Electrostatics -- Part 4-4: Standard test methods for specific applications - Electrostatic classification of flexible intermediate bulk containers (FIBC)

This part of IEC 61340 describes procedures for evaluating the ignition risk presented by electrostatic discharges from FIBC to flammable or explosive environments. The requirements of this standard are applicable to all types of FIBC, tested as manufactured, prior to usage, intended for use without liners in flammable or explosive environments with minimum ignition energy of more than 0,14 mJ, and where the charging currents do not exceed 3,0 μA. NOTE 0,14 mJ is the minimum ignition energy normally quoted for methanol. Although more sensitive materials exist, methanol has the lowest minimum ignition energy of any material that is likely to be present when FIBC are emptied. 3,0 μA is the highest charging current likely to be found in common industrial processes. This combination of minimum ignition energy and charging current represents the most severe conditions that might be expected in practice. Compliance with the requirements of this standard does not mitigate the need for full risk assessment. The test methods included in this standard may be used in association with other performance requirements, for example when a risk assessment has shown the minimum ignition energy of concern is less than 0,14 mJ or charging currents greater than 3,0 μA are present.

Elektrostatik -- Teil 4-4: Normprüfverfahren für spezielle Anwendungen - Einordnung flexibler Schüttgutbehälter (FIBC) in elektrostatischer Hinsicht

Electrostatique -- Partie 4-4: Méthodes d'essai normalisées pour des applications spécifiques - Classification électrostatique des grands récipients pour vrac souples (GRVS)

Décrit des procédures pour évaluer les risques d'inflammation présentés par les décharges électrostatiques des GRVS aux environnements inflammables ou explosifs. Les exigences de la présente norme sont applicables à tous les types de GRVS, essayés dans leurs conditions de fabrication, avant utilisation, destinés à être utilisés sans revêtement protecteur intérieur dans des environnements inflammables ou explosifs avec une énergie minimale d'allumage de plus de 0,14 mJ, et où les courants de charge ne dépassent pas 3,0 A. NOTE 0,14 mJ est l'énergie d'allumage minimale normalement citée pour le méthanol. Bien qu'il existe des matériaux plus sensibles, le méthanol possède l'énergie d'allumage minimale la plus faible de tout matériau qui est susceptible d'être présent lorsque les GRVS sont vidés. 3,0 uA est le courant de charge le plus élevé que l'on est susceptible de rencontrer dans des processus industriels communs. Cette combinaison d'énergie d'allumage minimale et de courant de charge représente les conditions les plus sévères auxquelles on pourrait s'attendre en pratique. La conformité avec les exigences de la présente norme ne réduit pas la nécessité d'une évaluation complète des risques. Les méthodes d'essai comprises dans la présente norme peuvent être utilisées en association avec d'autres exigences d'aptitude à la fonction; par exemple lorsqu'une évaluation des risques a montré que l'énergie d'allumage minimale concernée est inférieure à 0,14 mJ ou que des courants de charge supérieurs à 3,0 uA sont présents.

Elektrostatika - 4-4. del: Standardne preskusne metode za posebne aplikacije - Elektrostatična razvrstitev prožnih vmesnih vsebnikov (FIBC) - Preskusne metode in zahteve (IEC 61340-4-4:2005)

General Information

Status
Withdrawn
Publication Date
31-Jan-2006
Withdrawal Date
02-Nov-2016
Technical Committee
Current Stage
9900 - Withdrawal (Adopted Project)
Start Date
02-Nov-2016
Due Date
25-Nov-2016
Completion Date
03-Nov-2016

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SLOVENSKI SIST EN 61340-4-4:2006

STANDARD
februar 2006
Elektrostatika - 4-4. del: Standardne preskusne metode za posebne aplikacije
– Elektrostatična razvrstitev prožnih vmesnih vsebnikov (FIBC) - Preskusne
metode in zahteve (IEC 61340-4-4:2005)
Electrostatics – Part 4-4: Standard test methods for specific applications –
Electrostatic classification of flexible intermediate bulk containers (FIBC) (IEC
61340-4-4:2005)
ICS 17.220.01; 55.180.99 Referenčna številka
SIST EN 61340-4-4:2006(en)
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

---------------------- Page: 1 ----------------------

EUROPEAN STANDARD EN 61340-4-4
NORME EUROPÉENNE
EUROPÄISCHE NORM November 2005

ICS 17.220.99; 29.020; 55.080


English version


Electrostatics
Part 4-4: Standard test methods for specific applications –
Electrostatic classification of flexible intermediate bulk containers (FIBC)
(IEC 61340-4-4:2005)


