Aircraft hydraulic/pneumatic tubing/piping fabrication setup 1

[a5130]

Dear All,

I was tasked to set up a pipe/tube fabrication on-site shop for our hangar. We mainly operate Dash 8 and F100/70 aircraft and when there is a pipe leak or defect, the aircraft is normally grounded while our procurement team source for the part or pipe repair facility.

Can someone who is familiar with pipe fabrication advise on the basic tools/equipment required for initially setting up a shop? Certification requirement? etc...

 

[Sparweb]

Speaking from Dash-8 experience, you would consult the AMM for standard practices applicable to that aircraft, and contact Bombardier for copies of their "PPS" applicable to tubing bends and terminations. There are many types of fittings and splicing tools and fittings so rather obviously you would need to purchase the types that are used on the tubes you intend to repair. Deutch/Permaswage, etc... Different systems use different tube materials, too... A survey of one of your aircraft would also help familiarize you. There's nothing very special about the tubing bender that's used in our shop - you just have to have the right die for each tube size and bend radius being bent. The pressure testing stand we use is quite elaborate, though.

As for certification, that's a different subject altogether (not one of my strengths). Are you an approved repair or manufacturing facility? If you are, how do you control other processes your facility does perform? A documented quality control program for the tubing bending processes will need to be developed. This will include proof-pressure testing of completed tubing assemblies. Usually proof pressure is 2x the operating pressure.

STF

 

[WKTaylor]

a5130...

1. Recommend you consider getting copies of the following data [min]...

SAE AIR737 Aerospace Hydraulic and Pneumatic Specifications, Standards, Recommended Practices, and Information Reports
SAE AIR1379 Prestressing (Autofrettaging) of Hydraulic Tubing Lines
SAE AIR1388 Service Damage Limits for Aircraft Hydraulic Tubing
SAE AIR5378 Aircraft Tube Bending Methods, Techniques and Tooling
SAE ARP994 Recommended Practice for the Design of Tubing Installations for Aerospace Fluid Power Systems
SAE ARP1897 Clamp Selection and Installation Guide
SAE ARP4752 Design and Installation of Commercial Transport Aircraft Hydraulic Systems
SAE ARP5891 Achieving Cleanliness Standards for Aircraft Hydraulic Systems During Manufacture

SAE AMS2610 Pressure Testing, Gaseous Media Pressure as Specified
SAE AMS2615 Pressure Testing, Hydraulic Pressure as Specified
SAE AS130 TUBE BENDING RADIUS
SAE AS683 Installation Procedures and Torques for Fluid Connections
SAE AS33611 TUBE BEND RADII

SAE AS4330 TUBING, FLARED, STANDARD DIMENSIONS FOR, DESIGN STANDARD
SAE AS5131 TUBE END - BEADED, DESIGN STANDARD
SAE AS5440 Hydraulic Systems, Military, Aircraft Design and Installation Requirements for
SAE AS33583 TUBING END DOUBLE FLARE, STANDARD DIMENSIONS FOR

MIL-D-9898 DRAWING, TUBE BEND
MIL-STD-1247 Markings, Functions and Hazards Designations of Hose, Pipe, and Tube Lines for Aircraft Missile, and Space Systems

2. NOTES.

There are MULTIPLE specifications for fluid-system detail parts/materials that have been omitted from the list [above].

OBVIOUSLY refer to the Aircraft Maintenance Manual [AMM] for specific fabrication details, parts and materials.

Trying to 'wing' [second-guess, reverse engineer] the fabrication of a tubing Assy may be harder than it looks! Many manufacturers do not provide specific details [diameter and wall-thickness, material/material-spec, bend radii, etc that is important/relevant to Tubing or Hose Assy fabrication: they want to force YOU to buy the assembly from them or one of their qualified suppliers.

Making a tubing assembly without a formal tubing fabrication drawing [IE: MIL-D-9898] dimensions, or a certified 'master tubing assembly' risks a 'poor fit'. An odd Lesson-learned from military tubing fabrication [old acft]: the tubing that needs to be replaced MAY NOT be an original installation! IF this is the case then You may be hand-making a copy-of-a-copy-etc... so Your fabricated Assy may be substantially different than a production part made to master dimensions.

Tubing forming, flaring, cutting, etc are usually done with light lubrication to minimize sliding friction that will damage tubing.

Ensure that Your 'raw' tubing and bending/flaring/beading/forming tools are absolutely clean and burr free. Soil, dust, burrs, chips, rough-surface areas, etc can damage the tubing during forming, flaring, beading, etc.

Several vendors produce high quality tube bending, flaring, crimping, etc equipment... hand or NC controlled... for the tiniest ODs [fractional-inch] up-to many inches tubing ODs.

IF tubing assemblies use flareless, crimp or 'special' style fittings, then data/tooling specific to installation/testing those parts/assys will be absolutely necessary.

Specify/use ONLY aluminum [typ 5052-0, 6061-T6, etc], CRES [typ 304, 316, 321, 346 annealed or 1/8H; and 21-6-9] or titanium [typ Ti-3AL-2.5V] tubing that is designated 'hydraulic quality'. This tubing is specifically made for fluid/pressure applications and has certain features that facilitate fluid tubing manufacture and long-term durable service.

There may be several useful YouTube videos, this subject.

Any of the following documents, may be useful, IF you can find a copy...
USAF T.O. 42E1-1-1 [NAVAIR 01-1A-20] Organizational, Intermediate and Depot Maintenance - Aviation Hose and Tube Manual
AC43.13-1 ACCEPTABLE METHODS, TECHNIQUES, AND PRACTICESAIRCRAFT INSPECTION AND REPAIR [CHAPTER 9, Section 2 HYDRAULIC SYSTEMS]
FAA-H-8033-30 AVIATION MAINTENANCE TECHNICIAN HANDBOOK [Chapter 7. Fluid Lines & Fittings]

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"]
o Learn the rules like a pro, so you can b

 

[a5130]

Many thanks Wil Taylor for your detailed information and also a big thanks to SparWeb.

Cheers!

 

[verymadmac]

If you can make hydraulic/pneumatic tube assembles, undoubtedly you will be called upon to makeup oxygen line assemblies, capability to clean oxygen lines is probably worth it as well.

 

[WKTaylor]

a5130 ...For ...

O2 systems tubing...
SAE AIR1392 Oxygen System Maintenance Guide
SAE ARP1176 Oxygen System and Component Cleaning
SAE ARP1532 Aircraft Oxygen System Lines, Fabrication, Test, and Installation

Pneumatic Ducts...
ARP699 High Temperature Pneumatic Duct Systems for Aircraft

USAF T.O.
15X-1-1 MAINTENANCE INSTRUCTIONS - OXYGEN EQUIPMENT

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"]
o Learn the rules like a pro, so you can b

 

[tbuelna]

Fabrication and acceptance of hydraulic/gas formed metal tube assemblies would need to conform with the OEM's specifications. Things are much easier now days with the availability of CNC tube bending equipment. But the CNC tube benders also require a 3D digital geometry model of the formed tube to produce a CNC program. You may also need to have inspection equipment such as a CMM or laser tracker to validate the dimensions of the formed tube, fixtures for pressure/leak testing of the tube/duct assemblies, and NDI capability to check for surface defects or excessive wall thinning.

Unless you have a big demand for this in-house manufacturing capability, then it might be hard to justify the initial capital cost to buy the equipment, the cost to qualify your personnel and processes, and the ongoing cost to maintain the capability to produce the components.

 

[a5130]

Thank you all again for the vital information.

At least now I know which direction to head and start from scrapes.

Regards,