Abstract:
Apparatus and methods for operating a valve assembly for a dual chamber orifice fitting. The dual chamber orifice fitting comprises a body attached to a top. A passageway connects between the body and the top and allows an orifice plate carrier to move between the body and the top. A valve assembly selectably closes the passageway. Embodiments of the valve assembly comprise a seat, a plug, and a stem. The valve assembly has a closed position, wherein a curved outer surface of the plug sealingly engages a curved sealing surface of the seat and prohibits fluid communication through the passageway. The valve assembly has an open position, wherein a plug aperture is aligned with a seat aperture to allow the orifice plate carrier to move through the passageway.

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 methods and apparatus for monitoring characteristics of a flow stream in a pipeline, in particular to dual chamber orifice fittings. More precisely, the embodiments of the invention relate to an improved valve design for a dual chamber orifice fitting.  
         [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 a thin plate that includes a circular opening, or orifice, that is positioned within 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 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 a wide range of piping sizes and working pressures.  
         [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 a 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 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]     The slide valve arrangement, as shown in  FIG. 1 , includes valve seat  24 , slide valve plate  56 , and gear shaft  54 . To open aperture  30 , slide valve plate  56  must be moved laterally a sufficient distance to allow orifice plate carrier  32  through the aperture. Lower chamber  20  must be able to accommodate this lateral movement. Gear shaft  54  may also require several full rotations to fully move slide valve plate  56  to and from its sealed position.  
         [0010]     Valve designs that are more compact and require less movement for actuation potentially provide advantages both in reduced operating envelope requirements and in simplification of operation. Thus, the embodiments of the present invention are directed to valve 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 valve assembly for a dual chamber orifice fitting comprising a body attached to a top. A passageway connects between the body and the top and allows an orifice plate carrier to move between the body and the top. A valve assembly selectably closes the passageway. Embodiments of the valve assembly comprise a seat, a plug, and a stem. The valve assembly has a closed position, wherein a curved outer surface of the plug sealingly engages a curved sealing surface of the seat and prohibits fluid communication through the passageway. The valve assembly has an open position, wherein a plug aperture is aligned with a seat aperture to allow the orifice plate carrier to move through the passageway.  
         [0012]     In certain embodiments, a valve assembly for a dual chamber orifice fitting comprises a seat having a seat aperture and a curved sealing surface and a plug having a plug aperture and curved outer surface. A stem is coupled to an end of the plug and adapted to rotate the plug between a closed position, wherein the curved outer surface of the plug is sealingly engage with the curved sealing surface of the seat, and an open position, wherein the plug aperture is aligned with the seat aperture. In the closed position the plug is adapted to move relative to the stem. In selected embodiments the plug includes one or more equalizer ports connecting the plug aperture to the curved outer surface of the plug. The plug has a equalized position where the plug aperture is not aligned with the seat aperture and fluid communication across the plug is permitted through the equalizer port.  
         [0013]     In an alternative embodiment, a dual chamber orifice fitting comprises a body having a lower chamber in fluid communication with a pipeline and a top attached to the body, wherein the top has an upper chamber. A passageway between the upper and lower chambers allows an orifice plate carrier to be moveably disposable through the passageway between the upper chamber and the lower chamber. The fitting also comprises a valve seat having a seat aperture that is substantially aligned with the passageway. A rotatable plug, having a plug aperture therethrough, has a cylindrical outer surface operable to sealingly engage the valve seat when the rotatable plug is in a closed position. A stem is connected to the plug and operable to rotate the plug from the closed position to an open position wherein the plug aperture is aligned with the seat aperture and the passageway. The orifice plate carrier can move through the passageway when the rotatable plug is in the open position. The rotatable plug may have an equalized position wherein the plug aperture is not aligned with the seat aperture and fluid communication through the passageway is permitted through the equalizer port. The rotatable plug is rotated approximately 15 degrees between the closed position and the equalized position and rotated approximately 90 degrees between the closed position and the open position.  
