ISO/FDIS 23693-3

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ISO/DISFDIS 23693-3:2025(en)
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ISO/TC 92/SC 2
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Secretariat: ANSI
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Date: 20252026-01-08-06
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Determination of the resistance to gas explosions of passive fire
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protection materials — —
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Part 3: Style Definition
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Tubular and I-beam specimenssection substrates subject to elastic
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deformation only
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FDIS stage
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St l D fi iti
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All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
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may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
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Phone: + 41 22 749 01 11
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Website: www.iso.orgwww.iso.org
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Published in Switzerland
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ii
ISO/DISFDIS 23693-3:20252026(en)
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Contents
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Foreword . v
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1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Explosion loads . 2
5 Test methods . 4
5.1 General. 4
5.2 Method 1: measuring stagnation pressure and side-on overpressure . 4
5.3 Method 2: use of computation fluid dynamics (CFD) modelling . 11
6 Test specimens . 12
6.1 General. 12
6.2 Other section types . 13
7 Environmental conditions . 13
8 Instrumentation . 13
9 Test specification . 13
10 Data analysis . 13
11 Test acceptability criteria . 16
11.1 Test method 1 . 16
11.2 Test method 2 . 16
12 Test report . 16
Annex A (informative) Measurement of side-on overpressure . 18
Annex B (normative) Description of damage to PFP . 23
Bibliography . 25

Foreword . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Explosion loads . 2
5 Test methods . 3
5.1 Method 1: measuring stagnation pressure and side-on overpressure . 3
5.1.1 Testing with an instrumented tubular . 3
5.1.2 Testing without an instrumented tubular . 4
Figure 1 — Pressure gauge layout on an instrumented tubular . 4
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Figure 2 — Region in which pressure gauges can be located on instrumented tubular or I-beam
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specimens . 5
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Figure 3 — Pressure gauge layout on an instrumented I-beam – Flow impacting on web . 6
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Figure 4 — Pressure gauge layout on an instrumented I-beam – Flow impacting on flange. 6 Formatted: Font: 11 pt
5.1.3 Measuring side-on overpressure . 6
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iii
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Figure 5 — Pressure gauge layout with plane surface. 7
Figure 6 — Pressure gauge layout with streamlined housing . 7
5.2 Method 2: Use of computation fluid dynamics (CFD) modelling . 8
6 Test specimens . 8
6.1 Other section types . 9
7 Environmental conditions . 9
8 Instrumentation . 9
9 Test specification . 9
10 Data analysis . 9
Figure 7 — Analysis of overpressure profile . 10
Figure 8 — Drag Load Analysis . 11
11 Test acceptability criteria . 11
11.1 Test Method 1 . 11
11.2 Test Method 2 . 12
12 Test report . 12
Annex A (informative) Measurement of side-on overpressure . 13
A.1 General. 13
A.2 Transducer mounted on a surface . 13
A.3 Transducer mounted in a streamlined housing . 13
Annex B (informative) Description of damage to PFP . 16
B.1 General. 16
B.2 Displacement . 16
B.3 Discolouration . 16
B.4 Cracking . 16
B.5 Failure of adhesion . 16
B.6 Damage to fixings and cladding . 16
B.7 Crushing or tearing . 16
B.8 Failure of unsupported PFP . 17
Figure B.1 — Boxed in I-beam . 17
B.9 Movement of PFP relative to substrate . 17
B.10 Any other damage . 17
Bibliography . 18

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iv
ISO/DISFDIS 23693-3:20252026(en)
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Foreword
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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).
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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)
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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.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.
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This document was prepared by Technical Committee ISO/TC 92, Fire Safetysafety, Subcommittee SC 2, Fire
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ContainmentResistance.
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A list of all parts in the ISO 23693 series can be found on the ISO website.
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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. Formatted: Default Paragraph Font
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v
DRAFT International Standard ISO/DIS 23693-3:2025(en)

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Determination of the resistance to gas explosions of passive fire
protection materials — —
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Part 3:
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Tubular and I-Beam Specimenssection substrates subject to elastic
numbers
deformation only
1 Scope
This document describes methods for simulating the mechanical loads that couldcan be imparted to passive
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fire protection (PFP) materials and systems by explosions resulting from releases of flammable gas, Adjust space between Asian text and numbers
pressurized liquefied gas, flashing liquid fuels, or dust that can precede a fire.
These methods can be used to determine the resistance of passive fire protection materials to such events.
This standarddocument considers PFP materials applied to substrates that are subject to the combined effects
of pressure and drag that occur in the flow path of an explosion. This part of the standarddocument excludes
specimens wherebyin which the substrate is subject to plastic deformation or brittle failure
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 23693--1, Determination of the resistance to gas explosions of passive fire protection materials — Part 1:
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General requirements
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3 Terms and definitions
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For the purposes of this document, the following terms and definitions apply.
