ISO 8829-2:2006

Aerospace — Test methods for polytetrafluoroethylene (PTFE) inner-tube hose assemblies — Part 2: Non-metallic braid

ISO 8829-2:2006 specifies test methods for flexible polytetrafluoroethylene (PTFE) inner tubes with non-metallic braided hose and hose assemblies used in aircraft fluid systems, in the pressure and temperature ranges covered by pressure classes and temperature types, as specified in ISO 6771. ISO 8829-2:2006 applies to the hose and the hose coupling. The tests and assembly requirements for the connecting end fittings are covered in the procurement specification. ISO 8829-2:2006 is applicable when reference is made to it in a procurement specification or other definition document.

Aéronautique et espace — Méthodes d'essai des tuyauteries flexibles à tube intérieur en polytétrafluoréthylène (PTFE) — Partie 2: Tuyauteries à gaine non métallique

General Information

• Status: Published
• Publication Date: 21-Sep-2006
• ICS: 49.080 - Aerospace fluid systems and components
• ICS: 83.140.40 - Hoses
• Technical Committee: ISO/TC 20/SC 10 - Aerospace fluid systems and components
• Drafting Committee: ISO/TC 20/SC 10/WG 14 - Hose assemblies
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 06-Nov-2020

Relations

• Revises: ISO 8829:1990 - Aerospace — Polytetrafluoroethylene (PTFE) hose assemblies — Test methods
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 8829-2
First edition
2006-09-15


Aerospace — Test methods for
polytetrafluoroethylene (PTFE) inner-tube
hose assemblies —
Part 2:
Non-metallic braid
Aéronautique et espace — Méthodes d'essai des tuyauteries flexibles
à tube intérieur en polytétrafluoroéthylène (PTFE) —
Partie 2: Tuyauteries à gaine non métallique





Reference number
ISO 8829-2:2006(E)
©
ISO 2006

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ISO 8829-2:2006(E)
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ISO 8829-2:2006(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 Test temperature. 2
5 Tests on PTFE inner tubes . 2
5.1 Density and relative density . 2
5.2 Tensile tests . 2
5.3 Rolling and proof-pressure tests . 4
5.4 Electrical conductivity test . 6
6 Test on hoses and hose assemblies . 6
6.1 Stress degradation test. 6
6.2 Pneumatic effusion test . 8
6.3 Electrical conductivity test . 9
6.4 Visual and dimensional inspection. 10
6.5 Determination of elongation or contraction. 10
6.6 Volumetric expansion test . 10
6.7 Leakage test . 12
6.8 Proof-pressure test. 12
6.9 Burst-pressure tests. 12
6.10 Impulse test . 13
6.11 Flexure test. 13
6.12 Fuel resistance test . 15
6.13 Low-temperature flexure testing . 15
6.14 Pneumatic leakage test . 15
6.15 Vacuum test. 15
6.16 Pneumatic surge test. 16
6.17 Thermal shock test . 16
6.18 Light-radiation aging . 17
6.19 Push-pull test . 18
6.20 Fire test . 19
Annex A (informative) Test fluids . 20
Bibliography . 21

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ISO 8829-2:2006(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 8829-2 was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 10, Aerospace fluid systems and components.
ISO 8829-2 cancels and replaces ISO 8829:1990, which has been technically revised.
ISO 8829 consists of the following parts, under the general title Aerospace — Test methods for polytetra-
fluoroethylene (PTFE) inner-tube hose assemblies:
⎯ Part 1: Metallic (stainless steel) braid
⎯ Part 2: Non-metallic braid

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ISO 8829-2:2006(E)
Introduction
This part of ISO 8829 is intended to standardize the test methods for qualification of polytetrafluoroethylene
(PTFE) hose and hose assemblies used in aircraft fluid systems. The tests are intended to simulate the most
strenuous demands encountered in aircraft. Compliance with these test methods is necessary for hose and
hose assemblies which are used in systems where a malfunction could affect the safety of flight.

