ISO 21843:2023

Determination of the resistance to hydrocarbon pool fires of fire protection materials and systems for pressure vessels

This document specifies a test method for determining the fire resistance of pressure vessels with a fire protection system when subjected to standard fire exposure conditions. It does not address vessels cooled by water deluge or water monitor. The test data thus obtained permits subsequent classification on the basis of the duration for which the performance of the pressure vessel under these conditions satisfies specified criteria. The design of the pressure vessel is not covered in this document.

Détermination de la résistance aux feux de nappe d'hydrocarbure des matériaux et systèmes de protection incendie des récipients sous pression

General Information

• Status: Published
• Publication Date: 12-Jan-2023
• ICS: 13.220.50 - Fire-resistance of building materials and elements
• Technical Committee: ISO/TC 92/SC 2 - Fire containment
• Drafting Committee: ISO/TC 92/SC 2 - Fire containment
• Current Stage: 6060 - International Standard published
• Start Date: 13-Jan-2023
• Due Date: 24-Jul-2023
• Completion Date: 13-Jan-2023

Relations

• Revises: ISO 21843:2018 - Determination of the resistance to hydrocarbon pool fires of fire protection materials and systems for pressure vessels
• Effective Date: 06-Jun-2022

Overview

ISO 21843:2023 specifies a laboratory test method to determine the resistance of fire protection materials and systems on pressure vessels when exposed to standard hydrocarbon pool fires (unconfined pool fires fueled by LPG and petroleum distillates). The standard produces test data that permit classification based on the duration for which the vessel performance satisfies specified criteria. It does not cover vessel design or vessels cooled by water deluge or water monitors.

Key technical topics and requirements

• Test principle and equipment: Defines burner arrangement, fuel supply, test fluids and the test building required to reproduce representative hydrocarbon pool-fire exposure.
• Calibration tests: Procedures to confirm that the burner arrangement and test setup meet the standard’s exposure conditions prior to customer tests.
• Instrumentation: Requirements for thermocouples, directional flame thermometers (DFTs), pressure transducers and other sensors to measure wall temperature, radiation-convection balance and internal pressure.
• Test specimen construction: Guidance for preparing pressure vessel specimens and for affixing thermocouples (see normative Annex C).
• Performance criteria and classification: Criteria based on substrate temperature rise, coatings/spray-applied materials behavior, and pass/fail duration. Classification options include temperature-rise-based and duration-before-failure approaches (Clauses 17 and 19; Annex E).
• Data quality and analysis: Addresses repeatability, reproducibility, uncertainty of measurement and reporting requirements.
• Practical test controls: Includes rules for test termination, handling failures of sensors, and environmental tolerance limits.
• Informative annexes: example piping and instrumentation diagrams, DFT descriptions, radiation-convection balance guidance and additional classification procedures.

Practical applications and who uses it

ISO 21843:2023 is intended for:

• Fire test laboratories conducting hydrocarbon pool-fire resistance tests on pressure vessels and fire protection systems.
• Manufacturers of fire protection materials and thermal insulation systems seeking validated performance data for product development and certification.
• Oil & gas, petrochemical and LPG facility owners/operators who need evidence of fire protection performance for pressure vessels, storage spheres, and tanks.
• Regulatory bodies and certification agencies that require standardized test evidence for safety approvals and procurement specifications.
• Fire safety engineers and consultants specifying protection schemes, selecting materials or using test-based classifications for risk assessments.

Related standards and guidance (context)

• ISO 21843 is part of ISO/TC 92 work on fire safety (fire containment). It complements laboratory fire test standards and industry practices for hydrocarbon fire exposure, instrumentation and classification procedures referenced in its annexes.

