prEN 15089
(Main)Explosion isolation systems
Explosion isolation systems
This document specifies the general requirements for explosion isolation systems. An explosion isolation system is an autonomous protective system which aims to prevent an explosion pressure wave and a flame or only a flame from propagating via connecting pipes or ducts into other parts of apparatus or plant areas.
This document also specifies methods for evaluating the efficacy of the various explosion isolation systems, and methods for evaluating design tools for such explosion isolation systems when applying these in practice.
This document also sets out the criteria for alternative test methods and interpretation means to validate the efficacy of explosion isolation systems.
This document does not cover flame arresters, diverters, and explosion isolation flap valves. For these devices refer to EN ISO 16852:2016 , EN 16020:2011, and EN 16447:2014 respectively.
This standard covers e.g.:
a) general requirements for the explosion isolation components;
b) evaluating the efficacy of an explosion isolation system;
c) evaluating design tools for explosion isolation systems.
This document is applicable only to the use of explosion isolation systems that are intended for avoiding explosion propagation between interconnected enclosures, in which an explosion can result as a consequence of ignition of explosive mixtures, e.g. dust-air mixtures, gas-(vapour-)air mixtures, dust-, gas-(vapour-)air mixtures and mists. It is not applicable to detonation events.
Explosions-Entkopplungssysteme
Dieses Dokument beschreibt die allgemeinen Anforderungen an Explosions-Entkopplungssysteme. Ein Explosions-Entkopplungssystem ist ein autonomes Schutzsystem, das dazu dient, die Ausbreitung einer Explosionsdruckwelle und einer Flamme oder nur einer Flamme über Verbindungsohre oder -kanäle in andere Teile der Apparatur oder Anlagenbereiche zu verhindern.
Dieses Dokument legt darüber hinaus Verfahren zur Bewertung der Wirksamkeit von verschiedenartigen Explosions-Entkopplungssystemen und Verfahren für die Beurteilung von Auslegungshilfen für derartige Explosions-Entkopplungssysteme bei der praktischen Anwendung fest.
Dieses Dokument legt zudem die Kriterien für alternative Prüfverfahren und Interpretationsmittel zur Bestätigung der Wirksamkeit von Explosions-Entkopplungssystemen fest.
Dieses Dokument behandelt keine Flammendurchschlagsicherungen, Explosionsschlote und Explosions-Entkopplungsklappenventile. Für diese Vorrichtungen wird auf EN ISO 16852:2016 , EN 16020:2011 bzw. EN 16447:2014 verwiesen.
Diese Norm behandelt z. B.:
a) allgemeine Anforderungen an Bauteile zur Explosions-Entkopplung;
b) Bewertung der Wirksamkeit eines Explosions-Entkopplungssystems;
c) Bewertung von Auslegungshilfen für Explosions-Entkopplungssysteme.
Dieses Dokument gilt nur für die Anwendung von Explosions-Entkopplungssystemen, die zum Vermeiden einer Explosionsübertragung zwischen miteinander verbundenen Anlagen vorgesehen sind, in denen eine Explosion als Folge einer Entzündung eines explosionsfähigen Gemischs, z. B. Staub/Luft-Gemische, Gas-(Dampf-)Luft-Gemische, Staub-Gas-(Dampf-)Luft-Gemische und Nebel, eintreten kann. Es ist nicht für Detonationsereignisse anwendbar.
Systèmes d’isolation d’explosion
Le présent document décrit les exigences générales relatives aux systèmes d’isolation d’explosion. Un système d’isolation d’explosion est un système de protection autonome qui a pour but d’empêcher une onde de pression d’explosion et une flamme, ou uniquement une flamme, de se propager vers d’autres parties des équipements ou vers d’autres zones de l’installation, par l’intermédiaire de canalisations ou de conduites de raccordement.
Le présent document expose également les méthodes qui permettent d’évaluer l’efficacité des différents systèmes d’isolation d'explosion, ainsi que les méthodes d’évaluation des outils de conception destinés à ces systèmes lors de leur mise en œuvre.
Le présent document expose également les critères requis pour d’autres méthodes d’essai ainsi que des moyens d’interprétation destinés à valider l'efficacité des systèmes d’isolation d’explosion.
