Abstract:
A dual chamber orifice fitting, including a body with a lower chamber in fluid communication with a pipeline and a top with an upper chamber in fluid communication with the lower chamber. A valve assembly closes to hydraulically isolate the upper chamber from the lower chamber and opens to allow an orifice plate carrier to move between the chambers. When the orifice plate carrier is in the lower chamber is can be aligned with the flowbore of the pipeline. The orifice plate carrier can be removed from the fitting through the upper chamber. In the preferred embodiments, at least one of either the upper or lower chambers has a non-rectangular cross-section. The body and top may also have a curved outer surface to accommodate the non-rectangular cross-section of the interior chambers.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable.  
       BACKGROUND OF THE INVENTION  
       [0003]     The invention relates to apparatus for monitoring characteristics of a flow stream in a pipeline and in particular to dual chamber orifice fittings. More precisely, embodiments of the invention relate to an improved body design for dual chamber orifice fittings.  
         [0004]     In pipeline operations and other industrial applications, flow meters are used to measure the volumetric flow rate of a gaseous or liquid flow stream moving through a piping section. Flow meters are available in many different forms. One common flow meter is an orifice meter, which includes an orifice fitting connected to the piping section. The orifice fitting serves to orient and support an orifice plate that extends across the piping section perpendicular to the direction of flow stream. The orifice plate is generally a thin plate that includes a circular opening, or orifice, that is typically positioned concentric with the flow stream.  
         [0005]     In operation, when the flow stream moving through the piping section reaches the orifice plate, the flow is forced through the orifice, thereby constricting the cross-sectional flow area of the flow. Due to the principles of continuity and conservation of energy, the velocity of the flow increases as the stream moves through the orifice. This velocity increase creates a pressure differential across the orifice plate. The measured differential pressure across the orifice plate can be used to calculate the volumetric flow rate of the flow stream moving through the piping section.  
         [0006]     A dual chamber orifice fitting embodies a special design that enables the orifice plate to be removed from the fitting without interrupting the flow stream moving through the piping section. This specially designed fitting has been known in the art for many years. U.S. Pat. No. 1,996,192, hereby incorporated herein by reference for all purposes, was issued in 1934 and describes an early dual chamber orifice fitting. Fittings with substantially the same design are still in use in many industrial applications today. Although the design has remained substantially unchanged, operating conditions continue to expand and dual chamber fittings are now available for piping sizes up to 48-inches in diameter and for working pressures up to 10,000 psi.  
         [0007]     A common dual chamber orifice fitting  12  is illustrated in  FIG. 1 . Orifice fitting  12  includes body  16  and top  18 . Body  16  encloses lower chamber  20  which is in fluid communication with the interior  34  of pipeline. Top  18  encloses upper chamber  22  and is connected to body  16  by bolts  17 . Aperture  30  defines an opening connecting upper chamber  22  to lower chamber  20 . Valve seat  24  is typically connected to top  18  and provides a sealing engagement with slide valve plate  56 , which is slidably actuated by rotating gear shaft  54 . Lower drive  36  and upper drive  38  operate to move orifice plate carrier  32  vertically within fitting  12 .  
         [0008]     Orifice plate carrier  32  is shown in a metering position in alignment with bore  34 . To remove orifice plate carrier  32  from fitting  12  the following steps are used. First, gear shaft  54  is rotated to slide valve plate  56  laterally and away from valve seat  24  and open aperture  30 . Once aperture  30  is opened, lower drive  36  is actuated to move orifice plate carrier  32  upwards into upper chamber  22 . Once orifice plate carrier  32  is entirely within upper chamber  22 , aperture  30  is closed to isolate the upper chamber from bore  34  and lower chamber  20 . Any pressure within upper chamber  20  can then be relieved and orifice plate carrier  32  can be removed from fitting  12  by loosening clamping bar screws  46  and removing clamping bar  44  and sealing bar  40  from top  18 .  
         [0009]     Upper chamber  22  and lower chamber  20  are sized so as to accommodate upper drive  38  and lower drive  36  in order to allow orifice plate carrier  32  to move vertically. Lower chamber  20  must also accommodate the horizontal translation of slide valve plate  56 . In order to accommodate these components, lower chamber  20  and upper chamber  22  are constructed as generally rectangular cross-sectioned cavities within body  16  and top  18 . The general shape of the cavities is commonly formed during the casting process used to make the top or body components. Because of their size and complexity, these castings are often the most expensive components of a dual chamber orifice fitting.  
         [0010]     Improvements that decrease the weight of the top and body components or the processing required in producing these components can result in significant savings in the overall cost of producing the fitting. Therefore, the embodiments described herein are directed to apparatus for dual chamber orifice fittings that seek to overcome these and other limitations of the prior art.  
