  can therefore axially move within tubular post  132 . As best seen in  FIG. 7  a face  136  of stop member  118  contacts the housing extension inner wall  161  defining the outward axial stop position of sliding shaft  108 . A second O-ring  138  is positioned in a second O-ring groove  140  created in tubular post  132 . Second O-ring  138  prevents fluid and/or gas on the exterior side of bellows  100  or from the well assembly  14  from migrating beyond tubular post  132  and into the internal space of indicating dome  82 , and thereby prevents fogging of indicating dome  82 . 
         [0044]    The indicator ring  88  includes an inner bore  142  which is sized to be slidably received with respect to a post diameter  144  of tubular post  132 . Indicator ring  88  therefore can axially slide with respect to sensor longitudinal axis  92  about the post diameter  144  of tubular post  132 . As previously described, the indicator label  90  is attached, for example using an adhesive, to the outer perimeter of indicator ring  88 . Indicator label  90  can also be applied as a layer of paint to indicator ring  88 , or can be eliminated if indicator ring  88  is provided with a visual color such as orange or red. Indicator dome  82  further includes a third O-ring  146  seeded in a third O-ring groove  148  created in an outer perimeter surface  150  of indicator dome  82 . The third O-ring  146 , together with second O-ring  138 , provide atmospheric seals between perimeter surface  150  of indicator dome  82  and a housing inner bore  152  of housing extension  80  when perimeter surface  150  is slidably received in housing inner bore  152 . A passage seal member  154  is also provided with the assembly of sensor/indicator device  26 . The purpose for passage seal member  154  will be described in better detail in reference to  FIG. 7 . A plurality of sensor assembly fasteners  156  are inserted through apertures in inlet portion flange  78  to fastenably connect inlet portion  30 , using a plurality of internally threaded or self-threading fastener receiving tubes  158 , to sensor housing  74 . Bellows  100  is positioned substantially within sensor housing  74  when inlet portion flange  78  is either releasably or permanently coupled to housing flange  76 . 
         [0045]    Referring to  FIG. 7  and again to  FIG. 1 , sensor/indicator device  26  is shown in an exemplary installed condition with respect to well tube  18 . Indicator dome  82  has an internal space  159 , and as previously noted, is a transparent or semi-transparent material. Indicator dome  82  can further include a conical apex  160 , which is provided to allow moisture and dirt to run off from the exposed upper surface of indicator dome  82 , thereby minimizing the adherence of materials which can block the visibility of indicator label  90  through indicator dome  82 . As previously noted indicator dome  82  is releasably engaged to housing extension  80  and hermetically sealed using third O-ring  146 . The tubular post  132 , slidably received within indicator dome  82 , is atmospherically sealed using second O-ring  138  in contact with a housing extension inner wall  161  of housing extension  80  so that material, gas or fluid of well cavity  32  cannot enter internal space  159 . 
         [0046]    To simplify the following discussion of sensor/indicator device  26 , a well cap  162  is shown having inlet portion  30  in sealing contact therewith. It is anticipated that during normal use sensor/indicator device  26  will be connected using one or more apertures created in well cap  162  that permit the extension and sealing of sensor tube  34  independently with respect to well cap  162 , and therefore will provide a remote position for sensor/indicator device  26  with respect to well tube  18  and well cap  162 . With sensor tube  34  connected to sensor tube connector  84  as shown, a tubing inner bore  164  is aligned with an inlet pressure port  166  of inlet portion  30 . As fluid pressure within tubing inner bore  164  increases, caused by compression of the fluid/gas in level sensing tube  36  after fluid  16  contacts tube inlet end  40 , the pressurized fluid will travel from inlet pressure port  166  through a pressure passage  168  into a cylinder bore  170  of inlet portion  30  to contact a piston end  172  of sliding shaft  110 . Piston end  172  is slidably received within cylinder bore  170  such that sliding shaft  110  is axially movable with respect to sensor longitudinal axis  92 . A diameter of piston end  172  is less than an inner diameter of cylinder bore  170  such that a clearance path  174  is provided for the pressurized fluid or gas received within cylinder bore  170  to transfer between cylinder bore  170  and a bellows inner chamber  176  of bellows  100 . 
