Table 2 – Permissible configurations and requirements for Type L2 inner liners Configuration Parameters Resistivity of inside surface ρI Resistivity of outside surface ρO Breakdown
Principles of classification for FIBC
Type A
Type A FIBCs are constructed from fabric or plastic sheets and lack measures to prevent static electricity buildup Any FIBC that fails to meet the criteria outlined in Clause 7 or has not undergone the necessary testing is categorized as Type A.
Type B
Type B FIBC are made from fabric or plastic sheet designed to prevent the occurrence of sparks and propagating brush discharges.
Type C
Type C FIBCs are constructed from conductive materials, such as fabric or plastic sheets, and incorporate conductive threads or filaments These bags are specifically engineered to mitigate the risk of incendiary sparks and brush discharges To ensure safety during filling and emptying processes, Type C FIBCs must be grounded.
Type D
Type D FIBCs are constructed from static protective fabric that effectively prevents incendiary sparks and brush discharges, eliminating the necessity for an earth connection.
3.15 type qualification testing testing used to determine the type of FIBC as specified in 4.1 and to demonstrate that FIBC meet the requirements of Clause 7
3.16 quality control testing testing designed to provide manufacturers and users with information that demonstrates all
FIBC produced and delivered are substantially the same as the sample FIBC used to qualify the FIBC design
3.17 groundable point point on FIBC designated by the manufacturer as a location to attach a grounding or earth bonding cable or other means of earthing FIBC
Each FIBC may have one or more designated groundable points, including lift loops However, relying on lifting hooks for grounding is not advisable, as they may be painted, coated, or covered with powder, which can compromise the effectiveness of the earth path.
4.1 Principles of classification for FIBC
FIBCs are categorized into four distinct types: Type A, Type B, Type C, and Type D These classifications are based on the construction of the FIBC, the specific nature of their intended use, and the performance requirements associated with each type.
A single FIBC design can only be classified under one specific type, meaning it cannot be categorized as both Type B and Type D, or as Type CD at the same time.
Type A FIBCs are constructed from fabric or plastic sheets and lack measures to prevent static electricity buildup Any FIBC that fails to meet the criteria outlined in Clause 7 or has not undergone the necessary testing is categorized as Type A.
Type B FIBC are made from fabric or plastic sheet designed to prevent the occurrence of sparks and propagating brush discharges
Type C FIBCs are constructed from conductive materials, such as fabric or plastic, and feature conductive threads to mitigate the risk of incendiary sparks and brush discharges These bags are specifically engineered to be grounded during both filling and emptying processes, ensuring safety and preventing static electricity buildup.
Type D FIBCs are constructed from static protective fabric that effectively prevents incendiary sparks and brush discharges, eliminating the necessity for an earth connection.
Principles of classification and requirements for inner liners
Surface resistivity measurements for inner liners
Surface resistivity must be measured in accordance with IEC 61340-2-3, requiring at least ten measurements taken at evenly distributed points across the inner liner surface All measurements should fall within the specified limits for the tested inner liner type.
Special cases
Inner liners with a conductive layer between two insulating layers are prohibited in Type B and Type D FIBCs In Type C FIBCs, if such an inner liner is utilized, the conductive layer must be firmly connected to the earth Additionally, the insulating layers must have a thickness of less than 700 µm, and the breakdown voltage, measured between an electrode on each surface and the conductive layer, should be under 4 kV, following the measurement conditions outlined in section 8.2.
NOTE In order to avoid incendiary brush discharge, the thickness of any exposed insulating layers in contact with non-insulating layers is limited to a maximum of 700 àm.
Type L1
Type L1 inner liners are constructed from materials that exhibit a surface resistivity of 1.0 × 10^7 Ω or lower on at least one surface, as outlined in Annex F and measured according to the specifications in section 8.2 of this standard These liners are suitable for use in Type C Flexible Intermediate Bulk Containers (FIBC).
For multi-layered materials or those with a surface resistivity exceeding 1.0 × 10² Ω, the breakdown voltage must be below 4 kV, as measured in accordance with section 9.1 and the conditions outlined in section 8.2.
