ISO 13927:2023

INTERNATIONAL ISO
STANDARD 13927
Third edition
2023-08
Plastics — Simple heat release test
using a conical radiant heater and a
thermopile detector
Plastiques — Essai simple pour la détermination du débit calorifique
au moyen d'un radiateur conique et d'une sonde à thermopile
Reference number
ISO 13927:2023(E)
© ISO 2023

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ISO 13927:2023(E)
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© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
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ISO 13927:2023(E)
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Principle . 2
6 Apparatus . 2
6.1 General . 2
6.2 Cone-shaped radiant electrical heater . 4
6.3 Heat flux controller . 4
6.4 Chimney and thermopiles . . 5
6.5 Specimen holder . 5
6.6 Retainer frame . 5
6.7 Fume extraction system. 7
6.8 Ignition circuit . 8
6.9 Ignition timer . 8
6.10 Heat flux meter . 8
6.11 Calibration burner . 8
6.12 Data collection system . . 8
7 Suitability of a product for testing .10
7.1 Surface characteristics . 10
7.2 Asymmetrical products . 10
7.3 Thin materials . 10
7.4 Composite specimens . 10
7.5 Dimensionally unstable materials . 10
7.6 Materials that require testing under compression . 11
8 Specimen construction and preparation .12
8.1 Specimens .12
8.2 Conditioning of specimens .12
8.3 Preparation . 13
8.3.1 Specimen wrapping .13
8.3.2 Specimen preparation .13
8.3.3 Preparing specimens of materials that require testing under compression.13
9 Calibration .14
9.1 Heater calibration . 14
9.2 Thermopile calibration . 14
9.2.1 General . 14
9.2.2 Initial calibration . 14
9.2.3 Daily calibration . . .15
10 Test procedure .15
10.1 General precautions . 15
10.2 Initial preparation .15
10.3 Procedure . 16
11 Precision .16
12 Test report .16
Annex A (normative) Calibration of the heat flux meter .18
Annex B (informative) Guidance notes for operators .19
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ISO 13927:2023(E)
Annex C (informative) Guidance on measuring mass loss during testing .20
Annex D (informative) Example of thermopile calibration — Relation of heat release and
thermopile output .21
Annex E (informative) Calculation of effective critical heat flux for ignition .23
Bibliography .24
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ISO 13927:2023(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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received
notice of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 4, Burning
behaviour, in collaboration with the European Committee for Standardization (CEN) Technical
Committee CEN/TC 249, Plastics, in accordance with the Agreement on technical cooperation between
ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 13927:2015), which has been technically
revised.
The main changes are as follows:
— the normative references have been updated to the latest editions (see Clause 2);
— use of mass flow rate of methane gas corresponding to the net heat of combustion for calibration of
the thermopile has been added in Clause 9;
— a new Annex D giving an example of thermopile calibration has been added and subsequent annex
has been renamed as Annex E.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
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ISO 13927:2023(E)
Introduction
Fire is a complex phenomenon; its behaviour and effects depend upon a number of interrelated factors.
The behaviour of materials and products depends upon the characteristics of the fire, the method of use
of the materials, and the environment in which they are exposed (see also ISO 13943).
A test, such as the one specified in this document, deals only with a simple representation of a particular
aspect of the potential fire situation, typified by a radiant heat source, and it cannot alone provide any
direct guidance on the behaviour or safety in fire (see ISO/TS 3814). A test of this type can, however,
be used for comparative purposes or to ensure the existence of a certain quality of performance (in
this case, heat release from a composite material or an assembly) considered to have a bearing on fire
performance generally. It would be wrong to attach any other meaning to performance in this test. The
attention of all users of this test is drawn to the warning that immediately precedes Clause 10.
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INTERNATIONAL STANDARD ISO 13927:2023(E)
Plastics — Simple heat release test using a conical radiant
heater and a thermopile detector
1 Scope
This document specifies a method suitable for the production control or product development purposes
for assessing the heat release rate of essentially flat products exposed in the horizontal orientation to
controlled levels of radiant heating with an external igniter. The heat release rate is determined by the
use of a thermopile instead of the more accurate oxygen consumption techniques. The time to ignition
and sustained flaming are also measured in this test. The mass loss of the test specimen can also be
measured optionally.
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.
ISO 291, Plastics — Standard atmospheres for conditioning and testing
ISO 5660-1, Reaction-to-fire tests — Heat release, smoke production and mass loss rate — Part 1: Heat
release rate (cone calorimeter method) and smoke production rate (dynamic measurement)
ISO 13943, Fire safety — Vocabulary
ISO 14697, Reaction-to-fire tests — Guidance on the choice of substrates for building and transport products
ISO 14934-3, Fire tests — Calibration and use of heat flux meters — Part 3: Secondary calibration method
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13943 and the following apply.