         [0014]     In another alternative embodiment, a method for operating a dual chamber orifice fitting comprises rotating a valve assembly from a first position isolating a first chamber of the fitting from a second chamber of the fitting to a second position to expose a first aperture allowing fluid communication between the chambers, allowing fluid flow between the chambers, and rotating the valve assembly to an third position to place a second aperture in fluid communication with the first and second chambers. Then a drive mechanism is actuated to move an orifice fitting plate between the chambers by passing through the second aperture and the valve assembly is rotated back to the first position. In certain embodiments the valve assembly comprises a valve seat attached to the fitting, a plug adapted to engage the valve seat, a stem adapted to rotate the plug, wherein the plug is adapted to move relative to the stem and a bonnet attached to the fitting and supporting the stem. The bonnet engages a slot on the stem as the valve assembly is moved from the first position to the second position and the pin is removed from the slot before rotating the valve assembly to the third position.  
         [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 having a plug valve;  
         [0019]      FIG. 3  is a cross-sectional view of the dual chamber orifice fitting of  FIG. 2 ;  
         [0020]      FIG. 4  is a partial cross-sectional view of the plug valve assembly of  FIG. 2 ;  
         [0021]      FIG. 5  is an isometric view of the valve assembly of  FIG. 4 ;  
         [0022]      FIG. 6  is an isometric view of select components of the valve assembly of  FIG. 4 ;  
         [0023]      FIG. 7  is a partial cross-sectional view of an alternate embodiment of a plug valve assembly;  
         [0024]      FIG. 8  is an isometric view of the valve assembly of  FIG. 7 ;  
         [0025]      FIG. 9  is an isometric view of select components of the valve assembly of  FIG. 7 ;  
         [0026]      FIG. 10  is an isometric view of one embodiment of a stem and bonnet assembly;  
         [0027]      FIG. 11  is a partial sectional isometric view of one embodiment of a stem and bonnet assembly;  
         [0028]      FIG. 12A  is a sectional view showing a valve assembly in a closed position;  
         [0029]      FIG. 12B  is a sectional view showing a valve assembly in an equalized position; and  
         [0030]      FIG. 12C  is a sectional view showing a valve assembly in an open position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]     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.  
         [0032]     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 . 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 by clamping bar  175  and clamping bar screws  177 . Wall  165  supports upper drive assembly  145  and includes port  185 , which provides access to upper chamber  130 . Preferred configurations of a body and top are described in U.S. patent application XX/XXXXX, entitled “Dual Chamber Orifice Fitting Body,” (Atty. Ref. 1787-15200), which is incorporated by reference herein for all purposes.  
         [0033]     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 XX/XXXXX, entitled “Dual Chamber Orifice Fitting Plate Support,” (Atty. Ref. 1787-15000), which is hereby incorporated by reference herein for all purposes.  
         [0034]     Fluid communication and the movement of orifice plate carrier  140  between upper chamber  130  and lower chamber  120  are regulated by valve assembly  135 . Valve assembly  135  is illustrated as a plug valve that utilizes a cylindrical sealing surface that is rotated between and opened and closed position. A cross-sectional view of one embodiment of valve assembly  135  is shown in  FIG. 4 . Valve assembly  135  includes plug  200 , seat  202 , and saddle  204 . Seat  202  is a curved sealing member having aperture  209 . The ends of seat  202  are supported in grooves  206  formed in top  115 . Grooves  206  allow for easy assembly and disassembly of seat  202  from top  115 . Plug  200  has a substantially cylindrical body including a rectangular, longitudinal aperture  210  and relief port  212 . Seat  202  has an inside diameter slightly smaller than the outside diameter of plug  200  in order to promote sealing engagement between the seat and the plug. Plug  200 , seat  202  and saddle  204  can be constructed out a variety of materials selected for suitability with a particular working environment, such as alloys, steel, composites, and polymeric materials.  
         [0035]     Saddle  204  is disposed within body  110  and may be urged upward against plug  200  by spring  208 . In certain embodiments, spring  208  is located between saddle  204  and body  110  in order to bias plug  200  into contact with seat  202 . Spring  208  may be a round wire spring formed into a rectangle or other appropriate shape so as to apply a uniform force to saddle  204 . Spring  208  preferably provides sufficient force to effectuate a low-pressure seal between plug  200  and seat  202 .  
