The tube-to-tube sheet joint formed by mechanical or explosive expansion of the tube hole is known as what?

• A. Swaged joint
• B. Mechanical expansion joint
• C. Expansion joint "J" Factor
• D. Welded joint

Answer: (C)

When a tube hole in the tube sheet is expanded to fit the tube, the metal plastically flows and the tube is clamped into the sheet, forming a swaged joint. This can be done by mechanical swaging or by explosive expansion, and it creates a tight, leak-tight connection without welding. The term commonly used for this joint is swaged (or expanded) joint because the defining feature is the tube hole’s enlargement to grip the tube. The phrase “Expansion joint J Factor” refers to a design parameter used to describe how much movement an expansion joint can accommodate, not the name of the joint itself. So the essential idea is that expanding the hole yields a swaged joint, while the J Factor is about movement capacity in expansion joints rather than the joint type.