Method and apparatus for friction stir welding tube ends for a heat exchanger

A method for forming a joint between a first tube and a first tubesheet, and a second tube and a second tubesheet comprising:

• positioning a first end of the first tube substantially flush with a major surface of the first tubesheet, the first tube having a substantially same outer diameter from the first end of the first tube to a second end of the first tube, the outer diameter of the first tube being substantially equal to an inner diameter of an opening in the tubesheet;
• positioning a second end of the first tube through an opening in the second tubesheet, the outer diameter of the first tube being substantially equal to an inner diameter of an opening in the second tubesheet;
• inserting a first anvil assembly comprising an expandable anchor portion at least partially within the first end of the first tube;
• placing a washer over the first anvil assembly, the washer having an outer diameter sized to fit within an inner diameter of the first end of the first tube, the washer being placed at least partially within the first end of the first tube;
• expanding the expandable anchor portion of the first anvil assembly while the first anvil assembly is within the first end of the first tube to hold the first end of the first tube with respect to the first tubesheet;
• holding the second end of the first tube with respect to the second end of the second tubesheet;
• and
• welding the first end of the first tube to the first tubesheet.

A method for forming a joint between a tube and a tubesheet comprising:

• positioning a first end of a tube substantially flush with a major surface of a tubesheet, the outer diameter of the tube being substantially the same along the length of the tube, the outer diameter substantially equal to the inner diameter of an opening in the tubesheet;
• forming an anvil assembly having at least a portion within the tube near the first end;
• expanding the portion of the anvil assembly while the anvil assembly is within the tube, the anvil assembly serving as a removable backer to allow welding of the tube to the tubesheet;
• placing a washer over the anvil assembly and onto the interface between the first end of the tube and the major surface of the tubesheet;
• and
• welding the tube to the tubesheet, the washer being at least partially consumed during welding.

A method for forming a joint between a tube and a tubesheet comprising:

• positioning a first end of a tube substantially flush with a major surface of a tubesheet, the outer diameter of the tube being substantially equal along the length of the tube and substantially equal to the inner diameter of an opening in the tubesheet;
• forming an anvil assembly having at least a portion within the tube near the first end;
• expanding the portion of the anvil assembly while the anvil assembly is within the tube, the anvil assembly serving as a removable backer to allow welding of the tube to the tubesheet;
• placing a washer over the anvil assembly and onto the interface between the first end of the tube and the major surface of the tubesheet;
• and
• welding the tube to the tubesheet.