         [0036]     As is shown in  FIG. 4 , plug  200  is in a closed position preventing flow between lower chamber  120  and upper chamber  130 . Pressure  299  in lower chamber  120  pushes plug  200  against seat  202 . The force generated by pressure  299  seals plug  200  against the lower surface of seat  202  and seals the upper surface of seat  202  against top  115 . Plug  200  can be rotated between the closed position, as shown in  FIG. 4 , to an open position where seat aperture  209  is aligned with plug aperture  210 . The aligned apertures-provide a passageway that allows an orifice plate carrier to pass therethrough. Plug  200  also has an equalized position where port  212  provides a pathway for fluid communication between upper chamber  130  and lower chamber  120 , but this pathway does not support the movement of an orifice plate carrier.  
         [0037]     Referring now to  FIGS. 5 and 6 , valve assembly  135  is shown including stems  214  and bonnets  216 , which are used to rotate plug  200 .  FIG. 6  shows valve assembly  135  absent one stem  214  and bonnet  216 . Bonnets  216  connect to the fitting body and support stems  214  that interface with slots  218  on the ends of plug  200 . Slots  218  are oriented perpendicular to the aperture  210 . Slots  218  allow stems  214  to control the angular orientation of plug  200  without constraining the vertical movement of the plug when in the closed position.  
         [0038]     Slots  218  allow plug  200  to uniformly engage seat  202  when pressurized from the lower chamber. This uniform engagement allows plug  200  to bear against the seat with a consistent force along the entire contact length. Since the ends of plug  200  are not fixed to stems  214 , the plug does not deflect along its length.  
         [0039]     Referring now primarily to  FIGS. 7-9 , an alternative seal assembly  300  is shown including plug  302 , seat  304 , and saddle  306 . Seat carrier  308  connects seat  304  to top  315  while saddle  306  is supported by body  305 . Plug  302  is shown in the closed position where the plug seals against seat  304  and prevents fluid communication between upper chamber  330  and lower chamber  335 .  
         [0040]     Seat  304  is constructed from a polymeric material, such as PEEK™, and has an upper sealing surface  309  and a lower sealing surface  311 . Upper sealing surface  309  includes a seal groove  310  and has an aperture  312  sized to allow an orifice plate carrier to pass therethrough. When installed into a fitting assembly, seal groove  310  contains seal element  313 , which is compressed and seals against top  315 . Seat carrier  308  is connected to top  315  by fasteners  312  and maintains the position of seat  304 . Lower sealing surface  311  is curved and provides the sealing surface against which plug  302  seats when the fitting is pressurized. Saddle  306  is located immediately below plug  302  and is mounted to body  305 .  
         [0041]     In certain embodiments, spring  314  is located between saddle  306  and body  305  in order to bias the plug into contact with seat  304 . Spring  314  is preferably a round wire spring formed into a rectangle or other appropriate shape so as to apply a uniform force to saddle  306 . Spring  314  preferably provides sufficient force to effectuate a low-pressure seal between plug  302  and seat  304 .  
         [0042]     Plug  302  has a generally cylindrical outer surface  316 . Aperture  318  is formed through plug  302  and sized to allow an orifice plate carrier to pass therethrough. An equalizer port  320  provides a path for fluid communication between aperture  318  and the outside surface of plug  302 . Plug  302  is moved between the open and closed position by rotating stem  322  approximately 90 degrees, which rotates plug  302  along its longitudinal axis. Bonnets  324  seal against both stem  322  and body  305  also provide support to maintain the lateral position and rotatability of stems  322  and plug  302 .  
         [0043]     Each end  325  of plug  302  has a slot  326  perpendicular to the direction of aperture  318 . Slot  326  is adapted to interface with stem  322  and allows free vertical movement of plug  302  when the plug is in the closed position. This unrestricted movement allows plug  302  to bear against seat  304  with a uniform force along the entire contact length. Since the ends of plug  302  are not fixed to stems  322 , the plug does not deflect along its length and provides a uniform sealing engagement between the plug and seat  304 .  
         [0044]     Referring now to  FIG. 10 , stem  400  and bonnet  402  are shown. The end of stem  400  that engages with slot  218  ( FIG. 7 ) or  326  ( FIG. 9 ) has a boss  404  with a tab  406  on one end and a parallel shoulder  408  on the other. Tab  406  interfaces with the slot on the ends of a plug. Bonnet  402  fits over stem  400  and rests against boss  404 . Bonnet  402  has a bolt pattern  412  enabling attachment of the bonnet to body  110 . Bonnet  402  also has a pin  414  that engages shoulder  408  and limits the rotational travel of stem  400  to 90 degrees relative to bonnet  402 , effectively limiting the rotation of the plug between the open and closed position. Square end  418  of stem  400  provides an attachment location for a handle (not shown) that can be used to rotate the stem either manually or with an automated system.  
