Patent Publication Number: US-2016223089-A1

Title: Choke Valve Wear Monitoring System and Method

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 62/110,176 filed on Jan. 30, 2015, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     Choke valves are commonly used in the oil and gas industries, as well as mining industries, as part of an arrangement of valves and fittings that extend above the well head. In general, choke valves include a valve body having an axial bore, a body inlet (typically referred to as a side outlet) and a body outlet (typically referred to as an end outlet); a “flow trim” mounted in the bore between the inlet and the outlet, for throttling the flow moving through the body; and a mechanism for actuating the flow trim to close the end of the bore remotely from the outlet. 
     There are four main types of flow trims commonly used in commercial choke valves. Each flow trim involves a port-defining member, a movable member for throttling the port, and a seal for implementing a total shut-off. These four types of flow trim can be characterized as follows: (1) a needle-and-seat flow trim comprising a tapered annular seat fixed in the valve body and a movable tapered internal plug for throttling and sealing in conjunction with the seat surface; (2) a cage-with-internal-plug flow trim comprising a tubular, cylindrical cage, fixed in the valve body and having ports in its side wall, and a plug movable axially through the bore of the cage to open or close the ports with shut-off generally accomplished with a taper on the leading edge of the plug, which seats on a taper carried by the cage or a body downstream of the ports; (3) a multiple-port-disc flow trim comprising a fixed ported disc mounted in the valve body and a contiguous rotatable ported disc that can be turned to cause the two sets of ports to move into or out of register for throttling and shut-off; and (4) a cage-with-external-sleeve flow trim comprising a tubular cylindrical cage having ports in its side wall and a hollow cylindrical sleeve that slides axially over the cage to open and close the ports. The shut-off is accomplished with the leading edge of the sleeve contacting an annular seat carried by the valve body or cage. 
     In each of the above, the flow trim is positioned within the choke valve at the intersection of the choke valve&#39;s inlet and outlet. In most of the valves, the flow trim includes a stationary tubular cylinder referred to as a “cage” positioned transverse to the inlet and having its bore axially aligned with the outlet. The cage has restrictive flow ports extending through its sidewall. Fluid enters the cage from the choke valve inlet, passes through the ports, and changes direction to leave the cage bore through the valve outlet. This type of a flow trim also includes a tubular throttling sleeve that slides over the cage. The sleeve acts to reduce or increase the area of the ports. An actuator, such as a threaded stem assembly, is provided to bias the sleeve back and forth along the cage. The rate that fluid passes through the flow trim is dependent on the relative position of the sleeve on the cage and the amount of port area that is revealed by the sleeve. 
     Regardless of the flow trim configuration, the above described choke valves can be used to reduce the pressure of the fluid flowing from a well, for example, from a normally high pressure value to a lower pressure value. The pressure drop is accomplished in the choke valve by varying the cross-sectional area of the fluid flow stream to form a restriction for those fluids flowing from the well head. 
     The fluid stream flowing from an oil or gas well typically contains material which can be chemically corrosive and/or mechanically erosive to the choke valve. For example, the fluid stream can contain sand, and/or particulate material, as well as acids and corrosive harmful chemicals. Chemical corrosion and mechanical erosion are problems which have long plagued choke valve constructions. Many applications, such as oil and gas well installations, are in remote locations where a daily inspection of the choke valve is difficult or impossible. In these situations, undetected wear can create a valve failure situation, which can be not only damaging to the choke valve, but dangerous and possibly catastrophic. If the choke valve becomes eaten away because of corrosion or erosion, leakage of gas and/or oil could occur. 
     In the past, various types of liners were used to protect choke valves from erosion and corrosion. The prior attempts, which did not provide satisfactory results, included such components as pistons, sleeves, cages, plating or linings of tungsten carbide, chrome stainless, Stellite and ceramics. Typically, the liner was placed directly upon the housing or body of the choke. When the wear sleeve or liner was fully eroded or corroded by the flowing media, damage to the choke valve body was immediate. This type of damage to the choke valve body required extensive repair, which necessitated removal of the choke valve from the installation for repair at a machine shop. 
