prEN 14986
(Main)Design of fans working in potentially explosive atmospheres
Design of fans working in potentially explosive atmospheres
1.1 This document specifies the constructional requirements for fans constructed to Group II G (of explosion groups IIA, IIB and hydrogen) categories 1, 2 and 3, and Group II D categories 2 and 3, intended for use in explosive atmospheres.
NOTE 1 Operation conditions for the different categories of fans used in this document are defined in Clause 4.
NOTE 2 For category 1 D fans, requirements provided in this document are not sufficient to ensure safety. In addition, explosion protection measures as specified in EN 1127 1:2019 are required to prevent ignition in the case of rare malfunctions.
NOTE 3 Technical requirements for explosion group IIC (other than hydrogen) are not given in this document. Where such atmospheres are present, additional explosion protection measures as specified in EN 1127 1:2019 can be needed.
1.2 This document does not apply to group I fans (fans for mining), cooling fans or impellers on rotating electrical machines, cooling fans or impellers on internal combustion engines, vehicles or electric motors.
NOTE 1 Requirements for group I fans are given in EN ISO/IEC 80079 38:2016.
NOTE 2 The requirements for electrical parts are covered by references to electrical equipment standards.
1.3 This document specifies requirements for design, construction, testing and marking of complete fan units intended for use in potentially explosive atmospheres in air containing gas, vapour, mist and/or dusts. Such atmospheres can exist inside (the conveyed atmosphere (flammable or not)), outside, or inside and outside of the fan.
NOTE This document covers mechanical equipment, in particular fans. The “protection concept” as specified in EN ISO 80079 37:2016 is constructional safety. Requirements for marking are given in EN ISO 80079 37:2016.
1.4 This document is applicable to fans working in ambient atmospheres and with normal atmospheric conditions at the inlet, having
— absolute pressures ranging from 0,8 bar to 1,1 bar,
— and temperatures ranging from −20 °C to +60 °C,
— and maximum volume fraction of 21 % oxygen content,
— and an aerodynamic energy increase of less than 25 kJ/kg.
NOTE 1 25 kJ/kg is equivalent to 30 kPa at inlet density of 1,2 kg/m3.
This document can also be helpful for the design, construction, testing and marking of fans intended for use in atmospheres outside the validity range stated above or in cases where other material pairings need to be used. In this case, the ignition risk assessment, ignition protection provided, additional testing (if necessary), manufacturer's marking, technical documentation and instructions to the user, clearly demonstrate and indicate the equipment's suitability for the conditions the fan can encounter.
NOTE 2 Temperatures below −20°C can be considered. Material suitability can require specific evaluation for these temperatures. With lower temperature the explosion pressure increases, which leads to increased test pressures (see A.3) and can require specific testing. Although the standard atmospheric conditions in EN ISO 80079 36:2016 give a temperature range for the atmosphere of −20 °C to +60 °C the normal ambient temperature range for the equipment is −20 °C to +40 °C unless otherwise specified and marked.
Konstruktion von Ventilatoren für den Einsatz in explosionsgefährdeten Bereichen
1.1 Dieses Dokument legt die baulichen Anforderungen an Ventilatoren der Gruppe II G (der Explosionsgruppen IIA, IIB und Wasserstoff) Kategorien 1, 2 und 3 und Gruppe II D Kategorien 2 und 3 für die Verwendung in explosionsfähigen Atmosphären fest.
ANMERKUNG 1 Betriebsbedingungen für die verschiedenen Kategorien von Ventilatoren, die von diesem Dokument erfasst werden, sind in Abschnitt 4 definiert.
ANMERKUNG 2 Für Ventilatoren der Kategorie 1 D sind die in diesem Dokument angegebenen Anforderungen nicht ausreichend, um Sicherheit sicherzustellen. Zusätzlich sind wie in EN 1127 1:2019 festgelegte Explosionsschutzmaßnahmen erforderlich, um im seltenen Fall von Störungen Zündungen zu verhindern.
ANMERKUNG 3 Technische Anforderungen für Explosionsgruppe IIC (außer Wasserstoff) sind in diesem Dokument nicht enthalten. Wo solche Atmosphären vorhanden sind, können zusätzliche Explosionsschutzmaßnahmen wie in EN 1127 1:2019 festgelegt benötigt werden.
