Method for belling and expanding coils

A method of forming uniformly dimensional integral belled portions in the opened ends of tubes of a partially assembled plate fin heat exchanger, having a plurality of apertured plate fins parallelly spaced between two apertured tube sheets and a plurality of hair pin tubes extending through the apertured, and expanding the tubes of the partially assembled plate fin heat exchanger comprising the steps of:

• locating the partially assembled plate fin heat exchanger in a single station so that the open ends of the tubes extend a desired distance through a tube sheet proximate the open ends;
• locating a tube gripping means having tube gripper, a belling means, and a expanding means adjacent the open of the tube so that the belling means and the expanding means are axially aligned with the open end of the tube;
• clamping the tube with said tube gripper to prevent the tube from moving axially;
• driving said belling means and said expanding means into the open end of the tube to form a radially expanded bell therein;
• clamping said tube sheet proximate the open end of the tubes with a clamp means;
• releasing said tube gripper from clamping the tube so that the tube is free to move axially to the proximate tube sheet;
• driving said expanding means against the tube so that the formed bell is driven into contact with the tube sheet proximate the open end of the tube;
• and
• further driving said expanding means into the tube to expand the tube radially outward into contact with the proximate tube sheet, the plate fins, and then the other tube sheet in tension expansion.