Electrostatique Elektrostatik
Partie 4-4: Méthodes d'essai normalisées Teil 4-4: Normprüfverfahren für spezielle
pour des applications spécifiques - Anwendungen –
Classification électrostatique Einordnung flexibler Schüttgutbehälter
des grands récipients pour vrac souples (FIBC) in elektrostatischer Hinsicht
(GRVS) (IEC 61340-4-4:2005)
(CEI 61340-4-4:2005)




This European Standard was approved by CENELEC on 2005-10-01. CENELEC 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.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels


© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 61340-4-4:2005 E

---------------------- Page: 2 ----------------------

EN 61340-4-4:2005 - 2 -
Foreword
The text of document 101/211/FDIS, future edition 1 of IEC 61340-4-4, prepared by IEC TC 101,
Electrostatics and SC 3, Performance requirements and texts for means of packaging, packages and
unit loads, of ISO TC 122, Packaging, was submitted to the IEC-CENELEC parallel vote and was
approved by CENELEC as EN 61340-4-4 on 2005-10-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2006-08-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2008-10-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61340-4-4:2005 was approved by CENELEC as a
European Standard without any modification.
__________

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- 3 - EN 61340-4-4:2005
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications
The following referenced documents are indispensable for the application 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.
NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
1) 2)
IEC 60243-1 - Electrical strength of insulating materials - EN 60243-1 1998
Test methods
Part 1: Tests at power frequencies

1) 2)
IEC 60243-2 - Part 2: Additional requirements for tests EN 60243-2 2001
using direct voltage

1)
ISO 21898 - Packaging - Flexible intermediate bulk - -
containers (FIBCs) for non-dangerous
goods

1)
ASTM E582 - Standard test method for minimum ignition - -
energy and quenching distance in gaseous
mixtures





1)
Undated reference.
2)
Valid edition at date of issue.

---------------------- Page: 4 ----------------------

NORME

IEC

INTERNATIONALE
61340-4-4

INTERNATIONAL

Première édition
STANDARD First edition
2005-10

Electrostatique –
Partie 4-4:
Méthodes d'essai normalisées pour
des applications spécifiques –
Classification électrostatique des grands
récipients pour vrac souples (GRVS)

Electrostatics –
Part 4-4:
Standard test methods for specific applications –
Electrostatic classification of flexible intermediate
bulk containers (FIBC)
Numéro de référence
Reference number
IEC 61340-4-4:2005

---------------------- Page: 5 ----------------------

61340-4-4  IEC:2005 – 3 –
CONTENTS
FOREWORD.5
INTRODUCTION.9
1 Scope.11
2 Normative references .11
3 Terms and definitions .13
4 Labelling .13
5 Requirements .15
5.1 General remarks.15
5.2 Requirements for dust environments with ignition energies greater than 3 mJ .15
5.3 Requirements for vapour and gas atmospheres and for dust environments
with ignition energies of 3 mJ or less.17
6 Atmosphere for conditioning, calibrating and testing .17
7 Test procedures .17
7.1 Electrical breakdown voltage .17
7.2 Ignition testing.17
7.3 Resistance to groundable point .29
8 Report .31
8.1 For all types of testing .31
8.2 For electrical breakdown voltage testing.33
8.3 For ignition testing.33
8.4 For electrical resistance testing .33
Annex A (normative) Electrical breakdown voltage – Typical voltage/time graphs .45
Annex B (normative) Polypropylene pellets for ignition testing .47
Annex C (informative) Inter-laboratory trials.49
Bibliography.51

Figure 1 – Ignition probe.35
Figure 2 – Perforated brass plate for use in ignition probe .37
Figure 3 – Gas control and mixing apparatus (schematic) .39
Figure 4 – FIBC filling rig (schematic) .41
Figure 5 – Corona charging unit (schematic).43
Figure A.1 – Example of voltage/time graph for material showing distinct breakdown.45
Figure A.2 – Example of voltage/time graph for material showing reduction in rate of
voltage rise because of conduction within the test material .45

Table 1 – Volume concentrations of flammable gas mixture .19
Table 2 – Full sample description to be included in test report .33
Table B.1 – Particle size distribution of polypropylene pellets .47
Table C.1 – Ignition testing .49
Table C.2 – Resistance to groundable point.49

---------------------- Page: 6 ----------------------

61340-4-4  IEC:2005 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

ELECTROSTATICS –

Part 4-4: Standard test methods for specific applications –
Electrostatic classification of flexible
intermediate bulk containers (FIBC)


FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61340-4-4 has been prepared by IEC technical committee 101:
Electrostatics, and ISO SC3: Performance requirements and tests for means of packaging,
packages and unit loads, of ISO technical committee 122: Packaging.
It is published as a double logo standard.