1.2 Dieses Dokument ist nicht anwendbar auf Gruppe I Ventilatoren (Ventilatoren für den Bergbau), Kühlgebläse oder Flügelräder für drehende elektrische Maschinen sowie Kühlgebläse oder Flügelräder für Verbrennungsmotoren, Fahrzeuge oder Elektromotoren.
ANMERKUNG 1 Anforderungen an Gruppe I Ventilatoren sind in EN ISO/IEC 80079 38:2016 angegeben.
ANMERKUNG 2 Die Anforderungen an elektrische Bauteile werden durch Verweisungen auf Normen für elektrische Geräte behandelt.
1.3 Dieses Dokument legt Anforderungen an Konstruktion, Bau, Prüfung und Kennzeichnung kompletter Ventilatoreinheiten fest, die für den Einsatz in explosionsgefährdeten Bereichen, die durch Gase, Dämpfe, Nebel und/oder Staub entstehen, bestimmt sind. Solche Atmosphären können innerhalb (durch das geförderte Fluid (entflammbar oder nicht)), außerhalb oder innerhalb und außerhalb des Ventilators existieren.
ANMERKUNG Dieses Dokument behandelt mechanische Ausrüstung, insbesondere Ventilatoren. Das wie in EN ISO 80079 37:2016 festgelegte „Schutzkonzept“ ist konstruktive Sicherheit. Anforderungen an die Kennzeichnung werden in EN ISO 80079 37:2016 angegeben.
1.4 Dieses Dokument ist anwendbar auf Ventilatoren, die in Umgebungsluft und unter üblichen atmosphärischen Bedingungen an der Eintrittsseite betrieben werden, für die gilt:
— absolute Drücke von 0,8 bar bis 1,1 bar;
— und Temperaturen zwischen −20 °C bis +60 °C;
— und ein höchstmöglicher Volumenanteil des Sauerstoffgehalts von 21 %;
— und ein aerodynamischer Energieanstieg von weniger als 25 kJ/kg.
ANMERKUNG 1 25 kJ/kg entsprechen 30 kPa bei einer Eintrittsdichte von 1,2 kg/m3.
Dieses Dokument kann auch hilfreich sein für Konstruktion, Bau, Prüfung und Kennzeichnung von Ventilatoren, die für den Einsatz in Atmosphären bestimmt sind, die nicht in den Gültigkeitsbereich dieser Norm fallen, oder in Fällen, in denen andere Werkstoffpaarungen verwendet werden müssen. In diesem Fall weisen die Bewertung des Zündrisikos, der vorgesehene Zündschutz, zusätzliche Prüfung (falls erforderlich), Herstellerkennzeichnung, technische Dokumentation und Anweisungen an den Benutzer nach und deuten darauf hin, dass die Ventilatoren für die Bedingungen, auf die sie treffen können, geeignet sind.
ANMERKUNG 2 Temperaturen unter −20°C können in Erwägung gezogen werden. Die Eignung von Werkstoffen kann die spezifische Bewertung dieser Temperaturen erfordern. Bei geringeren Temperaturen steigt der Explosionsdruck, was zu erhöhten Prüfdrücken (siehe A.3) führt und spezifisches Prüfen erfordern kann. Obwohl die atmosphärischen Standardbedingungen in EN ISO 80079 36:2016 einen Temperaturbereich für die Atmosphäre von −20 °C bis +60 °C bieten, liegt der gewöhnliche Umgebungstemperaturbereich für die Ausrüstung zwischen −20 °C und +40 °C, sofern nicht anders festgelegt und gekennzeichnet.
