prEN 3475-408
(Main)Aerospace series - Cables, electrical, aircraft use - Test methods - Part 408: Fire resistance
Aerospace series - Cables, electrical, aircraft use - Test methods - Part 408: Fire resistance
This document specifies a method of testing the fire resistance of "fire-proof" electrical cables.
Luft- und Raumfahrt - Elektrische Leitungen für Luftfahrtverwendung - Prüfverfahren - Teil 408: Feuerbeständigkeit
No Scope available
Série aérospatiale - Câbles électriques à usage aéronautique - Méthodes d'essais - Partie 408 : Résistance au feu
Le présent document spécifie une méthode pour soumettre à essai la résistance au feu des câbles électriques ignifuges.
Aeronavtika - Električni kabli za uporabo v zračnih plovilih - Preskusne metode - 408. del: Požarna odpornost
General Information
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Standards Content (Sample)
SLOVENSKI STANDARD
01-junij-2023
Aeronavtika - Električni kabli za uporabo v zračnih plovilih - Preskusne metode -
408. del: Požarna odpornost
Aerospace series - Cables, electrical, aircraft use - Test methods - Part 408: Fire
resistance
Luft- und Raumfahrt - Elektrische Leitungen für Luftfahrtverwendung - Prüfverfahren -
Teil 408: Feuerbeständigkeit
Série aérospatiale - Câbles électriques à usage aéronautique - Méthodes d’essais -
Partie 408: Résistance au feu
Ta slovenski standard je istoveten z: prEN 3475-408
ICS:
29.060.20 Kabli Cables
49.060 Letalska in vesoljska Aerospace electric
električna oprema in sistemi equipment and systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2023
ICS 49.060 Will supersede EN 3475-408:2005
English Version
Aerospace series - Cables, electrical, aircraft use - Test
methods - Part 408: Fire resistance
Série aérospatiale - Câbles électriques à usage Luft- und Raumfahrt - Elektrische Leitungen für
aéronautique - Méthodes d'essais - Partie 408: Luftfahrtverwendung - Prüfverfahren - Teil 408:
Résistance au feu Feuerbeständigkeit
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee ASD-
STAN.
If this draft becomes a European Standard, 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.
This draft European Standard was established by CEN 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 CEN-CENELEC
Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 3475-408:2023 E
worldwide for CEN national Members.
Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Preparation of specimens . 4
5 Apparatus . 4
5.1 List of apparatus . 4
5.2 Burner . 4
5.2.1 Method A – Liquid combustible (kerosene) . 4
5.2.2 Method B – Gas combustible . 5
5.2.3 Burner calibration . 5
5.3 Test fixture . 7
5.4 Test fluids . 9
6 Method . 10
6.1 Preparation . 10
6.1.1 General. 10
6.1.2 Single core cable . 10
6.1.3 Multi core and screen cables . 11
6.2 Procedure . 11
7 Requirements . 13
European foreword
This document (prEN 3475-408:2023) has been prepared by the Aerospace and Defence Industries
Association of Europe — Standardization (ASD-STAN).
After enquiries and votes carried out in accordance with the rules of this Association, this document has
received the approval of the National Associations and the Official Services of the member countries of
ASD-STAN, prior to its presentation to CEN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 3475-408:2005.
EN 3475-408:2005:
a) Introduction of liquid burner requirements with test setup configuration.
1 Scope
This document specifies a method of testing the fire resistance of “fire-proof” electrical cables.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
EN 3909, Aerospace series — Test fluids and test methods for electrical and optical components and sub-
assemblies
ISO 2685:1998, Aircraft — Environmental test procedure for airborne equipment — Resistance to fire in
designated fire zones
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
4 Preparation of specimens
Six test specimens, 0,75 m minimum length, shall be selected at random from a quantity of cable.
5 Apparatus
5.1 List of apparatus
The following shall be required for this test: a burner, a burner calibration, a test fixture, and test fluids.
5.2 Burner
5.2.1 Method A – Liquid combustible (kerosene)
The burner shall be as described in ISO 2685:1998, Clause A.2 or any other burner or assembly of burners
satisfying the following conditions:
— liquid combustible type of kerosene shall be in accordance with EN 3909;
— the burner outlet shall be equipped with an extension of 318 mm, 152 mm high and 280 mm width;
— cable length exposed to the flame: 152 mm;
— flame characteristics as per ISO 2685:
— temperature: 1 100 °C ± 80 °C;
Published as AECMA Prestandard at the date of publication of this standard.
— heat flux density received by the calorimeter described in ISO 2685:1998, Annex B:
2 2
116 kW/m ± 10 kW/m .