---------------------- Page: 7 ----------------------

61340-4-4  IEC:2005 – 7 –
The text of this standard is based on the following documents:
FDIS Report on voting
101/211/FDIS 101/212/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table. In ISO, the standard has been approved by 11 P members
out of 11 having cast a vote.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
IEC 61340 consists of the following parts, under the general title Electrostatics:
1
Part 1: Guide to the principle of electrostatic phenomena ,
Part 2: Measurement methods
Part 3: Methods for simulation of electrostatic effects
Part 4: Standard test methods for specific applications
Part 5: Protection of electronic devices from electrostatic phenomena
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.


———————
1
 Under consideration.

---------------------- Page: 8 ----------------------

61340-4-4  IEC:2005 – 9 –
INTRODUCTION
Flexible intermediate bulk containers (FIBC) are widely used for the storage, transportation
and handling of powdered, flaked or granular material. Typically, they are constructed from
3
woven polypropylene fabric in the form of cubic bags of about 1 m volume. The fabric used
may be a single layer, a multi-layer laminate, or a coated fabric. Untreated polypropylene is a
good electrical insulator, as is often the case with the products placed in FIBC. There is
ample opportunity for the generation of electrostatic charge during filling and emptying
operations and in unprotected FIBC high levels of charge can quickly build up. In such cases
electrostatic discharges are inevitable and can be a severe problem when FIBC are used in
flammable environments.
A flammable environment can be generated when handling fine powders that create dust
clouds or thin layers of powder, both of which can be ignited by electrostatic discharges.
A flammable environment can also be generated when using gases or volatile solvents. In
these industrial situations there is clearly a need to eliminate incendive electrostatic
discharges.
As with any industrial equipment, a thorough risk assessment should always be conducted
before using FIBC in potentially hazardous situations. This International Standard describes
test methods that can be used by manufacturers, specifiers and end-users as part of a risk
assessment of any FIBC intended for use within a flammable or explosive environment.
However, it does not include procedures for evaluating the specific risks of electrostatic
discharges arising from products within FIBC, e.g. cone discharges, or from equipment used
near FIBC.
CAUTION: The test methods specified in this standard involve the use of high voltage power
supplies and flammable gases that may present hazards if handled incorrectly, particularly by
unqualified or inexperienced personnel. Users of this standard are encouraged to carry out
proper risk assessments and pay due regard to local regulations before undertaking any of
the test procedures.

---------------------- Page: 9 ----------------------

61340-4-4  IEC:2005 – 11 –
ELECTROSTATICS –

Part 4-4: Standard test methods for specific applications –
Electrostatic classification of flexible
intermediate bulk containers (FIBC)



1 Scope
This part of IEC 61340 describes procedures for evaluating the ignition risk presented by
electrostatic discharges from FIBC to flammable or explosive environments.
The requirements of this standard are applicable to all types of FIBC, tested as manufactured,
prior to usage, intended for use without liners in flammable or explosive environments with
minimum ignition energy of more than 0,14 mJ, and where the charging currents do not
exceed 3,0 µA.
NOTE 0,14 mJ is the minimum ignition energy normally quoted for methanol. Although more sensitive materials
exist, methanol has the lowest minimum ignition energy of any material that is likely to be present when FIBC are
emptied. 3,0 µA is the highest charging current likely to be found in common industrial processes. This combination
of minimum ignition energy and charging current represents the most severe conditions that might be expected in
practice.
Compliance with the requirements of this standard does not mitigate the need for full risk
assessment.
The test methods included in this standard may be used in association with other performance
requirements, for example when a risk assessment has shown the minimum ignition energy of
concern is less than 0,14 mJ or charging currents greater than 3,0 µA are present.
2 Normative references
The following referenced documents are indispensable for the application 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.
IEC 60243-1, Electric strength of insulating materials – Test methods – Part 1: Tests at power
frequencies
IEC 60243-2, Electric strength of insulating materials – Test methods – Part 2: Additional
requirements for tests using direct voltage
ISO 21898, Packaging – Flexible intermediate bulk containers (FIBCs) for non-dangerous
goods
ASTM E582, Standard test method for minimum ignition energy and quenching distance in
gaseous mixtures