Keywords: ISO 21843:2023, hydrocarbon pool fires, fire resistance test, pressure vessels, fire protection systems, directional flame thermometer, calibration test, classification.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 21843
Second edition
2023-01
Determination of the resistance
to hydrocarbon pool fires of fire
protection materials and systems for
pressure vessels
Détermination de la résistance aux feux de nappe d'hydrocarbure
des matériaux et systèmes de protection incendie des récipients sous
pression
Reference number
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 3
5 Principle . 4
6 Test equipment .4
6.1 General . 4
6.2 Burner arrangement . . 5
6.3 Fuel supply for burners . 5
6.4 Test fluids . 5
6.5 Test building . 5
7 Calibration tests . 5
7.1 General requirements . 5
7.2 Calibration test vessel construction . 6
7.3 Calibration test procedure . 7
7.4 Analysis of test data . 9
7.5 Requirements for successful calibration tests . 9
7.6 Environmental conditions . 10
7.7 Tolerances . 10
7.8 Calibration and test report . 11
8 Construction of fire test specimens .12
9 Instrumentation .12
10 Fire protection materials and systems .14
10.1 General . 14
10.2 Applied fire protection materials . 14
10.3 Assemblies and mounted fire protection systems . 16
11 Test procedure .16
12 Termination of the test.17
13 Repeatability and reproducibility .17
14 Uncertainty of measurement .17
15 Test report .17
16 Practical application of test results .18
16.1 Pressure relief valve (PRV) . 18
16.2 Propane (or alternative test fluid) fill level . 19
17 Performance criteria .19
17.1 General . 19
17.2 Substrate temperature . 19
17.3 Coatings and spray-applied materials . 19
17.4 Systems and assemblies . 20
18 Factors affecting the validity of the test .20
18.1 Interruption of the test .20
18.2 Failure of TCs and DFTs . 20
18.3 Failure of pressure transducers . 21
18.4 Test-related tube and pipe . 21
iii
18.5 Variation in environmental conditions . 21
18.6 Directional flame thermometer (DFT) results . 21
19 Recommended classification procedures .22
19.1 General .22
19.2 Type of fire . 22
19.3 Type of application . 22
19.4 Classification based on temperature rise and period of resistance .22
19.5 Classification based on duration before failure . 22
Annex A (informative) Example piping and instrumentation diagram for test facility .23
Annex B (informative) Directional flame thermometers (DFTs) .25
Annex C (normative) Method of affixing thermocouples .26
Annex D (informative) Radiation-convection (R-C) balance .27
Annex E (informative) Additional classification procedures: Classification based on
duration before failure . .29
Bibliography .34
iv
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation 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 92, Fire safety, Subcommittee SC 2, Fire
containment.
This second edition cancels and replaces the first edition (ISO 21843:2018), which has been technically
revised.
The main changes are as follows:
— the calibration conditions have been modified;
— an alternative method for confirming test conditions has been provided.
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.
v
Introduction
This document describes a test procedure for assessing the protection afforded by fire protection
materials and systems to pressure vessels. It gives an indication of how fire protection materials
perform when exposed to a set of specified fire conditions. Actual vessels can vary in construction from
that tested and can utilize additional protection systems. The test conditions have been shown to be
representative of the severity of unconfined pool fires fuelled by light and medium oil distillates such as
liquefied petroleum gas (LPG) and petroleum products.
vi
INTERNATIONAL STANDARD ISO 21843:2023(E)
Determination of the resistance to hydrocarbon pool fires
of fire protection materials and systems for pressure
vessels
1 Scope
This document specifies a test method for determining the fire resistance of pressure vessels with a
fire protection system when subjected to standard fire exposure conditions. It does not address vessels
cooled by water deluge or water monitor. The test data thus obtained permits subsequent classification
on the basis of the duration for which the performance of the pressure vessel under these conditions
satisfies specified criteria. The design of the pressure vessel is not covered in this document.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
blowdown valve
BDV
blowdown device
valve or device that opens to depressurize a pressure vessel