The thickness of any layer with surface resistivity greater than 1,0 × 10 12 Ω on the inside (product side) of the inner liner material shall be less than 700 àm
Permissible configurations and requirements for type L1 inner liners are summarized in Table 1
Table 1 – Permissible configurations and requirements for Type L1 inner liners
Parameters Resistivity of inside surface ρ I
1 ρ I ≤ 1,0 × 10 7 Ω ρ O ≤ 1,0 × 10 7 Ω No measurement required No limit
2A ρ I ≤ 1,0 × 10 7 Ω ρ O ≤ 1,0 × 10 12 Ω No measurement required No limit
2B ρ I ≤ 1,0 × 10 12 Ω ρ O ≤ 1,0 × 10 7 Ω No measurement required No limit
Type L2
Type L2 inner liners are constructed from materials that exhibit a surface resistivity ranging from \$1.0 \times 10^9 \, \Omega\$ to \$1.0 \times 10^{12} \, \Omega\$ on at least one surface, as detailed in Annex F and measured according to the specifications in section 8.3 These liners are suitable for use in Type B, Type C, and Type D Flexible Intermediate Bulk Containers (FIBC).
If Type L2 inner liners are used in Type C FIBC, the charging current shall not exceed 3 àA
For multi-layered materials or those with a surface resistivity exceeding \$1.0 \times 10^{12} \, \Omega\$, the breakdown voltage must be below 4 kV, as measured in accordance with section 9.1 under the specified conditions of section 8.2.
The thickness of any layer with surface resistivity greater than 1,0 × 10 12 Ω on the inside (product side) of the inner liner material shall be less than 700 àm
Permissible configurations and requirements for Type L2 inner liners are summarized in Table 2
Table 2 – Permissible configurations and requirements for Type L2 inner liners
Parameters Resistivity of inside surface ρ I
1 1,0 × 10 9 Ω ≤ ρ I ≤ 1,0 × 10 12 Ω 1,0 × 10 9 Ω ≤ ρ O ≤ 1,0 × 10 12 Ω No measurement required No limit
Type L3
Type L3 inner liners are made from materials with surface resistivity of greater than 1,0 × 10 12 Ω, measured under the conditions specified in 8.2 Type L3 inner liners may be used in Type B FIBC
The breakdown voltage through the material shall be less than 4 kV, measured according to 9.1 under the conditions specified in 8.2
Permissible configurations and requirements for Type L3 inner liners are summarized in Table 3
Table 3 – Permissible configurations and requirements for Type L3 inner liners
Parameters Resistivity of inside surface ρ I
Combination of FIBC and inner liners
The addition of an inner liner to a Flexible Intermediate Bulk Container (FIBC) does not alter its type classification For instance, a Type A FIBC equipped with Type L1 inner liners remains classified as Type A FIBC and must adhere to all usage restrictions applicable to Type A FIBCs.
The breakdown voltage requirements for FIBC and their inner liners must be assessed independently For Type B, Type C, and Type D FIBCs that have specific breakdown voltage criteria, two distinct sets of measurements are necessary: one for the FIBC material and another for the inner liner material For instance, when evaluating a Type B FIBC, it is essential to conduct these separate tests.
If Type L2 inner liners are used in Type C FIBC, the charging current shall not exceed 3 àA
For multi-layered materials or those with a surface resistivity exceeding \$1.0 \times 10^{12} \, \Omega\$, the breakdown voltage must be below 4 kV, as measured in accordance with section 9.1 and the conditions outlined in section 8.2.
The thickness of any layer with surface resistivity greater than 1,0 × 10 12 Ω on the inside
(product side) of the inner liner material shall be less than 700 àm
Permissible configurations and requirements for Type L2 inner liners are summarized in
Table 2 – Permissible configurations and requirements for Type L2 inner liners
Parameters Resistivity of inside surface ρ I
1 1,0 × 10 9 Ω ≤ ρ I ≤ 1,0 × 10 12 Ω 1,0 × 10 9 Ω ≤ ρ O ≤ 1,0 × 10 12 Ω No measurement required No limit
Type L3 inner liners are made from materials with surface resistivity of greater than
1,0 × 10 12 Ω, measured under the conditions specified in 8.2 Type L3 inner liners may be used in Type B FIBC
The breakdown voltage through the material shall be less than 4 kV, measured according to
9.1 under the conditions specified in 8.2
Permissible configurations and requirements for Type L3 inner liners are summarized in
Table 3 – Permissible configurations and requirements for Type L3 inner liners
Parameters Resistivity of inside surface ρ I
4.3 Combination of FIBC and inner liners
The inclusion of an inner liner in FIBC does not change the type classification of the FIBC
For example, Type A FIBC with Type L1 inner liners are still Type A FIBC and are subject to all the restrictions on use of Type A FIBC
The requirements for breakdown voltage for FIBC and inner liners shall be applied separately
For Type B, Type C and Type D FIBC with inner liners for which there is a breakdown voltage requirement, two sets of breakdown voltage measurement shall be required: one set on the
FIBC material and one set on the inner liner material For example, if a Type B FIBC is fitted
According to IEC 61340-4-4:2012, the breakdown voltage of FIBC material with a Type L3 inner liner must be measured independently, and it should be less than 6 kV Additionally, the inner liner material requires a separate breakdown voltage measurement, which must be below 4 kV.
