AMT

100
Fluid Lines and Fi2ngs
Chapter 7

 Used for:

Fluid Lines

Hydraulic uid
Fuel

May have insulaCon/protecCon

Fire exCnguishing agent

Compressed air
Drains
Instrument air - pitot and staCc air

Rigid Fluid Lines

Used where there is no relaCve moCon

between the tube and the aircraM
Made of:

Aluminum
Half-hard 1100 or 3003

Fuel lines, engine oil and instrument air

2024-T or 5052-0

Medium pressure hydraulic systems

 Made of:

Rigid Fluid Lines

Corrosion-RESistant steel (CRES or stainless steel)

Annealed or 1/4hard CRES

High pressure (3000 psi and higher) hydraulic uid

Harsh environments

Uses MS areless 2ngs or swaged 2ngs

Copper
Work hardens with Cme
If found, replace

Titanium
High pressure applicaCon
Dont use with oxygen

Reacts with oxygen

Rigid Fluid Lines Size

Sized by outside diameter

Available in 1/16 increments
Inside diameter =
outside diameter 2 X wall thickness
Example: #10 with 0.065 wall thickness
Outside diameter = 10 X 1/16 = 10/16 = 5/8
Inside diameter = 5/8 2 X 0.065 = 0.495

Rigid Fluid Lines Size

RelaConship between uid line size and its outside diameter.

Rigid Fluid Lines Cu2ng

Cut must be square and burr free

Use tube cufer

Hacksaw and cu2ng wheels should not be used on

aluminum
Fine tooth hacksaw or abrasive wheel should be
limited to CRES

Deburr inside of tube

Use ne sandpaper to polish outside end

Tube Bending

Tube Bending

Bending must maintain 75% of the tube

diameter
Small thin wall tubes (1/4 or less) can be bent
by hand with special coil bending spring
Bend with ll:
Fusible Alloy - low melCng point of 160 degrees. Boil in
water, melt, pour in tube, bend tube and boil the metal
back out
Fill with sand and block o ends
Frozen soap soluCons

Tube Bending

Large tubes must be bent with bending tools

Wrinkles, kinks, cracks and afening are causes
for rejecCon
Make a model of the layout with welding rod
Blend the tool marks to smooth
Maintain minimum bend radius

For the same size tube, CRES will requires a larger

bend radius

At least one bend for stress relief

Tube Bending

Tube Beading

Connects two rigid tubes

Provides stress relief
Used for low pressure applicaCons

Tube Beading

Tube Beading

Tube Flaring

Flare at a 37 angle

AutomoCve uses 45

1/8 to 3/8 5052-0 and 6061-T tubes must use a

double are

More resistant to damage when the joint is

Cghtened

Minimum diameter of a are is the small part of

the sleeve
Maximum diameter of a are is the large part of
the sleeve

Double Flare

Single Flare

Proper are dimensions.

Flared Tube End Fi2ngs

Two types:

Single piece AN817 nut

Should not be used near bend

Two piece AN818 nut and AN819 sleeve

Reduce wiping or ironing acCon on are

Over Cghtening a ared tube coupling nut will

likely weaken or damage the tube and it is most
likely to fail at the sleeve and are juncCon

Flared Tube End Fi2ngs

No tension on tube while Cghtening nut

PressurizaCon will cause tube to expand and
shiM
Put 2ngs on before aring tube

Flared Tube End Fi2ngs

MS Flareless Fi2ng

Used for high-pressure hydraulics and

pneumaCcs
Consists of body, sleeve and nut
Use hydraulic uid to assist in assembly
Tube must be preset before 2ng is installed
MS areless 2ngs are installed by hand
Cghtening and then turning 1/6 to 1/3 turn (one
to two nut faces)

No torque value used

MS Flareless Preset

MS Flareless Preset

MS Flareless Preset

Preset Cghtening depends on tube type & size

Aluminum 1/2 and less

Tighten 1 to 1 1/6 turns (1 turn plus a nut face)

Aluminum over 1/2 and steel

Tighten 1 1/6 turns (1 turn plus a nut face) to
1 1/2 turns (1 turn plus three nut faces)

Swaged Tube Fi2ngs

Tube Flaring Sequence

Tube Flaring Sequence

Put nut and sleeve on tube

Place tube in aring block
Center the plunger
Project the end of the tube slightly from the top
of the aring tool, about the thickness of a dime
Tighten the clamp bar securely to prevent
slippage
Strike the plunger several light blows with a
lightweight hammer or mallet and turn the
plunger one-half turn aMer each blow

Rigid Tube Damage

Scratches or nicks on the straight porCon of

aluminum alloy tubing may be repaired if they
are no deeper than 10 percent of the wall
thickness
Scratches and nicks should be burnished out of
the tube, to prevent stress concentraCons

InstallaCon of Rigid Fluid Lines

Fluid line should be installed below a wire

bundle to prevent a leak we2ng the wires
Each secCon of rigid tubing must have at least
one bend in it to absorb vibraCon and the
dimensional changes
The tubing should t squarely against the 2ng
before the nut is started
Metal uid lines are installed in an aircraM with
cushion clamps

InstallaCon of Rigid Fluid Lines

Metal uid lines are installed in an aircraM with

bonded cushion clamps
Bonded clamps have a strip of metal inside the
cushion that electrically connects the tubing to the
aircraM structure
To provide a good electrical connecCon, remove all
of the paint and the anodized oxide lm from the
locaCon to which the clamp is fastened

Distance Between Supports

AC 43-13-1B Sec0on 8-31

Minimize Overhang

InstallaCon of Rigid Fluid Lines

Correct and incorrect ways of installing the clamps to hold uid lines.