EXAMPLE Fusible plug.
3.2
burner arrangement
configuration of the equipment designed to engulf the test specimen in fire, with specific reference to
the size, orientation, frequency and spacing of burner heads, and the design of fuel supply piping
3.3
burst pressure
calculated burst pressure
pressure at which the vessel is expected to fail based on the known vessel and material
properties and the peak wall temperatures
Note 1 to entry: The burst pressure depends on how quickly and severely the vessel is heated. One approximate
estimate of the burst pressure is that pressure that gives a hoop stress equal to the yield strength of the vessel
material at the specific wall temperature of interest.
Note 2 to entry: Other failure criteria can be more appropriate. For long duration tests, high temperature stress
rupture analysis is also considered a realistic failure mode.
3.4
calibration test
test performed by the laboratory prior and separate to customer tests, to confirm that the chosen burner
arrangement in combination with the desired test specimen conforms to the required conditions of this
document
3.5
critical pressure
pressure calculated for a given critical wall temperature as the burst pressure divided by a factor of
safety (FOS)
3.6
critical temperature
design limiting temperature, or a specified limiting wall temperature, that the vessel wall temperature
is required not to exceed during fire exposure
Note 1 to entry: This temperature is related to a factor of safety (FOS) for the vessel when exposed to fire.
3.7
directional flame thermometer
DFT
passive thermocouple-based sensor that can be used for the estimation of the fire-effective blackbody
temperature and radiation convection balance
Note 1 to entry: Various designs are available. A simple design is described in this document.
3.8
factor of safety
FOS
ratio of the actual burst pressure of the vessel at the temperature of interest (e.g. critical temperature)
divided by the actual working pressure in the vessel
Note 1 to entry: A typical FOS at ambient temperature conditions is in the range of 2 to 3.
3.9
fire protection system
thermal protection system
protection afforded to the vessel to reduce the rate of heat transfer from the fire to the vessel, throughout
the period of exposure to fire, including any protection materials together with any encasement (such
as a jacket), and supporting system (such as mesh reinforcement or a framing system) and any specified
primer and top coat if applicable
Note 1 to entry: Often referred to as a thermal protection system in North America.
3.10
pool fire
hydrocarbon diffusion fire that occurs over a static or flowing release of flammable liquids
Note 1 to entry: It simulates large turbulent diffusion flames that are strongly radiating.
3.11
pressure relief valve
pressure safety valve
PRV
pressure-activated valve intended to limit pressure rise to a specified value
Note 1 to entry: These valves have set opening and reclosing pressures.
3.12
pressure vessel
vessel capable of containing pressures significantly above ambient, even if normal operational
procedure does not involve pressure rise above ambient
Note 1 to entry: Pressure vessels are often referred to as vessels or tanks.
3.13
radiation-convection balance
fraction or percentage of the total heat transfer to a cool surface that is due to thermal radiation
Note 1 to entry: The cool surface may be a water-cooled calorimeter at a temperature of under 120 °C.
3.14
test-related tube and pipe
additional tube or pipe added to the vessel for the purposes of performing the tests
Note 1 to entry: These can potentially not be present on the real application vessel.
3.15
vessel shell
primary wall of the vessel
4 Symbols
ΔT vessel shell temperature, at time m, assumed to be equal to ΔT
S,m w,m
ΔT result of T − T
w,m w,m w,0
A surface area of vessel shell
S
c specific heat capacity of steel
s
c specific heat capacity of water
w
e Euler's number
f radiation fraction
rad
h convection heat transfer coefficient
L length
L intermediate length
int
m mass of steel
s
m mass of water
w
P pressure
P measured pressure
m
P burst pressure based on the ultimate tensile strength
u
P burst pressure based on the yield strength
y
q convection component (heat flux due to convection)
conv
q net heat flux
net
q radiation component (heat flux due to radiation)
rad
r radius
T ambient temperature
amb
T calorimeter temperature
cal
T directional flame thermometer temperature
DFT
T flame temperature
f
T temperature of thermocouple n at time m.
n,m