FIBC requirements and specifications vary based on the nature and sensitivity of explosive atmospheres during filling and emptying The primary objective in constructing FIBC is to prevent incendiary discharges from the fabric during use However, compliance with these standards does not guarantee the absence of hazardous electrostatic discharges, such as cone discharges, which may arise from the contents within the FIBC For detailed information on the risks linked to cone discharges, refer to Annex E.
Electrostatic discharges, including sparks, brush discharges, and propagating brush discharges, have varying ignition capabilities The exclusion of these discharges and the corresponding requirements for Flexible Intermediate Bulk Containers (FIBCs) are determined by their intended applications Table 4 outlines the specific conditions for the use of each type of FIBC.
Table 4 – Use of different types of FIBC
Bulk product in FIBC Surroundings
MIE of dust a Non-flammable atmosphere Dust zones 21-22 b
Gas zones 1-2 b (Explosion groups IIA/IIB) b dust zones 21-22 or b (MIE ≤ 3 mJ) a
NOTE 1 Additional precautions are usually necessary when a flammable gas or vapour atmosphere is present inside the FIBC, e.g in the case of solvent wet powders
A non-flammable atmosphere is defined as one that includes dusts with a minimum ignition energy (MIE) greater than 1,000 mJ, as measured according to IEC 61241-2-3 using a capacitive discharge circuit without added inductance For further details on hazardous areas, zones, and explosion groups, refer to Annex D The use of Type D equipment is restricted to explosion groups IIA/IIB with an MIE of at least 0.14 mJ Additionally, Annex E provides an explanation regarding the 3 mJ limit in relation to cone discharges.
The safe use of FIBC in hazardous explosive atmospheres can be affected by the installation of an inner liner Table 5 outlines the combinations of FIBC and inner liners that are deemed safe for such environments Additionally, specific requirements for both FIBC and inner liners, as well as for certain combinations, are detailed in Table 5.
Table 5 – Inner liners and FIBC: combinations that are permissible and not permissible in hazardous explosive atmospheres
Type B Not permissible Permissible Permissible
Type C Permissible a Permissible Not permissible
Type D Not permissible Permissible b Not permissible
According to IEC 61340-4-4:2012, the breakdown voltage of FIBC material with a Type L3 inner liner must be measured independently, and it should be less than 6 kV Additionally, the inner liner material requires a separate breakdown voltage measurement, which must be below 4 kV.
FIBC requirements and specifications vary based on the nature and sensitivity of explosive atmospheres during filling and emptying The primary objective in constructing FIBC is to prevent incendiary discharges from the fabric during use However, compliance with these standards does not guarantee the absence of hazardous electrostatic discharges, such as cone discharges, which may arise from the contents within the FIBC For detailed information on the risks linked to cone discharges, refer to Annex E.
Electrostatic discharges, including sparks, brush discharges, and propagating brush discharges, have varying ignition capabilities The exclusion of these discharges and the corresponding requirements for Flexible Intermediate Bulk Containers (FIBCs) are determined by their intended applications Table 4 outlines the specific conditions for the use of each type of FIBC.
Table 4 – Use of different types of FIBC
Bulk product in FIBC Surroundings
MIE of dust a Non-flammable atmosphere Dust zones 21-22 b
Gas zones 1-2 b (Explosion groups IIA/IIB) b dust zones 21-22 or b (MIE ≤ 3 mJ) a
NOTE 1 Additional precautions are usually necessary when a flammable gas or vapour atmosphere is present inside the FIBC, e.g in the case of solvent wet powders
A non-flammable atmosphere is defined as one that includes dusts with a minimum ignition energy (MIE) greater than 1,000 mJ, as measured according to IEC 61241-2-3 using a capacitive discharge circuit without added inductance For further details on hazardous areas, zones, and explosion groups, refer to Annex D The use of Type D equipment is restricted to explosion groups IIA/IIB with an MIE of at least 0.14 mJ Additionally, Annex E provides an explanation regarding the 3 mJ limit in relation to cone discharges.
