NEW REQUIREMENTS FOR ELECTRICAL INSTALLATIONS IN HAZARDOUS LOCATIONS Copyright Material IEEE Estellito Rangel Jr.
Carlos Azevedo Sanguedo
Senior Member, IEEE Brasil
[email protected]
Senior Researcher Brasil
[email protected]
Abstract – This paper debates the requirements of some current IEC standards’ editions related to equipment and installations in hazardous locations. Index Terms — IEC, explosive atmospheres, hazardous locations, inspections, cables, gases, glands, motors.
I.
INTRODUCTION
This is an extract from the full text. The full text can be obtained at: http://ieeexplore.ieee.org/document/8188766/
II. NEW EDITIONS, NEW REQUIREMENTS When a new standard edition is issued, changes of technical requirements when compared with the previous edition, can result that an existing product which already is in conformity, may not be able to fulfill the new requirements. Some of the new requirements will be shown in this paper. A.
The fifth edition allows to use cable glands in accordance with IEC 60079-1 [3], certified as an equipment and combined with appropriate cables with a minimum length of the connected cable of 3 m. This “permission” was questioned by some countries, that decided to keep the older requirement in their IEC based National standards. As example, the current version of BS EN 60079-14 [4] does mirror the IEC Standard in respect of the above clause and requirements in the ‘Normative’ body of the standard, but it also contains a National Annex (NA) that acknowledges the British Standards Institution’s (BSI) concerns over the application of the IEC standard to the use of barrier glands. A barrier gland ensures that gas migration through the cable is prevented and also provides a flame barrier if an explosion occurs. Fig. 2 shows a cross view of a barrier cable gland.
Cable glands for Ex d enclosures
The fifth edition of IEC 60079-14 [1] liberated the use of a ‘standard’ Ex certified flameproof gland on flameproof enclosures bigger than 2 liters. Fig 1 shows the previous edition’s selection chart. Fig. 2 A barrier cable gland Despite the HSE concerns, there are countries that adopted the IEC 60079-14 ed. 5 without restrictions to this new criteria. B.
Fig. 1 Selection chart for cable entry devices into flameproof enclosures, from ed. 4.0
Switching motors above 1 kV
The current IEC 60079-14 alerts on its clause 5.11.5.1 that switching overvoltages can occur if vacuum circuit breakers or vacuum contactors are used, when the high voltage motor is switched off. These transients depend on various installations system and design factors, such as: arcextinguishing principle of the contactor or switch; size of the motor; length of the power supply cable; system capacitance, among others. Although the text seems to “suggest” for installation of surge suppressors, this should be a requirement.
On Appendix A of this paper, the results of a locked rotor test applied on the 4.16 kV Ex e induction motor, are presented. As a spark occurred, the installation of surge suppressors should be considered as mandatory. C. Optical radiation transmitting equipment The second edition of 60079-28 [11] describes precautions and requirements to be taken when using optical radiation transmitting equipment in explosive gas or dust atmospheres. It also outlines a test method, which can be used in special cases to verify that a beam is not ignition capable under selected test conditions, if the optical limit values cannot be guaranteed by assessment or beam strength measurement. D. Safety signalling An item not covered in IEC 60079-14 that contributes for a safer plant, is the safety signalization. Figure 3 shows a sign model that alerts workers, and also brings information about the zone, gas group and permissive temperature class. The hazardous area classification drawing’s number facilitates consultation at site.
[3] IEC 60079-1, Explosive atmospheres – Part 1: Equipment protection by flameproof enclosures “d”, edition 7.0. IEC: 2014. [4] BS EN 60079-14, Explosive atmospheres – Part 14: Electrical installations design, selection and erection. BSI: 2014. [5] RANGEL Jr., Estellito and SANGUEDO, Carlos, “International standards on explosive atmospheres: harmonization is a hard but necessary task”. In: 8th PCIC Europe Conference Record, 2011, Rome, pp. 91-94. [6] IEC 60079-6, Explosive atmospheres – Part 6: Equipment protection by liquid immersion "o", edition 4.0. IEC: 2015. [7] IEC 60079-7, Explosive atmospheres – Part 7: Equipment protection by increased safety ''e'', edition 5.0. IEC: 2015. [8] IEC 60079-15, Explosive atmospheres – Part 15: Equipment protection by type of protection "n", edition 4.0. IEC: 2010. [9] RANGEL Jr., Estellito, OLIVEIRA, Maurício F. and QUEIROZ, Alan R. S., “The importance of inspections on electrical installations in hazardous locations”. In: 61st PCIC Conference Record, 2014, pp 155-161. [10] IEC 60079-17, Explosive atmospheres - Part 17: Electrical installations inspection and maintenance, edition 5.0. IEC: 2013. [11] IEC 60079-28, Explosive atmospheres - Part 28: Protection of equipment and transmission systems using optical radiation, edition 2.0. IEC: 2015. [12] KEANE, Brian, SCHWARZ, Gerhard, and THURNHERR, Peter, “IEC 60079-14 Electrical installations design, selection and erection". In: 61st PCIC Conference Record, 2014, pp 145-154.
Figure 3 - An effective sign for classified locations.
III. CONCLUSIONS Although IEC standards are voluntary, it is important to know their requirements, especially in countries that usually translate them in order to issue their National standards. To keep the installation compliant, it is necessary that the registered professional (electrical engineer), in charge of the installation, be aware of the current standards’ editions. This can be a hard task, because different parts of IEC 60079 series can introduce new terms and requirements anytime. It is important to say that after a new standard’s edition is issued, it takes time for professionals to read, interpret and implement their new requirements.
IV. REFERENCES [1] IEC 60079-14, Explosive atmospheres – Part 14: Electrical installations design, selection and erection, edition 5.0. IEC: 2013. [2] IEC 60079-14, Explosive atmospheres – Part 14: Electrical installations design, selection and erection, edition 4.0. IEC: 2007.
[13] RANGEL Jr., Estellito, “Safety in electrical installations in petroleum industry”. In: 1st IEEE PCIC Mexico Conference Record, 2013, CD-ROM. [14] IEC 60079-0, Explosive atmospheres - Part 0: Equipment - General requirements, edition 4.0. IEC: 2004. [15] IEC 60079-0, Explosive atmospheres - Part 0: Equipment - General requirements, edition 5.0. IEC: 2007. [16] IEC 60079-0, Explosive atmospheres - Part 0: Equipment - General requirements, edition 6.0. IEC: 2011.
V. VITAE Estellito Rangel Junior. – is a Senior Member of IEEE, performs audits on electrical installations in explosive atmospheres. He is the first Brasilian representative at Working Groups of IEC Technical Committee TC-31 which issues the IEC 60079 standards series regarding hazardous locations. He is author of previous PCIC USA, PCIC Europe, PCIC Mexico and PCIC Brasil papers. Carlos Azevedo Sanguedo – Ex certification manager at Cepel, Brasil, member of the Brasilian Technical Standards Association (ABNT) in the Commission 03:31.03 which develops standards for Ex-e and Ex-n equipment.
