What components make up a flared tube fitting?

• A. An AN 774 and a cap
• B. An AN 774 and a nut
• C. An AN 774 and a washer
• D. An AN 774 and a bolt

Answer: (B)

A flared tube fitting is designed to provide a leak-tight seal in high-pressure fluid applications, commonly used in aerospace and automotive systems. The essential components of a typical flared tube fitting include a flared tube, which is often designated as AN 774 (a standard specification for the tube part), and a nut that secures the fitting.

The flaring process involves shaping the end of the tubing to create a conical surface, which then interfaces with the nut when assembled. Once the nut is tightened, it compresses the flared edge against the fitting body, creating a secure seal that can withstand high pressures without leaking.

The other choices involve components that do not serve the crucial role in the assembly of flared tube fittings. A cap and a washer do not provide the necessary functionality to ensure proper sealing between the flared tube and the fitting, while a bolt does not play a role in the assembly of tube fittings. Thus, the combination of the flared tube and the nut is essential for the operation and reliability of flared tube fittings in fluid lines.