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ISO and IEC maintain terminology databases for use in standardization at the following addresses:
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3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
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— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
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3.1 3.1
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congested region
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< explosion test rig> region that is occupied by items that provide obstacles to flow ahead of the flame, thereby
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
increasing flame velocity, the rate at which energy is released, and the overpressure produced
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3.2 3.2
numbers
drag load
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load on items resulting from the flow of gas generated by a gas explosion
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3.3 3.3
overpressure
difference between actual pressure and ambient pressure
3.4 3.4
pressure load
load on an object resulting from the overpressure (3.3)(3.3) generated by a gas explosion
3.5 3.5
projected area
part of the vent area that the instrumented test specimen covers
3.6 3.6
rise time
time for the pressure in a blast wave to rise to the peak overpressure (3.3)(3.3)
3.7 3.7
side-on overpressure
overpressure (3.3)(3.3) measured at right angles to the direction of travel of a blast wave
Note 1 to entry: It This can also be described as incident or free field overpressure.
3.8 3.8
stagnation pressure
pressure at a location perpendicular to and facing the direction of the flow, where the velocity of the explosion
gases havehas been reduced to zero
3.9 3.9
streamlined housing
housing that a pressure transducer can be mounted into that, which, if aligned with the direction of travel of
the blast wave and flow generated by a gas explosion that, allows the side-on overpressure (3.7) to be measured
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3.10 3.10
substrate
section to which the passive fire protection (PFP) materials are attached or mounted
4 Explosion loads
Methods for generating explosive loads are described in Part ISO 23693-1. Due to the nature of the specimen
being tested, it will be exposed to a combination of overpressure and drag loads. Pressure loads come from
the overpressure generated by the explosion; the drag loads are generated by the high velocity gas flow around
the object. To ensure that PFP systems applied to this type of object can survive a gas explosion it is necessary
to test them against a combination of pressure and drag loads.
To achieve a combination of drag and pressure and drag loads, the test specimen shall be located in, or near,
the vent of a confined gas explosion or at the edge of the congested region of an unconfined gas explosion,
where the velocity of the gas flow will produce a drag load.
The pressure load is obtained by measuring the side-on overpressure.
Drag load is characterisedcharacterized either by measuring the stagnation pressure on an instrumented
tubular positioned so as to receive the same drag load as the specimen being tested or by instrumenting the
specimen being tested. When the instrumented tubular is used, it shall be located in the same position as the
specimen during a calibration test conducted under the same test conditions.
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The drag load on an object in a flow is given by Formula (1):Formula (1):
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D = C A p (1)
L D dyn
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Where:
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D drag load, N;
L
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CD drag coefficient of object;
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3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
A projected area of object normal to flow direction, m ;
pdyn dynamic pressure, N/m .
where
DL is the drag load, in newtons (N);
CD is the drag coefficient of object;
A is the projected area of object normal to flow direction, in square metres (m );
p is the dynamic pressure, in newtons per square metre (N/m ), and is calculated using Formula (2):
dyn
pdyn = ρu /2 (2)
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where
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ρ is the gas density, in kilograms per cubic metre (kg/m );
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u is the flow velocity, in metres per second (m/s). stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
where:
ρ Gas density, kg/m
u Flow velocity, m/s
It is difficult to know the actual drag coefficient of an object as it changes with shape, orientation, flow velocity
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and flow conditions. When computer programmesprograms that model the effects of a gas explosion calculate
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drag load they typically assume a C C of unity, so drag load is equal to the dynamic pressure.
d D
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When conducting gas explosion trials, the dynamic pressure can be calculated from the measured stagnation
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pressure and side-on pressure using Formula (2):Formula (3):
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p = p – p (23) Formatted: Adjust space between Latin and Asian text,
dyn stag side
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p stagnation pressure, N/m ;
stag
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p side-on pressure, N/m .
side
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NOTE1: thewhere
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pstag is the stagnation pressure, in newtons per square metre, (N/m ); Formatted: Font: 10 pt
pside side-on pressure, in newtons per square metre, (N/m ).
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NOTE 1 The actual drag load on an object is dependent both on the flow velocity and the drag coefficient of the object.
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The drag coefficient is dependent on the geometry and orientation of the object being considered.
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NOTE2: NOTE 2 This document does not consider bending/ or deflection of samples. It should not beIf used for rating
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PFP performance of bending and deflection without, it is necessary to perform additional analysis.
