ISO 19631:2015

INTERNATIONAL ISO
STANDARD 19631
First edition
2015-09-01
Aerospace series — Tube fittings for
fluid systems, 5 080 psi (35 000 kPa)
— Qualification specification
Série aérospatiale — Raccordements de tubes pour les systèmes
fluides, 5 080 psi (35 000 kPa) — Spécification de qualification
Reference number
ISO 19631:2015(E)
©
ISO 2015

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ISO 19631:2015(E)

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© ISO 2015, Published in Switzerland
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ISO 19631:2015(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Requirements . 1
3.1 Qualification . 1
3.1.1 Manufacturer qualification . 1
3.1.2 Product qualification . 2
3.2 Materials . 2
3.2.1 Fittings . 2
3.2.2 Tubing . 2
3.2.3 Testfluid . 2
3.3 Environmental conditions . 3
3.3.1 Pressures . 3
3.3.2 Temperature . 3
3.4 Design and manufacture . 3
3.4.1 Fluid passages . 3
3.5 Performance . 3
3.5.1 Specimen preparation . 3
3.5.2 Proof pressure . 4
3.5.3 Gaseous pressure. 4
3.5.4 Hydraulic impulse resistance . 4
3.5.5 Ultimate pressure . 5
3.5.6 Flexure fatigue resistance . 5
3.5.7 Re-use capability . 5
3.5.8 Tensile load capability . . 6
3.5.9 Thermal shock . 6
3.5.10 Over-tightening . 6
3.5.11 Electrical conductivity . 6
3.5.12 Salt spray . 7
3.5.13 Vibration . 7
3.5.14 Fire test .11
3.5.15 System pressure test .11
3.5.16 Fuel ageing .12
3.5.17 Hydraulic fluid ageing .12
3.5.18 Tube twisting .12
3.5.19 Fitting/tube rotation torque .13
3.5.20 Stress corrosion .14
3.5.21 Lightning strike .16
Annex A (normative) Equivalent materials and processes .18
Bibliography .20
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ISO 19631:2015(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 10, Aerospace fluid systems and components.
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ISO 19631:2015(E)

Introduction
This International Standard establishes the basic performance for 5 080 psi (35 000 kPa) tube fitting
assemblies used in aerospace fluid systems.
The test requirements are intended to satisfy the most strenuous demands encountered in a high-
performance aircraft hydraulic system.
International Standards use the International System of units (SI); however, large segments of the
aerospace industry make use of other measurement systems as a matter of common working practice.
All dimensions and units used in this International Standard are given in SI units, with other units also
indicated for the convenience of the user.
The decimal sign used in International Standards is the comma (“,”); however, the comma is not used in
common working practice with non-SI dimensions. Therefore, in common with many other aerospace
standards, the decimal point (“.”) is used in this International Standard when providing dimensions in
inch-pound units.
NOTE The use of non-SI units and the decimal point in this International Standard does not constitute
general acceptance of measurement systems other than SI within International Standards.
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INTERNATIONAL STANDARD ISO 19631:2015(E)
Aerospace series — Tube fittings for fluid systems, 5 080
psi (35 000 kPa) — Qualification specification
1 Scope
This International Standard specifies performance and quality requirements for the qualification and
manufacture of standard tube fittings to ensure reliable performance in aircraft hydraulic 5 080 psi
(35 000 kPa) systems.
This International Standard specifies baseline criteria for the design and manufacture of system
fittings that are qualification tested on engines.
This International Standard covers fittings from size –04 to –20 used for the following:
— separable/permanent pipe end fittings;
— permanent connection fittings;
— separable connection fittings.
This International Standard covers fittings of the temperature types and pressure classes specified in
ISO 6771.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 2685, Aircraft — Environmental test procedure for airborne equipment — Resistance to fire in
designated fire zones
ISO 6772, Aerospace — Fluid systems — Impulse testing of hydraulic hose, tubing and fitting assemblies
ISO 6773, Aerospace — Fluid systems — Thermal shock testing of piping and fittings
ISO 7137, Aircraft — Environmental conditions and test procedures for airborne equipment
ISO 7257, Aircraft — Hydraulic tubing joints and fittings — Rotary flexure test
ISO 10583:1993, Aerospace fluid systems — Test methods for tube/fitting assemblies
EUROCAE ED-14E/RTCA DO-160E, Section 22, Lightning Induced transient Susceptibility
3 Requirements
3.1 Qualification
Fittings claiming conformity with this International Standard shall be representative of products,
which have successfully met the requirements and have passed the tests in this International Standard.
3.1.1 Manufacturer qualification
Manufacturer approval shall be granted by purchaser qualification procedure.
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ISO 19631:2015(E)