The safe use of FIBC in hazardous explosive atmospheres can be affected by the installation of an inner liner Table 5 outlines the combinations of FIBC and inner liners that are deemed safe for such environments In addition to the individual requirements for FIBC and inner liners, specific combinations must also meet certain criteria, which are detailed in Table 5.
Table 5 – Inner liners and FIBC: combinations that are permissible and not permissible in hazardous explosive atmospheres
Type B Not permissible Permissible Permissible
Type C Permissible a Permissible Not permissible
Type D Not permissible Permissible b Not permissible
FIBC requirements and specifications are influenced by the nature and sensitivity of explosive atmospheres during filling and emptying The primary objective in constructing FIBC is to prevent incendiary discharges from the fabric during use However, FIBC that meets the specified standards does not guarantee the absence of hazardous electrostatic discharges, such as cone or spark discharges from charged conductive materials For detailed information on the risks related to cone discharges, refer to Annex E.
To ensure proper earthing of the inner liner, the resistance from at least one side of the inner liner to the groundable points on the FIBC must be less than \$1.0 \times 10^7 \, \Omega\$, as measured according to section 9.3 under the specified conditions in section 8.2 Additionally, the combination of the FIBC and liner must comply with the requirements outlined in section 7.3.2, tested under the conditions specified in section 8.3.
Type A FIBC shall not be used in hazardous explosive atmospheres, irrespective of the type of liner used
Liners shall not be removed from emptied FIBC in hazardous explosive atmospheres
General remarks
FIBCs designed for environments with flammable materials or explosive atmospheres must not generate incendiary discharges To ensure safety, it is essential to verify the absence of such discharges for both the smallest and largest sizes of a specific FIBC design, in accordance with the requirements outlined in sections 7.2 and 7.3, prior to their use.
Quality control test methods described in Annex C shall not be used as a subsitute for type qualification test methods specified in Clause 9
Compliance with this standard does not apply to FIBCs that have been contaminated, degraded, or used against the manufacturer's recommendations For FIBCs intended for multiple fill, clean, and empty cycles, it is advisable to conduct tests as outlined in Clause 9 to ensure they meet the requirements of Clause 7 after the specified number of cycles.
Type qualification certificates for FIBC designs must be accompanied by a test report that includes the details outlined in Clause 10 Unless otherwise agreed upon by the involved parties, these certificates remain valid for three years from the date of issuance.
Requirements for dust environments with ignition energies greater than 3 mJ (apply to Type B FIBC, Type C FIBC and Type D FIBC)
To prevent propagating brush discharges in FIBCs used with combustible dusts and without flammable vapours or gases, the construction materials must have an electrical breakdown voltage of 6 kV or less, as per testing standards Additionally, materials for inner baffles, excluding mesh or net baffles, must also comply with this voltage requirement.
Requirements for vapour and gas atmospheres and for dust environments
Type C FIBC
A Type C FIBC designed for environments with flammable vapours, gases, or combustible dusts with ignition energies of 3 mJ or less must exhibit a resistance to groundable points of less than 1.0 × 10^7 Ω, as specified in Annex F Furthermore, the FIBC should be made entirely from conductive materials or incorporate fully interconnected conductive threads or tapes, ensuring a maximum spacing of 20 mm for stripe patterns and 50 mm for grid patterns.
For FIBC constructed of multi-layer materials, the inside or outside surface of the FIBC shall have a resistance to groundable point of less than 1,0 × 10 7 Ω when tested according to 9.3
If the inside layer does not have a resistance to groundable point of less than 1,0 × 10 7 Ω,
Figure 2 – Example of a label for Type C FIBC
Figure 3 – Example of a label for Type D FIBC
Replace the third and fourth paragraphs by the following new text:
IEC TS 60079-32-1 outlines the testing apparatus and procedures for charging materials and measuring charge transfer It is important to note that the recommended rubbing materials may not be suitable for all types of Flexible Intermediate Bulk Containers (FIBC), and alternative materials can be used when necessary.
The maximum charge transfer limits outlined in IEC TS 60079-32-1 are derived from electrostatic discharges originating from homogeneous, non-conductive materials However, the characteristics of electrostatic discharges from certain static protective Flexible Intermediate Bulk Containers (FIBCs) can vary in both spatial and temporal aspects.
