Abstract:
A valve actuator apparatus and method comprises an operator housing secured to a bonnet assembly. The bonnet assembly is secured to the valve body, and includes a bonnet stem movably within a bonnet housing for moving a gate within the valve body to open and close the valve. A downstop member is fixably secured to the bonnet stem and engages removable stem spacers which are added or removed to obtain a selected bonnet stem drift setting. The operator housing connects to a base ring that surrounds the bonnet housing and rotates to allow positioning of a fluid port in the operator housing. The operator housing may removed and replaced without altering the bonnet stem drift adjustment. A top shaft extends from the operator housing and rotates with respect to the bonnet stem to prevent torque transmission from the top shaft to the bonnet stem. A replaceable sealing cartridge sealingly supports the top shaft for axial movement within the operator housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a divisional of co-pending U.S. application Ser. No. 10/244,376, filed on Sep. 16, 2002, which is a continuation of U.S. application Ser. No. 09/888,194, filed on Jun. 23, 2001, and now U.S. Pat. No. 6,450,477, issuing Sep. 17, 2002, which is a continuation of U.S. application Ser. No. 09/538,881, filed on Mar. 30, 2000, and now U.S. Pat. No. 6,250,605, issuing Jun. 26, 2001, which is a continuation of U.S. application Ser. No. 08/968,904, filed on Nov. 6, 1997, and now U.S. Pat. No. 6,089,531, issuing Jul. 18, 2000, which is a continuation of U.S. application Ser. No. 08/206,424, filed on Mar. 4, 1994, and now abandoned. Each of the above applications is herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to an actuator apparatus and method and, more particularly, to a valve actuator including a bonnet assembly having an improved downstop mechanism that is rotatably free with respect to a floating top shaft and engageable with respect to a replaceable operator without affecting bonnet stem drift adjustment.  
         [0004]     2. Description of the Related Art  
         [0005]     Gate valves are generally comprised of a valve body having a central axis aligned with inlet and outlet passages, and a space between the inlet and outlet passages in which a slide, or gate, may be moved perpendicular to the central axis to open and close the valve. In the closed position, the gate surfaces typically seal against sealing rings which surround the fluid passage through the valve body. Gate valves have been used for centuries to control the flow of a great variety of fluids. Often the fluid to be controlled by the gate valve is under pressure. In the petroleum industry, gate valves are used along piping at various locations, and in particular are used in piping referred to in the petroleum industry as a Christmas tree, which is used as part of a drilling operation.  
         [0006]     Actuators to open and close the gate valves may include manual operators, diaphragm-type operators, and hydraulic operators. The actuator may include a bonnet assembly, which interconnects the valve body and the valve gate, and a bonnet stem which is movable with the gate via an operator. It is often desirable to be able to change the operator without changing the bonnet assembly. However, this is difficult because, among other reasons, such a change also requires changes in up-stop and down-stop adjustments which assure the drift of the gate is positioned correctly in the open and closed position. If the valve is connected to a Christmas tree or is under pressure, it may be difficult to determine whether drift adjustments have been made correctly when replacing the operator since the bore of the valve is not available to receive a drift alignment check tool. Removal of a valve under pressure in a Christmas tree to make drift adjustments may take considerable time and cause substantial inconvenience.  
         [0007]     It is desirable to combine a manual operator with a diaphragm-type or hydraulic operator for back-up and test purposes. This combination typically results in the presence of a top shaft extending from the operator that may also serve to indicate whether the valve is open or closed. Because the top shaft is often exposed to the atmosphere, it may attract contaminants that cause damage to the top shaft seals or bearings. In the past, close tolerances have been required in the top shaft that have exacerbated the contaminant problems. As well, torque applied to the top shaft, which may be caused by manual operation, may cause gate, gate seal, or drift misalignment. Furthermore, changing the top shaft or the top shaft seals has previously required removal of the operator housing.  
         [0008]     The operator typically has a maximum force capability for applying to the bonnet stem. It is sometimes desirable to provide additional opening/closing power on a temporary basis without having to remove the original operator. It is also desirable that the same operator be adaptable to various control accessories, such as a mechanical override, hydraulic override, heat sensitive lock open device, block open cap, electrical limit switch and/or other electrical accessories.  