T average water temperature at time m;
w,m
t time
t duration of test (time of termination)
T
mean average
X
ε fire emissivity
f
ε surface emissivity
s
−8 −2 −4
σ Stefan-Boltzmann constant (5,67 × 10 W·m ·K )
t time
5 Principle
The method described in this document provides an indication of how vessels protected with fire
protection materials or systems perform when exposed to pool fires on solid surfaces. It simulates the
thermal loads to a vessel engulfed in a large pool fire through the use of burners to create a flame
capable of engulfing a vessel. To ensure that suitable test conditions are achieved and maintained, it
describes calibration tests to be performed prior to fire testing, sets permitted tolerances from the
calibrated set-up, and delimits environmental conditions.
6 Test equipment
6.1 General
The test procedure is intended to simulate a liquid hydrocarbon pool fire that achieves a steady heat
2 2
flux to a cool surface of 90 kW/m to 120 kW/m over a specified period of time.
NOTE Literature suggests that heat flux to a cool surface in a large liquid hydrocarbon pool fire is 80 % to
90 % due to thermal radiation and the remainder is by convection.
An example piping and instrumentation diagram for a vessel testing facility is shown in Annex A. Test
equipment employed in the conduct of the test consists essentially of the following:
a) a specially designed burner arrangement to subject the test specimen to the conditions specified in
the calibration section;
b) propane storage capable of fuelling the test for the required duration;
c) equipment to control and monitor the propane flow rate throughout the test;
d) equipment to vent and purge the vessel after testing.
Test laboratories should be aware of the significant potential hazards involved in pressure vessels
testing. Facilities intending to undertake tests in accordance with this document should be designed to
be safe in the event of vessel failure.
6.2 Burner arrangement
This test procedure uses liquid-propane-fuelled burners to simulate a pool fire. Burners are used
because they provide more control over the test conditions. The burner system shall be designed to
produce a low momentum and luminous fire of sufficient thickness so that the resulting heat flux is
predominantly by radiation (i.e. radiation fraction greater than 75 %).
To simulate pool fire conditions a burner system shall be used. Burners shall be designed to achieve
total engulfment and uniformity of heating and shall be present on all four sides and both ends of the
vessel. The maximum nozzle spacing shall be no greater than 0,5 m.
The burner design can be varied by the test laboratory to meet the calibration requirements; for
informative purposes, an example of burner design is shown in Annex A.
The burner arrangement shall be designed to receive equal mass flow rates of propane to two
diametrically opposite locations at the ends of the vessel to ensure broadly symmetrical heating.
The supply line length and fittings shall also be designed to ensure equal propane flow to the burner
arrangement and all supply lines. Cooling of the supply shall be provided as necessary to protect the
burner supply for the duration of the test. The burner system shall be designed to ensure stabilization
of the fuel flow rate and stabilization of the flame temperatures [as defined by directional flame
thermometers (DFTs) in Clause 9 and Annex B] within 2 min of the flame ignition and test commencing.
6.3 Fuel supply for burners
The burner system fuel shall be commercial propane or LPG. The fuel supply shall be capable of
delivering up to 1,2 kg/s to the burner arrangement and controlling the flow rate to within ±0,05 kg/s
of the target flow rate as determined by calibration testing.
6.4 Test fluids
The test fluid for the test vessel shall be commercial propane or LPG or any other fluid specified by the
sponsor. Means of filling the test vessel (including air purge) prior to a test, and purging the vessel after
the test to allow safe inspection, shall be provided. Equipment to pump or push liquid propane from
the test vessel back to a storage vessel after the test may be utilized. A means of determining the total
propane loss from the test vessel throughout the test shall be available.
6.5 Test building
Large-scale exterior fire tests are subject to environmentally-induced variations due to wind. Stricter
tolerances in deviation from the as-tested environmental conditions are imposed for testing if the test
is not protected from the environment through the use of an enclosure in the form of a shed or building.