         [0045]     Referring now to  FIG. 11 , bonnet  402  may also have a spring-loaded pin  420 . Pin  420  is spring-loaded to the extended position where it engages groove  422  on stem  400  when the plug is in the closed position. Pin  420  is disengaged by pulling ring  424 . Groove  422  is sized such that stem  400  is rotationally limited. In certain embodiments, groove  422  is sized such that, with pin  420  engaged, rotational force applied to stem  400  can move the plug the 15 to 30 degrees required to move from the closed position to the equalized position, but pin  420  must be disengaged from groove  422  before rotating stem  400  and the plug the full 90 degrees to the opened position. In effect, pin  420  prevents unintentional movement of the plug from the closed position to the fully opened position.  
         [0046]     Referring now to  FIGS. 12A-12C , the operating positions of a schematic valve assembly  500 , including body  502  and rotatable plug  504  with aperture  506  and equalization port  508 , are shown. Plug  504  is used to control fluid communication between an upper chamber  510  and lower chamber  512  in body  502 . In  FIG. 12A , plug  504  is shown in the fully closed position. Pressure from lower chamber  512  pushes plug  504  upward and into body  502  forming a seal that prevents fluid communication between the upper and lower chambers.  
         [0047]      FIG. 12B  shows plug  504  in an equalized position where the plug has been rotated approximately 15 degrees. With respect to the embodiments described in reference to  FIG. 11 , this would be the point at which the spring-loaded pin  420  reaches the end of groove  426 . In this position, equalizer port  508  opens a fluid pathway between lower chamber  512  and upper chamber  510 . Although equalizer port  508  is shown as a single cylindrical penetration, in certain embodiments a plurality of penetrations may be used as well as penetrations of other sizes, shapes, and configurations.  
         [0048]      FIG. 12C  shows plug  504  in the fully opened position. Plug  504  has been rotated 90 degrees from the closed position to the limit of travel of pin  414  on shoulder  416  (see  FIG. 10 ). Spring-loaded pin  420  is pulled from groove  426  so that plug  504  can rotate past the equalized position (see  FIG. 11 ). In the opened position, aperture  506  through plug  504  is aligned with upper chamber  510  and lower chamber  512  so that the orifice plate carrier (not shown) can pass freely between the chambers.  
         [0049]     The equalized position provides for an intermediate position between the closed and opened positions where pressure is allowed to equalize between the upper chamber  510  and lower chamber  512 . For example, when a dual chamber orifice fitting is being taken out of service, lower chamber  512 , being in fluid communication with a pipeline, may be at a high pressure. In contrast, upper chamber  510  may be at a much lower pressure. The equalized position allows this pressure to be equalized before the aperture between the upper and lower chambers is opened completely.  
         [0050]     The plug valve arrangements described herein are capable of operating in less space than the slide valve arrangement shown in  FIG. 1 . This allows for smaller, lighter weight, and more compact dual chamber orifice fitting assemblies. The plug valve arrangement also provides a valve that is fully actuated with only 90 degrees of rotation. This provides significant advantages over a sliding valve that may need several full 360 degree rotations of a drive shaft to fully actuate. Not only does the plug valve operate quicker, but the limited rotation simplifies the automation of the actuation of the valve.  
         [0051]     The fully cylindrical plug also provides a more reliable sealing engagement capable of withstanding higher pressures and more extreme working environments. The fully cylindrical plug is resistant to bending stresses created by pressure differentials across the plug. Because the ends of the plug are also allowed to move vertically when in the closed position, the stress is further reduced in the plug in comparison to an arrangement where the ends of the plug were vertically fixed.  
         [0052]     The preferred embodiments of the present invention relate to apparatus for hydraulically isolating the two interior chambers of a dual chamber orifice fitting. The present invention is susceptible to 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 valve shapes and styles to improve operation of the fitting. Reference is made to the application of the concepts of the present invention to dual chamber orifice fitting with a plate orifice, 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 and orifice fittings. 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.  
         [0053]     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.