Electrical installations in hazardous areas
Electrical installations in hazardous areas – In Brazil, the electrical installation in areas classified as low voltage has additional requirements to those defined in the NBR 5410 standard, so as not to pose risks of ignition in an eventual explosive atmosphere that arises at the site. And the electrical and electronic equipment suitable for use in these regions, in addition to being designed and built according to the technical standards of the NBR IEC 60079 series, must have a “Certificate of Conformity” issued by a Product Certification Body duly accredited by INMETRO. The conformity certification is a legal requirement, originally given by INMETRO Ordinance 164/1991 and maintained today by INMETRO Ordinance 179/2010.
However, in the audits we carried out in several industries, we still found a large amount of non-conformities in these facilities, both originating in the assembly stage and in the maintenance stage. As such non-conformities compromise the safety of the industrial unit, as irregular electrical equipment may act as an ignition source, causing an explosion, we will address some of them in this article.
1. Signaling
A worrying factor is the lack of adequate signage. “The safety signs must be clear to all professionals involved in classified area services, in addition to providing information on the classification of the zone, the group (for the flammable gas atmosphere or combustible powders) and the temperature class of permitted electrical equipment “.
Unfortunately, board models outside the ISO standards can be found on the internet, either with a profusion of texts or with colored bands, which actually confuse the worker. IEC 61892-7:2014, a voluntary standard and only applicable to offshore installations suggested a model for Ex signaling, but such an idea has serious shortcomings, as shown in Figure 1
The board in Figure 1 is incomplete and compromises security because:
Redundancy: the yellow triangle with “Ex” inside, already means “explosive atmosphere”, and repeating its meaning below, adds nothing;
Text information needs to be written in different languages to be read by foreign workers, a situation commonly found in offshore units;
No information about the site’s Zone;
No information about the gas group;
No information on temperature class.
Another example of an inadequate sign that compromises safety in hazardous areas is shown in Figure 2:
Signposts are governed by the principles given by international ISO standards. This model in Figure 2 demonstrates why the security signs cannot be “hefted” by laymen, with colored bands, excessive text, in addition to the irregularities below:
- Triple redundancy: the yellow triangle with “Ex” inside, already means “explosive atmosphere”, which does not require putting the “title” and its definition;
- Excessive text: signs are to alert, not to remedy deficiencies or lack of training;
- No information about the Zone;
- No information about the gas group;
- No information on temperature class.
That is, if the worker only takes care of “using electrical equipment certified with the Ex marking”, he will be at risk if the equipment is not suitable for that area!
In conclusion, to promote effective security, the Ex board must have the region’s own information and follow the ISO!
Figure 3 shows the model that provides the necessary information for worker and industrial unit safety:
Figure 3: Ex plate model that meets all ISO recommendations for signaling environments subject to explosive atmospheres, having already been adopted by Petrobras
Note that the classified area symbol (ex triangle) already denotes the prohibition of the use of ignition sources, a requirement expressed in other normative documents, for example, in NR-37.
It should be noted that the signage does not replace the need for training, and the obligation of the employer to inform the worker of the risks to which he is subject in that environment
It is up to the employer to guide how the worker should proceed when seeing each of the various signage boards in that industrial plant, as provided for in NR-01. Signage is a warning, so it needs to be effective!
2. Workforce training
We still see a great lack of knowledge of contracting companies, which have been accepting “NR-10 40-hour course certificates” as if it were proof of training in explosive atmospheres, under the mistaken claim that one of the topics of such a course is “areas classified”, this would be “enabling”. In fact, this “40-hour course” is just about risk awareness, not technical training. NR-10 provides that the worker’s authorization will only be given for the 40-hour course added to the technical training necessary to correctly perform the scheduled activities.
