Abstract:
Disclosed herein is a gate valve design with a proportionally controlled orifice area. The moving element of the gate is shaped to cooperate with a fixed element so that as the gate opens, the open orifice area changes geometrically.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       REFERENCE TO A MICROFICHE APPENDIX 
       [0003]    Not applicable. 
       BACKGROUND 
       [0004]    It is common in the drilling, completion and servicing of subterranean wells to utilize large volumes of mixtures of components in both solid and fluid form. Examples of these mixtures include drilling, fracturing, and other well treatment mixtures. Fracturing mixtures include solid materials called proppants. Proppants are solid particles mixed in dry form with fracturing fluid to hold fractures open after a hydraulic fracturing treatment. In addition to naturally occurring sand grains, man-made or specially engineered proppants, such as resin-coated sand or high-strength ceramic materials like sintered bauxite, may also be used. As used herein, the term “dry particulate material” is used to refer to particulate materials which cannot be pumped or handled as a fluid. To be effective for their purposes, some mixtures require that components be mixed in precise quantities. In view of logistics and the volumes required, it is impractical to first measure quantities of the solids and liquids and then mix them together as a batch. Typically, mixing is accomplished, while adding the components to a mixing chamber and proportion control of the components is performed, using valves. 
         [0005]    Dry solid materials are commonly mixed by conveying them to a container, typically a hopper, where they are fed by gravity into the mixing chamber. It is common in the industry to use augers to meter dry solid material from bins and hoppers into the mixing chamber. Sliding gate valves have been used but suffers from the disadvantages described herein. As used herein, the term “sliding gate valve” is used to refer to a valve having a planar or wedge shaped a valve element that moves into and out of the flow path and cooperates with a fixed seat to meter flow through the valve orifice. In a gate valve, the area defined between the valve and its seat is sometimes called an “orifice.” Sliding gate valves can be controlled (opened and closed) manually or by electrical or fluid actuators. 
         [0006]    The ratio of the smallest dimension of an orifice is critical to the jamming probability caused by material bridging. The combination of the orifice area (size) and the critical dimension (smallest orifice dimension) contribute to the flow rate of material through the orifice. Typical sliding gate valves used to control the flow of materials have quadrilateral-shaped orifices. These gate valves are simple and easy to use to meter material flow by sliding the valve element into or out of the flow path to adjust the orifice size. 
         [0007]    In these existing gate valves, the width of the orifice is a fixed dimension and, as the valve opens, a quadrilateral orifice is created. Accordingly, these gate valves will have a large orifice area, compared to the smallest dimension of the orifice as the gate opens. Once the gate valve is open far enough to exceed the distance at which bridging occurs or far enough to diminish the entry effects of the minimum optimum dimension, the total, open area of the orifice allows more material to pass than is desired. Accordingly, these gate valves cannot accurately meter small flow rates. 
         [0008]    In these existing gate valves, small movements of the valve element cause proportionally large changes in orifice size. These gate valves do not provide fine metering control. 
         [0009]    Accordingly, there is a need for metering equipment that provides fine flow rate control, especially at lower flow rates where jamming can occur. 
       SUMMARY 
       [0010]    Disclosed herein is a gate valve with an orifice that varies in two dimensions as the valve element is moved. In one sliding gate valve embodiment, the gate valve orifice is quadrilateral shaped and varies in both width and length as the valve element is moved. In another circle orifice gate valve embodiment, a plurality of valve elements are mounted to pivot into and out of the flow to vary the orifice size in both length and width dimensions. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description: 
           [0012]      FIG. 1  is a schematic view, illustrating a typical particulate material supply system for use drilling, completion operations on a well according to the disclosure of the present invention; 
           [0013]      FIG. 2  is a top plan view of a prior art sliding gate valve, illustrating the valve in the closed position; 
           [0014]      FIG. 3  is a cross-sectional view of the prior art valve illustrated in  FIG. 2  taken along line  2 - 2 , looking in the direction of the arrows; 
           [0015]      FIG. 4  is a top plan view of the orifice portion of a sliding gate valve, illustrated in the closed position according to the present invention; 
           [0016]      FIG. 5  is a top plan view of the orifice portion of the sliding gate valve of  FIG. 4  illustrated in the partially opened or metering position according to the present invention; 
           [0017]      FIG. 6  is a top plan view of the orifice portion of the circle orifice gate valve, illustrated in the fully open position according to the present invention; and 
           [0018]      FIG. 7  is a top plan view of the orifice portion of the circle orifice gate valve of  FIG. 6 , illustrated in the partially closed or metering position according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0019]    In the drawings and description that follow, like parts are typically marked throughout the specification and drawings with the same or similar reference letters and numerals. 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. 