     Additionally, or alternatively, pressure and temperature transmitters have been installed into the flow lines upstream and downstream of the choke valve to determine whether the flow trim has been worn beyond its useful life. The sensor information is then sent to a remote location for monitoring, so that a choke valve controller can remotely bias the flow trim to affect the desired flow rate. The controller sends electrical signals to a mechanism associated with the choke valve for adjusting the flow trim. However, a problem exists with this process due to the unreliable nature of these electronic sensors, which have a limited service life. Replacing the sensors after they have served their useful life has required that the whole wellhead assembly be raised to the surface. This is a time-consuming and costly operation that shuts down well production for the duration of the repair. 
     SUMMARY 
     There is a need for a choke valve capable of detecting erosion on time by monitoring the wear status. Once erosion is detected, it would be desirable to keep the choke valve in line and only replace internal parts. In addition, there is a need for a tight shut off of the choke valve under the conditions of high differential pressure and flows of polluted fluids. 
     Embodiments of the invention overcome these problems by providing a wear monitoring system that is incorporated into a choke valve to detect erosion. The wear monitoring system provides a pressure sensor to detect a pressure increase in a depressurized cavity. The wear monitoring system ensures that only internal components (e.g., a rotating disc and a bean) need to be replaced if erosion occurs while the choke valve remains in service. Thus, the valve body is less affected by erosion, as is typically seen in choke valves, because the medium (e.g., fuel) is not filtered, causing wear and tear on the outlet piping. In addition, the choke valve improves laminar and non-turbulent flow through to limit erosion on the outlet piping. 
     In some embodiments, the wear monitoring system can include a pressure sensor, an outer depressurized cavity, a first cavity seal, and a second cavity seal. The pressure sensor can extend through a pressure port positioned above of the valve body to measure pressure within the depressurized cavity. The pressure port extends from an exterior environment of the choke valve to the depressurized cavity. The depressurized cavity can be defined by the space between the inner surface of the valve outlet and an outer surface of a bean. The first cavity seal is positioned between the inner surface of the outlet and the outer surface of the bean to seal off a bottom portion of the depressurized cavity. Similarly, the second cavity seal circumscribes the outer surface of a stationary disc to seal off a top portion of the depressurized cavity. If the pressure sensor detects a pressure greater than a predetermined threshold value, a signal is sent to close the choke valve and emergency shutdown (ESD) valves. This increase in pressure indicates that erosion has caused washing of the bean, resulting in the depressurized cavity becoming pressurized. A signal can then be sent from the pressure sensor to a remote user interface, for example, to alert a user that the choke valve requires service. The wear monitoring system ensures laminar and non-turbulent flow to limit erosion on the outlet piping by providing a larger diameter outlet than a passageway through the bean. 
     In other embodiments, a choke valve is provided that includes a valve body defining an inlet and an outlet. The choke valve further includes a stationary disc including a bean and defining a passageway arranged between the inlet and outlet of the valve body. A rotating disc is arranged adjacent the stationary disc, and the rotating disc is movable between an open position and a closed position. An actuator system is coupled to the rotating disc and arranged to actuate the rotating disc between the open position and the closed position. The choke valve further comprises a wear monitoring system that includes a port in communication with a depressurized cavity formed between the housing and the bean, and a pressure sensor monitoring the pressure in the depressurized cavity. 
     In other embodiments, a choke valve is provided that includes a valve body housing that defines an inlet and an outlet. The outlet defines an outlet diameter. A rotating disc is arranged between the inlet and the outlet and can be moved between an open position and a closed position, and a bean is positioned adjacent to and downstream of the rotating disc. The bean includes a passageway that defines a passageway diameter. A ratio of the outlet diameter to the passageway diameter is between about 1.3 and about 35. 
