Centrifugal Pump

Abstract

A centrifugal pump includes at least one impeller ( 11 ) fixed to a main shaft ( 10 ) and at least one casing which houses the impeller and is formed through press working of sheet metal such as a steel plate. The centrifugal pump further includes a casing cover configured to seal an open end of the casing hermetically, and a shaft seal device ( 12 ) provided at a portion where the main shaft passes through the casing cover. The casing cover has a thick member ( 6 ) made of castings, and a thin corrosion-resistant lining member ( 40 ) which is tightly fixed to the thick member.

1 . A centrifugal pump comprising: 
 at least one impeller fixed to a main shaft coupled to a prime mover;    at least one casing provided so as to correspond to said impeller;    a casing cover configured to seal an open end of said casing hermetically; and    a shaft seal device provided at a portion where said main shaft passes through said casing cover;    wherein said casing cover comprises a thick member made of castings, and a thin corrosion-resistant lining member which is tightly fixed to said thick member.    
   
   
       2 . A centrifugal pump according to  claim 1 , wherein said lining member comprises a press-formed member.  
   
   
       3 . A centrifugal pump according to  claim 1 , wherein said lining member is tightly fixed to said thick member by press fitting.  
   
   
       4 . A centrifugal pump according to  claim 1 , wherein said thick member has a hollow cylindrical portion which allows said main shaft to pass therethrough, and said lining member has an annular portion which is fitted over said hollow cylindrical portion.  
   
   
       5 . A centrifugal pump according to  claim 4 , wherein an end portion of said annular portion of said lining member is expanded radially outwardly so that said lining member is not detached from said thick member.  
   
   
       6 . A centrifugal pump according to  claim 5 , wherein said end portion of said annular portion of said lining member is expanded radially outwardly in a tapered shape so that said end portion of said annular portion of said lining member serves to guide a gasket of said shaft seal device when said gasket is inserted into said annular portion of said lining member.  
   
   
       7 . A centrifugal pump according to  claim 1 , wherein said thick member of said casing cover has a communication hole through which an atmospheric side and a liquid side communicate with each other, a corrosion-resistant pipe is fitted into said communication hole, and said corrosion-resistant pipe and said lining member are joined by welding.  
   
   
       8 . A centrifugal pump according to  claim 7 , wherein said welding is laser welding.  
   
   
       9 . A centrifugal pump according to  claim 1 , further comprising an outer barrel for preventing pressure liquid generated by operation of said pump from leaking to the outside of said pump, said outer barrel having at least one formed portion for mounting an O-ring at one end or both ends of said outer barrel.  
   
   
       10 . A centrifugal pump according to  claim 9 , wherein an end portion of said formed portion of said outer barrel is expanded radially outwardly to prevent said O-ring from falling off.  
   
   
       11 . A centrifugal pump according to  claim 10 , wherein a tapered portion expanded radially outwardly is formed on a member to which said outer barrel is attached so that insertion of said O-ring held by said outer barrel is facilitated.  
   
   
       12 . A centrifugal pump comprising: 
 at least one impeller fixed to a main shaft coupled to a prime mover;    at least one casing provided so as to correspond to said impeller;    said centrifugal pump comprising a multistage pump;    said casing including a plurality of stacked interstage casings which house a plurality of impellers, respectively;    said interstage casing comprising a first cylindrical portion, a first bottom portion which is held in contact with an axial end face of an adjacent interstage casing, a second cylindrical portion extending axially from said first bottom portion, and a second bottom portion extending radially inward from said second cylindrical portion; and    said second bottom portion of said interstage casing being formed into a curved shape of a hemisphere or substantially a hemisphere.    
   
   
       13 . A centrifugal pump according to  claim 12 , wherein a suction plate is attached to said second bottom portion of said interstage casing so that an outer circumferential end face of said suction plate is held in contact with an inner surface of a first cylindrical portion of said adjacent interstage casing; and 
 wherein said suction plate, said second cylindrical portion, said first bottom portion, and said inner surface of said first cylindrical portion of said adjacent interstage casing form a space for accommodating an O-ring.    
   
   
       14 . A centrifugal pump according to  claim 13 , wherein return guide vanes are interposed between said suction plate and a side plate.  
   
   
       15 . A centrifugal pump according to  claim 12 , wherein a baffle is provided in said interstage casing so as to cover at least one formed portion located at a corner between said first cylindrical portion and said second bottom portion.  
   
   
       16 . A centrifugal pump according to  claim 15 , wherein said baffle has a plurality of notches at a radially inner portion thereof.  
   
   
       17 . A centrifugal pump according to  claim 16 , wherein the maximum diameter of said notch is smaller than the outer diameter of said impeller.  
   
   
       18 . A centrifugal pump according to  claim 12 , further comprising an outer barrel for preventing pressure liquid generated by operation of said pump from leaking to the outside of said pump, said outer barrel having at least one formed portion for mounting an O-ring at one end or both ends of said outer barrel.  
   
   
       19 . A centrifugal pump according to  claim 18 , wherein an end portion of said formed portion of said outer barrel is expanded radially outwardly to prevent said O-ring from falling off.  
   