         [0020]    The various characteristics mentioned above, as well as other features and characteristics described in more detail below, will be readily apparent to those skilled in the art with the aid of this disclosure, upon reading the following detailed description of the embodiments and by referring to the accompanying drawings. 
         [0021]    Disclosed herein are solid particulate material supply and metering systems for oil well services, using an improved sliding gate valves. More specifically, gate valves are positioned to control the gravity flow of dry solid particulate material into a mixing chamber where the particulate is mixed in proportion with other components, including liquid components. The sliding gate valve of the present invention is characterized by being able to accurately meter the gravity flow of dry particulate materials and, in particular, to accurately meter small quantities of dry solid materials. 
         [0022]    Referring to  FIG. 1 , there is illustrated one embodiment of a material supply and metering system  10  for use in preparing mixtures for use in gas well servicing and drilling. System  10  comprises a hopper  12  for containing a quantity of dry particulate material, such as a proppant. A conveyor  14  is typically used to load hopper  12 . The particulate material flows by gravity through the valve  16  to a mixer  18 . The valve  16  is typically a sliding gate valve which is used to meter the flow of material into the mixer  18 . One or more fluid components are supplied to the mixer  18  from a tag  22  through a fluid pump  20 . A supply pump  24 , in the form of a positive displacement pump, provides particulate fluid mixture to the well  26 . 
         [0023]    A sliding gate valve  16  of conventional construction is illustrated in  FIGS. 2 and 3  in the slightly open position. Valve  16  comprises a frame  30  having with the feed opening and a flange surrounding the opening that is suitable for attachment of the valve  16  to the bottom of the hopper  12 . The quadrilateral-shaped frame  30  surrounds the feed opening and supports a valve seat  32 . The valve element  34  comprises a sliding plate which, when the valve is opened, cooperates with the valve seat  32  to define the valve orifice  38 . As will be appreciated, as the valve element  34  is moved in the direction of arrow  40  out of feed opening, a quadrilateral-shaped orifice  38  is formed. For purposes of description, the width dimension (W) of the orifice is defined transverse to the valve element&#39;s direction of movement, as illustrated by arrow  40 . The orifice length dimension (L) is defined parallel to the direction of movement  40 . In a rectangular orifice, the area (A) is computed by multiplying the length by the width. 
         [0024]    An actuator assembly  36  is connected to the valve element  34 . The actuator assembly  36  is operably associated with the valve element  34  to selectively move it into and out of the feed opening. Actuator assembly  36  is an electrically powered actuator  42  that can be operated to control the position of the valve element  34 . 
         [0025]    When metering of relatively smaller quantities of material, the orifice area A of the valve will be small. As illustrated in  FIG. 2 , as the valve opens, a rectangular orifice is formed with a length (L) that is multiples less than the width (W). At smaller areas, the length of the orifice is the critical, smallest dimension and is more likely to experience material bridging. Once the gate valve is open far enough to exceed the critical length distance (L) at which bridging occurs (and to diminish the entry effects), the total, open area of the orifice allows more material to pass than is desired. Accordingly, because of bridging, these conventional gate valves cannot meter relatively small flow rates. 