Conception des ventilateurs pour les atmosphères explosibles
Načrtovanje ventilatorjev za delovanje v potencialno eksplozivnih atmosferah
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN 14986:2023
01-februar-2023
Načrtovanje ventilatorjev za delovanje v potencialno eksplozivnih atmosferah
Design of fans working in potentially explosive atmospheres
Konstruktion von Ventilatoren für den Einsatz in explosionsgefährdeten Bereichen
Conception des ventilateurs pour les atmosphères explosibles
Ta slovenski standard je istoveten z: prEN 14986
ICS:
23.120 Zračniki. Vetrniki. Klimatske Ventilators. Fans. Air-
naprave conditioners
29.260.20 Električni aparati za Electrical apparatus for
eksplozivna ozračja explosive atmospheres
oSIST prEN 14986:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN 14986:2023
DRAFT
EUROPEAN STANDARD
prEN 14986
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2022
ICS 23.120 Will supersede EN 14986:2017
English Version
Design of fans working in potentially explosive
atmospheres
Conception des ventilateurs pour les atmosphères Konstruktion von Ventilatoren für den Einsatz in
explosibles explosionsgefährdeten AtmosphärenThis 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
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 14986:2022 E
worldwide for CEN national Members.---------------------- Page: 3 ----------------------
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prEN 14986:2022 (E)
Contents Page
European foreword ............................................................................................................................................ 4
Introduction .......................................................................................................................................................... 5
1 Scope .......................................................................................................................................................... 6
2 Normative references .......................................................................................................................... 7
3 Terms and definitions ......................................................................................................................... 7
4 Requirements for all fans ................................................................................................................... 8
4.1 Ignition hazard assessment .............................................................................................................. 8
4.2 Assignment of categories ................................................................................................................... 9
4.3 Temperatures....................................................................................................................................... 10
4.4 Mechanical design criteria .............................................................................................................. 11
4.5 Casing ...................................................................................................................................................... 12
4.6 Impellers ................................................................................................................................................ 12
4.7 Materials for rotating and stationary parts of fans ................................................................ 12
4.8 Linings and tip extensions ............................................................................................................... 20
4.9 Vibration ................................................................................................................................................ 20
4.10 Earthing conducting parts ............................................................................................................... 21
4.11 Electrostatic charges.......................................................................................................................... 21
4.12 Electrical equipment.......................................................................................................................... 21
4.13 Prevention of deposits inside the fan .......................................................................................... 21
4.14 Shaft seals .............................................................................................................................................. 21
4.15 Bearings.................................................................................................................................................. 22
4.16 Power transmission systems .......................................................................................................... 22
4.17 Clutches and couplings ..................................................................................................................... 22
4.18 Brakes and braking systems ........................................................................................................... 22
4.19 Impeller-shaft attachment ............................................................................................................... 22
4.20 Corrosion of fan components ......................................................................................................... 26
4.21 Fire resistance ...................................................................................................................................... 26
4.22 Protection against foreign particles............................................................................................. 26
5 Additional requirements for category 2 ..................................................................................... 26
5.1 General.................................................................................................................................................... 26
5.2 Impeller-shaft attachment ............................................................................................................... 26
5.3 Vibration ................................................................................................................................................ 26
5.4 Material pairings ................................................................................................................................. 27
6 Category 1 fans for specific use with a gaseous explosive atmosphere as a conveyed
atmosphere (flammable or not) .................................................................................................... 27
6.1 General requirements ....................................................................................................................... 27
6.2 Flame arresters ................................................................................................................................... 27
6.3 Casings .................................................................................................................................................... 27
7 Information for use ............................................................................................................................ 28
7.1 General.................................................................................................................................................... 28
7.2 Accompanying documentation ...................................................................................................... 28
7.3 Markings ................................................................................................................................................ 30
Annex A (normative) Additional requirements for category 1 G fans .......................................... 31
A.1 General.................................................................................................................................................... 31
A.2 Flame transmission test ................................................................................................................... 31
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A.3 Pressure test ......................................................................................................................................... 32
Annex B (informative) Classification of requirements for the different categories ................ 34
Annex C (informative) Checklist for verification of the safety requirements and/or
protective measures .......................................................................................................................... 38
C.1 General ................................................................................................................................................... 38
C.2 All categories ........................................................................................................................................ 38
C.3 Category 2 – Gas and dust ................................................................................................................ 39
C.4 Category 1 – Gas .................................................................................................................................. 39
Annex D (informative) Examples of types of fans showing ignition minimizing features .... 40
Annex E (normative) List of significant hazards ................................................................................... 48
Annex F (informative) Significant changes between this document and EN 14986:2017 .... 53
Annex ZA (informative) Relationship between this European Standard and the essential
requirements of Directive 2014/34/EU aimed to be covered ........................................... 55
Bibliography ....................................................................................................................................................... 59
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European foreword
This document (prEN 14986:2022) 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 14986:2017.
The significant changes with respect to EN 14986:2017 are listed in Annex F.
This document has been prepared under a Standardization Request given to CEN by the European
Commission and the European Free Trade Association, and supports essential requirements of
EU Directive(s) / Regulation(s).For relationship with EU Directive(s) / Regulation(s), see informative Annex ZA, which is an integral part
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Introduction
This document is a type C standard as stated in EN ISO 12100:2010.