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INTERNATIONAL STANDARD ISO 8829-2:2006(E)

Aerospace — Test methods for polytetrafluoroethylene (PTFE)
inner-tube hose assemblies —
Part 2:
Non-metallic braid
1 Scope
This part of ISO 8829 specifies test methods for flexible polytetrafluoroethylene (PTFE) inner tubes with
non-metallic braided hose and hose assemblies used in aircraft fluid systems, in the pressure and
temperature ranges covered by pressure classes and temperature types, as specified in ISO 6771.
This part of ISO 8829 applies to the hose and the hose coupling. The tests and assembly requirements for the
connecting end fittings are covered in the procurement specification.
This part of ISO 8829 is applicable when reference is made to it in a procurement specification or other
definition document.
NOTE Fluids used for the tests are listed in Annex A.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 2685:1998, Aircraft — Environmental test procedure for airborne equipment — Resistance to fire in
designated fire zones
1)
ISO 6771 , Aerospace — Fluid systems and components — Pressure and temperature classifications
ISO 6772:1988, Aerospace — Fluid systems — Impulse testing of hydraulic hose, tubing and fitting
assemblies
ISO 6773:1994, Aerospace — Fluid systems — Thermal shock testing of piping and fittings
ISO 7258:1984, Polytetrafluoroethylene (PTFE) tubing for aerospace applications — Methods for the
determination of the density and relative density

1) To be published. (Revision of ISO 6771:1987)
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ISO 8829-2:2006(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
fire sleeve
flame- and heat-retardant element, normally tubular, slipped over the hose assembly and fastened to the hose
fitting
3.2
fire-cover
flame- and fire-retardant element, normally (silicone) rubber, moulded over the hose and hose fittings
4 Test temperature
Unless otherwise specified, tests shall be conducted between 15 °C and 32 °C (59 °F and 90 °F).
5 Tests on PTFE inner tubes
5.1 Density and relative density
5.1.1 Principle
The test is intended to control the crystallinity of PTFE inner tubes.
5.1.2 Test methods
The relative density of the PTFE tubing shall be measured in accordance with ISO 7258:1984, method A or
method B. The density of the PTFE tubing shall be measured in accordance with ISO 7258:1984, method C.
5.2 Tensile tests
5.2.1 Principle
This test is intended to determine the mechanical properties of the PTFE tubing.
5.2.2 Test conditions
Test specimens shall be conditioned for at least 2 h at room temperature prior to testing.
5.2.3 Apparatus
5.2.3.1 Testing machine
The test shall be carried out using a power-driven machine which is capable of maintaining a uniform rate of
jaw separation at 50 mm/min (2 in/min) and which has a suitable dynamometer and a device for measuring
the force applied within ± 2 %. If the capacity range cannot be changed during a test, as in the case of
pendulum dynamometers, the force applied at breaking point shall be measured within ± 2 %, and the
smallest tensile force measured shall be accurate to within ± 10 %. If the dynamometer is of the compensating
type for measuring tensile stress directly, means shall be provided to make adjustments for the cross-
sectional area of the test specimen. The response of the recorder shall be sufficiently rapid for the force
applied to be measured accurately during the elongation of the test specimen to breaking point. If the test
machine is not equipped with a recorder, a device shall be provided that indicates, after fracture, the
maximum force applied during elongation. Testing machines shall be capable of measuring elongation in
increments of 10 %.
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ISO 8829-2:2006(E)
5.2.3.2 Micrometer
The micrometer used for measuring flat test specimen thickness shall be capable of exerting a pressure of
25 kPa ± 5 kPa (3,63 psi ± 0,7 psi) on the test specimens, and of measuring the thickness to within
± 0,025 mm (0,001 in).
Dial micrometers exerting either a force of 0,8 ± 0,15 N (0,18 lbf ± 0,034 lbf) on a circular foot 6,35 mm
(0,25 in) in diameter or a force of 0,2  ± 0,04 N (0,045 lbf ± 0,009 lbf) on a circular foot 3,2 mm (0,125 in) in
diameter conform to the pressure requirement specified above. A micrometer should not be used to measure
the thickness of test specimens narrower in width than the diameter of the foot, unless the contact pressure is
properly adjusted.
5.2.4 Calibration of testing machine
The testing machine shall be calibrated.
If the dynamometer is of the strain-gauge type, the test machine shall be calibrated at one or more forces at
regular intervals.
5.2.5 Test specimens
The specimens shall be in accordance with Figure 1.
NOTE Careful maintenance of the cutting edges of the die is extremely important and can be achieved by light daily
honing and touching up of the cutting edges with jeweler's hard honing stones. The condition of the die may be assessed
by determining the breaking point on any series of broken test specimens. When broken test specimens are removed from
the jaws of the test machine, it is advantageous to pile these test specimens and note if there is any tendency to break at
or near the same portion of each test specimen. Breaking points consistently occurring at the same place may be an
indication that the die is dull, nicked or bent at that particular position.
Dimensions in millimetres

