Recirculating Steam Generator U-Bend Hydraulic Tube Expansion

Abstract

A hydraulic expander for use in a tube containing a U-bend region is disclosed and claimed. The tool includes a sheath for transmitting hydraulic fluid therethrough to an inflatable bladder. The sheath is flexible, allowing it to be inserted through the U-bend region of the tube. The bladder is fluidly connected to the sheath and is thereby in fluid communication with a supply of hydraulic fluid. The length of the bladder and the metal end caps, along with the centering spacers on the expansion sheath, allows it to pass through the U-bend region of the tube such that it can be positioned inside the tube adjacent to a support outside the tube, such as an AVB. Hydraulic expansion of the bladder causes it to exert an outward force on the tube inner surface, causing it to plastically deform such that its outer surface comes into contact with the tube support, such as an AVB. This expansion will increase the friction between the tube and the AVB to minimize the risk of tube vibration damage.

What is claimed is: 
     
         1 . A hydraulic expander for use in a tube containing a U-bend region, comprising:
 a sheath for transmitting hydraulic fluid therethrough, said sheath being flexible; and   an inflatable bladder fluidly coupled to a first end of said sheath by end caps, said bladder and end caps having a longitudinal length allowing it to pass through the U-bend region of the tube, said bladder being adapted for radial expansion when hydraulically pressurized to exert an outward force on an inner surface of the tube.   
     
     
         2 . The hydraulic expander of  claim 1 , wherein said bladder has a longitudinal length of approximately 0.5 in. to 1 in. 
     
     
         3 . The hydraulic expander of  claim 1 , further comprising an eddy current coil coupled to said sheath. 
     
     
         4 . The hydraulic expander of  claim 1 , wherein said sheath includes graduated marks thereon for measuring an amount of insertion into the tube. 
     
     
         5 . The hydraulic expander of  claim 1 , further comprising a hardstop coupled to said sheath for limiting insertion of said sheath into the tube. 
     
     
         6 . The hydraulic expander of  claim 1 , further comprising at least one spacer coupled to said sheath, said spacer configured to center the hydraulic expander within the tube to facilitate expander insertion. 
     
     
         7 . The hydraulic expander of  claim 1 , wherein said sheath includes an outer protective tube and an inner tube in fluidly coupled to said bladder. 
     
     
         8 . A method of stabilizing a tube bundle of a heat exchanger having an anti-vibration bar positioned between adjacent tubes of the tube bundle, comprising:
 inserting a hydraulic expander within a tube of the tube bundle, said hydraulic expander including:
 a flexible sheath for transmitting hydraulic fluid therethrough, and 
 an inflatable bladder fluidly coupled to a first end of said sheath by end caps, said bladder and end caps having a longitudinal length allowing it to pass through a U-bend region of the tube, said bladder being adapted for radial expansion when hydraulically pressurized to exert an outward force on an inner surface of the tube; 
   positioning said hydraulic expander within the tube such that said bladder is located adjacent the anti-vibration bar; and   pressurizing said bladder and thereby plastically deforming the tube such that an outer surface of the tube contacts the anti-vibration bar.   
     
     
         9 . The method of  claim 8 , wherein said pressurizing includes deforming the tube with enough force that the tube outer surface remains in contact with the anti-vibration bar after said bladder has been depressurized and said hydraulic expander has been withdrawn from the tube. 
     
     
         10 . The method of  claim 8 , wherein:
 said hydraulic expander further includes an eddy current coil coupled to said sheath; and   said positioning includes using said eddy current coil to locate the anti-vibration bar so that said bladder can be positioned adjacent the anti-vibration bar.   
     
     
         11 . The method of  claim 8 , wherein:
 said sheath includes graduated marks thereon; and   said positioning includes using said graduated marks to determine an amount of expander insertion into the tube such that said bladder can be positioned adjacent the anti-vibration bar.   
     
     
         12 . The method of  claim 8 , wherein:
 said sheath includes a hardstop coupled thereto; and   said positioning includes using said hardstop to determine an amount of expander insertion into the tube such that said bladder can be positioned adjacent the anti-vibration bar