         [0009]     Another significant problem, especially related to diaphragm-type operators, is leakage of the diaphragms in the region adjacent the top shaft or bonnet stem. Such leakage may be caused by wear, loss of flexibility, and pinching or wear that occurs should the diaphragm make contact with the diaphragm case. This leakage may gradually develop, and may slowly reduce the operator power.  
         [0010]     In some cases, the positioning of the gate valves in the Christmas tree and other types of installations may be restricted because of piping which is supplied to operate an automatic actuator that controls gate movement. In the past, it has been difficult to use precisely laid piping because the position of the operator fluid port is fixed with respect to the operator housing. Allowing the operator to rotate with respect to the bonnet could result in leakage or cause misalignment of the up-stop and downstop drift adjustments of the valve gate.  
         [0011]     Thus, there has been a long felt need in the industry to provide an improved actuator that allows a more adaptable installation configuration, that reduces maintenance and installation time, and that increases long term durability. Persons skilled in the art will appreciate the present invention which provides solutions to these and other problems associated with valve actuators.  
       SUMMARY OF THE INVENTION  
       [0012]     The present invention relates to a valve actuator for moving a valve between open and closed states within a valve body. The valve actuator comprises an operator housing including a pressure chamber and a fluid port, and an operator member movable in response to the introduction of fluid into the pressure chamber through the fluid port. A bonnet housing is securable to the valve body and has a bonnet housing bore therethrough. A bonnet stem axially moves in the bonnet housing bore and is securable to the valve gate for moving the valve gate to the open and closed valve states. The bonnet stem is axially movable in response to movement of the operator member in an axial direction toward the valve body. The bonnet stem is rotatably free with respect to a top shaft.  
         [0013]     A downstop member rotatably and axially affixed to the bonnet stem is used for stopping axial movement of the bonnet stem in a direction toward the valve. The downstop is also rotatably free with respect to the top shaft. A stop surface is fixably positioned with respect to the bonnet housing. One or more bonnet stem spacers are disposed on the stop surface and engageable by the downstop to stop axial movement of the bonnet stem for selecting a desired bonnet stem drift.  
         [0014]     An object of the present invention is an valve actuator with improved versatility, reduced installation and maintenance, and/or increased life.  
         [0015]     Another object of the present invention is an actuator which allows removal or exchange of the valve operator while the valve is under pressure.  
         [0016]     Another object of the present invention is an actuator which allows removal or exchange of the valve operator without the need to reset drift adjustments or to examine the valve bore to determine if drift adjustments are correct.  
         [0017]     A feature of the present invention is a floating top stem which requires no metal-to-metal contact during operation.  
         [0018]     A further feature of a preferred embodiment of the present invention is an improved diaphragm having a metal insert ring to engage an elastomeric seal and thereby minimize or avoid in the diaphragm which may be caused by decreased diaphragm flexibility, leakage pinching or other reasons.  
         [0019]     Yet another feature of present invention is a replaceable seal cartridge that allows renewal of top stem seals without removing the operator.  
         [0020]     An advantage of the present invention is an economical construction for a valve actuator that is relatively simple yet reliable in construction, and is easy to service.  
         [0021]     These and other objects, features, and advantages of the present invention will become apparent from the drawings, the descriptions given herein, and the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]      FIG. 1  is an elevational view, partially in section, of a diaphragm-type valve actuator in accord with the present invention;  
         [0023]      FIG. 1A  is an elevational view, partially in section, of a block open cap attachable to the valve actuator of  FIG. 1 ;  
         [0024]      FIG. 2  is an elevational view, partially in section, of a bonnet assembly in accord with the present invention;  
         [0025]      FIG. 3  is an elevational view, partially in section, of the bonnet assembly of  FIG. 2  including drift adjustment lengths in accord with the present invention;  
         [0026]      FIG. 4  is an elevational view, of a replaceable operator without readjustment of the down-stop or up-stop drift in a bonnet assembly in accord with the present invention;  
         [0027]      FIG. 5  is a schematical representation of actuator accessory connections in accord with the present invention;  
         [0028]      FIG. 6  is an elevational view, partially in section, of a dual actuator assembly in accord with the present invention; and  
         [0029]      FIG. 7  is an elevational view, partially in section, of a hydraulic valve actuator in accord with the present invention. 