   
       20 . A centrifugal pump according to  claim 19 , wherein a tapered portion expanded radially outwardly is formed on a member to which said outer barrel is attached so that insertion of said O-ring held by said outer barrel is facilitated.  
   
   
       21 . A centrifugal pump comprising: 
 at least one impeller fixed to a main shaft coupled to a prime mover;    at least one casing provided so as to correspond to said impeller;    a casing cover configured to seal an open end of said casing hermetically; and    a mechanical seal provided at a portion where said main shaft passes through said casing cover;    wherein said mechanical seal comprises a sleeve which holds a rotating seal ring and is fixed to said main shaft, and a holder configured to hold a stationary seal ring, said holder comprising a cylindrical member which holds a seal member for sealing liquid between said casing cover and said cylindrical member, and a disk member; and    wherein said cylindrical member and said disk member are joined together to form said holder.    
   
   
       22 . A centrifugal pump according to  claim 21 , wherein said disk member comprises a flat plate made of sheet metal.  
   
   
       23 . A centrifugal pump according to  claim 21 , wherein said cylindrical member and said disk member are welded by lasers.  
   
   
       24 . A centrifugal pump according to  claim 21 , wherein a gap which is longer than the overall length of said mechanical seal is formed between said main shaft of said pump and a main shaft of said prime mover, and said mechanical seal can be removed through said gap by removing a coupling which couples said main shaft of said pump and said main shaft of said prime mover.  
   
   
       25 . A centrifugal pump according to  claim 21 , further comprising an outer barrel for preventing pressure liquid generated by operation of said pump from leaking to the outside of said pump, said outer barrel having at least one formed portion for mounting an O-ring at one end or both ends of said outer barrel.  
   
   
       26 . A centrifugal pump according to  claim 25 , wherein an end portion of said formed portion of said outer barrel is expanded radially outwardly to prevent said O-ring from falling off.  
   
   
       27 . A centrifugal pump according to  claim 26 , wherein a tapered portion expanded radially outwardly is formed on a member to which said outer barrel is attached so that insertion of said O-ring held by said outer barrel is facilitated.  
   
   
       28 . A centrifugal pump comprising: 
 at least one impeller fixed to a main shaft coupled to a prime mover;    at least one casing provided so as to correspond to said impeller;    a casing cover configured to seal an open end of said casing hermetically;    a mechanical seal provided at a portion where said main shaft passes through said casing cover;    wherein said mechanical seal comprises a sleeve which holds a rotating seal ring and is fixed to said main shaft, and a holder configured to hold a stationary seal ring, said holer comprising a cylindrical member which holds a seal member for sealing liquid between said casing cover and said cylindrical member, and a disk member; and    wherein a positioning member is attached to said main shaft, and said sleeve of said mechanical seal is held into contact with said positioning member, thereby positioning said mechanical seal.    
   
   
       29 . A centrifugal pump according to  claim 28 , wherein said holder has a step-like portion for holding said stationary seal ring.  
   
   
       30 . A centrifugal pump according to  claim 28 , further comprising an outer barrel for preventing pressure liquid generated by operation of said pump from leaking to the outside of said pump, said outer barrel having at least one formed portion for mounting an O-ring at one end or both ends of said outer barrel.  
   
   
       31 . A centrifugal pump according to  claim 30 , wherein an end portion of said formed portion of said outer barrel is expanded radially outwardly to prevent said O-ring from falling off.  
   
   
       32 . A centrifugal pump according to  claim 31 , wherein a tapered portion expanded radially outwardly is formed on a member to which said outer barrel is attached so that insertion of said O-ring held by said outer barrel is facilitated.  
   
   
       33 . A centrifugal pump comprising: 
 at least one impeller fixed to a main shaft coupled to a prime mover, said main shaft having a plurality of grooves in an outer circumferential surface thereof for allowing said impeller to be fitted over and allowing said impeller to be prevented from being rotated with respect to said main shaft;    at least one casing provided so as to correspond to said impeller;    a positioning member for positioning said impeller with respect to an axial direction of said main shaft; and    a retainer having a circular disk portion which is brought into contact with an end surface of said positioning member, and a cylindrical portion extending from said circular disk portion so as to enclose an outer peripheral portion of said positioning member.    
   
   
       34 . A centrifugal pump according to  claim 33 , wherein said retainer has an inner diameter shape which is fitted over said groove shape of said main shaft.  
   
   
       35 . A centrifugal pump according to  claim 33 , wherein said cylindrical portion of said retainer is brought into contact with said outer peripheral portion of said positioning member or is located in close proximity to said outer peripheral portion of said positioning member.  
   
   
       36 . A centrifugal pump according to  claim 33 , further comprising an outer barrel for preventing pressure liquid generated by operation of said pump from leaking to the outside of said pump, said outer barrel having at least one formed portion for mounting an O-ring at one end or both ends of said outer barrel.  
   
   
       37 . A centrifugal pump according to  claim 36 , wherein an end portion of said formed portion of said outer barrel is expanded radially outwardly to prevent said O-ring from falling off.  
   
   
       38 . A centrifugal pump according to  claim 37 , wherein a tapered portion expanded radially outwardly is formed on a member to which said outer barrel is attached so that insertion of said O-ring held by said outer barrel is facilitated.