Abstract:
In general, the invention relates to a ported slide gate valve having a gate for regulating the flow of a fluid through the valve, a seat located in the valve interior, and a means for causing the gate to move in such a manner that the gate fractures any scale built up in the lower portion of the valve interior, prior to the gate&#39;s movement to a valve closed position. The scale is fractured in a direction away from the seat and deposited in the fluid. More particularly, the means for causing the gate to move includes a primary piston and a secondary piston, where the primary piston is coupled to the gate. In the valve closed position, the secondary piston holds the primary piston in the desired position. A movement of the secondary piston causes the gate to move to fracture the scale in the lower portion of the valve interior.

Description:
PRIORITY FILING  
         [0001]    This application claims the benefit of the earlier filing date, under 35 U.S.C. 119, of commonly owned provisional patent application, serial No. 60/326,856 entitled “Slurry Valve With Operator Action to Break Pipeline Scale,” filed on Oct. 3, 2001.  
         FIELD OF THE INVENTION  
         [0002]    The present invention relates to valves in general and more particularly, to a ported gate valve for use in slurry service.  
         BACKGROUND OF THE INVENTION  
         [0003]    Ported slide gate valves are usually used in slurry service because these valves provide good wear resistance to abrasive slurries. Ported slide gate valves with rubber or elastomeric seats that allow tight shut-off provide the most efficient type of valve performance in these harsh environments. The rubber or elastomeric seats also serve as wear resistant liners for the valve interiors. Such a valve conventionally utilizes a gate with an aperture and an operator that opens or closes the gate in one motion.  
           [0004]    Some slurry systems generate a hard scale in the pipelines and valve interior surfaces. In those environments, operators are typically configured with larger than normal operating forces so that the opening or closing of the gate breaks the hard scale build up.  
           [0005]    However, when such a valve closes, the gate typically drags the scale fragments into the seats, thereby tearing them. This tearing destroys the valve seats and consequently, results in premature valve failure.  
           [0006]    Prior art systems occasionally used metal seats for such valves, in order to avoid seat damage. However, metal seated valves do not provide as tight of a shut-off as rubber or elastomeric seated valves.  
           [0007]    Therefore, a need exists for a ported slide gate valve which overcomes the problem of scale build up and also enables the utilization of rubber or elastomeric seats with such a valve. Eliminating those problems would improve overall valve performance, prolong valve life and reduce maintenance and downtime costs.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention relates to a ported slide gate valve where the gate has an open position, in which a portion of the gate having an aperture is aligned between ported elements to allow the passage of fluid through the valve, and a closed position, in which a solid portion of the gate is aligned between the ported elements. A means is coupled to the gate so that, prior to the movement of the gate to the closed position, the gate first has a reverse movement in a direction counter to the closing direction. This reverse movement breaks any scale buildup on a seat or seats, located in the valve interior, in such a manner that the scale is broken in a direction away from the seat or seats and deposited in the fluid.  
           [0009]    Another aspect of the invention includes having a primary piston and a secondary piston as part of the means for moving the gate, where the primary piston is coupled to the gate in order to cause the movement of the gate. In the valve open position, the secondary piston holds the primary piston in the desired position. A movement of the secondary piston causes the reverse movement to break the scale. 
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0010]    [0010]FIG. 1 is a perspective view of a valve according to the invention in an open position, partially in cross-section to show operation;  
         [0011]    [0011]FIG. 2 depicts the valve of FIG. 1 in a closed position, according to the invention;  
         [0012]    [0012]FIG. 3 depicts the valve in an intermediate position, according to the operation of the invention;  
         [0013]    [0013]FIG. 4 shows the valve in an open position depicting the scale build up and the operation shown in FIG. 3, where the gate operates upwardly to break the scale build up prior to being fully closed;  
         [0014]    [0014]FIG. 5 shows the gate of the valve in a fully closed position after the operation depicted in FIG. 4 occurs;  
         [0015]    [0015]FIG. 6 shows a cross-sectional view of the cylinder operator of the invention, with the operator holding the valve in an open position;  
         [0016]    [0016]FIG. 7 shows a cross-sectional view of the cylinder operator, with the operator holding the valve in the intermediate position; and  
         [0017]    [0017]FIG. 8 shows a cross-sectional view of the cylinder operator, with the operator holding the valve in a closed position.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    [0018]FIG. 1, shows a typical ported slide gate valve  10 . The valve  10  is shown in an open position. The valve  10  has a gate  15 , which is a planar member having an aperture  16  located in its surface. On each side of the valve are ported pipe-coupling elements  21  and  22 . Each pipe-coupling element has a seat located therein. The seats are typically made of a rubber or elastomeric material, as described above. They are designated on one side by the numeral  23 . On the other side, it is shown, along with the associated pipe-coupling element  22 , in cross section and designated by the numeral  24 .  