       SUMMARY OF THE PREFERRED EMBODIMENTS  
       [0011]     A dual chamber orifice fitting, comprising a body with a lower chamber in fluid communication with a pipeline and a top with an upper chamber in fluid communication with the lower chamber. A valve assembly closes in order to hydraulically isolate the upper chamber from the lower chamber and opens to allow an orifice plate carrier to move between the chambers. When the orifice plate carrier is in the lower chamber it can be aligned with the flowbore of the pipeline. The orifice plate carrier can be removed from the fitting through the upper chamber. In the preferred embodiments, at least one of either the upper or lower chamber has a non-rectangular cross-section. The body and top may also have a curved outer surface to accommodate the non-rectangular cross-section of the interior chambers.  
         [0012]     In one preferred embodiment, a fitting comprises a body portion having a lower chamber in fluid communication with a pipeline and a top portion connected to the body portion and having an upper chamber in fluid communication with the lower chamber. At least a portion of either the upper chamber or the lower chamber has a non-rectangular cross section. The fitting includes a valve adapted to isolate the upper chamber from the lower chamber and a plate having an orifice where the plate has a first position, aligned with the pipeline, where the plate is within the lower chamber and a second position wherein the plate is within the upper chamber.  
         [0013]     In certain embodiments, a portion of the upper chamber and/or the lower chamber has an elliptical cross-section. Either the top or body portion may also have a wall with a substantially constant thickness. The fitting may further include an upper flange on the top portion and a lower flange on the bottom portion, wherein the upper and lower flanges have a non-rectangular bolt pattern.  
         [0014]     In an alternate embodiment, a dual chamber orifice fitting comprises a body portion having a lower chamber in fluid communication with a pipeline and a top portion having an upper chamber in fluid communication with the lower chamber. At least a portion of either the upper chamber or the lower chamber has a cross-section with a variable interior radius. In some embodiments, the fitting also includes an orifice plate carrier selectably disposable in either the lower chamber or the upper chamber, wherein the orifice plate carrier has a rectangular cross-section. The variable radius cross-section may be elliptical and may be surrounded by a wall of substantially constant thickness.  
         [0015]     Thus, the embodiments of present invention comprise a combination of features and advantages that enable substantial enhancement of the operation of dual chamber orifice fittings. These and various other characteristics and advantages of the present invention will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention and by referring to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     For a more detailed understanding of the present invention, reference is made to the accompanying Figures, wherein:  
         [0017]      FIG. 1  is a partial sectional isometric view of a prior art dual chamber orifice fitting;  
         [0018]      FIG. 2  is an isometric view of a dual chamber orifice fitting;  
         [0019]      FIG. 3  is a cross-sectional elevation view of the fitting of  FIG. 2 ;  
         [0020]      FIG. 4  is a partial sectional isometric view of the fitting of  FIG. 2 ;  
         [0021]      FIG. 5  is a partial sectional isometric view of the top of  FIG. 2 ;  
         [0022]      FIG. 6  is a partial sectional isometric view of an alternate embodiment of a dual chamber orifice fitting;  
         [0023]      FIG. 7  is a partial sectional isometric view of the body of  FIG. 6 ; and  
         [0024]      FIG. 8  is an isometric view of another alternate embodiment of a dual chamber orifice fitting; and  
         [0025]      FIG. 9  is a cross-sectional elevation view of the fitting of  FIG. 8 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     In the description that follows, like parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawing figures are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness.  
         [0027]     Referring now to  FIGS. 2 and 3 , one embodiment of a dual chamber orifice fitting  100  is shown. Fitting  100  includes body  110  and top  115  connected by bolts  117 . Body  110  encloses lower chamber  120  and provides fluid communication with the interior of the pipeline by way of flange  125 . Plug  155  seals the lower end of body  110 . Top  115  encloses upper chamber  130  and includes aperture  140 , which provides a passageway between the upper chamber and lower chamber  120 . Valve assembly  135  is used to open and close the aperture  140 . One preferred valve assembly is described in U.S. patent application Ser. No. ______, entitled “Dual Chamber Orifice Fitting Valve,” (Atty. Ref. 1787-14900), which is incorporated by reference herein for all purposes.  
         [0028]     Orifice plate carrier  147  supports the orifice plate  149 . Upper drive assembly  145  and lower drive assembly  150  are used to move orifice plate carrier  147  between lower chamber  120  and upper chamber  130 . One preferred orifice plate carrier assembly is described in U.S. patent application Ser. No. ______, entitled “Dual Chamber Orifice Fitting Plate Support,” (Atty. Ref. 1787-15000), which is hereby incorporated by reference herein for all purposes.  
         [0029]     Top  115  includes flange  160 , for connecting with body  110 , and wall  165  surrounding upper chamber  130 . Upper chamber  130  is isolated from atmospheric pressure by sealing bar  170  and sealing bar gasket  172 , which are retained with clamping bar  175  and clamping bar screws  177 . Wall  165  support upper drive assembly  145  and includes port  185 , which provides access to upper chamber  130 .  
         [0030]      FIG. 4  shows an isometric cross-section view of fitting  100 . The internal components have been removed so that the features of body  110  and top  115  can be seen. Top  115  includes upper chamber  130  with curved wall  165 . Curved wall  165  gives upper chamber  130  a non-rectangular cross-section, a portion of which can be seen in  FIG. 5 . The exterior shape of wall  165  closely follows the shape of upper chamber  130  providing a substantially constant wall thickness surrounding the chamber. Wall  165  extends into flange  160  having bolt pattern  190 . Bolt pattern  190  is spaced so as to allow access to bolts  117  attaching top  115  to body  110 , which has a corresponding bolt pattern.  
