Steam valve

Abstract

In a steam valve, a strainer is arranged between a valve body and a valve casing in which the valve body is accommodated, and a screen assembly is mounted on an outer peripheral portion of the strainer. The screen assembly includes a temporary screen unit and a permanent screen unit which is arranged inside the temporary screen unit. Each of the screen units is a substantially cylindrical structure made of a plate formed with perforations.

1 . A steam valve comprising: 
 a steam inlet;    a valve body for regulating a flow of steam entering into said valve body through inlet;    a valve casing accommodating said valve body and communicated with said steam inlet;    a strainer arranged between said valve body and said valve casing so as to surround said valve body and adapted to remove a foreign object contained in the flow of steam; and    a screen assembly mounted to an outer peripheral portion of said strainer, said screen assembly including a plurality of screen units, wherein each of said screen units is formed from a perforated plate.    
   
   
       2 . The steam valve according to  claim 1 , wherein said screen assembly includes a temporary screen unit and a permanent screen unit, said permanent screen unit being arranged inside said temporary screen unit so as to contact said outer peripheral portion of said strainer.  
   
   
       3 . The steam valve according to  claim 2 , wherein said temporary screen unit and said permanent screen unit are formed with perforations, respectively, and a diameter of each of said perforations of said temporary screen unit is formed to be equal to or smaller than a diameter of each of said perforations of said permanent screen unit.  
   
   
       4 . The steam valve according to  claim 2 , wherein said temporary screen unit and said permanent screen unit are formed with perforations, respectively, and wherein said perforations of said temporary screen unit are displaced in positions from said perforations of said permanent screen unit.  
   
   
       5 . The steam valve according to  claim 2 , wherein said permanent screen unit is joined to said strainer by welding at both end portions of said permanent screen unit and is joined to said strainer by riveting at an intermediate portion between said end portions of said permanent screen, and wherein said temporary screen unit has an opening at an intermediate portion thereof so as to pass a rivet and rivet head therethrough and is joined to said permanent screen unit by welding at both end portions thereof.  
   
   
       6 . The steam valve according to  claim 1 , wherein said strainer has a cylindrical structure and said screen assembly is mounted on said outer peripheral portion of said cylindrical strainer.  
   
   
       7 . The steam valve according to  claim 6 , wherein said screen assembly is formed with a number perforations, and when a side portion of said screen assembly mounted on said outer peripheral portion of said cylindrical strainer is developed, said perforations formed to said screen assembly have an arrangement in a fashion that centers of neighboring three perforations constitute vertexes of a regular triangle having one side of a length corresponding to a pitch “a” of adjacent two perforations, the pitch “a” being a sum of a diameter “d” of the perforations and a distance L between the adjacent two perforations, the diameter “d” and pitch “a” being set to optional values, respectively, in accordance with the arrangement of said screen assembly relative to said strainer.  
   
   
       8 . The steam valve according to  claim 1 , wherein said strainer has a section of said outer peripheral portion to which holes are formed and another section of said outer peripheral portion thereof, facing said steam inlet, formed with no hole.  
   
   
       9 . The steam valve according to  claim 1 , wherein said strainer has said outer peripheral portion to which a number of holes are entirely formed.  
   
   
       10 . A steam valve comprising: 
 a valve casing having an inlet configured to receive a flow of steam;    a valve body provided within said valve casing, said valve body being configured to regulate the flow of steam received through said inlet;    a strainer provided across a flow path through said valve casing between said inlet and said valve body, said strainer being configured remove a foreign object contained in the flow of steam; and    a first screen unit and a second screen unit mounted to said strainer, said first screen unit being a first perforated plate, and said second screen unit being a second perforated plate.    
   
   
       11 . The steam valve according to  claim 10 , wherein said strainer has a cylindrical structure.  
   
   
       12 . The steam valve according to  claim 11 , wherein said first screen unit and said second screen unit are mounted on an outer peripheral portion of said strainer.  
   
   
       13 . The steam valve according to  claim 12 , wherein: 
 said first screen unit is a temporary screen unit;    said second screen unit is a permanent screen unit; and    said permanent screen unit is arranged inside said temporary screen unit so that said permanent screen unit contacts said outer peripheral portion of said strainer.    
   
   
       14 . The steam valve according to  claim 13 , wherein: 
 said temporary screen unit has first perforations therethrough;    said permanent screen unit has second perforations therethrough; and    said first perforations each having a diameter that is equal to or smaller than a diameter of each of said second perforations.    
   
   
       15 . The steam valve according to  claim 13 , wherein: 
 said temporary screen unit has first perforations therethrough;    said permanent screen unit has second perforations therethrough; and    said first perforations being displaced in positions from said second perforations.    
   
   
       16 . The steam valve according to  claim 13 , wherein: 
 end portions of said permanent screen unit are joined to said strainer by welds;    an intermediate portion of said permanent screen unit is joined to said strainer by a rivet;    end portions of said temporary screen unit are joined to said permanent screen units by welds; and    an intermediate portion of said temporary screen unit has an opening so as to allow said rivet to pass therethrough.    
   
   
       17 . The steam valve according to  claim 10 , wherein: 
 at least one of said first screen unit and said second screen unit has perforations therethrough;    each of said perforations having a same diameter; and    said perforations being provided in an arrangement such that centers of neighboring three perforations constitute vertexes of an equilateral triangle.    
   
   
       18 . The steam valve according to  claim 10 , wherein: 
 said strainer has a first section with holes formed therethrough;    said strainer has a second section with no hole formed therethrough; and    said second section faces said inlet.    
   
   
       19 . The steam valve according to  claim 10 , wherein said strainer has holes formed therethrough about an entire outer perimeter thereof.  
   
   
       20 . The steam valve according to  claim 10 , wherein said valve body is configured to be movable to regulate the flow of steam received through said inlet.