FIBC does not require earthing
• Permitted in dust zones 21- 22 and gas zones 1- 2 (explosion groups IIA/IIB with
MIE ≥ 0,14 mJ) and where charging currents ≤ 3 à A
• Electrical properties may be affected by general usage, contamination and reconditioning
• All conductive objects, including personnel shall be earthed during FIBC filling and emptying operations
FIBC shall be properly earthed according to manufacturer’s instructions
• Permitted in dust zones 21-22 and in gas zones 1-2 (explosion groups IIA/IIB)
• Electrical properties may be affected by general usage, contamination and reconditioning
• All conductive objects, including personnel shall be earthed during FIBC filling and emptying operations
IEC then the material shall also meet the requirements specified in 7.2 All layers of multi-layer materials shall remain in firm contact during filling and emptying operations
The materials used to construct inner baffles, other than mesh or net baffles, shall also meet these requirements and shall be included in the tests conducted according to 9.3.
Type D FIBC
A Type D FIBC is designed for environments with flammable vapours, gases, or combustible dusts that have ignition energies of 3 mJ or less When tested according to section 9.2, these bags must not cause any ignition.
Type D FIBCs, which feature an insulating layer such as a coating film or lamination on the interior, must comply with the specifications outlined in section 7.2 It is essential that all layers of multi-layer materials maintain firm contact throughout both filling and emptying processes.
For type qualification testing of a specific design with various outlet sizes, ignition testing must be conducted on a test FIBC using the smaller outlet size, which is either 400 mm or the maximum outlet size designated for the design being tested.
The materials used to construct inner baffles, other than mesh or net baffles, shall be the same as the materials used to construct the major panels of the FIBC
8 Atmosphere for conditioning, calibrating and testing
Conditioning time
For optimal testing, conditioning time must be a minimum of 12 hours, with test samples suspended freely to promote adequate air circulation During this period, pellets should be circulated at intervals to ensure proper conditioning, in accordance with section 9.2.
Electrical breakdown voltage and resistance to groundable point testing
Test samples and apparatus shall be conditioned, calibrated and tested under conditions of
Ignition testing
Test samples and apparatus shall be conditioned, calibrated and tested under conditions of a) (23 ± 2) °C and (20 ± 5) % relative humidity; b) (23 ± 2) °C and (60 ± 10) % relative humidity
Electrical breakdown voltage
The breakdown voltage is determined following IEC 60243-1 and IEC 60243-2 standards, specifically using the short-time (rapid-rise) test outlined in section 9.1 of IEC 60243-1:1998 This test involves applying direct voltage with unequal electrodes at a rise rate of 300 V/s, while ensuring that the maximum output current of the DC power supply does not exceed 1 mA.
For multi-layer materials, it is essential to test all layers simultaneously, ensuring that the test specimens are arranged with the high-voltage electrode in contact with the surface typically located on the interior of the FIBC.
– 18 – 61340-4-4 IEC:2012 then the material shall also meet the requirements specified in 7.2 All layers of multi-layer materials shall remain in firm contact during filling and emptying operations
The materials used to construct inner baffles, other than mesh or net baffles, shall also meet these requirements and shall be included in the tests conducted according to 9.3
A Type D FIBC is designed for environments with flammable vapours, gases, or combustible dusts that have ignition energies of 3 mJ or less When tested according to section 9.2, it must not cause any ignition.
Type D FIBCs, which feature an insulating layer such as a coating film or lamination on the interior, must comply with the specifications outlined in section 7.2 It is essential that all layers of multi-layer materials maintain firm contact throughout the filling and emptying processes.
For type qualification testing involving various outlet sizes for a specific design, ignition testing must be conducted on test FIBCs using the smaller outlet size, which is either 400 mm or the maximum outlet size designated for the design being tested.
The materials used to construct inner baffles, other than mesh or net baffles, shall be the same as the materials used to construct the major panels of the FIBC
8 Atmosphere for conditioning, calibrating and testing
For optimal testing, conditioning time must be a minimum of 12 hours, with test samples suspended freely to promote adequate air circulation During this period, pellets should be circulated at intervals to ensure proper conditioning, in accordance with section 9.2.
