EN 14090:2002

SLOVENSKI STANDARD
01-maj-2004
Space product assurance - Flammability testing for the screening of space
materials
Space product assurance - Flammability testing for the screening of space materials
Raumfahrtproduktsicherung - Brennverhaltenstest für die Auswahl von
Raumfahrtmaterialien
Assurance produit des projets spatiaux - Essai de flammabilité pour la sélection des
matériaux d'un projet spatial
Ta slovenski standard je istoveten z: EN 14090:2002
ICS:
13.220.40 Sposobnost vžiga in Ignitability and burning
obnašanje materialov in behaviour of materials and
proizvodov pri gorenju products
49.025.01 Materiali za letalsko in Materials for aerospace
vesoljsko gradnjo na splošno construction in general
49.140 Vesoljski sistemi in operacije Space systems and
operations
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 14090
NORME EUROPÉENNE
EUROPÄISCHE NORM
February 2002
ICS 49.025.01; 49.140
English version
Space product assurance - Flammability testing for the
screening of space materials
Assurance produit des projets spatiaux - Essai de Raumfahrtproduktsicherung - Brennverhaltenstest für die
flammabilité pour la sélection des matériaux d'un projet Auswahl von Raumfahrtmaterialien
spatial
This European Standard was approved by CEN on 26 December 2001.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2002 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 14090:2002 E
worldwide for CEN national Members.

Contents
page
Foreword. 5
Introduction . 6
1 Scope. 7
2 Normative references . 7
3 Terms, definitions and abbreviated terms . 7
3.1 Terms and definitions. 7
3.2 Abbreviated terms . 7
4 Test procedure . 8
4.1 Preparatory conditions . 8
4.1.1 Hazards, health and safety precautions . 8
4.1.2 Preparation of samples .8
4.1.3 Facilities . 8
4.1.4 Equipment. 9
4.2 Test methods . 9
4.2.1 Categories. 9
4.2.2 Screening tests . 10
4.2.3 Test 4: Configuration test method. 27
5 Quality assurance. 28
5.1 General. 28
5.2 Data. 28
5.3 Nonconformance. 28
5.4 Calibration . 28
5.5 Traceability. 28
Annex A (informative) Preparation and qualification of chemical igniters . 29
A.1 General. 29
A.2 Safety requirements . 29
A.3 Materials and equipment.29
A.3.1 Hexamethylenetetramine (HMT). 29
A.3.2 Anhydrous sodium metasilicate . 29
A.3.3 Gum arabic (acacia).29
A.3.4 Hammer mill. 29
A.3.5 Glove box with a temperature/humidity meter . 29
A.3.6 Bags  . 29
A.3.7 040 mesh screen. 29
A.3.8 Fume hood . 30
A.3.9 Respirator with organic canisters. 30
A.3.10 Deionized water . 30
A.3.11 250 ml burette. 30
A.3.12 Heavy duty electric mixer. 30
A.3.13 Spatula. 30
A.3.14 Plastic trays. 30
A.3.15 Conveyor belt. 30
A.3.16 Extruder . 30
A.3.17 Cutting tools . 30
A.3.18 Drying racks. 30
A.3.19 Desiccator and desiccant. 30
A.3.20 Scale .30
A.3.21 Plastic corrugated holder . 30
A.3.22 Certified breating air. 31
A.3.23 Voltage source. 31
A.3.24 90 mm, bare nickel chromium wire. 31
A.3.25 Calibrated ruler . 31
A.3.26 Test chamber. 31
A.3.27 Calibrated stop watch . 31
A.3.28 Soft bristled brush. 31
A.3.29 Plastic container (box) . 31
A.3.30 Foam corrugated wrap. 31
A.4 Grinding the igniter mix . 31
A.5 Weighing the igniter mix. 32
A.6 Adding water . 32
A.7 Extruding the igniters. 32
A.8 Curing, cutting and weighing the igniters . 33
A.9 Certifying the igniters. 33
A.10 Waste disposal . 34
A.11 Packaging and storing igniters . 34
Bibliography . 36
Figures
Figure 1 — Diagram of the equipment used to determine the oxygen concentration limit. 15
Figure 2 — Frame used to fix the sample . 16
Figure 3 — Sample holder. 17
Figure 4 — Sample holder. 18
Figure 5 — Samples from thermoplastic polymer materials. 19
Figure 6 — Test set up for flammability of electric wires under heated wire conditions at 25 % by
volume oxygen . 21
Figure 7 — General arrangement of modified burner and flame dimensions . 24
Figure 8 — General arrangement of apparatus for flammability test . 25
Tables
Table 1 — Description of test equipment (as per Figure 6). 22
Foreword
This document EN 14090:2002 has been prepared by CMC.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by August 2002, and conflicting national standards shall
be withdrawn at the latest by August 2002.
1)
It is based on a previous version originally prepared by the ECSS product assurance working group,
reviewed by the ECSS Technical Panel and approved by the ECSS Steering Board. The European Co-
operation for Space Standardization (ECSS) is a cooperative effort of the European Space Agency, Na-
tional Space Agencies and European industry associations for the purpose of developing and maintain-
ing common standards.
This standard is one of the series of space standards intended to be applied together for the manage-
ment, engineering and product assurance in space projects and applications.
Requirements in this standard are defined in terms of what shall be accomplished, rather than in terms
of how to organize and perform the necessary work. This allows existing organizational structures and
methods to be applied where they are effective, and for the structures and methods to evolve as neces-
sary without rewriting the standards.
The formulation of this standard takes into account the existing ISO 9000 family of documents.
Annex A is informative.
This standard includes a Bibliography.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the fol-
lowing countries are bound to implement this European Standard: Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,
Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom.