The machinery concerned and the extent to which hazards, hazardous situations and events are covered
and indicated in the scope of this document.When provisions of this type C standard are different from those, which are stated in type A or B
standards, the provisions of this type C standard take precedence over the provisions of the other
standards, for machines that have been designed and built according to the provisions of this type C
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1 Scope
1.1 This document specifies the constructional requirements for fans constructed to Group II G (of
explosion groups IIA, IIB and hydrogen) categories 1, 2 and 3, and Group II D categories 2 and 3, intended
for use in explosive atmospheres.NOTE 1 Operation conditions for the different categories of fans used in this document are defined in Clause 4.
NOTE 2 For category 1 D fans, requirements provided in this document are not sufficient to ensure safety. In
addition, explosion protection measures as specified in EN 1127-1:2019 are required to prevent ignition in the case
of rare malfunctions.NOTE 3 Technical requirements for explosion group IIC (other than hydrogen) are not given in this document.
Where such atmospheres are present, additional explosion protection measures as specified in EN 1127-1:2019 can
be needed.1.2 This document does not apply to group I fans (fans for mining), cooling fans or impellers on rotating
electrical machines, cooling fans or impellers on internal combustion engines, vehicles or electric motors.
NOTE 1 Requirements for group I fans are given in EN ISO/IEC 80079-38:2016.NOTE 2 The requirements for electrical parts are covered by references to electrical equipment standards.
1.3 This document specifies requirements for design, construction, testing and marking of complete
fan units intended for use in potentially explosive atmospheres in air containing gas, vapour, mist and/or
dusts. Such atmospheres can exist inside (the conveyed atmosphere (flammable or not)), outside, or
inside and outside of the fan.NOTE This document covers mechanical equipment, in particular fans. The “protection concept” as specified
in EN ISO 80079-37:2016 is constructional safety. Requirements for marking are given in EN ISO 80079-37:2016.
1.4 This document is applicable to fans working in ambient atmospheres and with normal atmospheric
conditions at the inlet, having— absolute pressures ranging from 0,8 bar to 1,1 bar,
— and temperatures ranging from −20 °C to +60 °C,
— and maximum volume fraction of 21 % oxygen content,
— and an aerodynamic energy increase of less than 25 kJ/kg.
NOTE 1 25 kJ/kg is equivalent to 30 kPa at inlet density of 1,2 kg/m .
This document can also be helpful for the design, construction, testing and marking of fans intended for
use in atmospheres outside the validity range stated above or in cases where other material pairings need
to be used. In this case, the ignition risk assessment, ignition protection provided, additional testing (if
necessary), manufacturer's marking, technical documentation and instructions to the user, clearly
demonstrate and indicate the equipment's suitability for the conditions the fan can encounter.
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NOTE 2 Temperatures below −20°C can be considered. Material suitability can require specific evaluation for
these temperatures. With lower temperature the explosion pressure increases, which leads to increased test
pressures (see A.3) and can require specific testing. Although the standard atmospheric conditions in
EN ISO 80079-36:2016 give a temperature range for the atmosphere of −20 °C to +60 °C the normal ambient
temperature range for the equipment is −20 °C to +40 °C unless otherwise specified and marked.
2 Normative referencesThe 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
methodologyEN ISO 80079-36:2016, Explosive atmospheres - Part 36: Non-electrical equipment for explosive
atmospheres - Basic method and requirements (ISO 80079-36:2016)EN ISO 80079-37:2016, Explosive atmospheres - Part 37: Non-electrical equipment for explosive
atmospheres - Non-electrical type of protection constructional safety ''c'', control of ignition sources ''b'',
liquid immersion ''k'' (ISO 80079-37:2016)EN IEC 60079-0:2018, Explosive atmospheres - Part 0: Equipment - General requirements
EN ISO 12100:2010, Safety of machinery - General principles for design - Risk assessment and risk reduction
(ISO 12100:2010)EN ISO 16852:2016, Flame arresters - Performance requirements, test methods and limits for use (ISO
16852:2016)EN ISO 13349:2010, Fans - Vocabulary and definitions of categories (ISO 13349:2010)
ISO 14694:2003, Industrial fans — Specifications for balance quality and vibration levels
3 Terms and definitionsFor the purposes of this document, the terms and definitions given in EN 1127-1:2019,
EN ISO 80079-36:2016 and the following apply.ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/— IEC Electropedia: available at https://www.electropedia.org/
3.1
externally mounted flame arrester
flame arrester consisting of a flame arrester housing and flame arrester elements mounted as a separate
equipment on the fan3.2
integrated flame arrester
flame arrester consisting of a flame arrester housing and flame arrester elements where the flame
arrester housing is part of the fan housing---------------------- Page: 9 ----------------------
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3.3
contact diameter
diameter of a rotating part at the point where it can contact a stationary part
4 Requirements for all fans
4.1 Ignition hazard assessment
4.1.1 General
A list of hazards considered is given in Annex E. These include hazards inside and outside the fan. Where
additional hazards could occur an ignition hazard assessment according to EN ISO 80079-36:2016 shall
be carried out.For the purposes of fans made according to this document the following operational conditions shall be
used as a basis for the ignition hazard assessment and for the assignment of a fan to a particular category.
