In the thickness calculation, which factor does the symbol Eff represent?

In the thickness calculation, which factor does the symbol Eff represent?

• A. MAWP
• B. SF
• C. RAD
• D. Joint Efficiency

Answer: (D)

Eff is joint efficiency, a modifier that accounts for how strong welded or attached joints are compared with the base material. In thickness calculations, you’re designing the wall to carry a certain internal pressure, and the presence of welds or joints reduces the effective strength. The joint efficiency (a value between 0 and 1) tells you how much of the base material’s strength the joint can reliably carry. A perfect, seamless part would have Eff about 1, while welded joints are typically less than 1, so the needed thickness increases to compensate. That’s why Eff is used here. It’s not MAWP, not a safety factor, and not a RAD term.