Steam valve

Abstract

A steam valve is provided with a valve body, a valve seat, and a valve rod provided for the valve body. The valve body has a bottom portion to which a recessed portion is formed, and the recessed portion has an edge, which is positioned on an upstream side of a place at which a shock wave is generated in steam flowing through a steam path defined by the valve body and the valve seat.

1 . A steam valve comprising: 
 a valve body;    a valve seat; and    a valve rod provided for the valve body,    the valve body having a bottom portion to which a recessed portion is formed, the recessed portion having an edge, wherein the edge is positioned on an upstream side of a place at which a shock wave is generated in a steam flowing through a steam path defined by the valve body and the valve seat.    
   
   
       2 . The steam valve according to  claim 1 , wherein the edge is positioned at a critical point of the steam flowing through the steam path.  
   
   
       3 . The steam valve according to  claim 1 , wherein a range of an edge diameter Di of the edge is set to  
       Di≧0.90Do  
     and a range of a valve-seat internal diameter Dth of the valve seat is set to  
       Dth≧0.80Do  
     where Do is a valve seat diameter of the valve seat.  
   
   
       4 . The steam valve according to  claim 1 , wherein a range of an edge diameter Di of the edge is set to  
         Di= (0.90 to 1.0) Do    
     and a range of a valve-seat internal diameter Dth of the valve seat is set to  
         Dth= (0.80 to 0.90) Do    
     where Do is a valve seat diameter of the valve seat.  
   
   
       5 . The steam valve according to  claim 1 , wherein a depth h of the recessed portion is set to h≦15 mm and a tilt angle θ of the edge is set to θ=45°.  
   
   
       6 . The steam valve according to  claim 1 , wherein a range of a curvature radius R of the valve body is set to  
         R= (0.52 to 0.6) Do    
     and a range of a curvature radius r of the valve seat is set to  
       r>0.6Do  
     where Do is a valve seat diameter of the valve seat.  
   
   
       7 . The steam valve according to  claim 1 , wherein a range of a curvature radius R of the valve body is set to  
         R= (0.6 to 0.85) Do    
     and the range of a curvature radius r of the valve seat is set to  
         r= (0.45 to 0.6) Do    
     where Do is a valve seat diameter of the valve seat.  
   
   
       8 . The steam valve according to  claim 1 , wherein a range of a curvature radius R of the valve body and a curvature radius r of the valve seat is set to  
         R=r= (0.45 to 0.85) Do    
     where Do is a valve seat diameter of the valve seat.  
   
   
       9 . The steam valve according to  claim 1 , wherein a range of a maximum valve lift La of the valve body combined with the valve seat is set to  
         La= (0.25 to 0.35) Do    
     where Do is a valve seat diameter of the valve seat.  
   
   
       10 . The steam valve according to  claim 1 , wherein a range of a maximum valve lift Lb of the valve body separated from the valve seat is set to  
       Lb<0.25Do  
     where Do is a valve seat diameter of the valve seat.  
   
   
       11 . The steam valve according to  claim 1 , wherein the valve body, the valve seat, and the recessed portion are formed with either one of a hardened heat-treated portion and a hard-alloy-surfaced portion.  
   
   
       12 . A steam valve comprising: 
 a valve body;    a valve seat; and    a valve rod provided for the valve body,    the valve body having a bottom portion to which a recessed portion is formed, the recessed portion having an edge, wherein a groove is provided along an entire circumferential surface of the valve body.    
   
   
       13 . The steam valve according to  claim 12 , wherein the groove is formed on a downstream side of a critical point of steam flowing through a steam path defined by the valve body and the valve seat.  
   
   
       14 . A steam valve comprising: 
 a valve body;    a valve seat; and    a valve rod provided for the valve body,    the valve body having a bottom portion to which a recessed portion is formed, the recessed portion having an edge, wherein at least one of the valve body and the valve seat is provided with a knurled portion formed on a downstream side of a critical point of steam flowing through a steam path defined by the valve body and the valve seat.    
   
   
       15 . The steam valve according to  claim 14 , wherein the knurled portion is provided along an entire circumferential surface of the valve body.