These tolerances are described in 7.7.
If used, environmental protection shall be suitably enclosed on all four sides and have full roof coverage.
Openings for ventilation shall be equally distributed and sized, so far as is practicable.
7 Calibration tests
7.1 General requirements
Due to the variations involved in external large-scale testing, it is required to successfully perform
three calibration tests before a particular fire burner system and test configuration is considered
suitable as the basis for fire testing.
The net heat flux to a water-filled vessel shall be determined and DFTs shall be used to assess both
the uniformity of heating and the radiation-convection balance. A thermal imager shall also be used to
confirm uniformity of heating and radiation-convection balance in the calibration tests. See Annex D for
methods to estimate the radiation-convection balance. All three tests shall be performed in accordance
with 7.2 and 7.3 and shall use the same vessel, burner configurations and test parameters.
The calibration test results shall be assessed in accordance with 7.4. Once a test configuration has
met the requirements in 7.5, it shall be considered suitable for testing of actual test specimens in
environmental conditions as defined in 7.6. The tolerances in variation from the calibration test set up
during actual fire testing are given in 7.7.
Calibration testing should be repeated in the event of any modifications to the test specimen beyond
the permitted tolerances in 7.7, any modifications to the burner or nozzle arrangement or propane flow
rate, any significant modifications to the test equipment or test building, or any departure from the
environmental conditions as defined in 7.6.
Calibration tests shall be performed at least every three years, even in the event of no changes as
listed above, to ensure equipment functions as intended. Calibration test results shall be written
up as calibration reports as described in 7.8 and retained by the test laboratory for reference when
conducting future fire tests.
7.2 Calibration test vessel construction
The calibration vessel shall be manufactured according to appropriate pressure vessel regulations. It
shall have a minimum diameter of 1 200 mm, and a minimum length of 2 000 mm. The vessel shall be
supported on two steel saddles, which shall be insulated or water-cooled. No fire protection materials
or system shall be installed on the calibration vessel shell.
An appropriately sized vent shall be cut at the top of the vessel to permit extraction of thermocouples
(TCs) and to prevent pressurization during calibration testing. An agitator shall be installed within
the vessel, located close to the middle to mix the water to maintain near uniform temperature. Only
connecting piping required for operation of the agitator is permitted, and this piping may be water-
cooled if necessary. Any covers or guards for gauges and connections shall be removed, and all
remaining connections shall be sealed.
The calibration vessel shell shall be instrumented with 16 DFTs. A simple design of DFTs is given as an
example in Annex B. DFTs shall be attached to the vessel facing out into the fire in locations shown in
Figure 1. Individual TCs that conflict with the position of lifting lugs or fittings may be moved by up to
0,15 m. TCs that conflict with saddles shall be moved horizontally towards the middle of the vessel until
they are at least 0,25 m from the saddle.
The calibration vessel shall be internally instrumented with 10 insulated type k TCs (1,5 mm minimum
diameter, 3 mm maximum diameter) for measurement of the water temperature. The internal TCs
shall be located at two stations 1/3 and 2/3 along the primary axis of the vessel between the tangent
lines (often referred to as tan lines) as shown in Figure 2. The TCs shall be spaced to measure the
temperature of five horizontal zones of equal volume. The vessel shall be filled 100 % with water and a
splash cover added to minimize splash cooling of the outer top surface of the vessel and DFTs during the
fire, without allowing pressurization of the vessel.
A thermal imager with an appropriate temperature range and resolution (at least 480 pixels × 240 pixels)
shall be used to view the fire to assist in the confirmation of radiation-convection balance.
Key
1 to 16 directional flame thermometer (DFT) positions
L length of cylindrical body part of vessel (tan to tan length)
L intermediate length, calculated using the following formula:
int
 1−e 
−1
Lr++1 tanh e
 