         [0047]    A pressure P 1  in the inlet pressure port  166  substantially equals the pressure within bellows inner chamber  176 . A pressure P 2  in reference port  72  is substantially equal to a pressure in a bellows receiving chamber  178  that is external to bellows  100 . As pressure P 1  increases, pressure P 1  will exceed pressure P 2  in reference port  72  and therefore in bellows receiving chamber  178  that is external to bellows  100 . This differential pressure between pressures P 1  and P 2  across bellows  100  causes bellows  100  to axially extend within bellows receiving chamber  178  in the indicator extending direction “A”. Because clamp  106  releasably couples mounting ring  102  of bellows  100  to sliding shaft  110 , extension of bellows  100  also co-translates sliding shaft  110  in the indicator extending direction “A”. The axial extension of bellows  100  in the indicator extending direction “A” therefore displaces first magnet  112 , or if first magnet  112  is not used, the magnetized magnet end  114  of sliding shaft  110 , within tubular post  132  to the fully extended position shown. As first magnet  112  or the magnetized magnet end  114  of sliding shaft  110  axially translates in the indicator extending direction “A”, the magnetic field generated by first magnet  112  or the magnetized magnet end  114  magnetically pulls the indicator ring  88  and thereby the indicator label  90  in the indicator extending direction “A” until indicator label  90  is at least partially visible through indicator dome  82 . 
         [0048]    Extension of bellows  100  in the indicator extending direction “A” continues until stop member  118  contacts extension inner wall  161  of housing extension  80 , defining a fully or maximum extended position of indicator member  87 . Indicator label  90  is fully visible through indicator dome  82  in the fully extended position. Indicator member  87  will remain in the extended condition until pressure P 1  reduces to or below pressure P 2 . It is noted that indicator label  90  will also be at least partially visible through indicator dome  82  as first magnet  112  axially translates between the retracted and maximum extended positions. 
         [0049]    When the pressure P 1  within bellows inner chamber  176  reduces to either equal to or less than pressure P 2 , a weight of both sliding shaft  110  and stop member  118  pulls sliding shaft  110  with first magnet  112  in the indicator retracting direction “B” by the force of gravity until indicator ring  88  is returned to the retracted or non-indicating position shown in phantom as indicator ring  88 ′. It is further noted that indicator label  90  will also be at least partially visible through indicator dome  82  as first magnet  112  axially translates back to the retracted position. 
         [0050]    Housing flange  76  can further include a housing flange counter-bore  180  which is aligned with counter-bore  96  in an assembled condition such that seating flange  98  of bellows  100  is retained within both counter-bore  96  and housing flange counter-bore  180  to radially restrain seating flange  98 , while providing the compressive force required to hermetically seal seating flange  98 . Bellows inner chamber  176  is therefore isolated from a bellows receiving chamber  178  defined by sensor housing  74 . It is also noted that an upward travel limit for sliding shaft  110  and first magnet  112  is provided by stop member  118  when stop member  118  contacts housing extension inner wall  161  of housing extension  80 . 
         [0051]    With further reference to  FIGS. 1 and 7 , further internal fluid flow paths are provided within sensor/indicator device  26  as follows. Bellows receiving chamber  178  is in fluid communication with well cavity  32  via the following path. A bellows chamber flow port  182  extends between bellows receiving chamber  178  and construction port  111 . Construction port  111  is provided such that bellows chamber flow port  182  can be created through the outer wall of sensor housing  74 . A bellows chamber connecting passage  184  is oriented substantially perpendicular to construction port  111  and bellows chamber flow port  182 . Bellows chamber connecting passage  184  is created through housing flange  76  and is coaxially aligned with a reference port connecting passage  186  created through inlet portion flange  78 . Reference port connecting passage  186  opens into reference port  72 . In turn, reference port  72  is connected, via a reference pressure passage  188  extending through inlet portion  30 , to well cavity  32 . The pressure within well cavity  32 , which can be maintained as a positive pressure or at a partial vacuum, is therefore present within bellows receiving chamber  178 , thereby providing a differential pressure between the higher pressure in bellows inner chamber  176  and the lower pressure within bellows receiving chamber  178  when fluid level within the well rises above tube inlet end  40 . A higher pressure P 1  within bellows inner chamber  176 , as fluid pressure increases within tubing inner bore  164 , provides the driving force for displacing sliding shaft  110  and first magnet  112  (or the magnetized magnet end  114  of sliding shaft  110 ) and thereby provides visual indication of an increased fluid level within well cavity  32  as indicator ring  88  and indicator label  90  are magnetically upwardly displaced. 