         [0019]    The gate  15  is connected to a piston rod  31 , which in operation moves the gate upwards and downwards. The piston rod is surrounded by a bellows  61 , which is typically constructed of a Hyperlon or nylon material and is used to prevent external contamination from damaging the piston rod  31 .  
         [0020]    The piston rod is secured to a piston head  32 . This piston rod and associated head comprise a primary piston  33 . Located near the primary piston  33  is a secondary piston  43 , comprising another piston rod  41  and head  42 . The primary piston head  32  is configured to move within a first cylinder  35 . The secondary piston head  42  is configured to move within a second cylinder  45 , and its associated rod  41  is movably placed within an aperture  48  in an intermediate member  55 .  
         [0021]    Also shown in FIG. 1 are hydraulic or control ports  51 ,  52  and  53 . These ports are conventionally coupled to a source of hydraulics or air and serve to operate the respective pistons in a well-known manner. Essentially, hydraulic fluid or air enters through the ports into the associated cylinders, thereby forcing the pistons to move to upper or lower positions. Port  53  communicates with the space  46  above the secondary piston head  42 . Port  52  communicates with the space  36  above the primary piston head  32 , while port  51  communicates with the space  37  below the primary piston head  32 .  
         [0022]    [0022]FIG. 1 depicts the gate  15  in an open position. The gate aperture  16  is aligned with ports  25  and  26  in the two pipe-coupling elements  21  and  22 , such that the interior circumference of the aperture  16  aligns with the interior circumference of the rubber or elastomeric seats  23  and  24 , creating a valve bore  11 . In this open position, a fluid such as slurry can flow through the valve bore  11 .  
         [0023]    Presumably, in this open position allowing fluid flow, scale builds up on the seats, which are part of the valve interior. Scale is a solid, rock-like deposit which, when broken, creates sharp fragments that may cut or fracture the rubber or elastomeric seats, thereby destroying them.  
         [0024]    In the open position shown in FIG. 1, the secondary piston  43  has been lowered until its downward movement is stopped by its head  42  contacting the intermediate member  55 . The primary piston  33 , on the other hand, has been raised until its head  32  is stopped by contact with the secondary piston rod  41 . The bellows  61  is contracted. Essentially, the secondary piston  43  stops the movement of the primary piston  33  and the two pistons hold the gate  15  in the open position. The cylinder operator of the present invention includes this cooperative operation of the two pistons, which will be elaborated upon further below.  
         [0025]    [0025]FIG. 2 illustrates the ported slide gate valve  10  in the closed position. The head  32  of the primary piston has now moved until it contacts the bottom of its cylinder  35 . The bellows  61  is now extended. This movement of the primary piston  33  moves the gate  15  so that a solid planar portion  17  of the gate is positioned between the two pipe-coupling elements  21  and  22 , thereby obstructing any fluid flow through the valve  10 .  
         [0026]    As shown in FIG. 2, the secondary piston  43  is now slightly moved upwards. Its head  42  is moved upwards in its cylinder  45  and no longer contacts the intermediate member  55 .  
         [0027]    [0027]FIG. 3 shows the present invention in a position that would typically occur between the positions shown in FIG. 1 and FIG. 2. In this intermediate position, the secondary piston head  42  has moved upwards so that it contacts the top its cylinder  45 . Meanwhile, the primary piston head  32  has moved upwards so that it contacts the bottom of the secondary piston rod  41 .  
         [0028]    Those piston movements cause the gate  15  to move slightly upwards, such that the periphery of the aperture  16  extends beyond the interior circumference of the seats  23  and  24 , as illustrated in FIG. 3. Thus, the bottom periphery of the aperture  16  moves upwards from between the seats  23  and  24 , thereby fracturing any scale built up in the bottom portion of the seats.  
         [0029]    [0029]FIG. 4 further illustrates this novel scale fracturing feature of the present invention. FIG. 4 shows the valve  10  in the same intermediate position as shown in FIG. 3. In FIG. 4, pipelines  71  and  72  are now shown connected to each of the pipe-coupling elements  21  and  22 , creating a passageway for fluid flow, which can be regulated by the opening or closing of the valve  10 .  
         [0030]    In the intermediate position detailed in FIG. 4, the bottom portion of the gate aperture  16  is in the slightly raised position, and the drawing shows the fractured scale fragments  81  from the build up of scale  82  in the bottom portion of the seats  23  and  24 . The slight upward movement of the gate aperture  16  breaks the scale build up  82  in such a manner that the scale fragments  81  are propelled into the fluid flow and transported away from the seats  23  and  24  by the fluid.  
         [0031]    Thus, the present invention involves a slight reverse-direction movement of the gate  15 , prior to moving downwards to a closed position. This movement fractures the scale build up  82  in the bottom portion of the seat area and deposits the scale fragments  81  in the fluid flow so that they can be carried away from the seat area.  
         [0032]    [0032]FIG. 5 shows the ported slide gate valve  10  in the closed position again, as also illustrated in FIG. 2. However, FIG. 5 also shows the associated piping  71  and  72  and the broken scale fragments  81 , now being suspended within a fluid  91 . As stated above, the consequent reopening of the valve  10  will allow the fragments  81  to be transported downstream and away from the valve seats  23  and  24 .  
