What size dent in a SCUBA tank is unacceptable?

• A. 1in in diameter or 0.02in in depth
• B. 3in in diameter or 0.08in depth
• C. 2in in diameter or 0.06in depth
• D. 4in in diameter or 0.1in depth

Answer: (C)

A dent in a SCUBA tank is unacceptable when it shows a significant deformation of the cylinder wall, because that weakens the metal where the high pressure operates and can create stress concentrations that lead to failure. The safety criteria use two measurements to decide if a dent is too severe: the diameter of the dent and the depth of the dent. If the dent is about two inches across, that wide deformity indicates a substantial loss of wall integrity. If the dent is about 0.06 inches deep, that level of indentation reveals a notable change in wall thickness at a localized point. In either case, the cylinder should be removed from service and inspected by a qualified cylinder inspector. Even smaller or shallower dents can be signs of potential problems and should be evaluated rather than ignored.