     In other embodiments, a choke valve is provided that includes a valve body housing that defines an inlet and an outlet. A rotating disc is arranged between the inlet and the outlet and can be moved between an open position and a closed position, and a bean is positioned adjacent to and downstream of the rotating disc and includes a passageway that defines a passageway diameter and a passageway length. A ratio of the passageway length to the passageway diameter is between about 5 and about 15. 
     These and other features, aspects, and advantages of the invention will become better understood upon consideration of the following detailed description, drawings, and appended claims. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial cross-sectional view of a choke valve including a wear monitoring system according to one embodiment of the invention. 
         FIG. 2  is a cross-sectional view of the choke valve including the wear monitoring system of  FIG. 1 . 
         FIG. 3  is an enlarged cross-sectional view of the wear monitoring system of  FIG. 2 . 
         FIGS. 4A-4C  is a schematic of a rotating disc and a stationary disc of the choke valve shown in an open, throttled, and shut position relative to each other. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
     The following discussion is presented to enable a person skilled in the art to make and use embodiments of the invention. Various modifications to the illustrated embodiments will be readily apparent to those skilled in the art, and the generic principles herein can be applied to other embodiments and applications without departing from embodiments of the invention. Thus, embodiments of the invention are not intended to be limited to embodiments shown, but are to be accorded the widest scope consistent with the principles and features disclosed herein. The following detailed description is to be read with reference to the figures, in which like elements in different figures have like reference numerals. The figures, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of embodiments of the invention. Skilled artisans will recognize the examples provided herein have many useful alternatives and fall within the scope of embodiments of the invention. 
       FIGS. 1 and 2  illustrate a choke valve  10  according to one embodiment of the invention. The choke valve  10  can include a valve body  12  and a valve bonnet  14  that is releasably secured in a flanged manner by equi-circumferentially spaced helically threaded bolts  16  receiving rotatable receiving nuts  18 . The choke valve  10  shown in  FIGS. 1-3  is an angled body choke valve; however, the choke valve can be of the inline Y-type body or inline body, for example. 
     The valve body  12  can include an upstream flange  20  and a downstream flange  22 . Each flange  20 ,  22  provides a flange face  24 ,  26  respectively that typically aligns with a similar flange of another, valve, or other section of pipeline, or such ancillary equipment as is commonly found at a well head or other valve assembly, for example. The valve body  12  also includes a flow annulus including an upstream inlet  28  and a downstream outlet  30  with arrows  32 ,  34  showing the direction of flow through the valve body  12  beginning with the upstream flow arrow  32  and continuing to the downstream flow arrow  34 . The downstream outlet  30  is equipped with a pressure sensor  36  for detecting erosion, as the downstream outlet  30  is normally encountered with high velocity flow and is an area subject to erosion and/or corrosion, as will be described in further detail below. 
     The bonnet  14  can be coupled to the valve body  12  via the bolts  16  and nuts  18 . One or more seals  38  can be provided where the valve body  12  contacts the bonnet  14  to inhibit fluid leakage from the choke valve  10 . A shaft  40  can extend through an opening  42  of the bonnet  14  into a component chamber  44  of the valve body  12 . At a distal end  46 , the shaft  40  can be coupled to an actuator (not shown) to actuate the choke valve  10 . The actuator can be, for example, a pneumatic, hydraulic, electric, hand knob, hand wheel, or hand lever type actuator that, when coupled to the shaft  40 , provides rotation to a rotating disc  48 . At an opposing end  50 , the shaft  40  can be coupled to a turning fork  52  that engages the rotating disc  48 . In addition, a spring  54  can be provided between the shaft  40  and the turning fork  52  to pre-load the rotating disc  48 , allowing the choke valve  10  to be mounted in any position. The spring  54  can also absorb thermal expansion due to temperature changes and vibrations, for example. 