Le présent document ne couvre pas les arrête-flammes, les dispositifs déviateurs et les vannes à clapet d’isolation d’explosion. Pour ces dispositifs, se référer respectivement à l’EN ISO 16852:2016 , l’EN 16020:2011 et l’EN 16447:2014.
La présente norme couvre par exemple :
a) les exigences générales relatives aux composants des systèmes d’isolation d’une explosion ;
b) l’évaluation de l’efficacité d’un système d’isolation d’explosion ;
c) l’évaluation des outils de conception destinés à des systèmes d’isolation d’une explosion.
Le présent document est uniquement applicable aux systèmes d’isolation d’explosion qui ont pour but d’éviter une propagation de l’explosion entre des enceintes communicantes dans lesquelles l’explosion résulte de l’inflammation d’une atmosphère explosive, constituée d’un mélange avec l’air de poussière, de gaz-(vapeur), d’un mélange hybride de poussières et de gaz-(vapeur), ou de brouillard. Il ne s’applique pas aux détonations.
Sistemi za ločitev eksplozij
General Information
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Standards Content (Sample)
SLOVENSKI STANDARD
01-oktober-2024
[Not translated]
Explosion isolation systems
Explosions-Entkopplungssysteme
Systèmes d’isolation d’explosion
Ta slovenski standard je istoveten z: prEN 15089
ICS:
13.230 Varstvo pred eksplozijo Explosion protection
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2024
ICS 13.230 Will supersede EN 15089:2009
English Version
Explosion isolation systems
Systèmes d'isolement d'explosion Explosions-Entkopplungssysteme
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 305.
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
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 15089:2024 E
worldwide for CEN national Members.
Contents Page
European foreword . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 6
4 Requirements of explosion isolation systems . 8
4.1 General . 8
4.1.1 Types of explosion isolation systems. 8
4.1.2 Explosion protection valve (active or passive) – F&P . 9
4.1.3 Extinguishing barrier (active) – F . 9
4.1.4 Rotary valve (passive) – F&P . 9
4.1.5 Explosion proof interlocked double valve arrangement (passive) – F&P . 9
4.1.6 Diverters, explosion isolation flap valves and flame arresters . 9
4.2 Essential requirements . 9
4.2.1 General . 9
4.2.2 Additional requirements to active systems .10
4.3 Functional safety .12
5 Environmental aspects .13
6 Selection and sizing of explosion isolation systems .13
6.1 General .13
6.2 Additional selection requirements .13
6.2.1 Explosion resistant design for the maximum explosion pressure – mechanical
barriers .13
6.2.2 Venting – isolation .13
6.2.3 Suppression – isolation .14
7 Experimental testing of the efficacy of an explosion isolation system .14
7.1 General .14
7.2 Special gases and dusts .14
7.3 Test Modules .15
7.3.1 General .15
7.3.2 Module B: Explosion resistance testing .16
7.3.3 Module A: Functional testing .17
7.3.4 Module C: Verification of design methods .34
7.4 Test report .36
8 Instructions .37
9 Marking .38
9.1 General .38
9.2 Marking of parts of an explosion isolation system .38
9.3 Marking of the explosion isolation system .40
9.4 Omission of marking .40
Annex A (informative) Example of the validation of a design model .41
Annex B (informative) Verification of design methods . 43
B.1 Design on the basis of an interpretation of test results . 43
B.2 Mathematical model . 44
Annex C (informative) Compilation of parameters influencing the performance of explosion
isolation systems . 48
Annex D (informative) Information on Functional Safety . 54
Annex E (informative) Stopping device for rotary valves . 56
Annex F (informative) Guidance regarding an analysis for the selection of explosion
isolation systems . 57
Annex G (informative) Environmental aspects . 62
G.1 Materials . 62
G.2 Suppressant . 62
G.3 Actuators and other components . 62
Annex H (informative) Significant changes between this document and EN 15089:2009. 63
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 2014/34/EU aimed to be covered . 64
Bibliography . 66
European foreword
This document (prEN 15089:2024) has been prepared by Technical Committee CEN/TC 305 “Potentially
explosive atmospheres – Explosion prevention and protection”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 15089:2009.
The significant changes between this document and EN 15089:2009 are given in Annex H.
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
For the relationship with EU Legislation, see informative Annex ZA, which is an integral part of this
document.