8.2 Electrical breakdown voltage and resistance to groundable point testing
Test samples and apparatus shall be conditioned, calibrated and tested under conditions of
Test samples and apparatus shall be conditioned, calibrated and tested under conditions of a) (23 ± 2) °C and (20 ± 5) % relative humidity; b) (23 ± 2) °C and (60 ± 10) % relative humidity
Breakdown voltage shall be determined in accordance with IEC 60243-1 and IEC 60243-2
The short-time (rapid-rise) test, as outlined in section 9.1 of IEC 60243-1:1998, involves conducting the test with unequal electrodes while applying direct voltage at a rise rate of 300 V/s The DC power supply must have a maximum output current of 1 mA.
For multi-layer materials, it is essential to test all layers simultaneously, ensuring that the test specimens are arranged with the high-voltage electrode in contact with the surface typically located on the interior of the FIBC.
Figure A.1 illustrates a voltage/time graph for materials that exhibit distinct breakdown characteristics Some materials used in FIBC construction possess conductivity that mitigates sudden breakdowns, leading to a slower voltage rise due to charge leakage This behavior is exemplified in Figure A.2 Such materials do not produce propagating brush discharges and comply with the requirements outlined in section 7.2.
If the output current of the DC power supply reaches 1 mA before the electrode voltage reaches 6 kV, the material under test shall be deemed to meet the requirements of 7.2.
Ignition testing
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
The ignition probe is a cylindrical device constructed from a rigid, non-conductive material like polycarbonate or acrylic It features an internal diameter of (70 ± 5) mm and an internal length of (100 ± 5) mm.
5) The material used for constructing the probe shall be of sufficient thickness and strength to withstand repeated ignition without cracking, distorting or otherwise failing
The cylinder features a closed end with a central port for the inflow of flammable gas While the inlet port size is not critical, it must be sufficiently large to maintain the necessary flow rate without causing excessive pressure build-up Additionally, a suitable flame arrestor should be installed in the gas supply line, positioned as close as possible to the ignition probe.
A metal plate is attached to one end of the cylinder, serving as a base for the discharge electrode This plate features holes with a diameter of (5 ± 1) mm, ensuring a uniform gas flow around the discharge electrode.
A spherical metal electrode with a diameter of (20 ± 5) mm is centrally mounted on a metal plate, with all metal components, including the electrode and plate, connected to a common earth point through a low impedance connection of less than 10 Ω This common earth point serves as the grounding for local structures and equipment associated with the FIBC, such as the conductive parts of the FIBC test rig, and may also be linked to the electricity supply earth It is essential that the connection between the electrode, metal plate, and earth connector is robust enough to endure physical and thermal stresses, and electrical continuity between the discharge electrode and the earth connector must be verified before use.
The ignition probe contains glass or porcelain beads, typically ranging from 1 mm to 2 mm in diameter, secured by fine metal gauze or mesh at both ends of the main cylinder These beads play a crucial role in gas mixing and help prevent the backpropagation of flames through the probe.
An adjustable insulating shroud is attached to the cylinder to channel gas over the discharge electrode and into the area where electrostatic discharges occur The shroud features an opening measuring (40 ± 5) mm.
2 adjustable shroud made from insulating material
3 cylinder made from insulating material
4 perforated metal plate (2 mm nominal thickness)
5 fine metal mesh or gauze (e.g copper)
6 beads (e.g glass or porcelain), 1–2 mm diameter (nominal)
9 inlet port for flammable gas
2 adjustable shroud made from insulating material
3 cylinder made from insulating material
4 perforated metal plate (2 mm nominal thickness)
5 fine metal mesh or gauze (e.g copper)
6 beads (e.g glass or porcelain), 1–2 mm diameter (nominal)
9 inlet port for flammable gas
2 mounting hole for discharge electrode
3 screw for securing plate to body of ignition probe
Figure 6 – Perforated metal plate for use in ignition probe
9.2.1.2 Gas control and mixing apparatus
Flammable gas is produced by combining ethylene with air, ensuring the ethylene has a minimum purity of 99.5% The air must consist of 21.0 ± 0.5% oxygen and 79.0 ± 0.5% nitrogen A gas control and mixing apparatus is utilized to deliver the gas in the correct proportions to the ignition probe.
The volume concentrations of gas used are shown in Table 6
Table 6 – Volume concentrations of flammable gas mixture
The control of the gas mixture within the specified tolerances shall be checked using, for example, an infra-red ethylene gas analyser sampling the gas mixture supply line
If a gas mixture other than that specified in Table 6 is used, the minimum ignition energy of the gas mixture shall be verified using the ASTM E582 method to be (0,14 ± 0,01) mJ
NOTE 1 If a gas other than ethylene is used, the critical quenching distance may be different to that specified in Table 6
Compressed gas cylinders are a convenient option for gas supply, though alternative sources are available A pre-mixed cylinder containing (21.0 ± 0.5)% oxygen and (79.0 ± 0.5)% nitrogen can serve as a substitute for air Additionally, molecular sieve filters should be utilized if required.
