Abstract:
A sight flow indicator having a viewing window for monitoring liquid flowing therethrough is disclosed. The flow indicator is configured to disentrain gas and particulate from a portion of the fluid. The flow indicator is also configured to reduce the velocity of fluid flowing therethrough. The portion of the fluid from which gas and particulate has been disentrained is diverted from the main flow stream, past the viewing window. The relatively clean liquid sample flowing past the viewing window lends itself to relatively accurate optical analysis using, compared to the bulk fluid flowing through the flow indicator. The flow indicator is well-suited for use with a spectrometer or other optical analyzer.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates generally to piping specialty items. More particularly, the invention relates to a sight flow indicator which allows optical monitoring of fluid in a piping system. 
     Sight flow indicators have long been known in the art. Prior art sight flow indicators commonly comprise a transparent body or an armored metal body with one or more glass viewing ports, a fluid inlet port, and a fluid outlet port. Sight flow indicators are commonly used in piping systems, such as petrochemical piping systems, to allow an operator to visually monitor the flow of fluids therein. However, sight flow indicators generally permit monitoring of bulk fluid flow only and do not provide a ready indication of the constituents of the bulk flow. For example, oil pumped from a well is likely to include produced water, produced gases, sediment, and other particulate matter. Although a conventional sight flow indicator allows an operator to monitor such bulk well flow, an operator generally cannot determine visually what percentage of the bulk well flow comprises, for example, oil vs. produced water. 
     Prior art techniques for determining the composition of oil versus produced water in bulk oil well flow generally involve collecting the bulk flow or a sample thereof in a separation vessel, or tank, and allowing the gases, the produced oil, the produced water, and the sediment to separate and stratify (a process that can take several days). Once the produced water and oil have been separated, the relative percentages of each can be readily determined. However, this technique operates on a sampling, not continuous, basis, and it does not provide real-time data that may be of vital importance to a well operator. 
     Techniques have been developed for analyzing multi-fluid flow to determine the percentages of the various components present therein. One such technique involves optical analysis of the flowing fluid. The technique may be implemented by associating an optical analyzer, such as a spectrometer, with the viewing region of a conventional sight flow indicator so that the optical analyzer can monitor and analyze the fluid flowing through the pipeline. Although this technique offers analysis and data output on a real-time or near real-time basis, its accuracy suffers when the fluid contains entrained gas and particulate matter. Accordingly, it would be desirable to provide a sight flow indicator which can provide a substantially gas- and particulate-free sample to a viewing region of the sight flow indicator. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a sight flow indicator for use in piping systems which provides optical indication of fluid flow therethrough. 
     It is another object of the invention to provide such a sight flow indicator which is configured to disentrain gas and particulate matter from at least a portion of the flow indicator which comprises a viewing window. 
     It is a further object of the invention to provide such a sight flow indicator which can be used in conjunction with an optical analyzer which can determine the relative percentages of different types of liquids, such as oil and produced water, comprising the bulk fluid flow through the sight flow indicator. 
     The apparatus of the present invention is a sight flow indicator which has an inlet port and an outlet port, with an expansion chamber disposed therebetween. The expansion chamber includes a diverging region, a main body portion, and a converging region. The diverging region is located between the inlet port and the main body of the expansion chamber, and the converging region is located between the main body of the expansion chamber and the outlet port. The main body of the expansion chamber has a relatively large cross section, compared to the inlet and outlet ports. In a preferred embodiment, one or more flow baffles are located within or near the inlet port, proximate the diverging region. 
     A sampling cavity extends radially outward from the main body of the expansion chamber. In a preferred embodiment, the sampling cavity is comma-shaped and has a thin cross section, compared to the main body of the expansion chamber, to allow for optical analysis of relatively opaque liquids, such as heavy crude oil. The sampling cavity includes one or more transparent viewing windows. 
     In use, the sight flow indicator is installed as an in-line element in a piping system. Typically, the inlet and outlet ports are sized to substantially match the inlet and outlet piping. 
     In a preferred embodiment and installation, the sampling cavity lies in a substantially horizontal plane and fluid flows through the flow indicator in a substantially horizontal direction. Also, in a preferred embodiment, a portion of the expansion chamber lies above the sampling cavity and a portion of the expansion chamber lies below the sampling cavity. 