1 Scope
This document specifies the general requirements for explosion isolation systems. An explosion isolation
system is an autonomous protective system which aims to prevent an explosion pressure wave and a
flame or only a flame from propagating via connecting pipes or ducts into other parts of apparatus or
plant areas.
This document also specifies methods for evaluating the efficacy of the various explosion isolation
systems, and methods for evaluating design tools for such explosion isolation systems when applying
these in practice.
This document also sets out the criteria for alternative test methods and interpretation means to validate
the efficacy of explosion isolation systems.
This document does not cover flame arresters, diverters, and explosion isolation flap valves. For these
devices refer to EN ISO 16852:2016 , EN 16020:2011, and EN 16447:2014 respectively.
This standard covers e.g.:
a) general requirements for the explosion isolation components;
b) evaluating the efficacy of an explosion isolation system;
c) evaluating design tools for explosion isolation systems.
This document is applicable only to the use of explosion isolation systems that are intended for avoiding
explosion propagation between interconnected enclosures, in which an explosion can result as a
consequence of ignition of explosive mixtures, e.g. dust-air mixtures, gas-(vapour-)air mixtures, dust-,
gas-(vapour-)air mixtures and mists. It is not applicable to detonation events.
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 1127-1:2019, Explosive atmospheres — Explosion prevention and protection — Part 1: Basic concepts
and methodology
prEN 13237:2022, Potentially explosive atmospheres — Terms and definitions for equipment and
protective systems intended for use in potentially explosive atmospheres
EN 14034-1:2004+A1:2011, Determination of explosion characteristics of dust clouds — Part 1:
Determination of the maximum explosion pressure p of dust clouds
max
EN 14034-2:2006+A1:2011, Determination of explosion characteristics of dust clouds — Part 2:
Determination of the maximum rate of explosion pressure rise (dp/dt) of dust clouds
max
EN 14373:2021, Explosion suppression systems
EN 14460:2018, Explosion resistant equipment
EN 15233:2007, Methodology for functional safety assessment of protective systems for potentially
explosive atmospheres
Will be replaced by EN ISO/IEC 80079-49:2024.
EN 15967:2022, Determination of maximum explosion pressure and the maximum rate of pressure rise of
gases and vapours
EN 16020:2011, Explosion diverters
EN 16447:2014, Explosion isolation flap valves
EN 61508:2010, (all parts) Functional safety of electrical/electronic/programmable electronic safety-
related systems (IEC 61508:2010)
EN ISO 13849-1:2015, Safety of machinery — Safety-related parts of control systems — Part 1: General
principles for design (ISO 13849-1:2015)
EN ISO 13849-2:2012, Safety of machinery — Safety-related parts of control systems — Part 2: Validation
(ISO 13849-2:2012)
EN ISO 16852:2016, Flame arresters — Performance requirements, test methods and limits for use (ISO
16852:2016)
EN ISO 80079-36:2016, Explosive atmospheres — Part 36: Non-electrical equipment for explosive
atmospheres — Basic method and requirements (ISO 80079-36:2016)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in prEN 13237:2022, EN 14373:2021,
EN 14460:2018 and EN ISO 16852:2016 the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
indicating equipment
IE
explosion protection equipment, which monitors the explosion sensors/detectors and the explosion
protection devices
3.2
carbonaceous
refers to any organic material that contains a large amount of carbon content such as char coal, coal, coke,
carbon black, lignite including carbon nanotubes (CNTs), graphine and activated carbon (AC)
3.3
closing time
time needed for closing an isolation device
Will be replaced by EN ISO/IEC 80079-49:2024.
As impacted by EN ISO 80079-36:2016/AC:2019.
3.4
closing time of the system
sum of the activation time of sensor, activation time of isolation device and closing time of the isolation
device
3.5
explosion diverter
mechanical device, which will divert the explosion to a safe area
Note 1 to entry: It prevents flame jet ignition and pressure piling but cannot effectively stop explosions from
travelling, see EN 16020.