Figure 1 — Test specimen for tensile test
5.2.6 Determination of tensile strength and elongation
5.2.6.1 Procedure
Place the test specimens (see 5.2.5) in the jaws of the testing machine (5.2.3.1), taking care to adjust the
specimen symmetrically so that the tension will be distributed uniformly over the cross-section. Start the
machine and note continuously the distance between the jaws, taking care to avoid parallax. At fracture,
measure and record the elongation to the nearest 10 % on the scale.
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ISO 8829-2:2006(E)
5.2.6.2 Expression of results
2)
Calculate the tensile strength, R , in newtons per square millimetre , using the following equation:
m
F
R =
m
S
where
F is the measured force, in newtons, required to fracture the test specimens;
S is the cross-sectional area, in square millimetres, of the test specimen before application of force.
Calculate the percentage total elongation at fracture, A , using the following equation:
t
⎛⎞
LL−
uo
A=×100
⎜⎟
t
⎜⎟
L
⎝⎠o
where
L is the length measured between the jaws at fracture of the test specimen;
u
L is the original length measured between the jaws before application of force.
o
5.3 Rolling and proof-pressure tests
5.3.1 Principle
This test is intended to check that there are no flaws in the sintered tube.
5.3.2 Rolling test — Procedure
Pass each tube, in a single pass, through six sets of metal rollers so that it is subjected to the sequence of
diametral flexings specified in Table 1; rollers shall be arranged to prevent inadvertent rotation in the tube. It is
assumed that the tube is in a horizontal position and that pressure of the first set of rollers is exerted vertically;
angles given for the final three sets of rollers may be taken as either clockwise or counterclockwise from the
vertical diameter of the tube. Roller angles shall be as specified in Table 1. A tolerance of ± 2° is allowed on
each roller angle. The roller gap dimensions shall not be larger than those specified in Table 2 for each size.
Table 1 — Roller functions and angles
Set of metal rollers Type of action Roller angle
1 Flattening 0°
2 Flattening 90°
3 Rounding 0°
4 Flattening 45°
5 Flattening 135°
6 Rounding 45°


2
2) 1 N/mm = 1 MPa
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ISO 8829-2:2006(E)
3)
Table 2 — Roller gap dimensions
Flattening gap Rounding gap
Hose size
max. max.
Metric part Inch part Class B Class D Class B Class D
10 500 kPa 21 000 kPa 10 500 kPa 21 000 kPa
(1 523 psi) (3 046 psi) (1 523 psi) (3 046 psi)
Equivalent

