Since tubing has different O.D. tolerances, it is important to have a common starting point to take out in dimensional variations. This is done by tightening the fitting slightly until the tubing can not freely rotate in the fitting as it can in the finger-tight position. At this point tighten the nut 1-1/4 turns.
Safety Considerations on Installations for High Pressure System
Make sure the proper tubing wall thickness is selected in accordance with pressure ratings.
(Tubing should have a hardness of HRB 80 or less)
Do not assemble or disassemble fittings when the sytem is pressurized.