1)
ECSS-Q-70-21
Introduction
All non-metallic materials are inherently flammable, the degree to which this is true is dependant on the
chemical nature of the material itself and the environment to which the material is exposed. In the closed
environment of a manned spacecraft this can lead to a potentially dangerous situation and close control
is therefore required.
1 Scope
This European Standard specifies a multi-test procedure for the determination of the flammability char-
acteristics of non-metallic materials under a set of closely controlled conditions. The test procedure cov-
ers both individual materials and materials used in configuration. This standard describes a series of
tests to provide data for aid in the evaluation of the suitability of materials for use in a space vehicle crew
compartment. The data obtained are in respect to the ease of ignition and the flame propagation char-
acteristics of materials.
2 Normative references
This European Standard incorporates by dated or undated reference, provisions from other publications.
These normative references are cited at the appropriate places in the text, and the publications are
listed hereafter. For dated references, subsequent amendments to or revisions of any of these publica-
tions apply to this European Standard only when incorporated in it by amendment or revision. For un-
dated references the latest edition of the publication referred to applies (including amendments).
EN 13701, Space systems - Glossary of terms.
EN 14097, Space product assurance — Nonconformance control system.
ECSS-Q-20, Space product assurance — Quality assurance.
ECSS-Q-70, Space product assurance — Materials, mechanical parts and processes.
DIN 50050-1,Testing of materials; burning behaviour of materials; small burning cabinet.
ISO 6941:1984, Textile fabrics — Burning behaviour — Measurement of flame spread properties of ver-
tically oriented specimens.
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this European Standard, the terms and definitions given in EN 13701, ECSS-Q-70
and the following apply.
3.1.1
C
lim
minimum volumetric concentration of oxygen contained in an oxygen-nitrogen mixture, in the presence
of which a material can still combust after ignition from the bottom
3.1.2
flammability
measure of the ease with which a material is set on fire
3.2 Abbreviated terms
The following abbreviated term is defined and used within this standard.
Abbreviation Meaning
r.m.s. root-mean-square
4 Test procedure
4.1 Preparatory conditions
4.1.1 Hazards, health and safety precautions
Particular attention shall be given to health and safety precautions. A safety checklist is produced below.
a. Hazards to personnel, equipment and materials shall be controlled and reduced to a minimum.
b. Hazardous substances, items and operations shall be isolated from other activities.
c. Items and controls shall be so located that personnel are not exposed to hazards such as chemical
burns, electric shock, cutting edges, sharp points or toxic atmospheres.
d. Suitable warning and caution notes shall be provided in operations, storage, transport, testing, as-
sembly, maintenance and repair instructions and distinctive markings placed on hazardous items,
equipment or facilities for personnel protection.
4.1.2 Preparation of samples
4.1.2.1 Configuration of samples
Sufficient specimens of the material in their minimum thickness of intended use shall be submitted for