     At a first end  56 , the turning fork  52  can be dimensioned to be received within the opposing end  50  of the shaft  40 . The first end  56  of the turning fork  52  can be square or hex shaped, for example, and received by a similar square or hex shaped opening in the opposing end  50  of the shaft  40 . When the shaft  40  is rotated, the turning fork  52  rotates as well. As shown in  FIG. 2 , the first end  56  of the turning fork  52  abuts a seat  58  provided within the opposing end  50  of the shaft  40 , restricting vertical movement, but allowing rotational movement of the turning fork  52 . A second end  60  of the turning fork  52  can be wedged or key shaped, for example, to engage a corresponding slot  62  on the surface of the rotating disc  48 . When the shaft  40  rotates, the turning fork  52  provides a corresponding rotational force to the rotating disc  48 . 
     As also shown in  FIGS. 1 and 2 , a protective bushing  64  can be provided in the component chamber  44  of the valve body  12 . The protective bushing  64  can be substantially cylindrical in shape and define an interior hollow cavity  66 . A centrally disposed aperture  68  can extend from a top portion of the protective bushing  64  into the interior cavity  66  and is configured to receive the turning fork  52 . Another aperture  70  is disposed on a side wall  72  of the bushing  64  and aligned with the inlet  28  to allow the medium to flow into the hollow cavity  66 . Also housed within the hollow cavity  66  of the bushing  64  is the rotating disc  48 . As the turning fork  52  and rotating disc  48  rotate within the hollow cavity  66 , the bushing  64  reduces friction and wear between the rotating parts, as well as constrains the motion of the parts. A pin  74  can extend between the bushing  64  and the bonnet  14  to ensure the bushing  64  remains stationary. 
     Downstream from the rotating disc  48  is a stationary disc  76  integrally coupled to a bean  78  that extends into the outlet  30  of the valve body  12 . The bean  78  provides restriction as is well known in the art. In one embodiment, the bean  78  can be an abrasion resistant tungsten carbide bean, which removes the majority of corrosion and erosion from the sealing surfaces and valve body  12 . As shown in  FIG. 3 , an orifice  80  extends through the rotating disc  48  to allow the medium to flow from the hollow cavity  66  of the bushing  64  through a fluid passageway  82 , extending through the stationary disc  76  and the bean  78  and exit through the outlet  30 . The orifice  80  of the rotating disc  48  can have a first diameter D 1 , and the passageway  82  of the stationary disc  76  and the bean  78  can have a second diameter D 2 . The first diameter D 1  and the second diameter D 2  can be substantially the same and be about 25 millimeters. In another embodiment, the first diameter D 1  and the second diameter D 2  can each be between about 3 millimeters and about 150 millimeters. The outlet  30  is defined by a third diameter D 3  that is about 97 millimeters. In another embodiment, the third diameter D 3  can be between about 6 millimeters and about 400 millimeters and is substantially larger than the first diameter D 1  and the second diameter D 2 , in order to provide a laminar outlet flow  34  to inhibit erosion on the outlet  30 . In one embodiment, a ratio D 3 /D 2  is about 4. In another embodiment, the ratio D 3 /D 2  is between about 1.3 and about 35. 
     The passageway  82  also defines a length L 1  that can be about 180 millimeters. In another embodiment, the length L 1  can be between about 21 millimeters and about 1,080 millimeters. In the illustrated embodiment, the ratio L 1 /D 2  is about 7.2. In another embodiment, the ratio L 1 /D 2  is between about 5 and about 15. 
     As shown in  FIG. 3 , the orifice  80  of the rotating disc  48  is in a first position  84  and aligned with the passageway  82  to indicate that the choke valve  10  is open. Upon rotation of the turning fork  52 , the rotating disc  48  can enter a second position  86 , as shown in  FIG. 4 . The second position  86  is a throttled position due to the orifice  80  of the rotating disc  48  partially overlapping the passageway  82  of the stationary disc  76 . Upon further rotation of the turning fork  52 , the rotating disc  48  can enter a third position  88 . The third position  88  is a closed position due to the orifice  80  of the rotating disc  48  not overlapping the passageway  82  of the stationary disc  76 . 