     As a fluid flows through the inlet port and across the baffles, the fluid&#39;s velocity is increased and its pressure is reduced as a consequence of the reduced flow area proximate the baffles. This effect tends to disentrain gases from the fluid. As the fluid exits the inlet port and baffle region and flows into the expansion chamber, the fluid&#39;s flow velocity is reduced as a consequence of the increasing cross sectional area of the diverging section of the expansion chamber. As a consequence of the initial increase and subsequent decrease in flow velocity, and of the expansion chamber&#39;s overall configuration, gases entrained in the fluid tend to rise out of the fluid into an upper region of the expansion chamber, to a level above the sampling cavity. Similarly, solids and particulate matter entrained in the fluid tend to settle into a lower region of the expansion chamber, to a level below the sampling cavity. 
     As the fluid passes over the baffles, at least a portion of the fluid flow is diverted away from the bulk flow centerline. An eddy current is thus established within the expansion chamber and through the sampling cavity. A person or an optical device can view the flow through the viewing window in the sampling cavity. 
     Since the sampling cavity lies substantially between the upper and lower regions of the expansion chamber, and because entrained gases and solids have risen and settled into the upper and lower regions of the expansion chamber, respectively, the flow through the sampling cavity and past the viewing window is relatively free from entrained gas and particulate matter. Consequently, optical detection means can be readily employed to analyze and determine the makeup of the liquid flow past the viewing window. 
     As the fluid flows out of the expansion chamber and through the outlet port, the fluid flow reconverges. Gases and solids that were disentrained from the bulk flow stream in the expansion chamber are substantially flushed out of the expansion chamber and into the outlet piping. The fluid&#39;s flow velocity and flow pressure are returned toward their upstream levels, subject to pressure losses caused by the sight flow indicator apparatus. But for such pressure loss, the flow through the remainder of the piping system is substantially unaffected by the sight flow indicator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a sight flow indicator according to the present invention; 
     FIG. 2 is a cross-sectional side elevation view of a sight flow indicator according to the present invention; 
     FIG. 3 is a cross-sectional side elevation view of a sight flow indicator according to the present invention; 
     FIG. 4 is a cross-sectional elevation view of a sight flow indicator according to the present invention; and 
     FIG. 5 is a cross-sectional side elevation view of a viewing port according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a preferred embodiment of a sight flow indicator apparatus  20  according to the present invention. Apparatus  20  includes an inlet port  22 , an outlet port  24 , and an expansion chamber  26  which is located between inlet port  22  and outlet port  24 . Inlet port  22  is shown as being coaxial with outlet port  24 . In alternate embodiments, inlet port  22  may be offset from outlet port  24 . Inlet port  22 , outlet port  24 , and expansion chamber  26  are illustrated as being substantially cylindrical, but they may take other shapes, as well. 
     In the embodiment illustrated in FIG. 2, apparatus  20  further includes an inlet port flange  32  adjacent to inlet port  22  and an outlet port flange  34  adjacent to outlet port  24 . Inlet port flange  32  and outlet port flange  34  facilitate installation of apparatus  20  into a piping system (not shown). 
     Expansion chamber  26  has a diverging section  26 A, a main body section  26 B, and a converging section  26 C. Diverging section  26 A and converging section  26 C are shaped like the frustum of a cone. In a preferred embodiment, diverging section  26 A and converging section  26 C are shaped like the frustum of an eccentric cone, while main body section  26 B is substantially cylindrical. Consequently, the centerline of main body section  26 B of expansion chamber  26  is offset from the centerlines of inlet port  22  and outlet port  24 . In the illustrated embodiment, the offset is such that the perimeter of center section  26 B is tangential with the perimeter of inlet port  22  and outlet port  24 . In other embodiments of the invention, main body section  26 B of expansion chamber  26  may be offset from inlet and outlet ports  22  and  24  to a greater or lesser degree. For example, main body section  26 B of expansion chamber  26  can be coaxial with inlet and outlet ports  22  and  24 . 
     A sampling cavity  28  projects radially from the perimeter of expansion chamber  26 . Sampling cavity  28  has an interior region  29  of substantially rectangular cross section. In a preferred embodiment, sampling cavity  28  is substantially comma-shaped to promote steady, laminar sampling flow therethrough, as will be discussed below. Sampling cavity  28  is defined by a first side wall  40 , a second side wall  42 , and an end wall  44 . End wall  44  extends about the perimeter of sampling cavity  28 , except for that portion of the perimeter of sampling cavity  28  which abuts expansion chamber  26 . Consequently, the interior region  29  of sampling cavity  28  is open to and communicates with the interior region  27  of expansion chamber  26 . 
     As illustrated in FIGS. 1-5, each of side walls  40  and  42  of sampling cavity  28  contains a viewing port  30 . Each viewing port  30  includes a counterbore  56 , a land  58 , and an aperture  46  defined by land  58 . Each counterbore  56  includes internal threads  54 . In a preferred embodiment, each land  58  is flush with the respective interior surface  41  an  43  of side wall  40  and  42 . 