and lower and higher and lower and higher
outside diameter of tube
nominal pressure nominal pressure nominal pressure nominal pressure
Size Size mm (in) mm (in) mm (in) mm (in) mm (in)
DN05 – 03 4,762 (0,187) 5,2 (0,203) 5,2 (0,203) 5,5 (0,218) 6,4 (0,250)
DN06 – 04 6,350 (0,250) 5,5 (0,218) 7,1 (0,281) 5,5 (0,218) 6,4 (0,250)
DN08 – 05 7,937 (0,312) 5,5 (0,218) — — 6,4 (0,250) — —
DN10 – 06 9,525 (0,375) 5,5 (0,218) 7,1 (0,281) 7,9 (0,312) 8,3 (0,328)
DN12 – 08 12,700 (0,500) 5,9 (0,234) 8,3 (0,328) 9,5 (0,375) 11,9 (0,469)
DN16 – 10 15,875 (0,625) 6,4 (0,250) 8,3 (0,328) 12,7 (0,500) 14,7 (0,578)
DN20 – 12 19,050 (0,750) 6,4 (0,250) 8,3 (0,328) 12,7 (0,500) 17,5 (0,688)
DN25 – 16 25,400 (1,000) 6,4 (0,250) 8,3 (0,328) 19,1 (0,750) 21,0 (0,828)
DN32 – 20 31,750 (1,250) 7,9 (0,312) 11,1 (0,438) 22,2 (0,875) 25,4 (1,000)
DN40 – 24 38,100 (1,500) 9,5 (0,375) — — 31,8 (1,250) — —

5.3.3 Proof-pressure test — Procedure
After the roll test, hold the tube for not less than 2 min. at proof pressures as shown in Table 3, using water or
air as the test medium.
3)
Table 3 — Proof pressure
Hose size Proof pressure
Metric part Inch part Class B Class D Nominal Nominal
10 500 kPa 21 000 kPa pressure pressure
(1 523 psi) (3 046 psi) 10 342 kPa 20 684 kPa
Equivalent
and lower and higher (1 500 psi) (3 000 psi)

outside diameter of tube
 and lower and higher
nominal pressure nominal pressure nominal pressure nominal pressure
Size Size mm (in) kPa (psi) kPa (psi) kPa (psi) kPa (psi)
DN05 – 03 4,762 (0,187) 2 690 (390) 3 310 (480) 2 690 (390) 3 310 (480)
DN06 – 04 6,350 (0,250) 2 480 (360) 2 620 (380) 2 480 (360) 2 620 (380)
DN08 – 05 7,937 (0,312) 2 000 (290) — — 2 000 (290) — —
DN10 – 06 9,525 (0,375) 1 590 (230) 1 930 (280) 1 590 (230) 1 930 (280)
DN12 – 08 12,700 (0,500) 1 240 (180) 1 520 (220) 1 240 (180) 1 520 (220)
DN16 – 10 15,875 (0,625) 1 170 (170) 1 170 (170) 1 170 (170) 1 170 (170)
DN20 – 12 19,050 (0,750) 965 (140) 890 (130) 965 (140) 890 (130)
DN25 – 16 25,400 (1,000) 621 (90) 660 (95) 621 (90) 660 (95)
DN32 – 20 31,750 (1,250) 448 65) 660 (95) 448 (65) 660 (95)
DN40 – 24 38,100 (1,500) 310 (45) — — 310 (45) — —

3) Special size high pressure hose assembly callout shall utilize lower hose size value noted.
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ISO 8829-2:2006(E)

