Tube Expanders
Tube expanding is the art of cold working the ends of tubes into intimate contact with the metal of the containing tube holes to form a leak proof mechanical seal and/or joint. In other words, it is a mechanical method of establishing a mechanical joint between a tube and a tube hole. Airetool manufactures condensed/ heat exchanger expanders, boiler expanders, furnace expanders and many special application expanders. Mandrel, Rolls and Cage are the three things common to all expanders.
Other parts added further classify the type of expander.
Thrust Assembly – This assembly attaches to the cage and allows adjustment of the expanding depth. The thrust collar will remain stationary against the tube sheet or tube end while the cage, mandrel and rolls expand the tube. A thrust assembly is used on condenser/heat exchanger expanders, some furnace expanders and special boiler expanders.
Tube expanders consist of
- Mandrel – A tapered pin through the center of the expander to which the power is attached and when advanced pushes the rolls against the tubes.
- Rolls – A set of (3 or more) of tapered cylindrical parts which are driven by mandrel and contact the tube wall to be expanded. The taper on the rolls is in the reverse direction and one-half the taper of the mandrel if it is a parallel roll expander.
- Cage – This is the expander body (or housing) that holds the mandrel and rolls in place. The slots which contain the rolls also provide a feed angle which helps pull the mandrel in to provide expansion of the rolls.