Valve actuator apparatus

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.

1 . A valve actuator for moving a valve gate between open and closed valve positions within a valve body upon movement in first and second directions of a bonnet stem secured to the valve gate, the valve actuator comprising: 
 an operator assembly comprising: 
 an operator housing; and  
 an operator member within the operator housing, wherein the operator member is drivable in the first direction in response to fluid pressure applied to the operator member; and  
   a bonnet assembly comprising: 
 a contact member with a first end configured to form a connection to the bonnet stem, wherein at the connection the first end of the contact member has a larger outer diameter than the bonnet stem, and wherein the contact member has a second end defining a surface configured to receive a drive force in the first direction from the operator member for moving the bonnet stem in the first direction;  
 a spring for producing a biasing force in the second direction opposite the first direction;  
 a spring retainer with an inner flange for engagement with an outer flange of the contact member, wherein the spring imparts the biasing force to the spring retainer that transmits the biasing force to the bonnet stem via the contact member for moving the bonnet stem in the second direction;  
   wherein the operator and bonnet assemblies are held together by attachment of the bonnet assembly to the operator housing while the operator member and the bonnet assembly are not held together within the operator housing, but form an abutting relationship with one another.    
   
   
       2 . The actuator of  claim 1 , wherein the operator assembly further comprises a shaft that is coaxial with the bonnet stem, extends from a shaft aperture in the operator housing and forms an abutting relationship with the bonnet assembly without the shaft and bonnet assembly being held together within the operator housing.  
   
   
       3 . The actuator of  claim 1 , wherein the contact member includes an internally threaded bore adapted to receive an external threaded surface of the bonnet stem to provide the connection.  
   
   
       4 . The actuator of  claim 1 , further comprising: 
 a seal assembly disposed within a shaft aperture of the operator housing, the seal assembly sealing an annulus between an inside diameter of the shaft aperture and an outside surface of a shaft coaxial with the bonnet stem and extending through the shaft aperture; and    a retainer ring disposed within the shaft aperture above the seal assembly for retaining the seal assembly within the shaft aperture, the retainer ring accessible from the exterior of the actuator to permit removal of the retainer ring and seal assembly without removing the operator assembly from the bonnet assembly.    
   
   
       5 . The actuator of  claim 1 , further comprising: 
 a flexible diaphragm covering a portion of the operator member and isolating a chamber within the operator housing; and    a diaphragm retainer having external threads threaded to a central internally threaded aperture of the operator member, wherein the diaphragm retainer provides a circular groove disposed therein for receiving a seal that engages the flexible diaphragm sandwiched between the operator member and the diaphragm retainer.    
   
   
       6 . The actuator of  claim 1 , wherein the contact member defines a downstop surface that limits travel of the contact member due to engagement with a stop surface fixed relative to the valve body.  
   
   
       7 . A valve actuator for moving a valve gate between open and closed valve positions within a valve body upon movement in first and second directions of a bonnet stem secured to the valve gate, the valve actuator comprising: 
 an operator assembly comprising: 
 an operator housing; and  
 an operator member within the operator housing, wherein the operator member is drivable in the first direction in response to fluid pressure applied to the operator member; and  
   a bonnet assembly comprising: 
 a contact member with an internal threaded bore engaged with an external threaded end of the bonnet stem, wherein the contact member defines a drive surface configured to receive a drive force in the first direction from the operator member for moving the bonnet stem in the first direction;  
 a spring for producing a biasing force in the second direction opposite the first direction;  
 a spring retainer with an inner flange for engagement with an outer flange of the contact member, wherein the spring imparts the biasing force to the spring retainer that transmits the biasing force to the bonnet stem via the contact member for moving the bonnet stem in the second direction;  
   wherein the operator and bonnet assemblies are held together by attachment of the bonnet assembly to the operator housing while the operator member and the bonnet assembly are not held together within the operator housing, but form an abutting relationship with one another.    
   
   
       8 . The actuator of  claim 7 , wherein the operator assembly further comprises a shaft that is coaxial with the bonnet stem, extends from a shaft aperture in the operator housing and forms an abutting relationship with the bonnet assembly without the shaft and bonnet assembly being held together within the operator housing.  
   