5.4 Electrical conductivity test
5.4.1 Preconditioning
The test specimen shall be a 350 mm (13,78 in) length of PTFE hose tube (without braid). The inner surface
of the tube shall be washed first with degreasing fluid (test fluid No. 1; see Annex A) and then with isopropyl
alcohol (test fluid No. 2; see Annex A) to remove surface contamination. The inside of the tube shall then be
thoroughly dried at room temperature.
5.4.2 Procedure
Arrange the test specimen vertically as shown in Figure 2. The relative humidity shall be kept below 70 %.
Apply 1 000 V ± 10 V d.c. between the upper and lower electrodes (salt water solution). The salt water
solution shall be a solution of sodium chloride in chemically pure water [ρ (NaCl) = 450 g/l].
− 6
Measure the current with an instrument having a sensitivity of at least 1 µA (= 1 × 10 A).
6 Test on hoses and hose assemblies
6.1 Stress degradation test
6.1.1 Principle
This test is intended to verify that the inner tube of the hose has been sintered and quenched to the proper
crystallinity to eliminate stress cracking or creep with subsequent leakage.
6.1.2 Procedure
6.1.2.1 Fill the hose assemblies with a high-temperature test fluid (test fluid No. 3; see Annex A) and
place in an oven maintained at the maximum working temperature specified in the procurement specification.
Apply to the hose assemblies the nominal pressure specified in the procurement specification, and hold that
pressure for at least 20 h.
Precautions shall be taken to ensure that the hose assemblies do not come into contact with parts of the oven
that are at a higher temperature.
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ISO 8829-2:2006(E)
Dimensions in millimetres

Key
1 probe
2 conductor tube
3 vent
4 upper electrode (salt water solution)
5 non-conductive plug
6 O-ring
7 vent (if any)
8 polytetrafluoroethylene (PTFE) (inner tube of the hose)
9 non-conductive container
10 lower electrode (salt water solution)
Figure 2 — Test set-up for electrical conductivity test on inner tubes
6.1.2.2 Gradually release the pressure, remove the assemblies from the oven, drain and cool to room
temperature. Then flush the assemblies with a quantity of fresh high-temperature test fluid (test fluid No. 3;
see Annex A) equivalent in volume to at least twice the volume of the test specimen volume, and drain.
6.1.2.3 Fill the hose assemblies with hydraulic test fluid (test fluid No. 4; see Annex A). Apply to the hose
assemblies the nominal pressure specified in the procurement specification, and hold that pressure for at least
2 h at room temperature.
6.1.2.4 Repeat the procedure specified in 6.1.2.1 to 6.1.2.3 a total of three times.
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ISO 8829-2:2006(E)
6.1.2.5 Within 4 h after the final pressurization period of 2 h, drain the hose assemblies, flush them using
a suitable cleaning process and place in an oven for at least 1 h at a temperature of 70 °C ± 5 °C
(158 °F ± 9 °F).
6.1.2.6 Within 8 h after the drying process has been completed, remove the hose assemblies from the
oven, cool to room temperature, and then subject them to a pneumatic effusion (air under water) test. For this
test, install the hose assemblies in a test set-up constructed similarly to that shown in Figure 3.
6.1.2.7 Immerse the test set-up with the hose assemblies installed in water. Apply nominal pressure for at
least 15 min to allow any entrapped air in the hose to escape.
6.1.2.8 Hold the pressure for a further period of 5 min. During this time, collect the gas escaping from the
test specimen, including the juncture of the hose and the fitting, but not including the juncture of the fitting to
the test set-up. After the pressurization period of 5 min, calculate the average rate of effusion through the
hose and two fittings, expressed as millilitres per minute per metre of the hose length.
6.2 Pneumatic effusion test
6.2.1 Principle
This test is intended to show that the inner tube of the hose does not have excessive porosity.
6.2.2 Procedure
Subject the hose assemblies for 1 h to nominal pressure using dry air or nitrogen gas (N ) at room
2
temperature.
Collect and measure the gas escaping from the hose assembly during the second half-hour, using the water
displacement method and an air-collecting device similar to that shown in Figure 3.
The fluid in the test set-up shall be water which has been treated for pH control and wetting of the hose by
adding 1,5 % (V/V) of water softener or wetting agent.

