Abstract:
An adjustable automatic recirculation valve includes a valve body, a main valve disk, a bypass valve and a dynamic adjustment assembly. The main valve disk is positioned within the valve body and opens in response to fluid flow between a main inlet and a main outlet. The bypass valve controls the flow of fluid between the main inlet and the recirculating outlet. A dynamic adjustment assembly, housed within the valve body controls the operating lift associated with the maximum opening of the bypass valve to regulate fluid flow capacity to the recirculating outlet.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to automatic recirculation valves and more particularly to recirculation valves having the ability to adjust the bypass recirculation flow to accommodate for various flow ranges. 
     BACKGROUND OF THE INVENTION 
     Automatic recirculation (ARC) valves are typically used in the oil and gas, power and chemical industries. In particular, ARC valves are used in connection with centrifugal pump applications to prevent pump overheating caused by the transfer of heat from a pump mechanism to the process fluid flowing through a system. During normal operation, this heat is transferred away from the pump and dissipated through the system via the process fluid. However, during periods of low process flow, the slower moving fluid does not dissipate the heat away from the pump sufficiently, thereby contributing to pump overheating. In addition, the vapor pressure increases as the temperature of the fluid within the pump increases, thereby increasing cavitation potential which damages the pump mechanism. 
     Recirculation valves are used to prevent this overheating by providing a path through which the pump maintains sufficient fluid flow during periods of low process flow through the system. Fluid enters a recirculation valve though a main inlet and exits the valve through a main outlet. The main valve element senses the rate of flow between the main inlet, and outlet. A pressure differential across the main valve element causes the valve to open to permit process flow to the main outlet. When the main valve is open, a recirculation or bypass portion of the valve is closed which prevents the flow of fluid to an associated recirculation outlet. During times of low downstream demand, the differential pressure across the main valve is insufficient to open the valve. When the main valve is closed, the recirculation or bypass valve is open which allows for the flow of fluid through the recirculation chamber and consequently to the recirculation outlet. 
     A drawback associated with the above referenced ARC valve is that the capacity through the bypass valve is fixed depending on the application. For example, the bypass valve may be configured to accommodate a particular bypass Cv. Unfortunately, when ARC valves are installed in the field, the Cv rating may or may not be ideal for actual process conditions. Thus, field changes must be done manually to accommodate for the design differentials. The above-referenced drawbacks and others are overcome by the present invention described herein with reference to the detailed description, drawings and appended claims. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an adjustable automatic recirculation valve having a main valve body, a main valve disk, a bypass valve and a dynamic adjustment assembly. The valve body includes a main inlet, a main outlet and a recirculating outlet. The main valve disk is positioned within the valve body opens in response to fluid flow between the main inlet and main outlet. A bypass valve, responsive to opening and closing of the main valve, controls the flow of fluid between the main inlet and the recirculating outlet. A dynamic adjustment assembly is housed within the valve body and is configured to control the operating lift associated with the maximum opening of the bypass valve to regulate fluid flow capacity to the recirculating outlet. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
       The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate an embodiment of the invention, and, together with the general description given above and the detailed description given below, serve to explain the features of the invention. 
         FIG. 1  illustrates a cut-away perspective view of an ARC valve in a closed position according to an embodiment of the present invention. 
         FIG. 2   a - 2   d  illustrates perspective views of individual members of adjustable recirculation assembly according to an embodiment of the present invention. 
         FIG. 3  illustrates a side cut-away view of an ARC valve according to an embodiment of the present invention. 
         FIG. 4  illustrates a cut-away perspective view of an ARC valve in an open position according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that the disclosure will be thorough and complete, and will convey the scope of the invention to those or ordinary skill in the art. In the drawings, like numbers refer to like elements. 
       FIG. 1  illustrates an exemplary embodiment of a recirculation main valve  10  in a closed position having housing sections  20   a  and  20   b , a valve disk  30  enclosed within the housing  20 , a bypass or recirculation portion  40  and an adjustable recirculation assembly  100 . The housing sections may be connected using bolts  25  to form an internal cavity  35  through which fluid flows. Valve  10  has an inlet  50  located at one end of housing portion  20   a  which is aligned with a downstream side of a centrifugal pump (not shown) for receiving process fluid. Flanged portion  21   a  of housing section  20   a  includes a plurality of mounting holes  22   a  for mounting valve  10  to the downstream side of a process system. Valve  10  also includes an outlet  55  located at the other end of housing portion  20   b  configured to provide process fluid away from valve  10 . Flanged portion  21   b  of housing section  20   b  includes a plurality of mounting holes  22   b  for mounting valve  10  to the upstream side of a process system. 