3.8
explosion isolation valve
fast acting valve able to stop explosions from travelling through pipelines
3.9
explosion proof interlocked double valve arrangement
device, which will act in closed position as isolation valve
3.10
extinguishing barrier
system that is used to discharge suppressant agent into ductwork to isolate a flame and keep it from
propagating to other process areas
3.11
suppressor
vessel with opening mechanism, which upon activation discharges the explosion suppressant into
ductwork
3.12
explosion detector
device that responds to an explosion (e.g. developing pressure and/or radiation) and provides a signal to
the control and indicating equipment
3.13
flame velocity
S
f
velocity of a flame front relative to a fixed reference point
3.14
installation distance
L
distance between outlet of the enclosure and isolation system
3.15
maximum installation distance
Lmax
longest distance from the outlet of the enclosure with the potential explosion to the isolation system,
which is limited by the explosion resistance of the isolation device or pipe but still guaranteeing a
successful isolation
3.16
minimum installation distance
L
min
shortest distance from the outlet of the enclosure with the potential explosion to the isolation system
guaranteeing a successful isolation
3.17
extinguishing distance
L
E
needed distance behind an extinguishing barrier to guarantee a proper isolation of the flame of an
explosion
3.18
barrier activity distance
L
chem
total distance given by the sum of the installation distance and the extinguishing distance
3.19
response time
time necessary for actuation of the system after a detection of an explosion
3.20
protected area
area beyond the isolation device, opposite to the ignition source
3.21
p
duct, max
maximum explosion overpressure measured directly in front of the explosion isolation device
3.22
MESG (dust)
maximum experimental safe gap for dusts, calculated from MIE and MIT
3.23
explosion duration
time period from ignition to the moment of reaching constant atmospheric pressure
4 Requirements of explosion isolation systems
4.1 General
4.1.1 Types of explosion isolation systems
There are several types of explosion isolation systems. They stop either flame or flame and pressure.
Flame (F): objective is to stop flame propagation from travelling beyond the isolation device into the
protected area.
Pressure (P): objective is to stop the pressure wave from travelling beyond the isolation device into the
protected area.
Explosion isolation systems mitigate against the effects of explosion pressure or flame but do not prevent
the transfer of hot or burning particles before or after an explosion.
4.1.2 Explosion protection valve (active or passive) – F&P
To prevent flame and damaging pressure propagation in pipes/ducts, valves or gates may be used which
close in a sufficient short time. The closure can be affected by means of an actuating mechanism initiated
by a pressure detector or a flame detector or a combination thereof or by the explosion overpressure
itself.
NOTE Explosion protection valves need not be gas tight.
4.1.3 Extinguishing barrier (active) – F
The extinguishing medium is dispersed into the pipe/duct to extinguish the flame. The extinguishing
medium shall be suitable for the specific explosive atmosphere according to the intended use.
4.1.4 Rotary valve (passive) – F&P
The effectiveness of the rotary valve against flame propagation and its explosion resistance shall be
proven. Depending on the number of rotor blades, gap width and gap length, a flame breakthrough can
be prevented.
Upon detection of an explosion the rotary valve should be stopped automatically to prevent the transfer
of burning material.
NOTE 2 Rotary valves are not gas tight.
4.1.5 Explosion proof interlocked double valve arrangement (passive) – F&P
Enclosures that are explosion-resistant can be protected by at least two explosion proof process valves
in series. By means of proper control, it shall be ensured that at least one of the valves is always closed.
Upon detection of an explosion the explosion proof interlocked double valve arrangement should be
stopped automatically.
4.1.6 Diverters, explosion isolation flap valves and flame arresters
The isolation systems diverters, explosion isolation flap valves and flame arresters are covered in
separate standards (see EN 16020:2011, EN 16447:2014 and EN ISO 16852:2016 ).
4.2 Essential requirements
4.2.1 General
• Explosion isolation system shall prevent an explosion flame from propagating via connecting pipes
or ducts from one part of the installation into other parts or plant areas.
• The system as installed or any of its components shall not introduce ignition hazards, such as
electrostatic discharge, mechanical friction, electrical sparks, hot surfaces, or hot gases (according to
EN 1127-1:2019).
• The explosion isolation system shall have a defined reliability for safety-functions under the process
conditions according to the intended use (according to EN ISO 80079-36:2016).
• The isolation system shall withstand the loads imposed by any explosion that can be expected in
accordance with its intended use, without losing its ability to perform its safety function. The
construction can be either explosion-pressure resistant or explosion-pressure shock resistant
according to EN 14460:2018.
Will be replaced by EN ISO/IEC 80079-49:2024.
