Thin walled tubing pressure test spec needed

[mtharp]

I am designing a ground air-conditioning duct out of .035 inch wall, 5 inch I.D. 6061-T4. Operating pressure is 13 psig. Per 14 CFR 25.1438, I need to proof test to 1.5X and burst test to 2X normal operating pressure. I have looked but can’t find an AMS, ANSI, or other specification that covers pressure testing of thin walled aluminum tubing.

Any thoughts?

 

[AviatorJim]

Design it, build 2, cap both ends. Pressurize with 26 psi and see if it pops. If it hold, pressurize the other to 20 psi and see if it distorts. If it held it's shape, it passed proof testing. Proof each one you make as part of the manufacture/QC process before you tag it and deliver it.

 

[mtharp]

Thanks Jim, I know how to proof test it. My ACO would reject your process. I need a spec that controls the process so I can call it out on the drawing.

 

[AviatorJim]

http://www.faa.gov/about/office_org...ety_Critical_Structures_Guide_v2.3_112205.pdf

Para 3.2.6 spells out the requirement.

 

[mtharp]

The testing requirements are governed by 14 CFR 25.1438. I am looking for a specification that governs the process of determining that the part meets the requirements.

 

[rb1957]

have your vendor make a test piece each batch, to meet the test described above.

 

[debodine]

I am not so sure that you need a spec as much as you need a written test plan your ACO would accept. I am not aware of an industry spec for such testing, so you may need to write your own test plan.

Anyway just my 2 cents, not sure it helps you.

 

[mtharp]

Thanks debodine. That's what I've decided to do.

 

[WKTaylor]

Mtharp...

I'm a bit curious: why design a ground air-conditioning duct out of .035 inch wall, 5 inch I.D. 6061-T4... when flexible or semi-rigid ducting is commonly used in this application [SAE AS38386, NAS1370--1379, SAE AS38386, AS150*, AS8796, etc]?

For instance... the AS38386 Duct Assembly, Ground, Conditioned Air, Insulated, Flexible... are intended for this very application: they also have insulation, are tough and damage resistant, come in various pressure ratings and a variety of materials.

There is also metal hose available if needed.

Be careful: 0.2thin aluminum ducting may be great weight savings in aircraft installation... but in GSE may prove to be flimsly... and needing a jacket for damage protection and thermal/acoustical insulation; etc...

Regards, Wil Taylor

 

[mtharp]

This ducting is installed on the aircraft, inboard of the of the check valve. For that application either fiberglass or aluminum are used. This is not part of the ground a/c unit.

 

[WKTaylor]

Mtharp

I stand corrected... although flexible hose might still be an option to consider... especially when insulation jacketing of the duct is needed [like a metal AC duct].

For giggles... are You designing this installation with the following specs in mind ??? NOTE: these docs have lots of embeded design references.

SAE ARP85(E) Air Conditioning Systems For Subsonic Airplanes.

SAE ARP217(D) Testing of Airplane Installed Environmental Control Systems (ECS)

or... very harsh design criteria of bleed air systems...

ARP1796(A) Engine Bleed Air Systems for Aircraft

Info...

AIR5378 Aircraft Tube Bending Methods, Techniques and Tooling



Regards, Wil Taylor