BS EN 61340-4-4:2012 ensure the gases have low moisture content This is particularly important, for example, when using air directly from a compressor Gases of at least 99,5 % purity shall be used
NOTE 2 “Breathing air” has a wider tolerance of oxygen concentration than is specified in Table 6 and should not be used Some molecular sieves may absorb ethylene so it is important to position the sieve filter before the gas reaches monitoring equipment
Each gas supply is controlled and monitored using flowmeters and valves The combined flow-rate of all gases through the ignition probe shall be (0,21 ± 0,04) l/s
A fast action shut-off valve is essential for halting the flow of ethylene during ignition events This valve effectively stops ethylene supply while allowing air to circulate freely, ensuring the cooling and drying of the ignition probe post-ignition The selection of the shut-off valve's type and location must be tailored to the specific design of the overall apparatus.
5 air or oxygen/nitrogen mixture
Figure 7 – Gas control and mixing apparatus (schematic)
– 22 – 61340-4-4 IEC:2012 ensure the gases have low moisture content This is particularly important, for example, when using air directly from a compressor Gases of at least 99,5 % purity shall be used
NOTE 2 “Breathing air” has a wider tolerance of oxygen concentration than is specified in Table 6 and should not be used Some molecular sieves may absorb ethylene so it is important to position the sieve filter before the gas reaches monitoring equipment
Each gas supply is controlled and monitored using flowmeters and valves The combined flow-rate of all gases through the ignition probe shall be (0,21 ± 0,04) l/s
A fast action shut-off valve is essential for halting the flow of ethylene during ignition events, while still allowing air to circulate for cooling and drying the ignition probe The selection of the shut-off valve's type and location must be tailored to the specific design of the apparatus.
5 air or oxygen/nitrogen mixture
Figure 7 – Gas control and mixing apparatus (schematic)
9.2.1.3 Re-circulating FIBC filling rig
A rigid steel framework or appropriate support is essential for holding test FIBCs during the filling process with charged products To reduce the impact of the steel framework on the electrostatic fields of the charged FIBC, it is crucial that any support structure surrounding the FIBC is positioned at least 1 meter away.
Test FIBCs are filled with homopolymer polypropylene pellets that have a minimum volume resistivity of 1.0 × 10^12 Ωm These pellets must not contain fillers, pigments, or antistatic additives Alternative materials may be considered only if they demonstrate equivalent performance and do not cause cone discharges.
NOTE 1 One way of checking the equivalence of different pellet materials is to carry out the procedures specified in 9.2.2 to establish that the voltage applied to the corona charging unit generates the same charging current
Establishing correct charging current
Ensure that the conductive FIBC is mounted on the filling rig, verifying that the resistance between the conductive FIBC and the filling rig, or any other earth connection, is a minimum of \$1.0 \times 10^{12} \, \Omega\$.
To ensure accurate measurements, connect the electrometer to the groundable point on the conductive FIBC and establish a ground connection If utilizing a separate averaging instrument, it should be connected to the electrometer for optimal functionality.
Begin pellet flow of (1,1 ± 0,1) kg/s into the FIBC and apply desired voltage to the corona charging unit
Once the bottom of the FIBC is filled with pellets and a consistent cone of pellets has been formed, proceed with performing average measurements
Using the average function on the electrometer or the separate averaging instrument, perform
The charging current was measured over three one-minute intervals, and the average current for each period was recorded These three one-minute averages were then averaged together to determine the overall average charging current, which was noted alongside the voltage applied to the corona charging unit.
Continue the process until the voltage level required for the corona charging unit to achieve a current of (3.0 ± 0.2) µA is established This voltage level will be utilized for all future testing with the corona charging unit.
Ignition tests
Ignition tests involve positioning the ignition probe against the wall of the charged test FIBC while a flammable gas mixture flows through it The testing sequence aims to conduct a minimum of 200 ignition tests on the test FIBC However, the sequence can be stopped at any point after a single verifiable ignition, indicating that the test FIBC has not met the requirements outlined in section 7.3.2.