---------------------- Page: 10 ----------------------

61340-4-4  IEC:2005 – 13 –
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply. Other definitions
are as given in IEC 61340-1-2 and ISO 21898.
3.1
quenching
effect of solid objects acting as heat sinks in close proximity to gas
3.2
critical quenching distance
maximum separation distance between opposing electrodes below which quenching prevents
ignition at a specified energy
NOTE For ignitions to take place, the gap between electrodes should be greater than the critical quenching
distance.
3.3
flammable substance
substance in the form of gas, vapour, liquid, solid, or mixture of these, capable of propagating
combustion when subjected to an ignition source
3.4
explosive atmosphere
mixture with air, under atmospheric conditions, of flammable substances in the form of gases,
vapours, mists or dusts in which, after ignition has occurred, combustion spreads to the entire
unburned mixture
3.5
hazardous explosive atmosphere
explosive atmosphere which, if it explodes, causes damage
3.6
minimum ignition energy
least electrical energy of a spark discharge required to ignite a gaseous mixture as
determined by the procedure specified in ASTM E582
3.7
charging current
quantity of charge per unit time flowing into FIBC
3.8
cone discharge
energetic discharge running outwards across the surface from the top of highly charged, non-
conductive powder heaps in large containers
4 Labelling
Flexible intermediate bulk containers (FIBC), for which claims of compliance with this
standard are made, shall be durably marked by means of a permanently attached label, or
other means, with at least the following information:
a) number of standard, i.e. IEC 61340-4-4;
b) either the phrase (for FIBC meeting the requirements of 5.3):
“Static control: use is acceptable in hazardous explosive atmospheres with minimum
ignition energies ≥0,14 mJ/charging currents ≤3,0 µA”,

---------------------- Page: 11 ----------------------

61340-4-4  IEC:2005 – 15 –
or the phrase (for FIBC only meeting the requirements of 5.2):
“Propagating brush discharge control: use is acceptable only in the absence of flammable
gases and vapours and in the absence of dust clouds with ignition energies of 3 mJ or
less”;
c) the phrase “Electrical properties may be affected by general usage, contamination and re-
cycling, or if an inner bag or liner is used”;
d) for FIBC earthed during testing the phrase “FIBC shall be properly earthed according to
manufacturer’s instructions”;
e) for FIBC not earthed during testing the phrase “FIBC does not require earthing”;
f) the phrase “Any conductive objects within 1 m of the FIBC in operation shall be earthed”.
NOTE Unearthed conductive objects within 1 m of an FIBC in operation may become charged by induction or from
corona discharging of the FIBC.
It is the responsibility of FIBC manufacturers to ensure the sample(s) tested are represent-
ative of the production FIBC to which labels shall be attached. When considering type testing,
users shall refer to ISO 21898. For the purposes of electrostatic testing, the presence or
absence of a liner constitutes a change of type.
5 Requirements
5.1 General remarks
A FIBC intended for use in the presence of a flammable material or in a hazardous explosive
atmosphere shall not itself produce incendiary discharges. The absence of incendiary
discharges shall be verified for at least the smallest and largest sizes of FIBC of a particular
design by meeting one of the requirements listed in 5.2 and 5.3 when tested as manufactured,
prior to usage. For the purposes of type testing where a range of outlet sizes are available,
ignition testing according to 7.2 shall be carried out on test FIBC with an outlet size that is the
smaller of a) (400 ± 50) mm, or b) the maximum outlet size for the type under test.
NOTE Compliance with the requirements of this standard may not extend to FIBC that have been contaminated or
degraded through use, or are used contrary to manufacturers’ recommendations. Where it is intended that FIBC be
used for multiple fill/clean/empty cycles, it is recommended that tests be conducted on packages to determine the
maximum number of such cycles for the products to be handled in order to ensure that end of life performance
complies with the requirements of this clause.
5.2 Requirements for dust environments with ignition energies greater than 3 mJ
To ensure propagating brush discharges cannot occur across the walls of a FIBC intended for
use in the presence of combustible dusts but in the absence of flammable vapours or gases, it
shall be constructed from materials having an electrical breakdown voltage of less than or
equal to 6 kV when tested according to 7.1.

