Method for lapping, grinding, honing and polishing seal surfaces on inner diameter of semi-blind cavity in valve body

Abstract

A tool assembly for lapping, grinding, honing and polishing seal surfaces on inner diameters of semi-blind cavities in valve bodies. The tool can bring seat surfaces up to specification with abrasive wheels having varying grit sizes. The wheels are provided in an array of sizes to form a set of tools for a range of diameters, abrasion and surface finish capacity. This design allows the first (i.e., smallest) tool to enter a cavity in a valve body to begin cutting. The larger size wheels increase the diameter of the cavity being machined until the desired size is achieved. Wheels with finer abrasive are then used to improve the surface finish of the cavity while minimizing the material removal. When the desired diameter and/or surface finish has been achieved, a felt wheel may be used with a fine abrasive paste to provide the cavity with the final surface finish specification.

1 . A method of finishing a surface of a seat pocket of a gate valve, the gate valve having a body with a central chamber intersected by co-axial flow passages, the seat pocket being a counterbore formed at an intersection of one of the flow passages with the central chamber, the method comprising:
 inserting a distal end of a cylinder member into one of the flow passages and into the chamber in the valve body;   attaching a wheel having an abrasive circumferential surface to the distal end of the drive shaft;   inserting a leading edge of the wheel into the seat pocket;   rotating the drive shaft and the wheel drive shaft as the abrasive surface on the wheel engages the inside diameter of the seat pocket; and   applying axial force to a proximal end of the drive shaft to advance the wheel into the seat pocket as it rotates.   
   
   
       2 . The method of  claim 1 , wherein the wheel has a larger diameter than the flow passage in which it is inserted, and the step of attaching a wheel further comprising attaching the wheel while the distal end of the drive shaft is in the chamber. 
   
   
       3 . The method of  claim 1 , wherein the drive shaft has an outer diameter selected such that it closely fits within said one of the flow passages. 
   
   
       4 . The method of  claim 1 , further comprising inserting the drive shaft within a bushing and placing the bushing within said one of the flow passages so as to maintain the drive shaft coaxial with an axis of said one of the flow passages. 
   
   
       5 . The method of  claim 1 , wherein:
 the step of applying axial force to a proximal end of the drive shaft comprises axially pushing on the drive shaft.   
   
   
       6 . The method of  claim 1 , wherein:
 the step of applying axial force to a proximal end of the drive shaft step comprises axially pulling the drive shaft.   
   
   
       7 . A method of finishing a surface of first and second seat pockets of a gate valve, the gate valve having a body with a central chamber intersected by co-axial first and second flow passages, the seat pockets being counterbores formed at intersections of the first and second flow passages, respectively, with the central chamber, the method comprising:
 inserting a distal end of a shaft into one of the flow passages and into the chamber in the valve body;   while the distal end is in the chamber, attaching a wheel having an abrasive circumferential surface to the distal end of the drive shaft, the wheel having an outer diameter greater than an inner diameter of the first and second flow passages;   inserting a leading edge of the wheel into the first seat pocket;   at a proximal end of the drive shaft, rotating the drive shaft and the wheel as the abrasive surface on the wheel engages the inside diameter of the first seat pocket; and   applying axial force to the proximal end of the drive shaft to advance the wheel into the first seat pocket as it rotates;   withdrawing the wheel from the first seat pocket and inserting the leading edge of the wheel into the second seat pocket;   rotating the drive shaft and the wheel as the abrasive surface on the wheel engages the inside diameter of the second seat pocket, applying an axial force to the proximal end of the drive shaft to advance the wheel into the second seat pocket as it rotates, the direction of the axial force being opposite to that applied to advance the wheel into the first seat pocket.   
   
   
       8 . The method of  claim 7 , wherein the drive shaft has an outer diameter selected such that it closely fits within said one of the flow passages. 
   
   
       9 . The method of  claim 7 , further comprising inserting the drive shaft within a bushing and placing the bushing within said one of the flow passages so as to maintain the drive shaft coaxial with an axis of said one of the flow passages. 
   
   
       10 . The method of  claim 7 , wherein:
 the step of applying axial force to a proximal end of the drive shaft comprises axially pushing on the drive shaft.   
   
   
       11 . The method of  claim 7 , wherein:
 the step of rotating the drive shaft and the wheel as the abrasive surface on the wheel engages the inside diameter of the second seat pocket, applying an axial force to the proximal end of the drive shaft comprises axially pulling on the drive shaft.   
   
   
       12 . A method of finishing a surface of first and second seat pockets of a gate valve, the gate valve having a body with a central chamber intersected by co-axial first and second flow passages, the seat pockets being counterbores formed at intersections of the first and second flow passages, respectively, with the central chamber, the method comprising:
 inserting a distal end of a shaft into one of the flow passages and into the chamber in the valve body, the drive shaft having an outer diameter selected such that it closely fits within said one of the flow passages or, alternatively, inserting the drive shaft within a bushing and placing the bushing within said one of the flow passages so as to maintain the drive shaft coaxial with an axis of said one of the flow passages;   while the distal end is in the chamber, attaching a wheel having an abrasive circumferential surface to the distal end of the drive shaft, the wheel having an outer diameter greater than an inner diameter of the first and second flow passages;   inserting a leading edge of the wheel into the first seat pocket;   at a proximal end of the drive shaft, rotating the drive shaft and the wheel as the abrasive surface on the wheel engages the inside diameter of the first seat pocket; and   applying axial force to the proximal end of the drive shaft to advance the wheel into the first seat pocket as it rotates;   withdrawing the wheel from the first seat pocket and inserting the leading edge of the wheel into the second seat pocket;   rotating the drive shaft and the wheel as the abrasive surface on the wheel engages the inside diameter of the second seat pocket, applying an axial force to the proximal end of the drive shaft to advance the wheel into the second seat pocket as it rotates, the direction of the axial force being opposite to that applied to advance the wheel into the first seat pocket.   
   
   
       13 . The method of  claim 12 , wherein:
 the step of applying axial force to a proximal end of the drive shaft comprises axially pushing on the drive shaft.   
   
   
       14 . The method of  claim 12 , wherein:
 the step of rotating the drive shaft and the wheel as the abrasive surface on the wheel engages the inside diameter of the second seat pocket, applying an axial force to the proximal end of the drive shaft comprises axially pulling on the drive shaft.