testing (for actual numbers see the individual test methods).
4.1.2.2 Cleaning
The cleaning and other treatment of the samples shall be the same as that to which the sample is sub-
mitted before incorporation into the spacecraft. Further cleaning or treatment shall not be carried out by
the test house.
4.1.2.3 Handling and storage
Contamination of the sample during handling shall be avoided by the use of, for instance, suitable pro-
tective gloves. In addition, samples shall be stored in a cleanliness-controlled area with an ambient tem-
perature of (22 ± 3) ºC and relative humidity of (55 ± 10) %. Coated surfaces shall be shielded from
contact by using polyethylene or polypropylene bags or sheets. Mechanical damage shall be avoided in
the standard way by packing the polyethylene- or polypropylene-wrapped test pieces in clean, dust- and
lint-free material.
Limited-life material shall be labelled with its relative shelf-life and date of manufacture, or date of deliv-
ery if date of manufacture is not known.
4.1.2.4 Identification
Materials submitted for testing shall be accompanied by a clear description of, for instance, the name
and nature of the material or processing.
4.1.3 Facilities
4.1.3.1 Cleanliness
The work area shall be clean and free of dust. Air used for ventilation shall be filtered to prevent con-
tamination of the workpieces by moisture, oil or dust.
4.1.3.2 Environmental conditions
a. Test process. Preferably the same as for conditioning (see below) unless otherwise stated.
b. Conditioning temperature. See 4.1.2.3 above. This can be achieved either in a conditioning
room, or by the use of desiccators filled with silica gel or a saturated salt solution.
NOTE A saturated salt solution of calcium nitrate gives approximately 51 % humidity at
the testing temperature.
4.1.3.3 Special utilities
Oxygen and nitrogen supplies (minimum purity 99,9 %).
4.1.4 Equipment
4.1.4.1 Test equipment
Suitable test equipment fulfilling the monitoring requirements detailed in the applicable test method shall
be available.
4.1.4.2 Special apparatus
As detailed in the applicable test method.
4.2 Test methods
4.2.1 Categories
Four test methods are included within this Standard. They can be divided into two different categories as
indicated below:
— Screening tests. These are the prime tests to be performed on a material to assess its basic ac-
ceptability or otherwise with respect to flammability. They are designed to test the material under
worst case test conditions, with respect to, for instance, environment, use, or thickness. Two tests
form the basis for acceptance or otherwise of most non-metallic materials (tests 1 and 2) but are
very different in the data generated. The choice of which test method should be used is depend-
ant on the project concerned and shall be specified within the business agreement. Test 3 is re-
lated specifically to wire insulation materials. Materials which meet the requirements of these tests
may be considered for general application, within the constraints of the test conditions used.
— Configuration test. Materials failing to meet the requirements of the applicable screening test
shall be subject to testing in configuration. Materials which are shown to be acceptable in this
manner may be accepted for restricted application, within the constraints of the test conditions
used. Materials which fail this test shall be subject to a deviation request. Examples are:

flammable adhesives where the use is to bond two non-flammable substrates together, or

flammable conformal coatings applied thinly to a non-flammable printed circuit board.
— These tests may be proposed related to the determination of such properties as
Additional tests.
flash and fire point, or heat of combustion. These shall, however, be decided on a case-by-case
basis.
4.2.2 Screening tests
2)
4.2.2.1 Test 1: Upward propagation test
a. Scope
The purpose of this test is to determine the flammability characteristics of candidate materials
supplied to a standard format when exposed to an ignition source applied at the bottom edge.
This test in general is applicable to NASA payloads (e.g. Space Station, STS). If the materials are
unavailable in the standard format then the test described in subclause 4.2.3 shall be followed.
b. Preparation of specimen
After visual inspection to verify that no cuts, abrasions or other flaws exist, the material samples
shall be prepared as follows:
1. films, fabrics, sheets and composites shall be tested in the “as received” condition. Samples
shall be cut in the form of rectangles 300 mm × 64 mm minimum. Foams and high-bulk materi-
als shall be tested in the “as applied” thickness and have the same minimum dimensions as
specified above;
2. primers, coating materials, paints and pressure-sensitive tapes shall be applied on the sub-
strate materials intended for use, if known. The coatings shall be applied in a thickness
equivalent to normal use and post-cured in accordance with prescribed manufacturing proc-
esses. If the spacecraft substrate is not available, the coatings shall be applied to 300 mm ×
60 mm × 0,075 mm aluminium panels;
3. the test specimens shall be conditioned at (22 ± 3) ºC and (55 ± 10) % relative humidity for
24 h before testing.
c. Test conditions: pressures and atmosphere
The test pressure and atmosphere shall be specified to represent the most hazardous atmos-
phere anticipated in the spacecraft.
d. Test equipment and apparatus

Chamber. The test chamber shall have a volume sufficient to ensure complete combustion of
the sample under test. It shall have therefore a minimum volume of 250 l and be suitably con-
structed to ensure safe operation. A window or viewing port for visual observation and record-
ing shall be included. Internal lighting should be installed. Suitable feed-throughs shall be
available for gas inlets, evacuation, venting to air, and electricity for ignition. Organic materials
used in the construction of the chamber shall be of a type that contribute little or no outgassing
to the chamber.

. Apparatus shall include a pressure gauge capable of measuring pressures
Pressure gauge
to an accuracy of 10 hPa.
2)
Based on NASA STD 6001 Test 1.

. Samples with sufficient rigidity or samples on substrates of sufficient rigidity
Sample holder
and which do not retreat from a heat source by distorting or violently shrinking may be sup-
ported using a simple clamp. Other samples shall be supported in a frame which holds them
taut. The sample holder shall be so constructed as to have the minimum influence on the re-
sult by conducting heat away from the sample.