     Disk  30  of the main valve is movably positioned along center shaft  31  which extends longitudinally from housing portions  20   a  to  20   b . Disk  30  communicates with disk seat  29  which is positioned between housing portions  20   a  and  20   b  and provides a seal to prevent process from reverse flow between outlet  55  and inlet  50 . Seat  29  extends circumferentially around the outer perimeter of disk  30 . Shaft  31  is fixedly attached at a first end  31   a  to the internal walls of housing portion  20   a  via bracket  33   a  which will be described in greater detail with reference to  FIG. 2A . Likewise, shaft  31  is fixedly attached at a second end  31   b  to the internal walls of housing portion  20   b  via bracket  33   b . Brackets  33   a  and  33   b  are substantially perpendicular to the longitudinal axis of shaft  31  and are configured to withstand the forces associated with fluid flow through valve  10 . Bracket  33   b  includes a circular base which is integrally formed with the interior wall of housing section  21   a  and a mid-diameter beam similar to that disclosed in  FIG. 2A  adapted to receive an end  31   b  of shaft  31 . However, bracket  33   b  does not include the side portions  202  shown in  FIG. 2A . 
     Sleeve  39  includes a annular internal recess  37  extending longitudinally from  36 A to  36 B. Recess  37  is configured to receive a bias spring  38  which, in its static position, exerts a force on disk  30  into a fully closed position such that disk  30  engages seat  29  to prevent reverse process flow through valve  10 . A shaft sleeve is connected to the disk  30  coaxial to the center of the disk. Sleeve  39  includes a threaded conical portion  41  which also extends around the lower side of disk  30  a radius distance from shaft  31 . Consistent with existing check valve functionality, when the differential pressure is sufficient, disk  30  is vertically displaced upward along shaft  31  toward outlet  55  against bias spring  38 . The vertical displacement of disk  31  breaks the seal with seat  29  causing process fluid to flow from inlet  50  through cavity  35  to outlet  55 . 
     Bypass or recirculation portion  40  generally includes a bypass valve  65 , body  60 , cavity  66 , recirculation port  52 , piston  80  and flanged portion  67 . A plurality of mounting holes  68  are spaced along flanged portion  67  for mounting recirculation portion  40  to bypass piping. Body  60  is integrally formed with valve housing section  20   a  and cavity  66  is defined by the interior walls of body  60 . Piston  80  is movably positioned within cavity  66  and corresponds to the movement of valve disk  30 . Piston  80  engages bypass valve seat  65   b  within cavity  66  to forma seal through which fluid can not flow. Piston  80  is positioned within cavity  66  and includes head portion  81  and a plurality of cascaded rings  82 . Piston  80  includes a central cylindrical passage  83  extending the length of piston  80 . The length of piston  80 , number of cascaded rings  82  depends on the recirculation pressure and flow needed for a particular application. For example, the number of cascaded rings  82  may be between 1 and 6 to accommodate Cv values typically from 0.2 to 75 and greater. In addition, the diameter of piston  80  is typically between about 1″ and 2.5″ and greater with cascaded rings  82  having the same diameter range. In this manner, a controlled multi stage pressure reducing bypass system is defined. 
       FIG. 2   a - 2   d  illustrates perspective views of individual members of adjustable recirculation assembly  100  positioned within housing section  21   a  and cavity  35 . Referring to  FIG. 2   a , pivot support ring  200  includes ring support  201 , bracket  33   a , pivot supports  202 , and shaft retaining cavity  203 . The diameter of retaining cavity  203  is sufficient to receive shaft  31 . Ring support  201  has a diameter and circumference such that it is fixedly attached or integrally molded with the interior of housing section  21   a . Pivot supports  202  include retaining bores  202   a  and  202   b  which are adapted to receive and retain pivot arm  210 .  FIG. 2   b  illustrates pivot arm  210  which is positioned and retained by pivot support ring  200 . Pivot arm  210  includes extension arms  211 , base support beam  212  and lever support arms  213 . Extension arms  211  each include receiving portions  212   a  and  212   b  which connect to pivot supports  202  via retaining bores  202   a  and  202   b .  FIG. 2   c  is a perspective view of pivot lever  204  which has a substantially horseshoe shape formed by walls  220   a ,  220   b  and  220   c  and is positioned around shaft  31 . The front portion of pivot lever  204  is defined by angular lever member  221  received between lever support arms  213 . Slots  222  formed in inner walls  220   a  and  220   c  are adapted to receive actuator pin  230  (shown in  FIG. 1 ). Turning briefly to  FIG. 1 , as sleeve  39  traverses shaft  31  in an upward direction toward outlet port  55  caused by the differential pressure about disk  30 , sleeve  39  pulls assembly  100  upwards. This movement upwards causes pivot lever  204  to pivot about pivot pin  69  forcing lever  204  to rotate down toward intake  50 . In particular,  FIG. 2   d  illustrates a perspective side view of lever  204  having slots  222 A and  222 C. Slot  222 A extends along a lower portion of the interior of wall  220   a  and slot  222 C extends along the lower portion of the interior of wall  220   c . Each of the slots  222 A and  222 C is configured to allow pin  230  (shown in  FIG. 1 ) to traverse within the slots when sleeve  39  traverses shaft  31  in an upward or downward direction caused differential pressure about disk  30 . 