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Test laboratories should be aware of the significant potential hazards involved in gas explosion resistance
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testing and take appropriate steps to ensure the safety of all concerned. Adjust space between Asian text and numbers
5 Test methods
5.1 General
Two test methods are available, both designed to ensure that the required levels of overpressure and drag
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load are attained. The two methods are: Adjust space between Asian text and numbers
a) a) Method 1: quantifying the drag and pressure loads by direct measurement of the stagnation
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pressure and side-on overpressure.
b, c, … + Start at: 1 + Alignment: Left + Aligned at: 0
cm + Indent at: 0 cm
b) b) Method 2: using computational fluid dynamic modelling to simulate the gas explosion such that
the drag load and overpressure load on the specimen under test can be calculated.
These methods are described in 5.1 and 5.2:5.2 and 5.3.
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5.15.2 Method 1: measuring stagnation pressure and side-on overpressure
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5.1.15.2.1 Testing with an instrumented tubular
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An instrumented tubular shall have a minimum external diameter of 100 mm. Its external diameter shall be
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within ±20 % of the tubular diameter or I-beam depth of the specimen to be tested. For testing involving an I-
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beam section, the depth of the section is the dimension of the specimen measured perpendicular to the flow
direction and perpendicular to the span. The instrumented tubular shall have three pressure gauges mounted
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to measure the stagnation pressure of the flow, see Figure 1.Figure 1. The pressure gauges shall be mounted
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in the central 50 % of the length of the tubular spaced 100 mm apart, see Figures 1 and 2. (see Figures 1 and
2). If multiple specimens are to be tested then the same number of instrumented tubulars shall be required in
a calibration test and put in the same positions in which the specimens are to be mounted. When a calibration
test has been carried out using an instrumented tubular(s) the result of the test will be considered valid for
any specimen tested to the same test conditions. The calibration would only need to be repeated if there is a
change in the test conditions.
NOTE I-beam refers to I sections of any dimension.
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5.1.25.2.2 Testing without an instrumented tubular
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3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
If an instrumented tubular is not used then the specimen(s) being tested shall be instrumented to measure
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stagnation pressure. This shall be done without impairing the PFP systems being tested. If the test specimen
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is a tubular, the three pressure gauges shall be mounted as shown in Figures 1 and 2.Figures 1 and 2. If the
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specimen to be instrumented is an I-beam then three pressure gauges are to be mounted on it as shown in
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Figures 3 or 4Figures 3 or 4 depending on the orientation of the I-beam relative to the flow path.
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ISO/DISFDIS 23693-3:20252026(en) Formatted: Font: 11 pt, Bold
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Dimensions in millimetres
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3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
Key
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p stagnation pressure transducer
stag
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1 Direction of gas flow.
numbers
pstag stagnation pressure transducer
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1 direction of gas flow
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Figure 1 — Pressure gauge layout on an instrumented tubular
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Key
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1 instrumented tubular or specimen
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2 region in which pressure gauges can be located stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
3 supports
L length of instrumented tubular or specimen
1 instrumented tubular or specimen
2 region in which pressure gauges can be located
3 supports
L length of instrumented tubular or specimen
Figure 2 — Region in which pressure gauges can be located on instrumented tubular or I-beam
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specimens Asian text, Adjust space between Asian text and
numbers
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Dimensions in millimetres
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cm + 1.4 cm + 2.1 cm + 2.8 cm + 3.5 cm + 4.2 cm +
Key
4.9 cm + 5.6 cm + 6.3 cm + 7 cm
Y Section.
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d section depth
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1 Direction of gas flow
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Y section
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d section depth
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1 direction of gas flow
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Figure 3 — Pressure gauge layout on an instrumented I-beam – Flow impacting on web
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numbers
Dimensions in millimetres
Key
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Y Section.
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cm + 1.4 cm + 2.1 cm + 2.8 cm + 3.5 cm + 4.2 cm +
1 Direction of gas flow
4.9 cm + 5.6 cm + 6.3 cm + 7 cm

Z section
d section depth
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1 direction of gas flow
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Figure 4 — Pressure gauge layout on an instrumented I-beam – Flow impacting on flange
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5.1.35.2.3 Measuring side-on overpressure
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numbers
Side-on overpressure shall be measured using three pressure gauges either positioned:
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— On--— on a plane surface, (see Figure 5,Figure 5; the plane surface can be any suitably located horizontal or
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vertical surface.); or
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Or
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— Inin a suitable streamlined housingshousing aligned with the direction of flow, (see Figure 6.Figure 6).
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Methods for measuring side-on overpressure are described in Annex A.Annex A. If multiple specimens are
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being tested then it would only be necessary to measure side-on overpressure using three gauges, provided
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that the side-on overpressure measured is representative of that to which all the specimens are exposed.