Outside agency procedure can be used if no specific procedure exists (see Annex A, Table A.3,
Procedure 1).
3.1.2 Product qualification
Product approval shall be granted by purchaser qualification procedure.
Outside agency procedure can be used if no specific procedure exists (see Annex A, Table A.3,
Procedure 1).
3.2 Materials
3.2.1 Fittings
Fitting parts shall be manufactured from materials as given in Table 1 or equivalent passing the specified
tests. The various materials shall be used according to the pressure and temperature requirements of
the system, as shown in Table 2.
Table 1 — Materials for fittings
a
Material Type Material code Starting stock
Titanium alloy I, II, III T Bar, forgings, or rings
Corrosion-resistant steel I, II, III, IV V Bar, forgings, or rings
Other To be defined To be defined To be defined
a
Temperature types and system pressure classes are defined in ISO 6771.
Magnesium and magnesium alloy shall not be used.
3.2.2 Tubing
Table 2 — Materials for tubing
Material Material code Starting stock
Titanium alloy T Hollows
Corrosion-resistant steel V Hollows
Other To be defined To be defined
3.2.3 Testfluid
Unless otherwise specified, fluid for testing shall be used in accordance with Annex A, Table A.1.
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ISO 19631:2015(E)

3.3 Environmental conditions
3.3.1 Pressures
Table 3 — Pressure test requirements, 35 000 kPa (5 080 psi) fittings
Dimensions in SI-metric (and imperial) units
Design operating pressure Proof pressure Burst pressure
Fitting and tube
(DOP) (2 × DOP) (3 × DOP)
a
size
kPa (psi) kPa (psi) kPa (psi)
04
06
08
10 35 000 (5 080) 70 000 (10 160) 105 000 (15 240)
12
16
20
a
Dash size in 1/16 in, example: 08 = 8/16 in diameter.
3.3.2 Temperature
3.2.2.1 Ambient Air: −54 °C to +135 °C
3.2.2.2 Hydraulic Fluid: −54 °C to +135 °C
3.4 Design and manufacture
3.4.1 Fluid passages
On fittings where the fluid passage is drilled from each end, the offset between the drilled holes at the
meeting point shall not exceed 0,25 mm (0.10 in). It shall be possible to pass through the fitting passage
a ball whose diameter is 0,37 mm (0.015 in) less than the minimum diameter specified for the passage.
Angular misalignment shall not exceed 1° for straight fittings and 2° for shaped fittings.
3.5 Performance
The tubing/fitting assembly shall be capable of meeting the performance requirements specified in
3.5.1 to 3.5.21.
3.5.1 Specimen preparation
Test specimens shall be assembled as specified in Table 11. Sleeve installations on the tube end shall be
in accordance with user instructions.
The fitting shall be assembled to tightening torques given by purchaser procurement specification, using
the maximum installing torque for half of the test specimens and the minimum torque for the other half.
3.5.1.1 Lubricants
Hydraulic system fittings shall be assembled using system fluid as lubricant on the union thread
and sleeve shoulder only. No lubricant on the sealing surfaces (especially during pneumatic leakage
testing) is allowed.
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ISO 19631:2015(E)

3.5.1.2 Qualification inspection
Test assemblies shall consist of the parts specified in 3.5.1. Tests shall be conducted in accordance with
Table 11 and with ISO 10583 for each size and material for which qualification is required.
Fittings claiming conformity with this specification shall be considered qualified if they are
manufactured to the same dimensions, using the same materials and processes as products that have
successfully met the requirements and have passed the tests in this specification.
3.5.2 Proof pressure
When testing in accordance with ISO 10583:1993, 5.1, the test assembly shall withstand the proof
pressure specified in Table 3 without leakage, evidence of permanent deformation, or other malfunction
that might affect the ability to disconnect or connect the joint in the normal manner (to the interface
point by hand and then using the specified range of torque values).
Specimens to be proof tested are given in Table 11.
3.5.3 Gaseous pressure
When tested in accordance with ISO 10583:1993, 5.2, assemblies shall pass the gaseous pressure test to
the DOP specified in Table 3 without leakage or other failure.
Specimens to be gaseous pressure tested are given in Table 11.
3.5.4 Hydraulic impulse resistance
Six specimens shall be tested with the following distribution:
— 2 non aged specimens;
— 2 fuel aged specimens as per 3.5.16;
— 2 hydraulic fluid aged specimens as per 3.5.17.
When tested in accordance with ISO 6772 and ISO 10583:1993, 5.3, the test assembly shall
withstand, without leakage, 300 000 impulse pressure cycles with pressure peaks specified and
temperatures in Table 4.
Table 4 — Peak pressure and temperature
Peak pressure Peak pressure
Maximum ambient Minimum ambient tem-
temperature perature
% of nominal pressure kPa (psi)
52 500 +94 °C −40 °C
150
(7 620) (+201 °F) (−40 °F)
After hydraulic impulse test, three specimens (1 non aged, 1 fuel aged, and 1 hydraulic fluid aged) shall
be tested at nominal torque and pass the pressure tests as per 3.5.3 and 3.5.15.
For ma
...