Key
1 air or nitrogen gas source
2 inverted graduated flask
3 funnel to cover hose plus one-half of each socket
4 water bath
5 hose assembly under test
Figure 3 — Test set-up for pneumatic effusion tests
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ISO 8829-2:2006(E)
6.3 Electrical conductivity test
6.3.1 Principle
This test is intended to show that the hose is sufficiently conductive to prevent build-up of excessive
electrostatic charges which could cause arcing and pin holes.
6.3.2 Preconditioning
The test specimen shall be a length of hose (with braid and one end fitting) as shown in Figure 4a) or 4b). The
inner surface of the tube shall be washed first with degreasing fluid (test fluid No. 1; see Annex A), and then
with isopropyl alcohol (test fluid No. 2; see Annex A) to remove surface contamination. The hose shall then be
thoroughly dried at room temperature. The wire braid shall flare out, as shown in Figure 4a) or 4b), to prevent
contact with the end of the PTFE inner tube.
One steel adaptor of appropriate size shall be fitted as shown in Figure 4a) or 4b).
Dimensions in millimetres

Key Key
1 conductor threaded into ring 1 electrode /2/
2 flare braid(s)/spiral 2 fitting nut
3 vent 3 fitting body
4 upper electrode (salt water solution) 4 hose braid
5 non-conductive plug 5 flared braid
6 O-ring 6 polytetrafluoroethylene tube
7 PTFE hose 7 electrode /1/
8 hose braid/spiral 8 non-metallic container
9 fitting body
10 fitting nut
11 vent (alternative)
12 adaptor (insulate electrode from ground)
Figure 4a) Figure 4b)
Figure 4 — Alternative test set-ups for electrical conductivity test on hose assemblies
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ISO 8829-2:2006(E)
6.3.3 Procedure
Arrange the test specimen vertically as shown in Figure 4a) or 4b). The relative humidity shall be kept below
70 %. Apply 1 000 V ± 10 V d.c. between the upper (salt water solution) electrode and the lower (adaptor)
electrode. The salt water solution shall be a solution of sodium chloride in chemically pure water
[ρ (NaCl) = 450 g/l].

−
6
Measure the current with an instrument having a sensitivity of at least 1 µA (= 1 × 10 A).
6.4 Visual and dimensional inspection
Hose assemblies shall be inspected using the normal tools and procedures.
6.5 Determination of elongation or contraction
6.5.1 Principle
This test is intended to check that the proper reinforcing braid angle was used to minimize axial motion due to
pressurization.
6.5.2 Procedure
Hold the unpressurized hose in a straight position, mark off on the hose a gauge length of 250 mm (10 in) and
then subject the hose to the nominal pressure specified in the procurement specification. After at least 5 min
and with the hose length still pressurized, measure the gauge length and calculate the change in length.
6.6 Volumetric expansion test
6.6.1 Principle
This test is intended to determine the increase in volume that occurs when a hose assembly is pressurized.
6.6.2 Apparatus
The test set-up, shown in Figure 5, shall be designed in such a way that air pockets cannot form. There shall
be only one low point between the reservoir and the pump (see Figure 5). The internal passages shall not
have constrictions or surface roughness that could allow air pockets. The hose end fittings and system tubes
shall be both strong and rigid enough to allow only negligible expansion under test pressure. The test fluid
shall be distilled water. The pump pressure shall be increased at a rate of 2 000 kPa/s to 4 000 kPa/s
(290 psi/s to 580 psi/s).
Before installing the hose assembly, measure the volumetric expansion of the test set-up (see 6.6.3.9).
6.6.3 Procedure
6.6.3.1 Install the hose assembly to be tested in the test set-up as shown in Figure 5.
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ISO 8829-2:2006(E)

Key
1 counter-weight for that part of the installation which is located above the hose assembly
2 pressure gauge
3 pump
4 tank of distilled water
5 graduated glass tube
6 valve A
7 valve B
8 hose assembly under test
9 three-way valve
10 graduated glass container
Figure 5 — Test set-up for volumetric expansion test
6.6.3.2 Set the three-way valve to the position indicated in Figure 5.
6.6.3.3 Open valve B and close valve
...