Ignition source. Ignition of the sample shall be accomplished by employing a regulated en-
ergy source. The ignition source shall consist of a length of AWG 20 gauge Nichrome wire
which has a nominal resistivity of 2,3 /m, sufficient to wind a minimum of three turns of a
3)
Solid igniter or equivalent. The nominal diameter of this igniter is 3 mm with a length of 32
mm. The flame temperature is (1 100 ± 100) ºC and burns for a duration of (25 ± 5) s. The ig-
niter shall be activated by means of a regulated DC power source. The igniter shall be posi-
tioned 6 mm from the lower edge of the sample.
e. Propagation rate indicator
Propagation rate shall be observed and recorded visually in combination with manually activated
timing devices to determine the propagation rate between markers on a scale positioned on the
sample holder. Timing shall be started at the first visual indication of combustion and stopped
when the flame ceases to propagate upwards. Where appropriate it is also acceptable to record
the total burn time and remove the sample to measure the total burn length either directly or by
subtraction. In this case care shall be taken to avoid overestimating the burn length by measuring
soot deposits higher up the sample.
f. Pretest procedure
Before each series of tests the equipment shall be calibrated in the following manner:
1. set the pressure regulators on the oxygen and nitrogen lines 0,17 MPa - 0,21 MPa. Close the
valve for the oxygen inlet to the equipment and open the nitrogen valve. Adjust the flow to give
a rate of 100 ml/min through the analyser. The meter reading with only nitrogen flowing should
be 0 %. Adjust the calibration zero until this value is obtained;
2. repeat the procedure, but with the nitrogen flow off and only oxygen passing through the
equipment. The meter should now read 100 %. If this is not the case, then adjust the calibration
control to bring it to 100 %;
3. repeat steps 1. and 2. if necessary.
Instead of the method referred to above, bottles of calibrated gasses having the worst-case at-
mosphere may be used.
g. Test procedure
1. Adjust nitrogen and oxygen needle valves to produce the test atmosphere (step f.).
2. Place the sample in position in the chamber.
3. Place igniter in coil of Nichrome wire and place between electrodes in the chamber.
4. Evacuate chamber to below 1 400 Pa.
5. Fill chamber with test atmosphere.
6. Allow the sample to soak in the test gas mixture for a period of at least three minutes.
7. Start video recording.
3)
A suitable source of igniters is available from NASA White Sands test facility. In addition a method for the prepa-
ration of suitable igniters is included in annex A.
8. Apply current to the igniter until it ignites and then immediately stop the current.
9. Record whether the sample is non-combustible or self-extinguishing or burning.
10. Note combustion characteristics (e.g. nature and colour of flame, amount of smoke, burning
drops, sputtering, glowing combustion).
11. Record the maximum pressure reached in the chamber.
h. Acceptance criteria
Materials shall be considered non-combustible, or self-extinguishing if the combustion zone
propagates less than 150 mm into the sample with minimum-use thickness and the time of burn-
ing does not exceed 10 min. There shall be no sparking, sputtering, or dripping of flaming parti-
cles from the test sample. A minimum of three samples shall be tested. Failure of any of the three
constitutes failure of the material.
i. Test results
The following properties shall be recorded:

Complete description of sample tested, including trade name, manufacturer, chemical nature,
dimensions, test atmosphere and processing details.

Time, length and rate of burning. Observations concerning the nature of the flame noted in
step g. and percentage oxygen remaining at the end of test. If the oxygen concentration shows
a value lower by 20 % of the original test atmosphere a re-test shall be required in a larger test
chamber.
4.2.2.2 Test 2: Standard test method for the determination of the oxygen concentration limit
4)
during the combustion of polymer materials
a. Scope
This procedure shall be used to determine the concentration limit of oxygen (C ) during the com-
lim
bustion of candidate materials. The applicability of this test shall be specified in the business
agreement.

The oxygen concentration limit during the combustion of polymeric materials is defined as the
minimum volumetric amount of oxygen contained in the nitrogen-oxygen mixture, in the pres-
ence of which the material can still combust after ignition from the bottom.

The oxygen concentration limit shall provide a comparative evaluation of the tendency of
polymeric materials to burn and to assess the fire resistance of these materials.

The oxygen concentration limit during the combustion of polymer materials should be consid-
ered as one of the main indices characterizing the risk of fire which materials present before
being considered for use in environments containing various oxygen levels.
b. Description of the equipment
The oxygen concentration limit, during the combustion of polymer materials, is determined using
equipment of which a sketch is shown in Figure 1. This equipment shall comprise:

a test column mounted vertically (no. 1 in Figure 1) made of quartz glass with an inside di-
ameter of 75 mm and a height of 370 mm. Under the column a quartz tube is placed with an
inside diameter of 75 mm and a height of 70 mm, filled with a layer of glass balls 3 mm to
5 mm in diameter, which are used to distribute the gaseous mixture evenly over the section of
the tube (no. 5 in Figure 1);
4)
Based on RKK Energia test method ZZU.0336.028.