Release of flammable material shall be considered in the ignition hazard assessment for the outside of
the fan, see 4.3.4.1.2 Normal operating conditions
Normal operating conditions shall be considered to occur in situations where the fan performs its
intended use within its design parameters. This includes conditions during start up and shut down (see
also EN ISO 12100:2010).For the purposes of fans made according to this document, failures (such as a breakdown of seals, flange
gaskets or releases of substances caused by accidents) which involve repair or shut-down are not
considered to be part of normal operation.4.1.3 Expected malfunction
An expected malfunction shall be considered to be a failure or fault in a fan which normally occurs in
practice. In addition, an expected malfunction shall be considered to occur when a fan or its components
do not perform their intended functions.For the purposes of fans made according to this document this can happen for a variety of reasons,
including:a) variation in the properties or dimensions of the fan assembly (e.g. warping of the casing);
b) disturbance to or failure of the power supply or other services;c) unnoticed long time operation with defective bearing and leading to contact between impeller and
housing;d) running for an extended period with high vibrations.
4.1.4 Rare malfunction
A rare malfunction is a type of malfunction which is known to happen but only in rare instances. Two
independent expected malfunctions which, separately, would not create an effective ignition source but
which, in combination, do create an effective ignition source, are regarded as a single rare malfunction.
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4.2 Assignment of categories
4.2.1 General
A fan may have a different category for the inside and outside. Fans which may be used both to convey an
explosive gas, vapour, mist or dust atmosphere and/or are located in an explosive gas, vapour, mist or
dust atmosphere are assigned categories internally and externally depending on the likelihood of them
acting as an effective ignition source.Category 3 fans shall not create an effective ignition source in normal operation, see 4.1.2.
Category 2 fans shall meet category 3 fans requirements, and in addition not create an effective ignition
source with expected malfunctions, see 4.1.3. Category 1 fans shall meet category 2 fans requirements,
and in addition not create an effective ignition source with rare malfunctions, see 4.1.4.
The manufacturer shall also consider following specific aspects in the ignition hazard assessment.
4.2.2 Influence of external parts on internal hazards and vice-versaFor all external parts used for fans with an internal category, the effects of external faults on the interior
shall be considered in the ignition hazard assessments.NOTE 1 An example is fans that use an external drive to support the impeller. Errors in the bearing of the drive
can lead to ignition sources in the interior of the fan housing.The effects of internal faults on the exterior shall be considered in ignition hazard assessments for fans
with an external category.NOTE 2 An example is an unbalanced impeller that results in overheating of an external bearing.
External parts which are in contact with the atmosphere inside the fan, and can create a potential ignition
source, shall have the same equipment category as is required for the interior of the fan. If the equipment
category is achieved by the use of additional instrumentation e.g. a temperature monitoring, then the
overall system shall be evaluated as part of the conformity assessment.NOTE 3 For a configuration shown in Figure D.4 the motor can be considered external to the fan casing. For
configuration shown in Figure D.5 or D.6 with a flange mounted motor the motor can be considered as an internal
part which can create a potential ignition source and is in contact with the atmosphere inside the fan.
4.2.3 LeakageThe manufacturer shall consider leak aspects in the ignition hazard assessment.
Fans, especially their shaft seals and flexible connections at the inlet and outlet, are possibly not
absolutely gas tight, and connected ducts are possibly not leak proof. The hazardous atmosphere can leak
either from the inside of the fan into the adjacent environment, or from a hazardous environment around
a fan, and into the fan casing through a leakage path e.g. a shaft seal when this is below atmospheric
pressure.NOTE 1 A leak is possible in either direction, depending on for example the installation configuration or/and, on
whether the fan is operating.The ignition hazard assessment shall evaluate leaks under all operating conditions that are specified in
the instructions for use as required in Clause 7.NOTE 2 Example situations include a fan which is category 1G or 2G outside and 3G or non-hazardous inside,
which on start-up can contain flammable material due to leaks into the fan housing; and fans which normally convey
gas above the UFL (Upper Flammability Limit), where in-leaks of air can result in the mixture becoming flammable.