         [0031]     Referring now to  FIG. 6 , an alternate embodiment of fitting  200  is shown having a body  210  and top  215 . Top  215  encloses upper chamber  230 , which has a non-rectangular cross-section and curved wall  232  such as those described in reference to  FIGS. 4 and 5 . Body  210  includes lower chamber  220 , which has a non-rectangular cross-section and a curved wall  240 . Body  210  provides fluid communication with the interior of the pipeline by way of flange  225  and weld neck  227 . Similar to body  110  described above, body  210  is adapted to support a lower drive mechanism (not shown) and valve assembly (not shown), but supports these components in a lower chamber  220  with a curved wall  240 . Lower chamber  220  accommodates a standard rectangular orifice plate carrier but expands the size of the chamber to a shape having a curved cross-section, a portion of which is shown in  FIG. 7 . In some embodiments, the chamber has an elliptical cross-section. In the preferred embodiments, wall  240  has a substantially constant thickness, creating a body  210  that has a curved outer shape surrounding lower chamber  220 .  
         [0032]     Referring now to  FIGS. 8 and 9 , an alternate embodiment of a dual chamber orifice fitting  300  is shown. Fitting  300  includes body  310  and top  315 . Body  310  encloses lower chamber  320  and provides fluid communication with the interior of the pipeline by way of flange  325 . Top  315  encloses upper chamber  330 . Shaft  335  is used to open and close a valve assembly  340  that isolates lower chamber  320  from upper chamber  330 . Valve assembly  340  is a slide-type valve as is known in the art and actuates by moving laterally across an aperture. Shafts  345  and  350  are used to move orifice plate carrier  355  between lower chamber  320  and upper chamber  330 .  FIGS. 8 and 9  illustrate that fittings with curved chambers can be adapted to different styles of valve fittings including plug valves, slide valves, ball valves and other types of dual and single chamber orifice fittings.  
         [0033]     The previously described embodiments include upper and lower chambers that have curved cross-sections. In certain embodiments, the cross-sections are elliptical. Other non-rectangular cross-sections, such as circles, oval, and variable radius curves, may also be used. It is also understood that the chambers may not have a consistent cross-section over their entire length. It may be desirable to vary the cross section of the chamber and/or wall in order to compensate for penetrations through the wall or to accommodate internal equipment.  
         [0034]     One important aspect of the invention is the use of non-rectangular upper and/or lower chambers, which provides several benefits over convention rectangular cross-section chambers. The non-rectangular cross section of the chambers provide a more uniform stress distribution through the wall surrounding the chamber than would be possible with a rectangular cross-section. By effectively managing this stress distribution, acceptable stress levels can be maintained with a thinner wall structure. A thinner wall structure requires less material and the overall weight of the fitting can be reduced. A lighter fitting reduces the costs of procuring and manufacturing the fitting. The curved wall structure also minimizes deflection of the wall under pressurized conditions, which gives greater reliability and allows for closer tolerances between the chamber wall and the interior components.  
         [0035]     The curved wall also allows the bolts that connect the flanges on the top and body components to be evenly spaced for easier access. Controlling the thickness of the wall allows for sufficient space to be provided around each bolt location to provide access to wrenches and other torque-applying tools.  
         [0036]     The curved chamber also provides advantages in the manufacturing of the top and the body. Conventionally, the top and body are cast components. When being cast, an insert is used to form the chamber within the components. Because the conventional chamber has a relatively thin rectangular cross-section, the insert used to form the chamber is susceptible to warping or moving due to the intense heat of the casting process. This warping or moving caused inconsistent castings and added complexity to the manufacturing process. The larger curved cross-section chamber requires a larger insert to form and is thus less susceptible to casting defects.  
         [0037]     The preferred embodiments relate to apparatus for housing a dual chamber orifice fitting but the concepts of the invention are susceptible to use in embodiments of different forms. There are shown in the drawings, and herein will be described in detail, specific embodiments of the present invention with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that illustrated and described herein. In particular, various embodiments of the present invention provide a number of different body shapes and styles to improve stress distribution through the body. Reference is made to the application of the concepts of the present invention to dual chamber orifice fitting with a plug valve arrangement, but the use of the concepts of the present invention is not limited to these applications, and can be used for any other applications including other dual chamber fittings, including slide valve fittings, tapered valve fittings, ball valve fittings and other orifice fittings utilizing rectangular orifice plate carriers. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results.  
         [0038]     The embodiments set forth herein are merely illustrative and do not limit the scope of the invention or the details therein. It will be appreciated that many other modifications and improvements to the disclosure herein may be made without departing from the scope of the invention or the inventive concepts herein disclosed. Because many varying and different embodiments may be made within the scope of the inventive concept herein taught, including equivalent structures or materials hereafter thought of, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.