a sample holder (no. 2 in Figure 1) clamping the sample from the top in a vertical position at
the centre of the quartz tube. A frame (Figure 2) is used to grip fabric, foils or film samples;

a gas burner (no. 4 in Figure 1), a tube made of copper with an inside diameter of 2,5 mm,
placed along the axis of the quartz column and through the glass balls layer. The flame tem-
perature is 850 ºC; the height of the flame is 25 mm; the pressure is (17 ± 2) kPa;

a spark igniter consisting of two insulated electrodes is located on both sides of the gas burner
tube (no. 7 in Figure 1);

an analyser module comprising a mixing chamber and an oxygen gas analyser is installed in
the oxygen-nitrogen mix line (no. 10 in Figure 1). Range: 0 % - 25 % and 0 % - 100 %; Accu-
racy: ± 0,1 %, with a paramagnetic detector;

a pressure reducing valve, a flowmeter and an on-off valve are installed in the fuel gas line
(no. 9 in Figure 1);

a chronometer.
The tests are carried out with a suitable exhaust connected.
c. Samples
The following points are relevant in addition to those identified in step b.

Conditions relative to the production of samples from thermosetting polymer materials not
melting when burning:
 the materials shall be in the form of a small bar with a section of
(4 ± 1) mm × (10 ± 1) mm and a length of (200 ± 5) mm;
 for the tests on woven and film materials, natural and artificial leather the samples are
required in their thickness, (50 ± 1) mm wide and (200 ± 5) mm long. These samples
shall be used fixed in a metal frame (see Figure 4);
 for tests carried out on fibres which do not deform and do not melt when burnt, samples
are produced from these fibres in the form of braids (200 ± 5) mm long and with a linear
density equal to (5 ± 0,3) g/m (mass (1 ± 0,3) g).

Conditions relative to the production of samples from thermoplastic polymer materials which
melt when burning:
 samples in the form of a small bar with a section of (4 ± 1) mm × (10 ± 1) mm and a
length of (200 ± 5) mm are surrounded with glass fibres into a lattice work (see Figure 5);
 to produce samples from film materials which melt take a sheet one side of which is
equal to 200 mm (length of the sample) with a mass equal to (8 ± 1) g. Roll the sheet into
a compact roll, and surround with glass fibre to form a bar. The mass of the glass fibres
shall not exceed 1,6 g (20 % of the mass of the sample).

Tests of coatings deposited on metallic surfaces (undercoat, paint, enamel, varnish) shall be
carried out on samples in configuration simulating a portion of actual equipment and shall be
supported in the sample holder shown in Figure 3.
d. Preparation of the test equipment
1. Choose the regulating flow for nitrogen and oxygen so that by regulating the pressure reducing
valves the composition specified for the gaseous mixture can be obtained. Check the composi-
tion of the gaseous mixture using the gas analyser.
2. Enter into the test column (no. 1 in Figure 1) a mixture of oxygen and nitrogen as per that
specified, the flow monitored on the flowmeter being equal to (442 ± 44) cm /s which enables
an average volumetric speed of flow of the mixture of (10 ± 1) cm/s to be obtained in the tube
(no. 1 in Figure 1). Monitor the level of the oxygen content in the gaseous mixture by means of
the automatic gas analyser.
3. Light the gas burner and regulate the flow of combustible gas to 0,03 l/min - 0,05 l/min using
the flowmeter.
4. After having checked that the gas burner (no. 4 in Figure 1) is functioning properly, cut off the
supply of combustible gas to the burner followed by that of the nitrogen-oxygen mix.
e. Test procedure

Tests shall be carried out at room temperature.

The material sample shall be fixed in the relevant sample holder and placed in the test column
in the vertical position so that the bottom edge of the sample is 10 mm from the burner, and
such that the vertical axis of the sample coincides with the axis of the gas burner.

Enter the gaseous mixture into the system for at least 30 s.

Ignite the gas burner and adjust the flow of combustible gas to 0,03 l/min - 0,05 l/min, using
the flowmeter.

