What torque profile should you follow for MS flareless fittings?

• A. Turn 1 full turn after snug.
• B. Do not rotate beyond snug.
• C. Turn 1/2 to 1 turn after snug.
• D. Hand snug, then turn 1/6 to 1/3 turn; never more than 1/3-turn

Answer: (D)

For MS flareless fittings, the seal is achieved by a precise, small amount of rotation after the nut is snug against the fitting body. After you feel the nut become snug, you don’t crank it tight like a traditional flare joint—you apply only a brief turn, typically about 1/6 to 1/3 of a turn, and never more than 1/3 turn. This limited movement allows the ferrule and compression features to bite into the tube just enough to form aLeak-tight seal without over-stressing the tube or crushing the ferrule.

Why this range matters: turning more than a third of a turn can over-compress the seal, deform the tube, or distort threads, leading to leaks or damage. The small, controlled rotation ensures proper seating and reliable sealing while preserving the integrity of the tube and fitting.