How tight should an MS flareless fitting be tightened?

How tight should an MS flareless fitting be tightened?

• A. Hand tight
• B. Hand snug
• C. Hand tight then 1/6 turn
• D. Hand snug, then turn 1/6 to 1/3 turn

Answer: (D)

MS flareless fittings create a seal by the compression of a sleeve as the nut is tightened after hand snug. Once you reach hand snug, give it a small final turn to seat the sleeve properly. Too little beyond hand snug may leave the seal incomplete and allow leaks; too much can over-compress or deform the sleeve and risk damage to the fitting or tube. The recommended final step is a light additional rotation of about 1/6 to 1/3 turn beyond hand snug, which provides a reliable seal without over-torquing. After tightening, check for leaks under pressure per procedure.

MS flareless fittings create a seal by the compression of a sleeve as the nut is tightened after hand snug. Once you reach hand snug, give it a small final turn to seat the sleeve properly. Too little beyond hand snug may leave the seal incomplete and allow leaks; too much can over-compress or deform the sleeve and risk damage to the fitting or tube. The recommended final step is a light additional rotation of about 1/6 to 1/3 turn beyond hand snug, which provides a reliable seal without over-torquing. After tightening, check for leaks under pressure per procedure.