Electrostatics - Part 4-4: Standard test methods for specific applications - Electrostatic classification of flexible intermediate bulk containers (FIBC)
|Publication Date:||1 November 2014|
|ICS Code (Sacks. Bags):||55.080|
|ICS Code (Electrical engineering in general):||29.020|
|ICS Code (Other standards related to electricity and magnetism):||17.220.99|
This part of IEC 61340 specifies requirements for flexible intermediate bulk containers (FIBC) between 0,25 m3 and 3 m3 in volume, intended for use in hazardous explosive atmospheres. The explosive atmosphere may be created by the contents in the FIBC or may exist outside the FIBC.
The requirements include:
− classification and labelling of FIBC;
− classification of inner liners;
− specification of test methods for each type of FIBC and inner liner;
− design and performance requirements for FIBC and inner liners;
− safe use of FIBC (including those with inner liners) within different zones defined for explosion endangered environments, described for areas where combustible dusts are, or may be, present (IEC 60079-10-2), and for explosive gas atmospheres (IEC 60079-10-1);
− procedures for type qualification and certification of FIBC, including the safe use of inner liners.
NOTE 1 Guidance on test methods that may be used for manufacturing quality control is given in Annex C.
The requirements of this standard are applicable to all types of FIBC and inner liners, tested as manufactured, prior to use and intended for use in hazardous explosive atmospheres: Zones 1 and 2 (Groups IIA and IIB only) and Zones 21 and 22 (see Annex D for classification of hazardous areas and explosion groups). For some types of FIBC, the requirements of this standard apply only to use in hazardous explosive atmospheres with minimum ignition energy of 0,14 mJ or greater and where charging currents do not exceed 3,0 μA.
NOTE 2 0,14 mJ is the minimum ignition energy of a typical Group IIB gas or vapour. Although more sensitive materials exist, 0,14 mJ is 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 specified in this standard does not necessarily ensure that hazardous electrostatic discharges, e.g. cone discharges, will not be generated by the contents in FIBC. Information on the risks associated with cone discharges is given in Annex E.
Compliance with the requirements of this standard does not mitigate the need for full risk assessment. For example, metal and other conductive powders and toner powders may require additional precautions to prevent hazardous discharges from the powders.
NOTE 3 In the examples mentioned in the paragraph above, additional precautions may be necessary in the case of metal or other conductive powder because if the powder is isolated and becomes charged, incendiary sparks may occur, and in the case of toner powders, incendiary discharges may occur during rapid filling and emptying operations.IEC TS 60079-32-1 1 gives guidance on additional precautions that may be necessary.
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, charging currents are greater than 3,0 μA, or the ambient conditions are outside of the range specified in this standard.
Compliance with the requirements specified in this standard does not necessarily ensure that electric shocks to personnel will not occur from FIBC during normal use.
1 Figures in square brackets refer to the bibliography.