e
 
x
where e =
r
e Euler's number
x length from cylindrical body part of the vessel to the end of the vessel
Figure 1 — Calibration test vessel
7.3 Calibration test procedure
Unless explicitly stated otherwise, the calibration tests shall be performed in accordance with Clause 11.
The calibration tests shall be initiated with water at a maximum temperature of 30 °C. The calibration
tests terminated at the termination time (t ), defined as the time when the average water temperature
T
reaches 90 °C or the time when an individual water temperature reaches 95 °C, whichever is achieved
first.
The environmental conditions, including wind speed and precipitation in the vicinity of the test vessel
or exterior of the test building, shall be monitored throughout the test. Results from the calibration test
shall be reported along with detailed descriptions of the calibration vessel dimensions, environmental
conditions, fuel mass flow rate and burner configuration. The report shall be retained by the test
laboratory for future reference when setting up and conducting vessel fire tests.
Key
1 to 10 thermocouple positions
L length of cylindrical part body of vessel (tan to tan length)
a
9/10 fill.
b
7/10 fill.
c
5/10 fill.
d
3/10 fill.
e
1/10 fill.
Figure 2 — Internal thermocouple positions for the net heat flux test
7.4 Analysis of test data
Prior to analysis of test results, calculation is required of the mass of water in the vessel, the surface
area of the vessel shell, excluding the saddle contact area if insulated, and mass of the vessel shell
excluding saddles, lifting lugs and connections. The average water temperature at any given time shall
be calculated using Formula (1):
__ _ _ _
XXXTT,,+ TT + TT,,+X TT +X TT,
() () () (() ()
1,mm6, 2,mm7, 3,mm8, 4,m 9,m 5,mm10,
T = (1)
w,m
where
T is the average water temperature at time m;
w,m
T is the temperature of thermocouple n at time m;
n,m
denotes the mean average.
X
The average net heat flux to the vessel, q , shall be calculated for t in accordance with Formula (2):
net,av T
Δ+Tm cTΔ mc
S,mmss w, ww
q = (2)
net,av
tA
TS
where
ΔT is the vessel shell temperature, at time m, assumed to be equal to ΔT (°C);
S,m w,m
ΔT is the result of T − T (°C);
w,m w,m w,0
m is the mass of steel (kg);
s
m is the mass of water (kg);
w
−1 −1
c is the specific heat capacity of steel (J·kg ·K );
s
−1 −1
c is the specific heat capacity of water (J·kg ·K );
w
t is the duration of test (time of termination) (s);
T
A is the surface area of vessel shell (m ).
S
7.5 Requirements for successful calibration tests
For the purposes of calculating all of the test data, the start time of the test is the lower value of the
following:
a) the time when the flame reaches steady conditions [at approximately (871 ± 56) °C] as indicated by
the average temperature of all DFTs; or
b) the ignition time plus 120 s. The ignition time is defined when the average of all DFTs exceeds
200 °C. All DFT temperatures shall start below 50 °C before ignition.
A successful test requires the fire to reach and maintain steady conditions. The necessary conditions
are given in the list below. The properties in a turbulent diffusion flame vary with time and position in
the fire. At a fixed position in the fire these properties can be defined by a time averaged value plus or
minus a fluctuating component. Here, a steady fire is defined as being when the DFT temperatures for
all the measured positions in the fire fall within the ranges specified below.
For the calibration test to be valid, the following criteria shall be met during the contiguous steady
period of the fire test:
1) a minimum of 8 internal TCs shall be valid throughout the test;
2) a minimum of 13 DFTs shall be valid throughout the test;
3) a minimum of 2 DFTs shall be valid along the top of the shell throughout the test;
4) at least 1 DFT shall be valid on each side, the bottom and both ends throughout the test.
For the calibration test to be successful, the following criteria shall be met:
— the calculated area and time average net heat flux to a cool surface, q , shall be a minimum of
net,av
90 kW/m ;
— the time average of all valid T values shall be within the range 816 °C to 927 °C;
DFT
— 80 % of individual valid T values shall be within the range 816 °C to 1 100 °C;
DFT
— 95 % of individual valid T values shall be within the range 670 °C to 1 100 °C;
DFT
— the ratio of the average (reading in °C) of the valid DFTs along the top of the vessel to the average
(reading in degrees Celsius) of all valid direction flame thermometers shall be no lower than 0,85;
— the time average radiation-convection balance for a cool surface from all working DFTs shall be
greater than or equal to 75 %.
Brief excursions from this specification are acceptable as long as the sum of all of their durations is less
than 5 % of the test duration. The excursions shall be included in the averages.
Failure to meet the above requirements shall require the calibration test to be repeated using a modified
set-up or under different environmental conditions.
7.6 Environmental conditions
The wind speed and direction throughout all calibration tests shall be monitored and recorded at an
interval of 5 s or less and the average overtime calculated for each test respectively. The average wind
speed recorded on the calibration report as the maximum permissible shall be the maximum recorded
from the three calibration tests. Precipitation shall be recorded through a detailed description including
type and severity (e.g. dry, snow, light rain, heavy rain).
7.7 Tolerances
On successful completion of all calibration tests, the test configuration is considered suitable to
perform fire tests under the same conditions as reported during calibration tests. The test article will
be instrumented with DFTs to ensure the test meets the required fire conditions. Other deviations in
test details are subject to the tolerances as described in Table 1.
Table 1 — Permitted deviations from calibration test conditions
Upper permitted Lower permitted
Category Parameter
deviation deviation
Outer diameter +50 mm −200 mm
Test specimen Length +50 mm −500 mm
Shell thickness No limit No limit