     
    
       [0030]     While the present invention will be described in connection with presently preferred embodiments, it will be understood that it is not intended to limit the invention to those embodiments. On the contrary, it is intended to cover all alternatives, modifications, and equivalents included within the spirit of the invention.  
       DETAILED DESCRIPTION  
       [0031]     Referring now to the drawings, and more particularly to  FIG. 1 , a diaphragm-type valve actuator  10  is shown in accord with the present invention. Top shaft  12 , which is preferably formed from stainless steel, effectively floats with respect to top diaphragm case  14 . As a general matter, all non-stainless metallic components in actuator  10  are preferably coated for protection against environmental conditions. Wear bearing  16 , as well as wear bearings  18  (shown in detail in  FIG. 2 ), are preferably nonmetallic to eliminate close tolerance problems normally associated with the actuator top shaft and bonnet stem. The wear bearings effectively suspend top shaft  12  and bonnet stem  20  to thereby prevent metallic contact during operation. Thus, the wear bearings are preferably non-metallic and made from relatively hard plastic-like materials, such as Molygard, Nylatron, or Delrin. The wear bearings and other plastic-like components discussed hereinafter may also be made from various plastic-like materials such as, but not limited to, nylons, thermoplastics, resins, polyurethanes, phenolics, acetals, polyacrylates, epoxides, polycarbonates, polyester, aramids, polymers, molythane  90 , and fluorelastomers.  
         [0032]     Top shaft  12  rotates independently of and is designed to eliminate transmission of torque to bonnet stem  20 , gate  22 , and/or gate seats (not shown) when using a manual override, such as manual override  24  shown in  FIG. 5 . Top shaft  12  preferably is large enough in diameter to prevent bearing and buckling stresses when loaded by manual override  24  or hydraulic override  26  shown in  FIG. 5 . (See also the dual actuator system of  FIG. 6  and hydraulic actuator of  FIG. 7 ). A large bottom shoulder  28  on top shaft  12  prevents top shaft  12  from being expelled from actuator  10 .  
         [0033]     Top seal cartridge  30  can be removed for replacement as a single unit without disassembling top diaphragm housing  14 . Top seal cartridge  30  is preferably formed of a plastic-like material such as Delrin and is held in place by retainer ring  32  which is preferably stainless steel. Top seal cartridge  30  incorporates rod wiper  34  to keep the shaft sealing region therebelow clean of dirt, grease, and other contaminants for longer life of the seals. Rod wiper  34  is preferably made from Molythane  90 . Top seal cartridge  30  contains dual reciprocating stem seals  36  and dual static seals  38  to ensure seal integrity and long life. These and other seals may be T-seals or other substantially elastomeric seals, such as O-ring seals.  
         [0034]     Diaphragm  40  is preferably formed of nitrile laminated with several layers of nylon to ensure strength and flexibility for years of service. Materials such as Viton, a fluoroelastomer, may be used for H.sub.2 S—CO.sub.2 applications. The layers of nylon in diaphragm  40  eliminate the need for lubrication and do not experience frictional wear. Diaphragm  40  includes stainless steel concentric insert seal ring  42  bonded thereto to act in conjunction with a static O-ring face seal  44 , which is provided in the diaphragm retaining nut  46 . This seal eliminates leakage in the stem area which may normally occur due to diaphragm aging, pinching, or reduced flexibility.  
         [0035]     Diaphragm retaining nut  46  threadably engages diaphragm retainer plate  48  for easy, accurate installation. On up strokes of actuator  10 , diaphragm retaining nut  46  prevents any possible pinching of diaphragm  40  by stopping movement of bonnet stem  20  should diaphragm retaining nut  46  engage top plug  50 . Diaphragm retaining nut  46  provides dual stem seals  52  to engage and reliably seal top shaft  12 . Diaphragm retaining nut  46  is preferably formed of stainless steel.  
