If a flared tube coupling nut is over tightened, where is the tube most likely weakened?

If a flared tube coupling nut is over tightened, where is the tube most likely weakened?

• A. Along the entire length of the sleeve and tube interface
• B. At the edge of the sleeve and straight portion
• C. At the sleeve and flare junction
• D. Near the flare end

Answer: (B)

Over-tightening a flared tube fitting creates a high local stress where the sleeve edge bites into the tube at the boundary between the straight portion and the sleeve. That edge becomes a stress concentration point, so the tube is most likely weakened right there as the sleeve compresses the straight section. The flare itself is intended to deform and seal, and the stress isn’t spread evenly along the entire interface, so the most vulnerable spot is at the sleeve-straight portion junction.

Over-tightening a flared tube fitting creates a high local stress where the sleeve edge bites into the tube at the boundary between the straight portion and the sleeve. That edge becomes a stress concentration point, so the tube is most likely weakened right there as the sleeve compresses the straight section. The flare itself is intended to deform and seal, and the stress isn’t spread evenly along the entire interface, so the most vulnerable spot is at the sleeve-straight portion junction.