     A gasket  48  is located within counterbore  56 , against land  58 . Gasket  48  is substantially annular. The outside diameter of gasket  48  is slightly smaller than the diameter of counterbore  56  so that gasket  48  may be easily installed in and removed from counterbore  56 , as desired. The inside diameter of gasket  48  is substantially the same as the diameter of aperture  46 . 
     A transparent viewing window  50  is located within each counterbore  56 , against gasket  48 . In a preferred embodiment, as illustrated in FIG. 5, viewing window  50  resembles a flat disc having a protruding portion  60  which protrudes from one surface of the disc. Protruding portion  60  is shaped and sized to extend through gasket  48  and aperture  46 . When viewing window is tightened against gasket  48 , as will be explained below, protruding portion  60  of viewing window  50  extends slightly beyond the respective interior surface  41  or  43  of side wall  40  or  42 . In an alternate embodiment, protruding portion  60  of viewing window  50  may be flush with the respective interior surface  41  or  43  of side wall  40  or  42 . In another alternate embodiment, viewing window S 0  may be a d with substantially flat sides which does not penetrate gasket  48  or aperture  46 . 
     A viewing window retainer  52  holds each viewing window  50  in place within counterbore  56 . In a preferred embodiment, viewing window retainer  52  is an externally threaded annular cylinder. A protective washer  64  and cushioning gasket  65  are installed between viewing window  50  and viewing window retainer  52 . Viewing window retainer  52  is threaded into counterbore  56  and tightened against viewing window  50 . Viewing window  50  in turn compresses gasket  48  against land  58 , thus forming a leak-tight seal between viewing window  50  and walls  40  and  42  of sampling cavity  28 . 
     Viewing port  30  is configured to allow an optical analyzer, such as a spectrometer (not shown), to be adapted thereto. 
     In the embodiments illustrated in FIGS. 2 and 3, a first elongated flow baffle  36  is located within inlet port  22 , near the transition from inlet port  22  to diverging section  26 C of expansion chamber  26 . Flow baffle  36  spans two points on the inside perimeter of inlet port  22 . See FIG.  4 . In the embodiment illustrated in FIGS. 2 and 4, a second flow baffle  37  is similarly located and spans two other points on the inside perimeter of inlet port  22 . In the embodiment illustrated in FIG. 3, flow baffle  37 ′ is integral with a portion of side wall of inlet port  22 . Other embodiments may have more or fewer than two flow baffles and may or may not include a flow baffle which is integral with side wall  23  of inlet port  22 . 
     In a preferred embodiment, first and second flow baffles  36  and  37  (or  36  and  37 ′) are substantially parallel to each other and are inclined at an angle of about 15° from the flow axis in a direction away from sampling cavity  28 . In other embodiments, flow baffles  36  and  37  (or  36  and  37 ′) may be set at other angles which cause diversion and turbulent mixing of a fluid flowing across them. First and second flow baffles  36  and  37  (or  36  and  37 ′) need not be parallel to each other. 
     The components of sight flow indicator  20  can be made of any suitable material. Gasket  48  and cushioning gasket  65  can be made of any conventional gasket material. Viewing window  50  can be made of tempered glass or any other suitable transparent, optical quality material. Protective washer  64  can be made of steel, polymer, or other suitable load-bearing material. Viewing window retainer may also be made of steel, polymer, or other suitable material. The remaining components of sight flow indicator  20  can be made of any materials suitable for use in the piping system in which sight flow indicator  20  is to be installed. Such materials typically comprise various grades of steel or polymer, but other materials may be selected, as well. 
     An embodiment of sight flow indicator  20  having inlet and outlet flanges  32  and  34 , such as that shown in FIGS. 2 and 3, can be bolted into a piping system (not shown) having mating flanges. Alternative embodiments of sight flow indicator  20  can be installed into a piping system in any suitable manner, such as by threaded connection or by welding. 
     In the Figures, inlet port  22  and outlet port  24  are illustrated as being of the same size. In practice, inlet port  22  and outlet port  24  are typically sized to match the inlet and outlet piping, respectively (not shown). The inlet and outlet piping may be the same size, or of different sizes. Consequently, inlet port  22  and outlet port  24  need not be the same size. 
     In a typical piping system installation, it is preferred that sight flow indicator  20  be installed such that fluid flows through sight flow indicator  20  in a substantially horizontal direction. It is also preferred that sight flow indicator  20  be installed such that sampling cavity  28  is substantially horizontal. 