     The functioning of assembly  100  and in particular lever  204  may be seen in  FIG. 3  which is a side cut-away view of valve  10  with recirculation valve  65  in a open position. As can be seen, head  81  of piston  80  is positioned on angular lever member  221 . The position of head  81  on lever member  221  may be adjusted depending on the bypass recirculation valve opening required for a particular application. Thus, if head  81  is positioned higher on angular member  221 , i.e. toward end  221   a , head  81  will traverse the surface of angular member  221  from the point of contact toward end  221   a . Likewise, if head  81  was positioned lower on angular member  221 , towards end  221   b , head  81  will traverse the surface of angular member  221   a  lesser distance and thereby force valve  65  to close a lesser distance D. Again, as sleeve  39  traverses shaft  31  in an upward direction toward outlet port  55  caused by the differential pressure about disk  30 , sleeve  39  pulls assembly  100  upwards and actuator pin  230  traverses within channel  231  of shaft  31 . This movement upwards causes pivot lever arm  210  to rotate downward and pivot lever  204  to pivot about pin  69  once pin  69  is fixed in position due to adjustment of operator shaft  401  (shown in  FIG. 4 ). 
       FIG. 4  illustrates valve  10  in an open position whereby the seal between disk  30  and seat  29  is broken allowing process fluid to flow from inlet  50  to outlet  55 . As the sleeve  39  and disk  30  vertically traverse shaft  31  toward outlet  55 , bypass recirculation assembly  40  likewise moves in relation to shaft  31  as described above. This displacement causes angular member  221  to pivot in direction A. Because piston head  81  is in contact with a point along the surface of angular member  221 , the rotation of angular member  221  forces piston head  81 , and likewise piston  80 , to move toward recirculation outlet  52  within cavity  66 , thereby closing bypass valve  65  a distance D (as shown in  FIG. 3 ). 
     An operator shaft  401  has a first end  401   a  located at locking plate  402  near the outer surface of housing  20   a  and extends to a second end  401   b  for connection with pivot arm  210 . Locking plate  402  retains operator shaft  401  in position with housing  20   a . Operator shaft  401  is connected to pivot arm  210  which is connected to pivot lever  204 . As stated above, pivot lever  204  surrounds shaft  31  on at least three sides with a horseshoe shape and contacts head portion  81  via angular member  221 . The first end  401   a  of operator shaft  401  includes an adjustment head  401   c  used to adjust operator shaft  401  in receiving portion  212   a  thereby changing the angle of pivot arm  211  and likewise changing the angle of pivot lever  204 . This change forces angular member  221  of pivot lever  204  to move thereby adjusting the point at which head  81  of piston  80  contacts angular member  221 . In particular, as operator shaft  401  is adjusted in direction A, pivot arm  211  is displaced downward in direction A which causes pivot lever  204  in direction A. The change in position of pivot lever  204  in direction A also moves angular member  221  and causes the point of contact with head  81  to move along the surface of angular member  221  in direction B. Likewise, if operator shaft  401  is adjusted in direction B, piston head  81  moves downward along the surface of angular member  221  in direction A. The movement of piston head  81  in directions A or B with respect to angular member  221  controls the opening and closing displacement of bypass valve  65 . 
     If the static relationship between piston head  81  and angular member  221  is changed either in direction A or B as described above, the distance piston  80  will travel within cavity  66  will change proportionally. Angular member  221  has an upper portion  221   a  and a lower portion  221   b . By adjusting the static contact point of head  81  along the surface of angular member  221  toward either portions  221   a  or  221   b , head  81  will be displaced based on this static (or starting) position. For example, if angular member  221  is adjusted such that head  81  has a static contact point closer to portion  221   a , head  81  has less surface area of angular member  221  to traverse. With less surface area of angular member  221  to traverse, shaft  80  will be displaced more within cavity  66 . 
     The displacement of shaft  80  within cavity  66  determines the open distance D of the bypass valve  65 . Likewise, if angular member  221  is adjusted such that head  81  has a static contact point closer to portion  221   b , head  81  has more surface area of angular member  221  to traverse, i.e. toward end  221   a . With more surface area of angular member  221  to traverse, piston  80  will be displaced a lesser distance within cavity  66 , thereby increasing the open distance D of bypass valve  65 . In other words, the distance which piston  80  travels (and consequently the distance D bypass valve  65  opens) depends on the static contact point between head  81  and angular member  221 . By adjusting the point at which head  81  contacts angular member  221  using operator pin  401 , an operator may field adjust the flow capability through bypass portion  40  of valve  10  quickly and easily. 
     In previous ARC valves, the bypass valve opening parameter D was factory set prior to shipment to a customer. However, if adjustments were needed during field installation, an installer had to remove the piston  80 , and update as to the needed adjustment parameters and reassemble the valve. The present invention avoids these issues by providing a bypass flow valve capable of easy field adjustability. 
     While the present invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the present invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims, and equivalents thereof.