Once the sample has started to burn at a stable rate, but at the latest 60 s after the igniter
flame has caused ignition of the sample, cut off the supply of combustible gas to the burner;
measure the duration of combustion. While the sample burns maintain the composition and
flow of the gaseous mixture constant using the mixer.

If the sample burns over its whole length or if combustion lasts for at least 120 s, the test shall
be repeated with a lower concentration of oxygen.

When the anticipated value of the oxygen concentration limit is not known in advance, the first
test shall be carried out using only air. If the sample does not burn in air, a second test shall be
started with an oxygen concentration of 30 % - 35 %.

A new sample of material shall be used for each test.

In the subsequent tests the oxygen concentration of the gaseous atmosphere shall be varied
until the difference of the concentrations at which the sample burns or extinguishes is within
1 %.
f. Results

The oxygen concentration limit (C ) is expressed as a percentage and determined using the
lim
equation:
i.e. the arithmetic average of the concentration limit calculated as a function of the results of
unit measurements of (C ).
lim,i
At least five samples shall be used.

The results of the tests shall be entered in a report. This report shall contain:
 the trade name and chemical nature of the material, the production date of the material,
if known;
 the name of the manufacturer;
 a brief description of the nature of the sample (e.g. size, thickness);
 the oxygen concentration limits for each test taken separately and their average value;
 the date on which the tests were carried out.
1. Test column
2. Threaded shaft 4 mm
3. Sam
4. Gas burner
5. Diffuser place holder
6. Inox grid mesh 1 mm
7. Spark igniter
8. Insulating ceramic
9. Fuel gas line
10. O + N mix line
2 2
Figure 1 — Diagram of the equipment used to determine the oxygen concentration limit
25 mm

R 400 mm

250 mm
Arc 5 mm - 8 mm
3 mm

Clamping device: wire diameter 3 mm
46 mm
Drawing not to scale
Figure 2 — Frame used to fix the sample
5 mm
A A
210 mm
220 mm
3 mm
4 mm
5 mm
Tube
46 mm
6 mm × 1 mm

A - A
1 mm
R = 23 mm
Drawing not to scale
Figure 3 — Sample holder
 25 mm
4 mm
5 mm
210 mm
(milled 1/2  6mm)
A A
200 mm
(sample)
Sample on fabric
5 mm
40 mm
Tube
6 mm × 1 mm

Wire 3 mm

AA
Sample on fabric
Drawing not to scale
Figure 4 — Sample holder
(10 ± 1) mm
(50 ± 1) mm

(4 ± 1) mm
2 mm - 5 mm
2 mm - 5 mm
(200 ± 5) mm
(200 ± 5) mm
Glass fibre
<< 1 mm

2 mm - 5 mm
2 mm - 5 mm
2 mm - 5 mm
Drawing not to scale
Figure 5 — Samples from thermoplastic polymer materials
4.2.2.3 Test 3: Electrical wire insulation flammability test method
a. Scope
This test is designed to screen wire insulation for flammability characteristics. The test is limited to
gauges AWG 20 to AWG 10 with copper conductors and is limited to normal pressures with a
maximum oxygen concentration of volume fraction 25 %.
b. Preparation of specimens
Insulated wire samples shall be free of cuts, abrasions and other flaws as determined by close
visual inspection. Samples shall also be accompanied by full material identification as outlined in
subclause 4.1.2.4. Five specimens, each a metre in length, shall be cut consecutively from the
same coil of wire and shall be cleaned of foreign matter and residue, using a method compatible
with the insulation being tested. The specimens shall be conditioned prior to testing, at
(55 ± 10) % relative humidity and at a temperature of (22 ± 3) ºC for a period of at least 16 h.
Remove approximately 25 mm of the insulation from both ends of the test specimen, measure
and record the conductor resistance and ambient temperature, and position in the test chamber
following the test procedure set out in subclause f.
c. Test conditions: pressure and atmosphere
The test pressure and atmosphere shall be designated by the project office and shall represent
the most hazardous atmosphere anticipated in the spacecraft within the confines of the scope of
this test (see subclause a.).
d. Test equipment and apparatus