InstallaCon of Rigid Fluid Lines

EAA clamp video

Grommets

Bonded Clamps

Repair of Rigid Fluid Lines

Scratches and nicks that are no deeper than

10% of the wall thickness of a piece of metal
tubing can be repaired by burnishing
Tubing containing damage in the heel of a bend
must be replaced
Dents that are less than 20% of the tube
diameter are permissible
Flafening of tubing by not more than 25
percent of the original diameter is permissible

Comes from Bending must maintain 75% of the

tube diameter

Repair of Rigid Fluid Lines

Repair with a Swage

A. A pinhole leak may be repaired with a single swaged 2ng.

B. An extensively damaged tube may be repaired by cu2ng out the damaged area and
splicing in a new secCon of tubing using two swaged 2ngs.

IdenCcaCon of Fluid Lines

Rigid tubing is marked with colored tape and

symbols to idenCfy its contents.
Symbols are always black against a white
background regardless of line content.

IdenCcaCon of Fluid Lines

Rigid tubing idenCcaCon.

Hazardous Fluid Labels

IdenCcaCon of uid lines carrying hazardous uids.

 Used for:

Flexible Fluid Lines

ConnecCng components that move

InstallaCons in which the line must be frequently
connected and disconnected

Reminder: Use only the manufacturers

recommended hose or an approved subsCtute
Flexible hoses have a lay line printed along the
outside

Use the lay line to insure the uid line is not twisted

All exible hose installaCons should be

supported at least every 24

Flexible Fluid Lines Sizing

Specied in 1/16
Represents the approximate inside diameter of
the line
The size is a refers to the outside diameter of a
rigid tube that has the equivalent ow
characterisCcs
The actual inside diameter is smaller than the
sizing number indicates

This compensates for the wall thickness of a rigid

tube

Flexible Fluid Lines

Low-pressure hose

MIL-H-5593
SyntheCc rubber inner liner, a cofon braid, and a
syntheCc rubber outer cover
Maximum pressure of 300 psi
IdenCed by a broken yellow lay line; the lefers LP;
and the manufacturer's code number and date
marking

Flexible Fluid Lines

Medium-pressure hose

MIL-H-8794
Seamless syntheCc rubber inner line; a syntheCc
rubber-impregnated cofon braid reinforcement;
and a steel wire braid reinforcement; encased in a
rough syntheCc rubber-impregnated cofon braid
Maximum pressure of 1,500 psi

Flexible Fluid Lines

High-pressure hose

MIL-H-8788
Seamless syntheCc rubber inner tube; either two or
three carbon steel wire braid reinforcements; and
covered with a smooth syntheCc rubber cover
Pressure range of 1,500 to 3,000 psi

Flexible Fluid Lines

Extra-high-pressure hose

Reinforced with layers of spiral-wound stainless

steel wire encased in a special syntheCc rubber
Pressure range of 3,000 to 6,000 psi
Can withstand temperatures up to 400F

Teon Flexible Fluid Lines

Tetrauoroethylene, TFE or Teon

Material that is used for the inner liner of hoses
Carries uids at temperatures up to 400F
Chemically inert
Resists reacCng with other chemicals
Used for fuel, petroleum, or syntheCc-base
lubricants, phosphate-ester base hydraulic uid,
alcohol, coolants, and solvents

Teon Flexible Fluid Lines

Strong and highly resistant to vibraCon and

faCgue
Takes a permanent set aMer it has been in
service

Remembers its shape/curves and wants to remain

in that shape

Store Teon hoses in the shape used in the

aircraM

Teon Flexible Fluid Lines

A support wire should be used to prevent a preformed tube or one that has taken a
permanent set from being inadvertently straightened when it is removed from the aircraM.

Butyl Flexible Fluid Lines

Another inner liner material

Not suitable for use with petroleum products
Good for phosphate-ester base hydraulic uid

InstallaCon of Flexible Hoses

Flexible hoses should be approximately 5% to

8% longer than the distance between the
2ngs

Example: Fi2ngs are 50 inches apart

50 X 1.05 = 52.5

Hoses should be long enough to enable full

movement of connecCons
Check full range of connecCon movement to
ensure hoses doesnt bind or knick

InstallaCon of Flexible Hoses

Correct and incorrect installation of flexible hose.

A. Flexible hose should be 5% to 8% longer than the distance between the 2ngs to prevent
straining the 2ngs.
B. Elbow 2ngs should be used to keep exible hose from having to bend at a sharp angle.
C. Flexible hose should be installed on a movable actuator in such away that the hose is not
crimped in any posiCon of the actuator.

Cold Flow

Any permanent deformaCon due to pressure or

mechanical force
Improper clamps can leave permanent
impressions in plasCc and rubber hoses
If cold ow is found, replace hose and improve
support/clamping system

Flexible Hose End Fi2ngs

Types:

Swaged
If damaged, replace whole hose

Replaceable
Three pieces:
Nut
Nipple
Socket

Replaceable Flexible Hose Fi2ngs

TesCng:

43.13-1B (secCon 9-30) & TSO-C75 (Hydraulic Hose

Assemblies) says 150% for 30 seconds (type I & II)
and 5 minutes (type III high temp)

Fluid Line Fi2ngs

Specied in 1/16
NaConal Pipe Taper (NPT)

Thread is taper
Be careful not to over Cghten to insure socket
doesnt crack

AN 2ng Current 2ng

37
Recessed threads

Thread has a shoulder

Blue is aluminum; Black is steel

Fluid Line Fi2ngs

AC 2ng old 2ng

35
Gray or yellow

Fluid Line Fi2ngs

AN and AC are-type 2ngs.

Bulkhead Fluid Line Fi2ngs