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/
3.1
flat surface
surface whose irregularity from a plane does not exceed ±1 mm
3.2
ignition
onset of sustained flaming (3.7)
3.3
material
single substance or uniformly dispersed mixture, for example, metal, stone, timber, concrete, mineral
fibre or polymer
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ISO 13927:2023(E)
3.4
orientation
plane in which the exposed face of the test specimen (3.6) is located during testing either vertical or
horizontal face upwards
3.5
product
material (3.3), composite or assembly, about which information is required
3.6
test specimen
representative piece of the product (3.5) which is to be tested together with any substrate or surface
treatment
Note 1 to entry: The test specimen may include an air gap.
3.7
sustained flaming
existence of flame on or over the surface of the test specimen (3.6) for a period of over 10 s
3.8
transitory flaming
existence of flame on or over the surface of the test specimen (3.6) for a period of between 1 s and 10 s
4 Symbols
t time to ignition (onset of sustained flaming), expressed in seconds (s)
ig
2
′′
q
heat release rate per unit area at 180 s after ignition, expressed in kilowatts (kW/m )
180
2

q′′
heat release rate per unit area at 300 s after ignition, expressed in kilowatts (kW/m )
300
2
q′′
maximum heat release rate per unit area, expressed in kilowatts (kW/m )
max
5 Principle
The heat release rate is assessed by measurement of the output of a thermopile located in a chimney
situated above a burning test specimen that is subjected to a known heat flux from a conical heater.
2
The output (in mV) is converted into heat release rate per unit area (in kW/m ) by use of a calibration
graph obtained previously by burning methane gas of known heat of combustion in the same apparatus.
Guidance is given in Annex B. The specimen mass loss rate during the test can also be measured by
continuously recording the specimen load cell output. Guidance is given in Annex C.
6 Apparatus
6.1 General
The test apparatus shall consist essentially of the following components: a cone-shaped radiant
heater, a chimney housing a thermopile, a load cell, a specimen holder, and a fume extraction system. A
schematic representation of the assembly is given in Figure 1. The individual components are described
in this clause.
Intoleranced dimensions are recommended values. Accrual dimensions of apparatus should be close to
the dimensions as much as practicable.
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ISO 13927:2023(E)
Dimensions in millimetres
Key
1 thermopile
2 chimney
3 cone heater
4 spark igniter
5 specimen
6 load cell (optional)
Figure 1 — Schematic drawing of apparatus
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ISO 13927:2023(E)
6.2 Cone-shaped radiant electrical heater
The active element of the heater shall consist of an electrical heater rod, capable of delivering 5 000 W
at the operating voltage, tightly wound into the shape of a truncated cone (see Figure 2). The heater
shall be encased on the outside with a double-walled, stainless-steel cone filled between the walls
3
with a refractory blanket of nominal thickness 13 mm and nominal density 100 kg/m . The heat flux
from the heater shall be maintained at a pre-set level by controlling the average temperature of three
thermocouples (type K stainless-steel sheathed thermocouples have provided suitable), symmetrically
disposed and in contact with, but not welded to, the heater element (see Figure 2). 1,0 mm to 1,6 mm
outside diameter sheathed (unearthed) thermocouples with an unexposed hot junction may be used.
2
The heater shall be capable of producing heat fluxes on the surface of the specimen of up to 75 kW/m .
The heat flux shall be uniform within the central 50 mm × 50 mm area of the exposed specimen surface
2
to within ±2 % for an irradiance of 50 kW/m .
The cone heater shall be provided with a removable radiation shield to protect immediately the
specimen from heat prior to the start of the test.
6.3 Heat flux controller
The heat flux control system shall maintain the average temperature of the heater element steady to
within ±2 °C.
Dimensions in millimetres
Key
1 inner shell
2 refractory-fibre packing
3 thermocouple
4 outer shell
5 spacer block
6 heating element
Figure 2 — Cross-sectional view through heater
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ISO 13927:2023(E)
6.4 Chimney and thermopiles
A circular cross-section chimney 600 mm ± 2 mm long and 115 mm ± 2 mm internal diameter
constructed from 1 mm-thick stainless steel shall be used to house the thermopiles. This shall be fixed
on top of the top-plate of the cone heater. The axis of the chimney shall coincide with the axis of the
cone heater.
Each thermopile shall consist of four 1,6 mm ± 0,2 mm outside diameter type K sheathed thermocouples.
The tips of the thermocouples shall be fixed 17 mm from the centreline of the chimney. The four
thermocouples shall be connected in series and the two ends shall be connected to the data collection
system.
A thermopile shall be housed within the chimney at a height of 550 mm above the cone top-plate and
the chimney penetration points shall be equally distributed about the circumference of the chimney.
Another thermopile shall be housed 275 mm above the cone top-plate and the chimney penetration
points are equally distributed across, about the circumference of the chimney.
The arrangement of the chimney and thermopiles is shown in Figure 1.
Both thermopiles shall be calibrated individually according to Clause 9.
6.5 Specimen holder
The specimen holder is shown in Figure 3.