     In operation, as illustrated by flow arrows  66  in FIG. 2, fluid flows predominantly from the upstream portion of the piping system (not shown), through inlet port  22 , across flow baffles  36  and  37 , through expansion chamber  26 , and through outlet port  24  into the downstream portion of the piping system (not shown). As fluid flows through inlet port  22  and across baffles  36  and  37 , the fluid&#39;s velocity is increased and its pressure is reduced as a consequence of the reduced flow area proximate the baffles. This effect tends to disentrain gases from the fluid. As the fluid exits inlet port  22  and flows into expansion chamber  26 , the fluid&#39;s flow velocity is reduced as a consequence of the increasing cross sectional area of diverging section  26 A of expansion chamber  26 . As a consequence of the initial increase and subsequent decrease in flow velocity, the corresponding initial decrease and subsequent increase in pressure, and the overall configuration of expansion chamber  26 , gases entrained in the fluid tend to rise out of the fluid into an upper region of expansion chamber  26 , to a level above sampling cavity  28 . Similarly, solids and particulate matter entrained in the fluid tend to settle into a lower region of expansion chamber  26 , to a level below sampling cavity  28 . 
     Although the fluid predominantly flows through sight flow indicator  20  as described above and as illustrated in FIG. 2, a portion of the fluid, hereinafter referred to as the cross-channel flow, is diverted through sampling cavity  28 . As the flowing fluid crosses flow baffles  36  and  37  (or  36  and  37 ′, as shown in FIG.  3 ), the flow baffles tend to divert the fluid away from the flow centerline and towards side wall  25  of expansion chamber  26 . A portion of the flow thus diverted, i e the cross-channel flow, is directed towards and impinges side wall  25 . After impinging side wall  25 , the cross-channel flow is re-diverted across the main flow channel. The main flow tends to impel this cross-channel flow towards and into the main body section  26 B of expansion chamber  26  and towards the end of sampling cavity  28  near the outlet end of expansion chamber  26 . 
     The main flow and cross-channel flow paths are shown by the flow arrows  66  in FIG.  3 . Although FIG. 3 illustrates an embodiment of a sight flow indicator  20  having a flow baffle  37 ′ integral with side wall  23  of inlet port  22 , the foregoing concepts also apply to embodiments having only non-integral flow baffles, such as those illustrated in FIG.  2 . 
     As the fluid flows across flow baffles  36  and  37  (or  36  and  37 ′) and is diverted towards the side wall of expansion chamber  26 , a reduced-pressure region  68  is created near flow baffles  36  and  37  (or  36  and  37 ′). The pressure in reduced-pressure region  68  is somewhat lower than the pressure in the region immediately downstream of flow baffles  36  and  37  (or  36  and  37 ′). The reduced pressure in reduced-pressure region  68  tends to draw the cross-channel flow through the sampling cavity, and towards reduced-pressure region  68 , adjacent to flow baffles  36  and  37  (or  36  and  37 ′). The main flow immediately downstream of flow baffles  36  and  37  (or  36  and  37 ′) then tends to reentrain the cross-channel flow back into the main flow stream. This merged flow then substantially proceeds towards and through outlet port  24 , although a portion of the merged flow may again be diverted through the sampling cavity as described above. 
     Since entrained gases and solids respectively tend to rise and settle out of the flow stream above and below the plane in which sampling cavity  28  lies as a result of the decreased flow velocity and the configuration of expansion chamber  26 , the liquid which passes through sampling cavity  28  tends to be relatively free of entrained gases and solids. As such, the flow through sampling cavity  28  tends to be in a better condition for optical sampling than does the bulk flow with its entrained gases and solids. 
     Since transparent viewing windows  50 , in the preferred embodiment, project slightly beyond of the interior surfaces  41  and  43  of first and second walls  40  and  42  of sampling cavity  28 , it is relatively unlikely that particulate will accumulate on the viewing windows. However, in the event that particulate does accumulate on viewing windows  50 , the liquid flowing through sampling cavity  28  and past viewing windows  50  tends to “wash” the viewing windows of such substances. Since the flow velocity through expansion chamber  26  and sampling cavity  28  is reduced from the flow velocity in the inlet piping due to the increased cross sectional area of expansion chamber  26 , the likelihood of flow-induced damage to the viewing windows is also reduced. 
     Flow reconverges at the outlet end of the expansion chamber. As the fluid flows through converging section  26 C of expansion chamber  26  and through outlet port  24 , the flow velocity increases towards the entry velocity. As a consequence of the increased flow velocity and the configuration of expansion chamber  26 , disentrained gases and particulate matter tend to be swept back into the main flow stream and into the outlet piping (not shown). 
     Although a specific embodiment of the invention is described herein, the scope of the invention is limited only by the claims appended hereto. It is understood that those skilled in the art may make modifications to the embodiments described herein without departing from the spirit of the invention.