   
       9 . The actuator of  claim 7 , further comprising: 
 a seal assembly disposed within a shaft aperture of the operator housing, the seal assembly sealing an annulus between an inside diameter of the shaft aperture and an outside surface of a shaft coaxial with the bonnet stem and extending through the shaft aperture; and    a retainer ring disposed within the shaft aperture above the seal assembly for retaining the seal assembly within the shaft aperture, the retainer ring accessible from the exterior of the actuator to permit removal of the retainer ring and seal assembly without removing the operator assembly from the bonnet assembly.    
   
   
       10 . The actuator of  claim 7 , further comprising: 
 a flexible diaphragm covering a portion of the operator member and isolating a chamber within the operator housing; and    a diaphragm retainer having external threads threaded to a central internally threaded aperture of the operator member, wherein the diaphragm retainer provides a circular groove disposed therein for receiving a seal that engages the flexible diaphragm sandwiched between the operator member and the diaphragm retainer.    
   
   
       11 . The actuator of  claim 7 , wherein the contact member defines a downstop surface distal from the drive surface to limit travel of the contact member due to engagement of the downstop surface with a stop fixed relative to the valve body.  
   
   
       12 . The actuator of  claim 7 , wherein the contact member includes a formation protruding from a center region thereof, which is coaxial with the bonnet stem and surrounded by the drive surface.  
   
   
       13 . The actuator of  claim 12 , wherein the formation is configured for engagement by a tool capable of rotating the contact member to tighten the contact member onto the bonnet stem.  
   
   
       14 . A valve actuator for moving a valve gate between open and closed valve positions within a valve body, the valve actuator comprising: 
 an operator assembly comprising: 
 an operator housing defining a pressure chamber therein and having a fluid entry port; and  
 an operator member within the operator housing movable toward the valve body in response to pressurized fluid introduced into the operator housing pressure chamber through the fluid entry port; and  
   a bonnet assembly comprising: 
 a bonnet housing securable to the valve body, the bonnet housing having a bonnet housing bore therethrough;  
 an elongated bonnet stem having first and second ends, the stem axially movable in the bonnet housing bore, and securable at the second end to the valve gate for moving the valve gate to the open and closed valve positions;  
 a spring for producing a biasing force opposing axial movement of the operator member toward the valve body;  
 a contact member, separate from the operator member, having an outer flange, and rotatably and axially affixed to an outside diameter of the first end of the bonnet stem, and having a surface facing the operator member for drive contact with the operator member;  
 an upper spring retainer having an inner flange for engagement with the outer flange to transmit the biasing force to the bonnet stem and to receive the movement of the operator member toward the valve body; and  
 a base ring coupled to and coaxially surrounding the bonnet housing, wherein at least one fastener secures the operator housing to the base ring while the operator member and the bonnet assembly are not held together within the operator housing, but form an abutting relationship with one another.  
   
   
   
       15 . The actuator of  claim 14 , wherein the operator assembly further comprises a shaft that is coaxial with the bonnet stem, extends from a shaft aperture in the operator housing and forms an abutting relationship with the bonnet assembly without the shaft and bonnet assembly being held together within the operator housing.  
   
   
       16 . The actuator of  claim 14 , wherein the contact member includes an internally threaded bore adapted to receive an external threaded surface of the bonnet stem.  
   
   
       17 . The actuator of  claim 14 , further comprising: 
 a seal assembly disposed within a shaft aperture of the operator housing, the seal assembly sealing an annulus between an inside diameter of the shaft aperture and an outside surface of a shaft coaxial with the bonnet stem and extending through the shaft aperture; and    a retainer ring disposed within the shaft aperture above the seal assembly for retaining the seal assembly within the shaft aperture, the retainer ring accessible from the exterior of the actuator to permit removal of the retainer ring and seal assembly without removing the operator assembly from the bonnet assembly.    
   
   
       18 . The actuator of  claim 14 , further comprising: 
 a flexible diaphragm covering a portion of the operator member and isolating a chamber within the operator housing; and    a diaphragm retainer having external threads threaded to a central internally threaded aperture of the operator member, wherein the diaphragm retainer provides a circular groove disposed therein for receiving a seal that engages the flexible diaphragm sandwiched between the operator member and the diaphragm retainer.    
   
   
       19 . The actuator of  claim 14 , wherein the contact member defines a downstop surface that limits travel of the contact member due to engagement with a stop surface fixed relative to the valve body.  
   
   
       20 . The actuator of  claim 14 , wherein the contact member includes a nut portion protruding from a center region thereof, which is coaxial with the bonnet stem and surrounded by the drive surface.