Abstract:
The present invention is directed to a technique of purging unwanted particles from the interior of a valve body. Inlet and outlet ports are formed in the valve housing to allow for circulation of the fluid within the valve body. The flow path of the fluid is isolated from the main fluid flow path when the valve is in the open or closed position. Additionally the pressure of the fluid is at a level higher than that of the main fluid flow.

Description:
BACKGROUND OF INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to ball type or hemi-wedge valves designed for use in pipelines such as those used for conveying oil or gas from wells to other facilities such as storage tanks, production facilities, etc. A hemi-wedge valve is distinguishable from a typical ball type or gate valve in that it employs a curved wedge formed as a tapered section rotatable through the fluid path. In particular this invention is directed to an arrangement for preventing the buildup of foreign material in the interior of a ball or hemi-wedge type valve. 
         [0003]    2. Description of Related Art 
         [0004]    Different types of valves are known for use in gas and oil pipelines. Typical valves include hemi-wedge valves, ball valves, gate valves, and plug valves. Oil and gas contain different types of contaminates such as black powder. Additionally precipitates often form in gas transmission pipelines after continuous use, especially where ambient temperatures vary widely or where daytime temperatures are hot. The precipitates form a very fine powder whose microscopic particles are very hard. These particles attach to the inner surface of the pipeline. 
         [0005]    In order to clean the interior of the pipelines, devices known as pigs are placed in the pipeline and pressurized fluid is used to push the pig (which is a plug that closely engages the wall of the pipeline) along the pipeline to dislodge the particles from the inner surface of the pipe and discharge the particles from the pipeline through outlets spaced along the pipeline. The inlets and outlets for the pigs are isolated from the main transmission pipelines by large valves, such as a ball or gate valve. The above mentioned particles, which are dislodged from the interior surface of the pipeline, work their way into the seals and clearances of the valve, eventually causing it to either malfunction or fail. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    To overcome the buildup of harmful particles in valve bodies as described above, the present invention utilizes a flow of secondary flow through the valve body to purge the particles from sealing surfaces and clearances within the valve body. The fluid is circulated at a pressure greater than that of the main fluid in the pipeline and is isolated from the main flow path in the open and closed positions of the valve. This technique is especially effective when used in conjunction with the three piece valve core design of the hemi wedge valve as will be explained in greater detail below. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0007]      FIG. 1  is a top view of a hemi-wedge valve according to the present invention. 
           [0008]      FIG. 2  is a top view of a hemi-wedge valve in the closed position. 
           [0009]      FIG. 3  is a schematic of the valve shown in  FIG. 1  placed in a pipeline with supporting equipment. 
           [0010]      FIG. 4  is a top view of the invention as applied to a conventional ball valve shown in the open position. 
           [0011]      FIG. 5  is a top view of the ball valve of  FIG. 4  shown in the closed position. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]      FIG. 1  illustrates a specific embodiment of a hemi-wedge valve to which the invention had been applied. The valve body  20  includes an inlet  2  and outlet  3  for the main fluid flow which is being regulated by the valve. The valve also includes a hemi-wedge valve element  7  which includes an upstream valve surface  31  and a downstream valve surface  30 . Valve seat seals are provided at  12  and  10  respectively. The hemi-wedge valve of  FIG. 1  has a core member that defines the main fluid flow path through the valve. In this example of a hemi-wedge valve, the valve member includes three portions,  4 ,  5 , and  6 . Upstream portion of valve core member  4  includes a seal  16  that engages a surface at the inlet  2 . Intermediate valve core member  5  has an outer cylindrical portion  51  that receives a reduced diameter portion  52  of valve core member  4 . Valve core member  5  also has a stepped portion  59  that forms a chamber for a seal  53  between valve core members  4  and  5 . Valve portion  6  also includes a sealing ring  12 . 
         [0013]    The downstream surface of hemi-wedge valve member  7  is in sealing contact with seal  10  which is supported by valve seat member  8 . A unique feature of a hemi-wedge valve is that the valve member  7  has a thickness that increases from its leading edge to its tailing edge as the valve closes. This in conjunction with the three piece valve core construction as described above, results in a closing force being applied to both sides of the valve member  7 . 
         [0014]    This design in and of itself tends to minimize the buildup of particulate material in the sealing components of the valve. In addition, in order to prevent buildup of particulate material, the present invention provides for a flow of secondary fluid within the housing of the valve. As shown in  FIG. 1 , an inlet port  61  for the secondary fluid is formed in the housing and an outlet port  62  is formed in the housing for exit of the secondary fluid from the valve housing. The secondary fluid inlet and outlet may be located anywhere in the housing. As shown, it can be seen that the inlet and outlet secondary fluid ports are isolated from the main fluid flow when the valve is in the open or closed position. Other hemi-wedge valves to which the present invention may be applied are shown and described in U.S. Pat. Nos. 4,962,911 and 7,357,145, the contents of both disclosures being expressly incorporated herein. 
         [0015]    A system for supplying the secondary purging fluid will now be described by reference to  FIG. 3 . Hemi-wedge valve  20  located in a fluid pipeline  130  as described above. A fluid supply tank  101  is provided. In the embodiment shown, the fluid can be pressurized by a pump  102  connected to inlet port  61 . Alternately the fluid tank could be constructed at a higher elevation with respect to the pipeline and a pressure increasing pump provided if needed. Also as a third embodiment, fluid under pressure from the pipeline could be diverted to the upper portion of the purging fluid tank as shown at  120  to pressurize the contents of the tank by exerting a force on a flexible diaphragm or a piston within the tank as is well known in the art. If the fluid in the pipeline is a gas and the purging fluid is a liquid, then the diaphragm or piston would not be needed. A filter  103  and a variable choke valve  104  are also provided in a return conduit  106 . 
         [0016]    In order to make sure that the pressure of the secondary fluid is greater than that of the fluid in the pipeline, two pressure sensors  110 ,  111  are provided at the upstream and downstream sections of hemi-wedge valve  20 . A third pressure sensor  107  is placed in the return conduit  106 . Information from the three sensors is sent to a microprocessor  113 . Microprocessor  113  analyzes the information and regulates variable choke valve  104  as necessary to maintain the pressure of the secondary liquid above that in the main flow line. Microprocessor  113  is also used to monitor the position of the valve actuator  112 , and to turn pump  102  on and off. 
         [0017]    Power for the microprocessor may be provided by conventional land power lines or by a battery  114  that is connected to a charging solar cell  115  as is known in the art. Furthermore the microprocessor may be connected to a satellite link  116  for sending and receiving information and commands as is known in the art. 
         [0018]      FIGS. 4 and 5  illustrate the invention as applied to a conventional ball valve  200 . Ball valve  200  has a main fluid inlet  202  and outlet  203 . The ball valve  205  has a central bore  206  to provide a flow path for the main fluid. Valve seats  212  and  210  are provided and include seals  213  and  211  as shown in  FIG. 4 . Valve  200  includes an inlet  261  and outlet  262  formed in the housing  215  for circulation of a secondary fluid for purging and cleaning of the internal parts of the valve. Ball valve  200  is positioned in a pipeline in the same manner as hemi-wedge valve  20  is positioned as shown in  FIG. 3 . 
         [0019]    Although the present invention has been described with respect to specific details, it is not intended that such details should be regarded as limitations on the scope of the invention, except to the extent that they are included in the accompanying claims.