• The explosion pressure acting on the explosion isolation device may be higher than the (reduced)
explosion pressure of the vessel being isolated as a result of flame accelerations through the ducting
and reflections.
• Installation instructions, service and maintenance requirements and intervals shall be specified in
the system documentation, (see Clause 7).
4.2.2 Additional requirements to active systems
4.2.2.1 Explosion detector
Explosion detector shall identify the onset of the explosion or the passage of a flame and communicate
that to the CIE in time to achieve successful isolation.
NOTE 1 Detection methods can be e.g. based upon static pressure, rate of pressure rise and/or radiation.
If bursting discs, vent panels or explosion doors are fitted with switches or break wires, which actuate an
isolation system, the tolerance in activation pressure of the venting device shall be taken into account in
the design of the explosion isolation system.
NOTE 2 The performance of explosion detectors depends upon the response time of the detector from detection
criteria.
4.2.2.2 Control and indication equipment (CIE)
CIE will actively control the operation of the protection device and provide status indication of the device
and is therefore critical for the correct functioning of the device/system.
Control and indication equipment (CIE) shall have a defined reliability in accordance with
EN 61508:2010, and ensure explosion isolation system functionality by undertaking the following:
• process detection signals;
• initiate the isolation device;
• initiate interlocks/alarms;
• enable safe isolation;
• enable an automatic and orderly safe-mode of the protected process upon activation, fault / trouble
condition.
4.2.2.3 Emergency power
Emergency power shall be specified and facilitated such that full uninterrupted explosion protection is
ensured at least four hours after a mains power failure to enable the CIE to accomplish the following
actions:
1) power all detection devices;
2) energize all electrically operated actuating devices;
3) initiate visual and audible alarms;
4) transfer all auxiliary control and alarm contacts;
5) control system–disabling interlock and process shutdown circuits;
6) provide interlocks / alarms to signal power failure.
Emergency backup power is not required when the isolation valve closes (fast acting valve) in a failsafe
mode automatically at power failure.
4.2.2.4 Extinguishing barriers
4.2.2.4.1 General
Unlike mechanical isolation devices, extinguishing barriers are transient in nature since the duration and
pressure of the initiating explosion can cause the extinguishing barrier to become purged from the
connection.
Consequently, special design constraints apply to the concept of explosion isolation where extinguishing
barriers are used. Their use is typically limited to applications where the source vessel(s) are protected
by venting or suppression, but not normally by containment.
Since extinguishing barriers are transitory, scenarios where explosion detection is early or the source
explosion pressure pulse duration is very long increase the risk that flame can pass the barrier location
and therefore certain limitations are apparent regarding the applicability of specific hardware and
process/plant scenarios.
4.2.2.4.2 Suppressors
Suppressors shall inject sufficient suppressant into the duct to establish an effective barrier in the
required time and duration. The extinguishing barrier is effective as long as the minimum sectional
density of suppressant is maintained.
NOTE The performance of suppressors depends upon at least:
• volume, shape and outlet diameter of the suppressor;
• filling ratio and pressure inside the suppressor;
• opening time of the suppressor.
4.2.2.4.3 Dispersion assembly
The dispersion assembly (nozzle, flexible, hose) shall spread the suppressant into the ductwork to
achieve both required throw and spatial distribution / concentration.
NOTE The performance of a dispersion nozzle depends upon at least:
• design of the nozzle;
• characteristics of the suppressor and the suppressant;
• length and diameter of flexible, hose.
Depending on the intended use specific dispersion nozzles can be applied, with special performances, for
example to obtain strong directional effects.
4.2.2.4.4 Suppressant
The suppressant shall have dispersion characteristics and extinguishing properties allowing for
extinguishing an explosion flame for a given intended use.
NOTE The properties influencing these characteristics include:
• the particle/droplet size distribution;
• chemical and thermal properties.
Apart from the effectiveness of the suppressant applied, also the compatibility of the suppressant with
the process shall be considered:
• temperature stability;
• any adverse reaction with the process products;
• toxicity levels of the suppressant.
4.3 Functional safety
Systematic and transparent system analyses shall be made in all design stages to prevent potential
defects. This methodical and comprehensible design approach ensures a clearly specified level of
functional safety.
Dependent on the specific type of application a first identification of the required level of safety and the
resulting safety functions for the explosion isolation system followed by an assessment of functional
safety shall be done (see Annex D for further information).