To complete the required number of ignition attempts, it may be necessary to fill and empty the test FIBC multiple times For FIBCs lacking an outlet, a properly sized cut should be made in the base Additionally, using several FIBCs of the same design and size may be required to finish the full test sequence.
Ignition attempts must be evenly distributed across the four walls of the test FIBC, with 50 attempts on each wall For FIBCs lacking clearly defined sides, a total of 200 ignition attempts should be conducted across the entire area Additionally, 10 ignition attempts are required on any attached panels, such as flaps covering spouts, on panels with significant construction differences, and on labels or document pouches exceeding 100 cm² in area.
100 cm 2 and lifting straps do not need to be tested
Ignition attempts may be conducted at locations beyond those specified in the standard, provided there is an agreement among the interested parties The test report must detail the positions of any additional measurement points If any verifiable ignition occurs during testing, the FIBC being tested will not meet the requirements outlined in section 7.3.2.
Begin the flow of pellets at a rate of (1.1 ± 0.1) kg/s with the discharging spout of the FIBC closed, and apply the specified voltage to the corona charging unit as outlined in section 9.2.2 Allow the pellets to fill the designated area.
Ensure that the conductive FIBC is mounted on the filling rig, verifying that the resistance between the conductive FIBC and the filling rig, or any other earth connection, is a minimum of \$1.0 \times 10^{12} \, \Omega\$.
To ensure accurate measurements, connect the electrometer to the groundable point on the conductive FIBC and establish a ground connection If utilizing a separate averaging instrument, it should be connected to the electrometer for optimal functionality.
Begin pellet flow of (1,1 ± 0,1) kg/s into the FIBC and apply desired voltage to the corona charging unit
Once the bottom of the FIBC is filled with pellets and a consistent cone of pellets has been formed, proceed with performing average measurements
Using the average function on the electrometer or the separate averaging instrument, perform
Record the average charging current over three one-minute intervals and calculate the overall average from these three readings Additionally, document the average charging current alongside the voltage applied to the corona charging unit.
Repeat the procedure until the voltage level applied to the corona charging unit to produce
(3,0 ± 0,2) àA is determined For subsequent testing, this voltage level shall be applied to the corona charging unit
Ignition tests involve positioning the ignition probe against the wall of the charged test FIBC while a flammable gas mixture flows through it The testing procedure aims to conduct a minimum of 200 ignition tests on the test FIBC However, the sequence can be halted after a single verifiable ignition, indicating that the test FIBC has not met the criteria outlined in section 7.3.2.
To complete the required number of ignition attempts, it may be necessary to fill and empty the test FIBC multiple times For FIBCs lacking an outlet, a properly sized cut should be made in the base Additionally, using several FIBCs of the same design and size may be required to fulfill the complete test sequence.
Ignition attempts must be evenly distributed across the four walls of the test FIBC, with 50 attempts on each wall For FIBCs lacking clearly defined sides, a total of 200 ignition attempts should be made across the entire area Additionally, 10 ignition attempts are required on any attached panel, such as flaps covering spouts, on panels with significant construction differences, and on labels or document pouches larger than 100 cm².
100 cm 2 and lifting straps do not need to be tested
Ignition attempts may be conducted at locations beyond those specified in the standard, provided there is an agreement among the interested parties The test report must detail the positions of any additional measurement points If any verifiable ignition occurs during these tests, the FIBC being tested will not meet the requirements outlined in section 7.3.2.
Begin the flow of pellets at a rate of (1.1 ± 0.1) kg/s with the discharging spout of the FIBC closed, and apply the voltage specified in section 9.2.2 to the corona charging unit, allowing the pellets to fill the designated area.
When the fill level begins to rise along the walls of the FIBC, initiate the gas mixture flow through the ignition probe and maintain this flow for a minimum of 30 seconds prior to attempting ignition.
To initiate ignition, the ignition probe should be positioned at least 100 mm below the fill level of the FIBC wall The probe must approach at a speed of (0.75 ± 0.25) m/s; an approach that is too slow may lead to a reduction in local charge levels due to corona, while an excessively fast approach could extinguish the developing flame kernel.
NOTE The occurrence of cone discharges is avoided during this test procedure by bringing the ignition probe up to the FIBC at least 100 mm below the fill level
If no ignition occurs, remove the ignition probe and wait 10 s to 15 s before approaching the probe toward the next measurement point and continue with the ignition testing procedure
Make as many attempts as possible at different points on the wall of the FIBC including edge seams, until the FIBC is three-quarters full