5.2.2 Method B – Gas combustible
The burner shall be as described in ISO 2685:1998, Annex A or any other burner or assembly of burners
satisfying the following conditions:
— cable length exposed to the flame: 152 mm;
— diameter or width of the flame at the base of the burner(s) ≥ 2 D (D diameter of the cable under test);
— Flame characteristics as per ISO 2685:
— temperature: 1 100 °C ± 80 °C;
— heat flux density received by the calorimeter described in ISO 2685:1998, Annex B:
2 2
116 kW/m ± 10 kW/m .
5.2.3 Burner calibration
5.2.3.1 Temperature
5.2.3.1.1 Temperature measurement
The calibration in temperature of the burner consists of adjusting the mixing ratio of air and combustible,
until the flame is delivering a standard flame. A flame is characterized by its temperature and its heat
flux. As the quantitative value is directly dependent on the instrumentation, it is necessary to respect a
common tool to ensure uniformity between tests.
Before calibrating the burner, allow the apparatus to run for at least 5 min for stabilizing the heating
conditions.
During and after calibration, the burner shall not be extinguished until the end of the fire test.
The surface calibrated is only valid as long as the burner settings was not changed or turned off.
The temperature of each thermocouple shall be recorded at least every 5 s intervals during minimum
2 min.
5.2.3.1.2 Temperature measuring equipment
It is important that the temperature measuring equipment (including the thermocouple and the
acquisition tools) ensures an accuracy and compatible reactivity with the values sought.
The temperature-measuring tool is composed of thermal sensors placed in a manner that it ensures a
good overview of the flame temperature distribution without disturbing it.
The temperature measuring equipment shall have an allowable overall error of 1 % at 1 100 °C and shall
have a temperature range between at least from 900 °C to 1 200 °C.
The diameter of the thermocouple wire shall be between 0,6 mm and 1 mm.
The thermocouple shall have an exposed junction over at least 10 mm.
A thermocouple type K or N, unshielded (exposed probe) and non-aspirated, with a wire between 0,6 mm
and 1 mm, is compliant with this requirement.
5.2.3.2 Heat flux
5.2.3.2.1 Heat flux measurement
The heat flux, also known as the thermal flux, is defined as the rate of heat transfer per unit cross-sectional
area (kW/m ), and quoted “q”.
As the heat flux measured is directly dependent on the measuring tool, the measuring apparatus and heat
flux burner calibration shall be as described per ISO 2685:1998, Clause B.4.
5.2.3.2.2 Heat flux measuring equipment
A heat transfer tube device (also known as a continues flow calorimeter) shall be in copper and it is used
to measure the flame in heat flux.
The tube shall be in copper, the copper tube shall be set up without any type of backing plate behind it.
Prior each measurement, the exposed surface of the copper tubing shall be cleaned with a fine steel wool.
Inspect the tubing bore for corrosion and remove any scale of accumulation.
Since the temperature rise across the heat-transfer tube is small, it is necessary to have an accurate
thermocouple. The water temperature sensor shall be capable of measuring at least a delta of 0,1 °C.
Minimum segment length of calorimeter tube to be exposed to the flame during its calibration shall be
12 mm to control thermal flux density calibration “q” in kW/m as per the formula:
The heat flux density is to be calculated using the following method:
q ρ T − T
( )
Vc 21
q=
−3
37,7× 10 × L
where
q is the water volume flow rate in cubic meters per second;
V
r is the density of water in kilograms per cubic meter, at mean temperature (T + T )/2, or
1 2
approximately 1 000 kg/m ;
c is the specific heat capacity of water in kilojoules per kilogram Kelvin at the mean
temperature (T + T )/2, i.e. approximately 4,185 kJ/(kg⋅K);
1 2
T is the temperature of the water in degrees Celsius, averaged over time, at the entrance of
the heat transfer tube;
T is the temperature of the water in degrees Celsius, averaged over time, at the outlet of the
heat transfer tube;
L is the length in meters, of the portion of the tube exposed to the flame.
5.2.3.3 Burner calibrated distance
5.2.3.3.1 Burner for liquid combustible (kerosene)
Minimum axial distance “h” between the burner extension outlet extremity and the surface calibration of
device (calorimeter and thermocouple) shall 100 mm ± 10 % as per ISO 2685.
5.2.3.3.2 Burner for gas combustible
Minimum axial distance “h” between the burner extension outlet extremity and the surface calibration of
device (calorimeter and thermocouple) shall 75 mm. (−0; +5 mm to include tolerance Max) as per
ISO 2685.
Temperature measurement:
The calibration shall be a free burning calibration (i.e.: In the vicinity of the sensor, nothing shall perturb
the flame measurement).
From the t
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