The reliability of the isolation system shall be quantified by the manufacturer according to
EN 61508:2010 and EN ISO 13849-1:2015 and EN ISO 13849-2:2012 where appropriate.
The minimum requirements shall include supervision of the following:
a) wiring circuits for continuity, earth faults and open circuits;
b) mains power supply;
c) emergency power supply;
d) system safety interlock circuitry;
e) system-disabling interlock circuitry;
f) electrically operated actuating devices;
g) detection devices;
h) health monitoring of isolation device (e.g. pressure of suppressors).
In addition, one shall assess the functional safety according to EN 15233:2007 where appropriate. As a
minimum the following aspects shall be addressed:
1) design faults in the hardware;
2) adverse environmental conditions, including electromagnetic disturbance;
3) design faults in the software.
In case of an identifiable fault such that the safety function of the system cannot be guaranteed to the
agreed level of safety integrity, the isolation system shall provide a fail-safe means to place the installation
into a safe condition.
Reliability and functional safety of the mechanical parts shall be assessed according to the application.
Regular maintenance shall be described in relationship to the application.
5 Environmental aspects
Dispositions shall be taken to limit the impact of the explosion isolation devices on the environment. More
information can be found in Annex G.
6 Selection and sizing of explosion isolation systems
6.1 General
It is very important for the selection and sizing of an explosion isolation system that a detailed analysis
is made considering all relevant characteristics and conditions according to the intended use. This
analysis shall at least include:
• Flow conditions (air flow or not, pulsed flow or not);
• Physical characteristic limitations of the connected equipment where the isolation device shall be
installed (mechanical strength, volume protected vessel, presence of bends, etc.);
• Prevailing process conditions (temperature, pressure, product, etc.);
• Type of isolation device (extinguishing barrier, active isolation valve, etc.);
• Possibilities for maintenance (accessibility, technology, competence, etc.).
Annex F gives detailed guidance on these aspects and the selection of the properties of an explosion
isolation system.
6.2 Additional selection requirements
6.2.1 Explosion resistant design for the maximum explosion pressure – mechanical barriers
Explosion isolation of explosion resistant equipment designed to withstand the maximum explosion
pressure is typically performed using mechanical barriers. For this means of protection the explosion is
allowed to run its full course, high pressure and high temperatures will remain in the contained system
for a long period of time. Therefore, the isolation system/mechanical barriers shall be able to withstand:
a) the highest pressures up to the location of isolation using explosion resistant design;
b) exposure to heat.
The effectiveness of the barrier shall be maintained during the explosion duration.
6.2.2 Venting – isolation
In case of applying venting in combination with mechanical barriers as isolation system the barriers shall
be able to withstand:
a) the highest pressures up to the location of the barrier,
b) exposure to heat where applicable,
and the effectiveness of the barrier shall be maintained during the explosion duration.
Applying extinguishing barriers in combination with venting as isolation system also the ducting and
other equipment beyond the barrier shall be able to withstand:
a) the highest pressure generated by an explosion;
b) heat exposure where applicable.
There shall be sufficient distance downstream of the barrier to ensure full flame extinguishment.
6.2.3 Suppression – isolation
In case of applying explosion suppression in combination with mechanical barriers as isolation system
the barriers shall be able to withstand:
a) the highest pressures up to the location of the barrier,
b) exposure to heat where applicable,
and the effectiveness of the barrier shall be maintained during the explosion duration.
Applying extinguishing barriers in combination with suppression as isolation system also the ducting and
other equipment beyond the barrier shall be able to withstand:
d) the highest pressure generated by an explosion;
e) heat exposure where applicable.
There shall be sufficient distance downstream of the barrier to ensure full flame extinguishment.
Usually, the detection and the CIE of an explosion suppression system are at the same time used to trigger
active isolation systems. If not, precautions shall be taken to activate the isolation system appropriately.
7 Experimental testing of the efficacy of an explosion isolation system
7.1 General
The information in Clause 5 and the intended use shall be considered prior to testing.
