Fittings, 37 Degree Internal Flare, Fluid Connection, Procurement Specification
|Publication Date:||1 April 2021|
This SAE Aerospace Standard (AS) establishes the requirements for 37 degree flared tube fittings or machined internal cone fluid connection fittings for use with 37 degree external cone, spherical nose, and seal ring fittings in all types of aerospace fluid systems (see Section 6).
Tube fittings shall be furnished in types, styles and sizes designated by the applicable AS, AN, and MS standards. This specification is a similar and an improvement to MIL-F-5509 for 37 degree flared tube fittings. It is intended to serve as the procurement specification for the fittings described herein.
Hydraulic and fluid Tube fittings covered within this standard are intended for use in all types of fluids and are considered a replacement for MIL-F-5509. These parts are used in various... View More
Hydraulic and fluid Tube fittings covered within this standard are intended for use in all types of fluids and are considered a replacement for MIL-F-5509. These parts are used in various applications through the aerospace industry and the DoD.
The previous listed capabilities for flared fittings are for reliable fitting joints based upon operational experience using AS, AN, MS, and fittings, nuts, sleeves, and flares. By using nonstandard design joints (thicker walled nuts or fittings, special seals, etc.), burst pressures of 20000 to 25000 psi have been obtained with correspondingly higher operating pressures and proof pressures and qualified with impulse test. These nonstandard fittings may be used at more severe conditions (load, vibration, corrosion, etc.) than specified in this document, but the design and supporting test data are the designer's responsibility and are subject to approval by the procuring activity. In addition, the Barlow formulae as defined in ASTM A370 may be used to determine the wall thickness using the yield strength of the metal with some safety factor and then tested with higher proof pressures, burst pressures, and impulse test.
This document is intended to be an improved suitable designation as a procurement specification for flared tube fittings incorporating internal nominal 37 degree conical sealing surfaces. This document is also an improvement as a primary procurement specification for the following known fittings and other associated part standard fittings that use MIL-F-5509, as follows:
Lessons Learned, Aluminum Fittings and Their Use on Commercial Jet Aircraft
The use of aluminum sleeves in conjunction with aluminum fittings for sizes -10 and -12 on 3000 psi systems resulted in unacceptable performance levels on commercial aircrafts. Replacing aluminum sleeves with CRES sleeves improved performance levels. As a result, manufacturers of commercial aircrafts discontinued the use of the aluminum sleeve/fitting combinations as well as aluminum fittings having the flared feature as part of the fitting, for 3000 psi systems entirely.
The use of any aluminum fittings on 3000 psi systems is not recommended for new design but remain supported for legacy systems, at user's discretion.View Less