The specimen holder shall have the shape of a square pan with an opening of (106 ± 1) mm × (106 ± 1) mm
and a depth of 25 mm. The holder shall be constructed from stainless steel with a thickness of
(2,4 ± 0,15) mm. It shall include a handle to facilitate insertion and removal and a mechanism to ensure
central location of the specimen under the heater and proper alignment with the weighing device. The
distance between the bottom surface of the cone heater and the top of the specimen shall be adjusted
to 25 mm, except when testing dimensionally unstable materials, in which case, the distance shall be
adjusted to 60 mm ± 1 mm. All tests shall be conducted with the retainer frame shown in Figure 4.
Details of specimen and specimen holder preparation are given in 8.3.
6.6 Retainer frame
The frame shall be constructed of stainless steel with a thickness of (1,9 ± 0,1) mm in the shape of a
box with an inside dimension of each side (111 ± 1) mm and a height of (54 ± 1) mm. The opening for
2
the specimen face shall be (94,0 ± 0,5) mm as shown in Figure 4. The retainer frame shall have an
appropriate means to secure it to the specimen holder with a specimen in position.
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ISO 13927:2023(E)
Dimensions in millimetres
Figure 3 — Specimen holder
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ISO 13927:2023(E)
Dimensions in millimetres
Key
1 tapped holes in four places (M3 or 10 × 32 recommended)
Figure 4 — Retainer frame
6.7 Fume extraction system
The apparatus shall be used under a hood or in a fume cupboard with adequate ventilation to remove
safely combustion products from the laboratory.
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ISO 13927:2023(E)
6.8 Ignition circuit
Specimen ignition shall be accomplished by a spark plug powered by a 10 kV transformer or a 10 kV spark
generator capable of continuous sparking. The spark electrodes shall have a gap of 3 mm ± 0,5 mm. If
a transformer is used, it shall be of a type specifically designed for spark ignition use. The transformer
shall have an isolated (unearthed) secondary to minimize interference with the data transmission
lines. The electrode length and location of the spark plug shall be such that the spark gap is located
13 mm ± 2 mm above the centre of the specimen in the horizontal orientation.
6.9 Ignition timer
The timer shall be capable of recording elapsed time to the nearest second and accurate to within 1 s in
1 h.
6.10 Heat flux meter
The heat flux meter shall be of the Schmidt-Boelter (thermopile) type with a design range of up to about
2
100 kW/m . The target receiving radiation, and possibly to a small extent convection, shall be flat and
circular of approximately 12,5 mm in diameter and coated with a durable matt-black finish of surface
emissivity ε = 0,95 ± 0,05. The target shall be water-cooled, but care shall be taken that this does not
cause water condensation on the target surface of the meter.
Radiation shall not pass through any window before reaching the target. The instrument shall be
robust, simple to set up and use, and stable in calibration. The instrument shall also have an accuracy of
within ±3 % and a repeatability of within 0,5 %.
The calibration of the heat flux meter shall be checked whenever recalibration of the apparatus is
carried out, as described in Annex A or ISO 14934-3.
6.11 Calibration burner
+0 +0
The calibration burner shall consist of a square pan with a top opening of 100 mm × 100 mm,
() ()
−2 −2
constructed from stainless steel of thickness 2,4 mm ± 0,1 mm, and filled with sand. The burner shall
have a handle to facilitate insertion and removal, and a mechanism to ensure central location of the
burner under the heater and proper alignment with the weighing device. The burner shall be designed
so that a metered supply of methane of at least 99,5 % purity can be introduced through a tube in the
side wall as shown in Figure 5. The flowmeter used to monitor the methane flow shall be one of the
following: a rotameter, a dry-test meter, a wet-test meter, or an electronic mass flow controller.
The distance between the bottom surface of the cone heater and the top of the calibration burner shall
be adjusted to 25 mm.
6.12 Data collection system
This system shall record the output from thermopile and the load cell (optional). It shall have an
accuracy of 0,01 % of the full-scale output of the load cell (if used) and shall be capable of recording
data every 5 s or less for at least 1 h and measuring temperature to a resolution of 0,5 °C.
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ISO 13927:2023(E)
Dimensions in millimetres
Key
1 square stainless-steel pan
2 sand, grain size approximately 1 mm to 2 mm
3 tube, inner diameter 8 mm
3
4 ceramic-fibre blanket, 100 mm × 100 mm × 12 mm, density approximately 100 kg/m
3
5 ceramic-fibre blanket, 50 mm × 50 mm × 22 mm, density approximately 100 kg/m
6 handle
Figure 5 — Typical calibration burner design
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ISO 13927:2023(E)
7 Suitability of a product for testing
7.1 Surface characteristics
A product having one of the following properties is suitable for testing:
a) an essentially flat exposed surface;
b) an irregular surface whose irregularity is evenly distributed over the exposed surface, provided
that
2
1) at least 50 % of the surface of a representative 100 mm area lies within a depth of 10 mm from
a plane taken across the highest points on the exposed surface, or
2) for surfaces containing cracks, fissures, or holes not exceeding 8 mm in width or 10 mm in
depth, the total area of such cracks, fissures, or holes at the surface does not exceed 30 % of a
2
representative 100 mm area of the exposed surface.
When an exposed surface does not meet the requirements of either a) or b), the product shall be
tested in a modified form, conforming as nearly as possible to the requirements giv
...