7.2 Special gases and dusts
Explosion isolation systems may be tested and considered adequate for a wide range of explosion
properties and test conditions. There are, however, a number of gases and dusts for which application of
the explosion isolation system is only possible after having been tested directly for the specific gas or
dust. This despite explosion properties of these gases and dusts sometimes being within the range for
which the explosion isolation system is considered to be adequate. Reasons for this include a combination
of low minimum ignition energy and autoignition temperature or contribution of radiation to the flame
propagation mechanism.
Explosion isolation systems shall be tested for the following gases and dusts specifically, before one can
apply these systems for an application involving such a dust or gas:
Gases and vapours
• carbon disulfide, acetylene, ethylene oxide, silane or mixtures of these gases or mixtures of these
gases with other gases.
Dusts
• light metals: aluminium, magnesium, titanium, zirconium, hafnium, tantalum, silicon, strontium,
calcium and niobium and similar alloys;
• sulphur;
• coal dusts;
• any mixtures of the dusts mentioned above
Hybrid mixtures
• any mixture of the gases, vapours or dusts mentioned above
For the light metal dusts the system shall either be tested for the dust involved in the application or using
a more reactive dust of the same light metal. To judge the reactivity the K -value of the two dusts shall
St
be determined in the same explosion vessel (i.e. 20 l sphere or 1-m vessel as given in
EN 14034-2:2006+A1:2011).
It is emphasized that the list mentioned above is not exhaustive. Other gases, vapours or dusts may need
special consideration such as iron.
7.3 Test Modules
7.3.1 General
The experimental testing consists of three different modules:
Module A: Functional testing.
Module B: Explosion resistance testing
Module C: Verification of design methods
Explosion isolation systems shall always be tested according to Module A, as it covers pressure resistance
testing (Module B) and flame transmission testing as well. In cases where testing according to Module A
does not cover pressure resistance testing Module B can be executed separately.
NOTE Module B is typically used to check pressure resistance in case of testing of minor variations in design of
devices which have undergone Module A already.
Module C shall be used if extrapolation to installations is desired which deviate from the test set-up of
Module A. Module C can be applied only for passive and active explosion protection valves, and for
extinguishing barrier systems.
The generation and the ignition of the explosive atmosphere are described in EN 14034-1:2004+A1:2011
and EN 14034-2:2006+A1:2011 for dusts and EN 15967:2022 for gases and vapours. However,
deviations from these standardized methods are necessary depending on the module. These deviations
have been specified in each of the modules.
Table 1 — Type of modules as a function of type of isolation system
Type of modules
Type of isolation system
Module A: Module B:
Functional testing Explosion resistance testing
Passive isolation valves X X
Explosion proof interlocked
X X
double valve arrangement
Active isolation valves X X
Extinguishing barriers X —
Rotary valves X X
7.3.2 Module B: Explosion resistance testing
Explosion resistance shall be confirmed by explosion testing according to the following procedure:
1) Test arrangement:
The explosion isolation system shall be tested in the closed position and is mounted to a test vessel
according to Figure 1. The explosive atmosphere inside the test vessel and the pipe connecting the
valve may be of any type (gas or dust), provided the pressure generated is sufficient to subject the
device to the required pressure.
2) Test assignment/records:
As a minimum, the maximum pressure recorded at the location of the device. Flame transmission
recorded by at least one camera.
3) Number of tests:
Minimum 1 per size tested. For devices constructed in the same way (with respect to the geometrical
similarity, material specifications, welding specifications or specifications of other ways of
connecting parts, wall thickness, safe gap, sealing, etc.) only the largest size needs be tested.
4) Evaluation:
Permanent deformation is allowed provided the device does not fail in its function and will not give
rise to dangerous effects to the surrounding. No permanent deformation is allowed for brittle
material.
The maximum pressure recorded at the location of the valve corrected according to EN 14460:2018.
Key
1 Location of ignition source 2 Pressure transducer (Pt) 3 isolation device
Figure 1 — Test arrangement for explosion resistance testing
7.3.3 Module A: Functional testing
7.3.3.1 General
The main objective of functional testing is to assess the efficacy of the device/system as an explosion
isolation device/system according to the intended use as specified by the manufacturer and to
determine/verify the minimum/maximum installation distance of the isolation device dependent on the
detection method (active systems) or functional design (passive systems).