         [0052]    A bore end wall  190  is created at a lower end of cylinder bore  170 . Bore end wall  190  provides a positive stop for a lower end travel path of piston end  172 . Piston end  172  is provided and sized to maintain axial alignment of sliding shaft  110  during its sliding motion in the indicator extending direction “A” or the indicating retracting direction “B”. The passage seal member  154  is positioned between housing flange  76  and inlet portion flange  78  to seal the junction between bellows chamber connecting passage  184  and reference port connecting passage  186 . The sealing capability provided by seating flange  98  of bellows  100  and passage seal member  154  allows the installation of the sensor assembly fasteners  156  without requiring the use of additional seal members. 
         [0053]    Referring to  FIG. 8  and again to  FIG. 7 , according to additional embodiments of the present disclosure, a sensor/indicator device  200  is modified from sensor/indicator device  26  by the inclusion of an inlet portion  202  releasably connected to sensor housing  74 ′ and housing extension  80 ′. An indicator dome  204  is modified from indicator dome  82  and further includes an indicator retainer assembly  206  slidably received in a conical apex  208  of indicator dome  204 . 
         [0054]    Referring to  FIG. 9  and again to  FIG. 7 , indicator ring  88 ′ and indicator label  90 ′ are shown in their retracted or non-indicating condition positioned within housing extension  80 ′. Indicator retainer assembly  206  is slidably disposed through an aperture  210  created in conical apex  208 . A second magnet  212  is fastenably connected to a retainer tube  214  which can extend above conical apex  208  by an extension height “D”. Second magnet  212  is therefore positioned within indicator dome  204 . 
         [0055]    Referring to  FIG. 10  and again to  FIGS. 7 and 9 , when indicator ring  88 ′ and indicator label  90 ′ extend to the indicating condition above housing extension  80 ′ and therefore within indicator dome  204 , indicator ring  88  comes within the magnetic influence of second magnet  212 . Second magnet  212  can thereafter retain indicator ring  88 ′ and therefore indicator label  90 ′ in the extended position (indicating condition) shown after the pressure P 1  within sensor/indicator device  200  reduces to pressure P 2  re-establishing the non-indicating condition. The use of second magnet  212  can thereby provide for a continuing indication of an alarm or high fluid level condition whether the high fluid level condition is sustained or not. This can provide indication to an operator that a high fluid condition has occurred at any time following a last inspection of sensor/indicator device  200 . 
         [0056]    Referring to  FIG. 11 , further components of sensor/indicator device  200  include an O-ring  211  engaged with a retainer tube  214 , which seals aperture  210  at a junction between indicator retainer assembly  206  and conical apex  208 . A fastener  216  releasably couples second magnet  212  to retainer tube  214  having fastener  216  threadably engaged in a threaded aperture  218  of retainer tube  214 . A fastener head  220  of fastener  216  can contact a post end wall  222  of tubular post  132 ′ when first magnet  112 ′ is raised and positioned in its fully extended position in the indicator extending direction “A”. The indicator retainer assembly  206  allows retainer tube  214  to be axially slidable partially into the indicator dome  204  in a first position “E” (shown in  FIG. 11 ) providing the indicating condition of indicator member  87 ′ and slidable away from the sliding shaft  110  to a second position “F” (shown in phantom) releasing indicator member  87 ′ for return to the non-indicating condition. 
         [0057]    A vented plug  224  is seated in inlet pressure port  166 . Vented plug  224  can include a screened or filtered flow passage  226  which is provided to prevent passage of particulate matter into inlet pressure port  166 ′. A reference pressure passage  228  in the normal operating mode of this embodiment is blocked from reference port  72 ′. Reference port  72 ′ is provided with a second vented plug  230  having a screened or filtered flow passage  232  similar to flow passage  226  of vented plug  224 . Reference port  72 ′ is in fluid communication with construction port  111 ′ via bellows chamber connecting passage  184 ′ and reference port connecting passage  186 ′. Reference pressure passage  228  is isolated from reference port  72 ′ by use of a threaded connecting passage  234  having a threaded plug  236  installed therein. When threaded connecting passage  234  is blocked by threaded plug  236 , bellows receiving chamber  178 ′ can be directly vented to atmosphere via construction port  111 ′, bellows chamber connecting passage  184 ′, reference port connecting passage  186 ′, reference port  72 ′, and flow passage  232  of second vented plug  230 . The differential pressure acting across bellows  100 ′ is therefore the pressure within the flow passage  226  of vented plug  224  and atmospheric pressure at flow passage  232  of second vented plug  230 . The configuration of  FIG. 11  having threaded plug  236  installed can therefore be used in well applications that contain flammable gas such as methane gas and/or that can be directly vented to atmosphere. 