Chamber. The test chamber shall have a volume of at least 250 l and shall conform to
DIN 50050-1 with the height modified according to ISO 6941: 1984 (see Figure 6). Further
modifications shall include feed-throughs for the supply of the test atmosphere, an arrange-
ment for the diffusion of the test atmosphere to eliminate high flows, feed-throughs for air and
fuel gas for the burner, electricity for the sample and an arrangement for mounting the sample
under slight tension at 75º to the horizontal.

Electrical supply. The external electrical supply shall be capable of providing a large steady
DC current up to 100 A and shall include accurate voltage and current meters capable of
measuring the voltage drop across the wire and the current flowing through it to two decimal
places.

Resistance meter. A resistance meter capable of measuring resistances under 100  to an
accuracy of 0,01  shall be available.

Burner. The burner shall be of a Bunsen or Tirrill type, with a 9,5 mm bore modified to supply
an external supply of air to the burner collar (Figure 7).

Flame temperature. The flame temperature shall be (1 100 ± 100) ºC measured at a point
35 mm from the end of the burner barrel. This can be achieved with commercial grade fuel gas
(minimum 85 % purity) and forced air to produce a flame 75 mm high with an inner blue cone
of 25 mm.

Burner mounting. The burner shall be mounted perpendicular and at 30º to the vertical plane
of the specimen as shown in Figure 8.

Wire tension. The specimen shall be kept taut by suspension of a weight as shown in Fig-
ure 8. The value of the weight shall be such that no undue strain is placed on the wire and can
be adjusted to accommodate samples of different size and stiffness.

Visual record. Visual records shall be made and retained of all flammability tests. A timer shall
be so positioned that it is visible to the camera.
3 (V1)
Modification
as per
ISO 6941:
90º
75º
Seal
5(V2)
Filter
12 14
Figure 6 — Test set up for flammability of electric wires under heated wire conditions at 25 % by
volume oxygen
Table 1 — Description of test equipment (as per Figure 6)
Item no. Description Remarks
1 Test chamber DIN 50050-1, modified as per Figure 5
Volume of chamber = 250 l
2 Upper adapter — To open/close outlet of item 1
— Equipped with two outlets:

for sampling of gasses

for measurement of oxygen measurement
3 Shut-off valve V1 To open/close the line for oxygen measurement
4 Distribution unit For distribution of test atmosphere
5 Shut-off valve V2 To open/close the atmosphere inlet
6 Burner supply inlet Fuel gas/air supply for burner
7 Feed-through For electrical current load of test sample
8 Sample and burner as- 60º test
sembly
Burner 90º relative to wire
30º relative to vertical plane of specimen
9 Burner Bunsen/Tirrill burner type as Figure 7
Length of flame:75 mm
Length of cone: 25 mm
Temperature: (1100 ± 100) ºC
Measured: 35 mm above burner
External gas/air: fuel gas/air
10 Igniter Electrical, of the continuous spark type
11 Support structure Used for example:
— sample holder
— burner
— igniter
— electrical connectors
Design as Figure 8
The support structure does not influence the test atmosphere
distribution
12 Test atmosphere supply Gas mixture of nitrogen and oxygen ((25 ± 0,2) % volume frac-
tion of oxygen) at ambient conditions
Option 1: supply of pre-mixed gasses
Option 2: unit for mixing gasses from separate bottles
and measuring oxygen concentration (see item
14)
13 Flowmeter Capable of measuring 2 l/min - 25 l/min
14 Oxygen measuring unit (Optional)
15 Electrical power source Capable of providing a large steady DC current (e.g. 0 A -
100 A) sufficient to raise the condu
...