Explosive atmospheres reflecting worst case conditions shall be present in the vessel and the connecting
duct at least up to the position of the explosion isolation device during the test (initial turbulence in the
duct; fuel concentration, may deviate from closed vessel optimum concentration; see also Annex C). The
process of generating the explosible atmosphere shall not affect the functionality of the explosion
isolation device. The explosion characteristics of the explosible atmosphere generated in the test vessel
shall reflect the intended use. The test setup for the minimum installation distance shall be in such a way
that both a low and a high flame speed and both low and high pressure rise is addressed.
A way to achieve a high flame speed and pressure rise is to use a test vessel volume, which is at least twice
the volume of the connected duct up to the minimum installation distance. For special applications with
smaller vessel volumes additional tests with the smallest vessel size acc. to the intended use are required.
An explosive atmosphere with minimum ignition energy and minimum ignition temperature, K /K , p
St G max
according to the intended use shall be used. To represent the worst-case conditions the explosive
dust/air- resp. gas/air-mixture shall be dispersed homogenously in the volume.
Dust shall be injected into the vessel via fast-acting valves by means of dust containers, which are
pressurized with air. The test rig including its boundary conditions like ignition delay and initial pressure
of the dust containers must be able to represent the results of EN 14034-1:2004+A1:2011 and
EN 14034-2:2006+A1:2011 within the required range of dust concentration. In case a hybrid mixture is
simulated by an appropriate turbulent gas/air-mixture the turbulence in the gas-filled vessel shall be
generated by injecting air in the same way.
The arrangement of the injection positions as well as the ignition time delay to be chosen for the desired
turbulence state inside the vessel depends on the geometry and the volume of the test vessel and shall be
determined in pre-tests.
Backward calculation of the reactivity by vented pre-tests and by the use of published vent area
calculation formulas should be avoided as it gives unrealistic high reactivity values. Preferred are closed
vessel pre-tests.
For gases the explosible atmosphere shall extend throughout the enclosure and the entire pipe. This
accounts also for dusts unless the volume of the connected pipe to the isolation device is less or equal half
the vessel volume.
The tests shall be performed aiming at exposing the explosion isolation device to both low and high
explosion pressure over the full range of explosion pressure as indicated in the intended use. For details
see 7.3.3.2 to 7.3.3.6. If testing is performed for explosion venting the results are applicable to both
venting and suppression. If testing is performed with suppression the results are only applicable to
suppression systems.
Calibration tests shall be performed to ensure that the flame reaches the foreseen position of the
explosion isolation device and also propagates through the duct passing the position of the explosion
isolation device. If not, an appropriate explosive atmosphere shall be generated in the duct.
7.3.3.2 Passive explosion protection valve
a) Aim of the functional testing
The test shall assess the efficacy of the valve at the minimum and maximum installation distance.
This shall be determined by varying the location of the ignition source in the test enclosure and other
influencing parameters e.g. enclosure volume, maximum explosion overpressure in the enclosure
according to the intended use.
b) Test set-up
The test rig consisting of a compact enclosure (with a length (height) to diameter ratio of less than
2) in combination with a pipe (see Figure 2) shall reflect the specified intended use (orientation of
the isolation valve, presence of restrictions, elbows, volume of enclosure). There shall be a pipe on
both sides of the valve. The length of the pipe on the side of the valve not exposed to the explosion
shall be 5 times the diameter, but at least 5 meters.
If a deviating L/D of the compact enclosure is used it should be indicated and the orientation of the
vessel to the connected pipe is important to be considered.
If the intended use requires a straight duct of 5 times the diameter of the valve flange, but at least 5
meters on both sides of the device no additional test with elbows or restrictions are required. If the
curvature ratio of elbows present amounts to R/D ≥ 3 these elbows can be considered as straight
pipes.
Depending on the intended use, the test vessel is explosion proof, vented or suppressed. The
generation of the explosion characteristics in the test vessel shall reflect the explosion characteristics
required.
For determination of flame break-through a flame sensor (only possible when a pipe is connected to
the test set-up downstream of the isolation device) or alternatively cameras shall be used if windows
or transparent sections of the pipe allow to capture flame breakthrough downstream of the device.
The length of the pipe downstream of the isolation device shall be at least 5 times the diameter or
according the manufacturer's installation specification if a certain length after the device is required
for its functionality. If the intended use requires testing with a reduced overpressure in the vessel
higher than 200 kPa the requirement for a pipe downstream of an isolation device is no longer there.
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