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NOTE Additional gauges can be installed to measure the stagnation and side-on pressures, to provide redundancy.
Asian text and numbers
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stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
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Dimensions in metres
Key
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1 test specimen
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2 Direction of gas flow. stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
pside side-on overpressure transducer
1 test specimen
2 direction of gas flow
pside side-on overpressure transducer
Figure 5 — Pressure gauge layout with plane surface
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ISO/DISFDIS 23693-3:20252026(en) Formatted: Font: 11 pt, Bold
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Dimensions in metres
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Key
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1 test specimen
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2 Direction of gas flow. stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
pside side-on overpressure transducer
1 test specimen
2 direction of gas flow
pside side-on overpressure transducer
Figure 6 — Pressure gauge layout with streamlined housing
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5.25.3 Method 2: use of computation fluid dynamics (CFD) modelling
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If it is not practicable to measure stagnation pressure, the test configuration can be validated using a
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combination of explosion modelling and calibration tests. This combination of modelling and testing mustshall
provide sufficient evidence that the test configuration is suitable for determining if a specimen can withstand
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the required explosion loads.
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The explosion modelling shall be carried out using a computer program that employs Computational Fluid Formatted: Default Paragraph Font
Dynamicscomputational fluid dynamics (CFD). The CFD application shall output dynamic pressure in the form
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given in formula 1, section 4. Formula (1). The CFD code shall be a publicly or commercially available code,
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with published validation studies on its suitability for modelling of gas explosions, with reference to publicly
available test data. These tests shall be representative of the conditions being modelled.
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The modelling shall be carried out to determine the optimum arrangement to demonstrate that the flow field
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established prior to interaction with the specimen achieves the required drag parameter. Prior to interaction
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shall mean a minimum of one specimen diameter upstream of the specimen.
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Where an overpressure criterion is also specified, the CFD modelling shall be employed to ensure that both
the pressure and drag conditions are met.
When the required test conditions have been identified using the CFD modelling, then a calibration test shall
be carried out to confirm the overpressures calculated by the CFD modelling. The test conditions in the
calibration test shall be the same as those used in the CFD modelling. In the calibration test, the overpressure
generated in the test facility shall be measured at a minimum 3 locations. These shall be at positions that yield
good measurements of the overall static explosion pressure and may not be in locations that are significantly
influenced by blast wave reflections or flow effects. The measured peak overpressures and durations shall
agree with those calculated by the CFD modelling within ±15 %.
When the specimen is tested the overpressure shall be measured at the same locations as in the calibration
test, to confirm that the calibration conditions have been replicated. The measured peak overpressures and
durations shall be within ±15 % of those measured in the calibration test and shall not deviate by more than
±20 % from those estimated by the CFD modelling.
The calibration of a test configuration does not need to be repeated for tests on further specimens with the
same, or sufficiently similar, form and layout. Where the specimen dimensions are the same as previously
tested and all other aspects of the test configuration are the same, reference can be made to a calibration
process carried out previously. However, measurement of pressure shall be made to confirm that the
calibration conditions have been replicated in the test on the specimen.
6 Test specimens
6.1 General
PFP coatings or PFP dry fit systems shall be tested attached to a suitable test specimen. In a gas explosion,
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damage to the PFP is caused by a combination of the effects of the gas explosion on the test specimen and the Adjust space between Asian text and numbers
distortion of the test specimen resulting from the explosion loads applied to it.
NOTE Clause 6This clause describes the testing of specimens which are relatively rigid and unlikely to distort
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significantly. This part of the standard shall not beIf this clause is used to assess bending and deflection on the
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performance of PFP without, further analysis is necessary.
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3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
Test specimens of either a tubular or an I-beam shape may be tested. Any size tubular section of more than
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100 mm external diameter including the PFP may be used. Any I-beam section with a minimum size of 100 mm
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in either dimension including the PFP may be tested. An I-beam specimen may be mounted with its web either
parallel or perpendicular to the venting flow direction.
The specimen shall be located within the flow path of the explosion so that it is exposed to high velocity flow.
To achieve the required loading regime with a confined gas explosion, the specimen should be mounted in or
close to a vent. When the gas explosion is unconfined, the specimen should be located at the edge of the
congested region.
The length of the test specimen shall be chosen to suit the geometry of the test facility but shall not be less
than 2 m. Test specimens shall be rigidly supported only at their ends. For confined explosions the test
specimen(s) including coating or jacket shall not have a projected area of more than 30 % of the area of the
vent into which it is installed. If necessary, the test specimen(s) can extend beyond the edge of the vent.
The geometry of the gas explosion may allow more than one specimen to be exposed to the required loads and
if this is done, the spe
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