         [0036]     Diaphragm retainer plate  48  engages downstop element  54  for downward axial movement of gate  22  via bonnet stem  20  when the cavity defined by top diaphragm housing  14  is filled with pressurized fluid, i.e. compressed air. Breather port  62  allows fluid (air) to flow out of lower diaphragm housing  64  as diaphragm retainer plate  48  moves downwardly. Downstop element  54  preferably is connected to bonnet stem  20  via large threads designed to withstand high load impacts and cycling for preventing changes in drift settings, as discussed hereinafter. Downstop element is also engaged by upper spring retainer  56  for upward movement of bonnet stem  20  induced by spring  58  and/or pressure within valve body  60 .  
         [0037]     Top diaphragm housing  14  is sealingly secured to lower diaphragm housing  64  by bolts  66  and nuts  68  which secure diaphragm  40  therebetween. Diaphragm  40  is thus anchored by this connection and acts as a seal between the top diaphragm housing  14  and the lower diaphragm housing  64 . Base plate ring  70  is secured to lower diaphragm housing  64  by bolts  72 . Base plate ring  70  allows for 360 degree actuator rotation when exacting plumbing is required for connections to control pressure inlet  74 . Lower spring retainer  88  secures spring  58  into a centralized position. In  FIG. 1A  is shown lock open cap  76  which threadably engages top plug  50  and is secured to top shaft  12  with bolt  78  to secure the valve in the open position.  
         [0038]      FIG. 2  discloses a portion of bonnet assembly  90 . Bonnet assembly  90  is shown complete with spring  58  in  FIG. 4 . Preferably stainless steel stem spacers  92  are positioned on top of bonnet ring  94 . Stem spacers  92  are used to determine the downward stop drift by controlling the length of the stroke of bonnet stem  20  toward valve body  60 . Packing cartridge  96  acts in a similar manner as top seal cartridge  30  to seal between bonnet stem  20  and bonnet housing  98 . Packing cartridge  96  preferably is formed of stainless steel. Packing cartridge  96  contains O-ring seals  100 . Seals  102  are preferably T-seals comprised of Viton 90 rings with nylon backups. Packing cartridge  96  also includes rod wipers  104  to protect and maintain the long life of the sealing elements by preventing contaminants in the region of the sealing elements.  
         [0039]     Bonnet stem threads  21  are designed so that no injury to the seals occurs when the stem is passed through packing cartridge  96 . Dual bearings  18  suspend bonnet stem  20  to preferably prevent contact of any metal surface thereby eliminating wear and galling to either the bonnet stem  20  or the packing cartridge  96 . To prevent rotation of bonnet ring  94  with respect to bonnet housing  98 , screw  106  is tightened into the corresponding groove or inset disposed adjacent the end portion of bonnet housing  98 . Rotation of bonnet ring  94  with respect to bonnet housing  98  may alter the stroke length adjustments as discussed hereinafter. Bonnet ring  94  retains packing cartridge  96  in position within bonnet housing  98 . Bonnet ring  94  also preferably includes an additional seal  102  for safety purposes.  
         [0040]     To set the downward stroke length or drift  106  of bonnet stem  20 , stem spacers  92  are removed or added as necessary to increase or decrease the combined spacer width  108  as indicated in  FIG. 3 . In setting the bonnet stem drift, downstop  54  is first tightened to bonnet stem  20  with drive nut  110 . Bonnet stem  20  is placed in its furthermost downward position. The position of the gate bore (not shown) through gate  22  is determined by running an appropriate drift tool (not shown) through valve body  60 . The number of stem spacers  92  may then be removed or added as necessary to provide an accurate drift setting.  
         [0041]     Secondary metal-to-metal stem seal  112  provides sealing in the event of fire damage to the other seals and also acts as a stop for upward movement of gate  22 . The adjustment of the up-stop drift is made in a manner dependent upon valve manufacture designs but may typically involve threadably engaging the gate stem with the bonnet stem and rotating until the correct adjustment is reached. Further rotation may be prevented by such means as a pin or other retainer means.  
