Which statement about Military Standard (MS) flareless fittings is/are correct?

Which statement about Military Standard (MS) flareless fittings is/are correct?

• A. During installation, MS flareless fittings are normally tightened by turning the nut a specified amount, rather than being torqued
• B. New NS flareless fittings/tubing should be assembled clean and dry without lubrication
• C. During installation, MS flareless fittings are normally tightened by applying a specified torque to the nut
• D. They require lubrication during installation

Answer: (A)

MS flareless fittings seal through mechanical seating as the nut is advanced a fixed amount, not by applying a specific torque. The design relies on a precise amount of nut rotation after the sleeve makes contact so the tube is clamped correctly and the ferrule creates the seal. Friction can vary a lot, so tying the assembly to a torque value would risk under- or over-tightening, leading to leaks or damage. Because of this, lubrication is not used during installation and the parts are kept clean and dry to ensure consistent seating. So tightening by a specified amount of nut rotation is the correct method.

MS flareless fittings seal through mechanical seating as the nut is advanced a fixed amount, not by applying a specific torque. The design relies on a precise amount of nut rotation after the sleeve makes contact so the tube is clamped correctly and the ferrule creates the seal. Friction can vary a lot, so tying the assembly to a torque value would risk under- or over-tightening, leading to leaks or damage. Because of this, lubrication is not used during installation and the parts are kept clean and dry to ensure consistent seating. So tightening by a specified amount of nut rotation is the correct method.