         [0058]    Referring to  FIG. 12  and again to  FIG. 1 , a sensor system  238  is modified from sensor system  10  and provides a pneumatic level sensor assembly  12  which is either directly or indirectly connected to a fluid tank  240 . Fluid tank  240  can be any type of fluid holding tank, including but not limited to sump tanks, sewage treatment tanks, sludge tanks, underground water runoff tanks that may be accessible by a man-way or manhole cover, and the like. Fluid tank  240  can include an outer wall  242 , a tank bottom  244 , and a tank top  246 . Level sensor assembly  12  can have the sensor/indicator device  26  directly or indirectly mounted to tank top  246  or tank outer wall  242 . Level sensing tube  36  is positioned within fluid tank  240  but a sensor tube  248  connecting level sensing tube  36  to sensor/indicator device  26  can be significantly shortened compared to sensor tube  34  to accommodate a height of fluid tank  240 . 
         [0059]    An elevation of an inlet end  252  of level sensing tube  36  with respect to tank bottom  244  is chosen such that fluid entering level sensing tube  36  provides a visual signal at indicator portion  38 . When a changing fluid level in fluid tank  240  reaches a predetermined fluid level  254 , a high level indication signal is generated by a sensing device  250 . According to several embodiments sensing device  250  includes a reed switch which closes to send the high level indication alarm signal as an electrical signal to a control system  256 . The high level indication alarm signal can result from a predetermined differential pressure which corresponds to a difference between a first pressure in level sensing tube  36  as fluid reaches inlet end  252  and a second pressure corresponding to a water level reaching predetermined fluid level  254 . The high level indication alarm signal can also be based only on a predetermined pressure when a water level reaches predetermined fluid level  254 . 
         [0060]    Control system  256  can be a program logic controller (PLC), a microcontroller, a datalogger, or similar device having a memory device  259 . The control system  256  receives the high level indication alarm signal  257  from sensing device  250  via a communication line  258 , and is pre-programmed to generate a corrective action signal  266 . In addition to the visual alarm condition provided at indicator portion  38 , the high level indication alarm signal  257  can also be sent to a remote site, for example by wireless transmission using a transmitter and antenna system  260  of control system  256 , or by a direct communication channel. Control system  256  can also incorporate an audible alarm  261 , or remotely trigger an audible alarm. The corrective action signal  266  can be for example an electrical signal forwarded from control system  256  to a fluid transfer device  262  via a communication path  264 . The fluid transfer device  262  can be a pump, a venturi flow device, an electrically operated valve, or a similar device which operates to discharge fluid from fluid tank  240  until a fluid level in fluid tank  240  drops below either the predetermined fluid level  254  or inlet end  252 . Control system  256  can compare the signal  257  to data in the memory device  259  to determine an approximate period of time for operation of fluid transfer device  262  based on fluid tank volume data stored, compare pressure signal data sensed by sensing device  250  to pressure data in memory device  259 , or trigger operation of fluid transfer device  262  which can include its own level detection device, float, or the like to determine itself when to stop operating. 
         [0061]    Referring to  FIG. 13  and again to  FIG. 12 , according to further embodiments, a pneumatic level sensor/indicator device  268  is modified from pneumatic level sensor assembly  12  to incorporate sensing device  250  directly into a modified transparent or semi-transparent indicator dome  270 . A U-shaped switch  272  such as a reed switch extends from sensing device  250  to a position above and proximate to indicator member  87 ″ when indicator member  87 ″ is in the fully extended position shown. 
         [0062]    Referring to  FIG. 14  and again to  FIG. 13 , switch  272  extends into an interior portion of indicator dome  270 . Switch  272  can extend to the longitudinal axis  92 ′ of level sensor/indicator device  268 . 