---------------------- Page: 12 ----------------------

61340-4-4  IEC:2005 – 17 –
5.3 Requirements for vapour and gas atmospheres and for dust environments with
ignition energies of 3 mJ or less
A FIBC intended for use in the presence of flammable vapours or gases, or combustible dusts
with ignition energies of 3 mJ or less shall meet the requirements of 5.2 and shall not cause
any ignition when tested according to 7.2.
Alternatively, if the FIBC is of a design that relies on earthing to prevent hazardous electrical
8
discharges, then it shall have a resistance of less than 10 Ω when tested according to 7.3.
Additionally the FIBC shall be constructed entirely from conductive material or at least shall
contain fully inter-connected conductive threads or tapes with a maximum spacing of 20 mm if
the threads or tapes are in a stripe pattern or 50 mm if they are in a grid pattern. For FIBC
constructed of multi-layer materials, at least one surface of the FIBC shall have a resistance
8
of less than 10 Ω when tested according to 7.3.
In cases of dispute, all designs of FIBC intended for use in the presence of flammable
vapours or gases, or combustible dusts with ignition energies of 3 mJ or less shall be tested
according to 7.2 and shall not cause any ignition.
6 Atmosphere for conditioning, calibrating and testing
Test samples and apparatus shall be conditioned under both the following atmospheres:
a) (23 ± 2) °C and (20 ± 5) % relative humidity;
b) (23 ± 2) °C and (60 ± 10) % relative humidity.
The conditioning time shall be at least 12 h prior to testing. When tests are to be conducted in
accordance with 7.2, pellets shall be circulated at intervals during this period to ensure
adequate conditioning.
7 Test procedures
7.1 Electrical breakdown voltage
Breakdown voltage shall be determined in accordance with IEC 60243-1 and IEC 60243-2.
The method used is specified in 9.1 of IEC 60243-1, the short-time (rapid-rise) test. The test
shall be conducted with unequal electrodes under the application of direct voltage at a rate of
rise of 300 V/s. For certain materials used in the construction of FIBC there may be some
conductivity which will prevent a sudden breakdown occuring. Typically such materials will
cause a reduction in the rate of voltage rise as charge leaks through the material. An example
is shown in Annex A, Figure A.2. Materials of this nature will not give rise to propogating
brush discharges and shall be deemed to meet the requirements of 5.2.
7.2 Ignition testing
7.2.1 Apparatus
Apparatus other than that specified below may be used, provided that it satisfies the same
functional requirements and is shown to give the same results.

---------------------- Page: 13 ----------------------

61340-4-4  IEC:2005 – 19 –
7.2.1.1 Ignition probe
The ignition probe is a cylinder made from rigid non-conductive material such as poly-
carbonate or acrylic with an internal diameter of (70 ± 5) mm and an internal length of (100 ±
5) mm (see Figure 1). The material used for constructing the probe shall be of sufficient
thickness and strength to withstand repeated ignition without cracking, distorting or otherwise
failing.
One end of the cylinder is closed apart from a central port to allow the inflow of the flammable
gas. The size of the inlet port is not critical but shall be large enough to allow the required
flow rate to be achieved without excessive pressure build-up. A suitable flame arrestor shall
be installed in the gas supply line as close as possible to the ignition probe.
A brass plate is fitted to the other end of the cylinder to form a fixing base for the discharge
electrode (see Figure 2). The brass plate is drilled with holes, (5 ± 1) mm in diameter to allow
the uniform flow of gas through it and around the discharge electrode.
A spherical brass electrode of diameter (20 ± 5) mm is mounted centrally to the brass plate.
The electrode, brass plate and any other metal or conductive material in the ignition probe are
connected to a common point earth via a low impedance (<10 Ω) connection. The earth point
shall be the common point earth for local structures and equipment to the FIBC such as
conductive parts of the FIBC test rig. The common earth point may, or may not, be connected
to the electricity supply earth. The connection between the electrode, the brass plate and the
earth connector shall be sufficiently robust to withstand physical and thermal impacts. The
electrical continuity between the discharge electrode and the earth connector shall be
checked prior to use.
The ignition probe is filled with glass beads, nominally 1 mm to 2 mm diameter, which are
retained by a fine copper gauze or mesh at either end of the main cylinder. The glass beads
assist in the mixing of the gases and also contribute to preventing propagation of any flame
back through the probe.
An adjustable shroud is fitted to the cylinder to direct gas over the discharge electrode and
into the region in front of the discharge electrode where electrostatic discharges take place.
The opening in this shroud is (40 ± 5) mm
7.2.1.2 Gas control and mixing apparatus
The flammable gas is generated by mixing ethylene with air. The air used shall contain
(21,0 ± 0,5) % oxygen and (79,0 ± 0,5) % nitrogen. The gas control and mixing apparatus is
used to direct the gas in the appropriate proportions to t
...

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