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6061 T-6 hydraulic lines

6061 T-6 hydraulic lines

6061 T-6 hydraulic lines

Seeking information on use of 6161 T-6 for hydraulic lines (2000psi max service pressure). Can 6061 T-6 5/16 tubing be properly bent, and flared for AN-5 fittings without structural damage to the tubing wall? I am having difficulty sourcing -0 or T-4 tubing which I understand is malleable enough for bending and flaring. Can the ends and bend locations of the T-6 tubing be returned to -0 or -4 for forming?

RE: 6061 T-6 hydraulic lines

The aircraft industry has decades of experience with aluminum hydraulic systems. I suggest looking there for guidance and materials.

I also suggest using flareless MS type fittings on hard tubing.

RE: 6061 T-6 hydraulic lines

Sure - you can anneal the tubing and destroy the mechanical properties. Or use steel tubing and not worry about it.

Why the interest in using aluminum for this?

RE: 6061 T-6 hydraulic lines

Suggest using 'aerospace hydraulic quality' 6061 tubing... not general purpose/older spec... drawn tubing.

The following tube-specs pass rigorous inspection/testing for this very purpose...

6061-T4 HYDRAULIC TUBING MIL-T-7081 or AMS-T-7081 or AMS4081
6061-T6 HYDRAULIC TUBING MIL-T-7081 or AMS-T-7081 or AMS4083

A. System working pressure, proof-pressure [test] and burst-pressure [ultimate] requirement should be carefully evaluated for intended use... so Diameter-VS-[standardized] wall thickness has to be determined by YOU.
B. WW-T-700/6 and AMS4082 or AMS4080 or any commercial grade [ASTM, etc] drawn tubing... are also acceptable when carefully evaluated/tested... but these are made to older standards which are not optimized for applications where tight/quality-bending, single or double-flaring and swaging are required.
C. DRAWN or extruded/drawn Tubing... ONLY... never simply extruded tubing... should be used in fluid applications. Lotsa reasons.

There are several documents/manuals for aircraft quality tubing-assembly [tube selection, cutting/trimming/bending + flared and/or swaged end-fittings + corrosion protective finishes + inspections and proof-testing + installation + markings]...

BTW: 'AN-5 fluid fitting(s)' simply don't exist... no earthly idea what You are referring to.

There are however hundreds of different aerospace fluid-fitting types available.

I have a nicely illustrated catalog that is useful for-pick-n-choose... but it's too large a file to be up-loaded, in E-T. Other fluid-component document references are meaningless without access to the other documents it references.

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

RE: 6061 T-6 hydraulic lines

There are also hydraulic tube specs in ASM for SS (304 and 21-6-9) at various strength levels, as well as for Ti 6-4.
In high strength 21-6-9 (150ksi UTS 125ksi Yld, >20 elong) they use 1" x 052" (1/2" x 028", 3/8" x 0.22") for 3,000 psi suffice. But SS has infinite fatigue life at this strength/stress.
The Ti tubing (and I would expect Al) have a very finite fatigue life. So great care need to exercise using them.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: 6061 T-6 hydraulic lines

SAE -5 and JIC -5 both exist. JIC shares dimensions with AN so that could be a source of confusion. -5 and -10 sizes are obsolete and should be avoided if possible.

RE: 6061 T-6 hydraulic lines


Per most documentation/tech data Ti-3Al-2.5V tubing for 3000-up-to-5000(+)-PSI service MUST be autofrettaged after forming and before swaging-on fittings. Pretty impressive process to pressurize the raw-formed-tubes to 12000-PSI for strain/stress relief. I happened to be in the shop where a line was being Autofrettaged... always in a safety-water-tank... when a it failed [blew-out]. Good thing it was pressurized with water... in-water!

As I understand-it, 21-6-9 tubing is sometimes autofrettaged for service above 3000-PSI... and/or for cases where pressure spikes are frequent.

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

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