TTabablele 1 1 ((ccoonnttiinnueuedd))
Upper permitted Lower permitted
Category Parameter
deviation deviation
No limit as long as test
Average wind speed DFTs are within range No limit
specified
Wind direction No limit No limit
Environmental conditions:
Tests shall be performed when there is a rea-
enclosed tests
sonable expectation of no precipitation. Short
Precipitation periods of light precipitation (< 2,5 mm/h) shall
not invalidate a test if less than 10 % of the test
duration is affected.
No limit as long as test
Average wind speed DFTs are within range No limit
specified
Average wind direction No limit
Environmental conditions:
Tests shall be performed when there is a rea-
external (open) tests
sonable expectation of no precipitation. Short
Precipitation periods of light precipitation (< 2,5 mm/h) shall
not invalidate a test if less than 10 % of the test
duration is affected.
Propane flow rate +0,05 kg/s −0,05 kg/s
Burner arrangement No modifications permitted
Commercial propane or LPG with minimum pro-
Test burner parameters
pane 90 %, maximum propylene 5 % maximum
Fuel composition
butane and heavier hydrocarbons 2,5 % by
liquid volume.
Table 1 shall apply for the test duration. In the event of changes in wind and environmental conditions
during a test causing conditions to fall outside the permitted values, the DFT data shall be used to
assess test validity, using the criteria stated in 18.6.
7.8 Calibration and test report
The calibration and test report shall contain the following:
a) the name of the testing laboratory, test date, unique test reference number and report identification;
b) complete description of the calibration or test specimen, including vessel dimensions; parameters
and details of additional gauges present; details of additional insulation systems used for tubing,
piping and saddles;
c) complete description of instrumentation used, including pressure transducers and TCs and the
positions and method used to affix them;
d) when appropriate, details of any deviations from the normal test configurations and the reasons
for them, and any unusual features observed;
e) record of test details and post fire characterization including:
1) ambient conditions including precipitation, temperature, humidity, wind speed and wind
direction (in the vicinity of the test specimen or test building) throughout the test at intervals
of 5 s or less,
2) fuel pressure and temperature at intervals of 2 s or less throughout the test, where these are
used to calculate mass flow rate, and the method of control and calculation,
3) fuel mass flow rate at intervals of 2 s or less throughout the test and total mass of fuel used,
4) fuel composition;
f) the test result, in the format given below:
1) the behaviour and appearance of the test specimen during and after the test and photographs,
2) temperature/time graphs and spreadsheets of temperatures at no more than 2 s intervals for
each TC and DFT;
g) the results and intermediate calculation steps of calculations performed in accordance with 7.4;
h) a comparison of test results against the requirements in 7.5 and a statement of whether the test
configuration meets the requirements and is suitable for fire testing;
i) an assessment of the environmental conditions in accordance with 7.6, including mean wind speed
and precipitation throughout the test;
j) a description of permitted tolerances, in accordance with 7.7, for future fire testing;
k) the International Standard used (including its year of publication), i.e. ISO 21843:2022.
8 Construction of fire test specimens
Fire test specimens shall be manufactured according to appropriate pressure vessel standards (e.g.
BS PD 5500, DIN 4680) and hydrostatically tested prior to fire testing. Test specimens shall be bullet-
type vessels with rounded ends of dimensions identical to those used for calibration testing under
Clause 7, subject to the tolerances in 7.7. The vessel shall be supported on two steel saddles, which
may be insulated if required to ensure stability for the duration of the test. Unnecessary valves and
gauges shall be removed, and all remaining connections shall be sealed. Covers or guards for gauges
and connections shall be removed.
Any piping connecting to propane storage or venting that is to remain in place during the test shall
be insulated for the duration of the test. Alternative insulation systems to the primary fire protection
material or system tested may be used, provided that:
— the termination detail at the joint of two insulation systems is designed to minimize the area of the
vessel shell not protected by the primary test material; and
— this is documented in the test report.
Pressure relief valve (PRV) or blowdown valve (BDV) performance in a fire test are variables outside
the scope of fire protection material or system performance determination. These variables are
addressed in other International Standards (e.g. ISO 23251). PRVs or BDVs shall be simulated through
the use of piping extending outside the fire engulfed zone to a fast-acting (<0,5 s) full-port actuated
valve connected to a discharge nozzle. The design of the discharge nozzle shall give the same flow
capacity as the required PRV or BDV design standard, and control of the ball valve shall be set to mimic
the appropriate activation pressure and re-close pressure as appropriate. A pilot flame shall be used to
prevent formation of a cloud of unburnt gas. Further commentary on PRV and BDV and the applicability
of test results is given in 16.1.
Pressure gauges, level gauges and any other vessel monitoring equipment utilized shall have a fire
rating, or be insulated, equivalent to that of the design rating of the fire protection material or system.
Further commentary on the applicability of results in consideration of fill level is given in 16.2.
9 Instrumentation
The pressure vessel wall shall be fitted with 21 insulated type k TCs (1,5 mm minimum diameter and
3 mm maximum diameter) positioned in accordance with Figure 3. All TCs shall be attached to the
vessel in accordance with the method in Annex C. Individual TCs th
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