And the confusion in the market has become greater since the NBR IEC 60079-14:2016 standard included in the “normative” Annex A4, that “The competence of Responsible Persons, Contractors and Designers must be verified and assigned, at intervals…”, inducing readers to think that Ex certification was now mandatory, with a massive reference to the units of the IECEx scheme (a commercial organization of the IEC group dedicated to the certification of products, companies and services, based solely on the standards issued by the IEC, and that receives royalties from all certificates issued with the brand). We even found on the Internet mistaken quotes that the “UN recommends such a scheme”, which leads the reader to think that the diplomats at the UN headquarters in New York – including the Brazilian delegation – would have issued such a decision to all countries.
In fact, the body that issued such a “recommendation” was the UNECE – United Nations Economic Commission for Europe (a UN commission dedicated solely to European economic matters, which had the “cooperation” of the IEC and IECEx (interested parties). It should be noted that there are other similar commissions at the UN, aimed at the commercial interests of other regions of the globe, such as the ECLAC – Economic Commission for Latin America and the Caribbean). The UNECE “recommendation”, in the form of a Common Regulatory Objective (CRO), is addressed to member countries of the European Union that do not have a regulation on Ex equipment, as it is in the ECE/TRADE/391 document.
On pg. 8 of that document, in item B.22, it is that European countries (under the scope of UNECE) will be considered to be in line with the CRO if they adopt an Ex certification scheme in their legislation, such as that offered by the IECEx scheme, which would allow a direct acceptance of products placed on the market with such certificates. And on the same pg. 8, in items B.28 and B.29, it appears that including such a proposal in the legislation of each country would consolidate the objective of certifying EVERYTHING (equipment and companies providing any services – projects, area classification, selection, installation, inspection , maintenance and repairs), ALL (own and outsourced workers) and ALWAYS (through renewals of all certificates for “the life of the facilities”), which would guarantee a lifetime source of income for the scheme (which also receives from the membership dues from affiliated certifiers), as all certificates need to be renewed periodically!
In Brazil, some entities then started to offer Ex personal certification with units similar to those of the IECEx Scheme; however, it should be noted that for the certificate to bear such a logo, the certifier must be affiliated (pay fees and annuities) to the scheme. In any case, only the Ex 000 and Ex 001 units are being offered here (December 2017), which are not sufficient for the certification of professionals (this observation appears in the IECEx certificate), as they are limited to evaluation by multiple choice questionnaire .
According to the IECEx Scheme, for example, an “Ex assembler” certification will need his approval on the Ex 001, Ex 003, Ex 006 and Ex 008 units, which denotes a high cost, as each unit is paid individually.
In short: what the law requires – NR-10 – is the technical training of the worker. In addition to “Ex certification” not being mandatory, a “certification” without effective practical assessment does not guarantee that the worker correctly performs the Ex installations.
3. Changes to Ex facilities and equipment
Explosion-proof enclosures (Ex d) are designed in such a way that gases resulting from an eventual internal explosion are conducted to the outside through suitably designed gaskets. And it is up to the user to ensure that these joints are at a minimum distance from any solid obstacle, as provided for in table 13 of NBR IEC 60079-14.
The non-conformity we will highlight here in Ex d boxes is the application of a “grease tape” (used to protect metal pipes against corrosion) around the flanged joint. Such practice, despite being mentioned in the standard, is wrong, as in addition to the product not being certified for such use, the CEPEL DLA 43410/2011 report showed a 16% increase in internal pressure in the propagation test, denoting a risk that does not has been assessed in the certificate of conformity, and therefore invalidates it! It is clear that changes to equipment and facilities can compromise the safety of facilities and people.
Conclusions
For these reasons, it is essential that companies that process, handle, store and transport flammable or combustible products have experienced and updated advice on the new requirements of the Ex standards, because the texts of the standards are extensive and require solid technical knowledge for their correct interpretation. In addition, it appears that much information available on the internet is wrong, and that, if not properly evaluated, will lead to non-conformities in the installation with the potential to cause great damage to workers, installations, the neighboring community, and even interruption of the company’s activities!
AUTHOR: Estellito Rangel Jr. Consultant in industrial systems, installations in hazardous areas and safety in electricity.