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NOTE 3 In normal operation, leakage of flammable material into the fan (gas or dust) is not a hazard as this
would be immediately dissipated by air/gas flow within the fan. Leakage of dust from inside the fan to the external
surroundings would not be sufficient to require the outside of the fan to be additionally rated for dust.
The manufacturer shall give information about possible leakage rates relevant for the actual application
in the information for use. Where the leakage rates are not known, the manufacturer shall construct the
fan so that there is no more than one category difference between the inside and the outside.
Where the fan has an open inlet and/or outlet (installation modes A, B, C according to
EN ISO 13349:2010) the inside and the outside of the fan shall have the same category.
4.3 Temperatures4.3.1 General
Both the temperature of potentially hot surfaces and the temperature of the conveyed atmosphere
(flammable or not) and/or of the atmosphere surrounding the fan shall be considered.
4.3.2 Maximum surface temperatureThe maximum surface temperature of the fan characterizes the hottest part of the equipment that can
come in contact with the explosive atmosphere or the maximum temperature of the conveyed
atmosphere (flammable or not) which can act as an ignition source.The maximum surface temperatures of both the inside and outside parts of the fan that can come in
contact with the explosive atmosphere shall be determined in accordance with EN ISO 80079-36:2016.
In addition to that, the maximum surface temperature marked for the inside of the fan shall be the greater
of either:— the maximum surface temperature determined in accordance with EN ISO 80079-36:2016
including the appropriate safety margins for the different categories; or— the maximum temperature of the conveyed atmosphere (flammable or not) at the outlet with a
safety margin of 20 % (with temperatures measured in °C).These temperatures are determined considering the highest inlet temperature specified in 4.3.3.
NOTE This safety margin of 20 % has been chosen because of the enhanced ignition risk at higher gas
temperatures.The maximum surface temperature of the equipment is used – after the application of the above safety
margins – for marking of the equipment with a defined temperature, a temperature class of the
equipment or an appropriate explosive atmosphere.EXAMPLE A fan with the following parameters: The maximum surface temperature of the inside, measured
according to EN ISO 80079-36:2016 with the appropriate safety margin is 90 °C, the temperature of the conveyed
atmosphere (flammable or not) measured at the outlet is 80 °C for an inlet temperature of 60 °C. With a 20 % safety
margin the maximum outlet temperature is 96 °C. Therefore, the maximum temperature marked for the inside of
the fan is 96 °C.4.3.3 Temperature of the conveyed atmosphere (flammable or not)
While it is only the ambient and the inlet temperature which is generally known by the user, it is the
normally higher outlet temperature which determines the suitability of the fan for the intended use.
As well as temperature increases during normal service, extraordinary temperature increases shall be
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The fan manufacturer shall ensure that the appropriate temperature limits are maintained between
−10 % or +20 % of nominal gas flow, and at maximum and minimum expected densities. The
manufacturer may specify a wider operating range where the temperature limits are maintained.
Generally maximum temperature rise will occur at minimum flow and maximum density. For variable
speed fans the calculation shall be carried out at maximum fan speed and/or the speed which gives
maximum fluid outlet temperature. For fans with motor mounted in conveyed atmosphere (flammable
or not) consideration shall be given to the heating effect from the motor. The manufacturer's instructions
shall include the minimum and maximum air flow rates which are required to maintain the temperature
rating.The manufacturer shall measure or calculate the maximum gas temperature for an inlet gas temperature
of 60 °C within the gas flow limits or - 10 % to 20 % of nominal gas flow.Where the maximum inlet temperature is below 60 °C, the above calculation shall be made with this
lower maximum temperature and the manufacturer shall mark the fan appropriately.Electric motors and other temperature sensitive components shall receive special attention as they
generally are designed for a maximum ambient temperature of +40 °C.4.4 Mechanical design criteria
4.4.1 General
Fans for operation in potentially explosive atmospheres shall be of rigid design. This requirement is
considered as fulfilled for casings, supporting structures, guards, protective devices and other external
parts if the deformation resulting from an impact test at the most vulnerable point is so small t
...
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