         [0063]    Referring to  FIG. 15  and again to  FIGS. 13 and 14 , switch  272  is positioned within an internal housing  274  created of the same transparent or semi-transparent material of indicator dome  270  when indicator dome  270  is molded, for example from an injection molding process. Internal housing  274  permits switch  272  to be removed from indicator dome  270  for service or replacement, and to seal the internal space  159 ′ of indicator dome  270  from atmospheric contaminants. When indicator ring  88 ″ of indicator member  87 ″ is in the upward or extended position, switch  272  is activated which sends an electrical signal indicating a high fluid level condition via communication line  258 . Sensing device  250  is weather-proof and is partially received and retained in a cavity  276  created in indicator dome  270 . 
         [0064]    Referring to  FIG. 16 , a remote sensing and operating system  278  using pneumatic level sensor/indicator device  268  includes the capability to remotely control operation of a pump/air compressor assembly  280  using a pump timer panel  282  remotely positioned from well cavity  32 ′. Level sensor/indicator device  268  is mounted to well tube  18 ′ and uses sensor tube  34 ′ as previously described herein. Pump/air compressor assembly  280  delivers air pressure to operate an air driven pump  284  positioned in well cavity  32 ′ to remove liquid such as leachate from well cavity  32 ′. Air is delivered to pump  284  via a pump air line  286  which is connected to a pressure supply line  288  using a pump air solenoid valve  290 . Pump air solenoid valve  290  is electrically controlled using a signal from switch  272  via a signal line  294  and from a signal transmission line  296  from pump timer panel  282 . A second signal transmission line  298  from sensing device  250  is also connected to pump timer panel  282 . 
         [0065]    Pump timer panel  282 , when receiving the high fluid level condition of well cavity  32 ′ from sensing device  250  and switch  272  via second signal transmission line  298 , signals pump air solenoid valve  290  to open allowing compressed air from pump/air compressor assembly  280  to operate pump  284 . When indicator ring  88 ′ moves downwardly away from switch  272  indicating the high fluid level condition is no longer present, the changed signal from switch  272  via pump timer panel  282  shuts pump air solenoid valve  290 . Pump timer panel  282  is one example of a control unit for remote sensing and operating system  278 . Pump timer panel  282  can also be replaced by a computer, a control chip/controller circuit, or similar logic device that can also remotely operate remote sensing and operating system  278  via a wireless transmission system as previously described herein, or via the Internet, so that an operator can monitor the fluid level status of multiple wells having multiple level sensor/indicator devices  268 . 
         [0066]    Pneumatic level sensor/indicator devices  26 ,  200 ,  268  of the present disclosure offer several advantages. By providing an internally sealed indicator ring having an indicator label  90  connected thereto which is displaced by magnetic attraction with a magnet or magnetized shaft moving in response to a pressure differential within the well, a local visual indication of a high fluid level within the well is provided without requiring the well to be opened or exposed to atmospheric pressure, while also preventing materials, fluids or gas within the well from contaminating the indicator label  90 . By further use of an indicator retainer assembly  206  of the present disclosure, a high pressure or high fluid level indication occurring following a previous inspection will be retained such that the operator does not need to be present at the time the high fluid level occurs in the well. This provides the operator with the opportunity to conduct further tests to determine if high pressure in the well is a continuing condition warranting remediation or a condition that requires subsequent follow up. By further addition of an electrical switch or transmitter to the sensor/indicator devices or system, a remote sensing and well pump operating system can be controlled. 
         [0067]    Pneumatic sensor/indicator devices of the present disclosure can also be used in an opposite manner, i.e., to provide visual indication of a falling fluid level in liquid storage tank. For this use and referring again to  FIGS. 7 and 12 , the presence of liquid in a liquid storage tank such as a cistern would be indicated by the visible presence of indicator member  87  in indicator dome  82 . Downward motion of indicator member  87  would thereafter provide visual indication over time of a decreasing volume of useable liquid in the tank. The condition when indicator member  87  is completely disposed within housing extension  80  would provide, for example, visual indication that the tank requires refill, or impending loss of liquid supply. 
         [0068]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. For example, a “well” or a “fluid tank” as referred to herein can broadly include any fluid containing member in which a liquid level can be present and sensed by a sensor/indicator device of the present disclosure.