         [0042]      FIG. 4  discloses the relative ease with which various operators  114  may be changed out without altering the up-stop and down-stop drift as discussed hereinbefore. Thus the operator may be exchanged with the valve under pressure. No additional drift adjustments are necessary because the alignment is not altered and remains accurate for the particular valve. This feature is especially useful where it may be difficult to make drift realignment. Base plate ring  70  may be rotated without changing the drift to accommodate the piping to inlet  74 .  
         [0043]      FIG. 5  is a schematic disclosing numerous attachments that can be made to upper plug  50  and inlet valve  74  of actuator  10 . Upper plug  50  preferably includes a substantially large diameter threaded outer connection to avoid stresses when using accessories. Clear stem protector  116  protects top shaft  12  from adverse effects of weather, sandblasting, contaminating operating environments, and painting. Heat sensitive lock open device  118  mechanically holds open the actuator and valve when other safety systems are inoperative. This device locks the device in the down position allowing it to rise only in the event of fire. Mechanical override  24  is used to mechanically stroke the valve, and is preferably used on low pressure valves or during installation and testing. Electrical limit switch contact  20  permits remote indication of gate valve position. Various types of fusible plugs  122 , quick exhaust valves  124 , pneumatic relays  126 , and other sensors  128  may be used with inlet  74  and top stem  12 .  
         [0044]     In the operation of diaphragm-type actuator  10  of the present invention, pressure is applied through fluid port  74  which moves both diaphragm  40  and diaphragm retainer plate  48  axially towards valve body  60 . This movement engages downstop  54  to move bonnet stem  22  downward (towards valve body  60 ) until downstop  54  contacts stem spacers  92 , whereupon further downward movement of bonnet stem  22  is prevented. At this point, gate  22  is properly aligned so that the valve is open (assuming a normally configured gate valve). If pressure is lost or purposely evacuated, the valve is closed via pressure from spring  58  acting against downstop  54  to move bonnet stem  22  axially away from valve body  60  until metal-to-metal contact is made at secondary stem seal  112 . This action is referred to as fail-closed operation. If required, the valve can be configured with a fail open gate design for vent or blow-down systems.  
         [0045]      FIG. 6  discloses a dual actuator system which may be used to double the stroke power. Secondary operator  140  preferably threadably attaches to plug  143  via connector  141 . Lock down plug  154  prevents rotation of operator  140  with respect to operator  10 . Operation of secondary operator  140  is similar to that of single actuator  10 . Pressurized fluid enters fluid port  142  causing diaphragm plate  144  to move downwardly, thereby forcing stem adaptor  146  and top shaft  148  downwardly. Air is vented from vent hole  150  during the down stroke. Downstop  152  controls the down stroke drift in the manner discussed hereinbefore.  
         [0046]      FIG. 7  discloses a hydraulic valve actuator  200  embodiment of the present invention. Top shaft  202  is kept clean via rod wiper  204  disposed within removable top plug  206 . Dual wear bearings  208 , preferably formed of molygard, are used to support top shaft  202 . Top plug  206  also includes a Polypak seal  210 , preferably formed of Nitroxile. Hydraulic pressure moves piston  212  axially downwardly to move downstop  214  into engagement with stem spacers  216  as described hereinbefore. Piston  212  floats on preferably non-metallic wear bearings  218  and is further sealed with seals  220 . Upper spring retainer  222  applies force from coil  224  to move downstop  214  upwardly. Base plate ring  226  is bolted to housing  228  and provides support for lower spring retainer  230  as described with respect to diaphragm-type actuator  10 .  
         [0047]     The foregoing detailed disclosure and description of the invention is illustrative and explanatory thereof, and it will be appreciated by those skilled in the art, that various changes in the size, shape and materials as well as in the details of the illustrated construction, reliability configurations, or combinations of features of the various valve actuator elements of the present invention may be made without departing from the spirit of the invention.