         [0026]    Referring to  FIGS. 4 and 5 , an embodiment of a sliding sleeve gate valve  116  is illustrated. In  FIG. 4 , the valve is illustrated in the closed position, and in  FIG. 5 , the valve is illustrated in the partially open position. The valve seat  132  is in the form of a plate, positioned in the feed opening. The seat  132  has a right-angled, triangular-shaped opening  133 , formed there through which particulate material can flow when the valve is open. The valve element  134  is mounted to slide in the direction of arrow  140  with respect to the seat  132 . As illustrated, the valve element  134  has a right-angled, triangular-shaped cutout portion  135 . 
         [0027]    In operation, as the valve element  134  moves in the direction of arrow  140 , the triangular cutouts  133  and  135  will begin to overlap, forming a quadrilateral-shaped orifice  138 . In the preferred embodiment, orifice  138  is substantially square shaped, with equal length sides. The orifice area (A) is defined by the square of any one side. It is envisioned, however, that depending on the shapes of the triangular cutouts, the orifice can take on different shapes and proportions. As the valve element  134  moves in the direction of arrow  140 , the lengths of the four sides (S) defining the orifice  138  all increase equally and the length (L) of the orifice becomes greater in the same amount as the width (W). In orifices of the same area (flow rate), the smallest or critical dimension of a square-shaped orifice is greater than the smallest dimension of a rectangular shaped orifice. This allows the sliding gate valve embodiment illustrated in  FIG. 5  to operate at lower flow rates than other quadrilateral orifice shapes. 
         [0028]    As illustrated in  FIG. 5 , when the triangular cutouts overlap slightly, orifice  138  is formed with a small cross-section area but with no one dimension substantially smaller than the other dimensions. In the  FIG. 5  embodiment, the gate valve orifice  138  is quadrilateral shaped and varies both width and length as the valve element is moved. 
         [0029]    In an alternative embodiment, a particulate material gate valve  216  is illustrated in  FIGS. 6 and 7 . In  FIG. 6 , valve  216  is shown in the completely open condition. In  FIG. 7 , valve  216  is shown in the partially open or metering position. In this embodiment, valve  216  is in the form of a circle orifice gate valve. Valve  216  comprises an annular seat  232  that surrounds a circular particulate material feed opening. 
         [0030]    A plurality of adjacent pedals-shaped valve elements  234  are mounted to pivot into and out of the material feed opening. In the illustrated embodiment, six separate elements are shown, however, more or less elements could be utilized. In the illustrated embodiment, each of the valve elements  234  comprise a flat plate. The valve elements  234  are formed with arcuate or curved, interior facing edges  235 , however, it is envisioned that the interior edges could be defined by one or more straight lines or other shapes. The valve elements  234  are illustrated in  FIG. 6 , positioned out of the feed opening and under the seat  232 . The valve elements  234  are mounted to rotate about pivots  239 . An actuator (not illustrated) is operably connected to the valve elements  234  to rotate the elements in the forward and reverse directions of arrow  240 . 
         [0031]    As illustrated in  FIG. 7 , as the valve elements move in the direction of arrow  240 , the cross-sectional area of the orifice  238  becomes smaller. When it is desired to meter a small quantities of particulate materials through the valve  216 , the orifice  238  formed by the valve elements  234 . In the preferred embodiment, the elements define an orifice that is roughly polygon shaped. The more valve elements are present in the valve, the more the orifice approximates a circle. As will be appreciated, as the shape approaches a circular shape, the orifice surface effects would be reduced. As in the above-described embodiment, this shape of the orifice  238  is conducive to reducing bridging of the particulate material at lower flow rates. 
         [0032]    According to a particular feature of the present invention, the valve embodiments illustrated and described herein can be utilized in the system illustrated in  FIG. 1  to meter small quantities of particulate materials, while reducing material bridging and jamming. 
         [0033]    At least one embodiment is disclosed and variations, combinations, and/or modifications of the embodiment(s) and/or features of the embodiment(s) made by a person having ordinary skill in the art are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Use of broader terms, such as “comprises,” “includes,” and “having,” should be understood to provide support for narrower terms, such as “consisting of,” “consisting essentially of,” and “comprised substantially of.” Accordingly, the scope of protection is not limited by the description set out above but is defined by the claims that follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated as further disclosure into the specification, and the claims are embodiment(s) of the present invention.