     There are several advantages to the above described rotating disc principle. First, because the rotating disc  48 , the stationary disc  76 , and the bean  78  are manufactured out of tungsten carbide, Stellite or Ceramics with sufficient corrosion resistant, anti-eroding and wearable capability, for example, the simple and robust design allow for excellent control and a long service life. Furthermore, the rotating disc  48  enhances easy and low cost maintenance. Another advantage of the rotating disc principle is the protection of the sealing surfaces of the discs against the erosive influence of the medium when the choke valve  10  is in the first open position  84 . To provide the required overlap, the choke valve  10  features a rotation angle of 180 degrees between the first open position  84  and the closed position  88 . Using this principle, positive shut off can be ensured for an extended service life because the flowing medium does not contact the seat area. 
     Should erosion occur, a wear monitoring system  90  can be provided to detect the erosion, as shown in  FIG. 3 . The wear monitoring system  90  can include the pressure sensor  36 , an outer depressurized cavity  92 , a first cavity seal  94  and a second cavity seal  96 . The pressure sensor  36  can extend through a pressure port  98  positioned above the downstream flange  22  of the valve body  12 , as shown in  FIG. 1 . The pressure port  98  extends from an exterior environment of the choke valve  10  to the depressurized cavity  92 . In one embodiment, the pressure sensor  36  can be a ROSEMOUNT 2501 or 3051 type pressure sensor to measure a pressure in the depressurized cavity  92 . 
     The depressurized cavity  92  can be defined by the space between the inner surface of the outlet  30  and an outer surface of the bean  78 . The first cavity seal  94  can be an o-ring, for example, that is positioned between the inner surface of the outlet  30  and the outer surface of the bean  78  to seal off a bottom portion  100  of the depressurized cavity  92 . Similarly, the second cavity seal  96  can be an o-ring, for example, that circumscribes the outer surface of the stationary disc  76  to seal off a top portion  102  of the depressurized cavity  92 . Thus, the depressurized cavity  92  forms a sleeve like cavity around the bean  78 . 
     During normal operation of the choke valve  10 , the pressure inside the depressurized cavity  92  can be between about 0 PSI and about 15 PSI. If the pressure sensor  36  detects a pressure greater than a predetermined threshold value, for example 60 PSI, a signal is sent to close the choke valve  10  and emergency shutdown (ESD) valves (not shown). This increase in pressure indicates that erosion has caused washing of the bean  78  resulting in the depressurized cavity  92  to become pressurized. A signal can then be sent from the pressure sensor  36  to a remote user interface, for example, to alert a user that the choke valve  10  requires service. 
     One advantage of the above described choke valve  10  and wear monitoring system  90  is that only the rotating disc  48  and the bean  78  (i.e., internal components) need to be replaced if erosion occurs, and the choke valve  10  remains in service. The valve body  12  is not affected by erosion, as is typically seen in choke valves, because the medium (e.g., fuel) is not filtered causing wear and tear on the outlet  30  piping. 
     Another advantage is that the passageway  82  of the bean  78  has a diameter D 2  that is less than the diameter D 3  of the outlet  30 , causing the outlet flow  34  to be laminar and non-turbulent to limit erosion on the outlet  30  piping. As previously described, the ratio D 3 /D 2  is advantageously between about 1.3 and about 35 to provide the laminar outlet flow. However, if erosion does occur, it will occur inside the bean  78  which can be detected by the wear monitoring system  90 . 
     It will be appreciated by those skilled in the art that while the invention has been described above in connection with particular embodiments and examples, the invention is not necessarily so limited, and that numerous other embodiments, examples, uses, modifications and departures from the embodiments, examples and uses are intended to be encompassed by the claims attached hereto. The entire disclosure of each patent and publication cited herein is incorporated by reference, as if each such patent or publication were individually incorporated by reference herein. Various features and advantages of the invention are set forth in the following claims.