         [0033]    Essentially, scale build up was first observed as a serious problem during field operations of this type of valve. However, the scale build up typically did not cause damage to the seats in their top portions. It was discovered that this lack of damage was due to the fact that, when the gate moved downwards to reach a closed position, the bottom edge of the gate fractured any scale built up in the top portion of the valve interior. This fracturing occurred in such a manner that the scale fragments were pushed into the fluid flow and were carried away from the seats by the fluid flow.  
         [0034]    However, it was also discovered that, during the same closing movement of the gate, the bottom edge of the gate sheared the scale build up in the bottom portion of the valve into the seats. Thus, the seats would experience tearing and destruction in their bottom portions.  
         [0035]    The subject invention provides the advantageous feature of incorporating an intermediate gate position, as illustrated in FIGS. 3 and 4. This feature accomplishes an additional fracturing of the scale build up  82  in the bottom portion of the seats, in a manner similar to that conventionally achieved at the top portion. It is noted that, due to the circular shape of the valve bore, the bottom portion typically comprises the bottom half, whereas the top portion comprises the top half.  
         [0036]    Thus, this solution accomplishes, in a highly simple and effective manner, the fracturing of the scale build up in both the top and bottom halves of the seats. It also avoids the long established problem of the scale being driven into the rubber or elastomeric seats during the valve closing process and destroying them.  
         [0037]    [0037]FIGS. 6, 7 and  8  further detail the sequencing of the simple cylinder operator of the present invention. FIG. 6 shows the positioning of the pistons  33  and  43  when the valve is in the open position. Both the space  46  above the secondary piston head  42  and the space  37  below the primary piston head  32  are charged at the same pressure, through the respective control ports  53  and  51 . However, the presence of the primary piston rod  31  in the lower cylinder space  37  results in a force differential (the presence of the piston rod  31  reduces the piston&#39;s effective area, or the area on the bottom side of the piston head  32  that creates a force resulting from the applied pressure). Therefore, the pressure above the secondary piston head  42  exerts a slightly higher force, resulting in the downward force of the secondary piston rod  41  stopping the opposingly upward movement of the primary piston head  32 . This halting of the piston movements holds the gate in the valve open position.  
         [0038]    Referring to FIG. 7, the pistons are now shown in the intermediate position of the present invention. The pressure has now been vented from the space above the secondary piston head  42  through control port  53 , allowing the secondary piston  43  to move upwards until its head  42  contacts the top of the cylinder  45 . Since the space below the primary piston head  32  is still charged at a pressure, the primary piston  33  moves upwards, thereby lifting the gate to the aforementioned intermediate position, wherein the scale build up in the bottom portion is fractured. Thus, this cylinder operator provides a simple means of accomplishing the slight reverse-direction movement of the gate.  
         [0039]    [0039]FIG. 8 now shows the pistons as they are positioned when the valve is closed. To move the gate to this position, the space  36  above the primary piston head  32  is charged through control port  52 . This charging of pressure moves the primary piston head  32  down until it contacts the bottom of its cylinder  35 . The gate, which is coupled to the primary piston rod  31  as described above, is thus driven down into the valve closed position.  
         [0040]    To reopen the valve, the same pressure is again charged to the space  46  above the secondary piston head  42  and the space  37  below the primary piston head  32 , as illustrated in FIG. 6. The primary piston  33  moves upward, raising the gate to a valve open position. As described above, the secondary piston  43  exerts a slightly higher force than the opposing force from the primary piston  33 . Thus, the secondary piston  43  halts the upward movement of the primary piston  33  and holds the gate in the valve open position. The sequencing of this operator can by accomplished by conventional means as is well-known in the art, such as by the use of limit switches and solenoids.  
         [0041]    The above described cylinder operator provides a highly simple and effective means of cycling among the three gate positions required by the subject invention. However, it is anticipated by the invention that the valve operation could be implemented in various ways, as in commonly known or to be known in the industry. The above-described hydraulic or pneumatic operators provide sufficient operating forces to break the hard scale build ups. Their air-tight constructions also provide durability and longevity in the highly polluted environments in which they typically must perform. However, other means of operation, such as electronic actuator or manual hand wheel means, may also fall within the scope of the present invention.  
         [0042]    Although the foregoing description of the embodiments of the invention refers to the movements of the valve elements in terms of “upwards” and “downwards” and their positioning as “upper” and “lower” or “top” and “bottom”, it is not intended that the invention be limited to such movements or positioning. Obviously, many modifications and variations are possible. For example, the gate may be operated in horizontal or other directions, as well. Additionally, the invention may also have utility for breaking other types of deposits, besides scale, that are left by fluid flowing through the valve. All such modifications and variations that may be apparent to a person skilled in the art are intended to be included within the spirit and scope of this invention as defined by the accompanying claims.