Protecting Electrical Equipment

Doors of electrical cabinets should be cleaned free of carbon fiber debris using a vacuum cleaner prior to opening or, as a better option, using a factory installed dust extraction system with portable cleaning tool attachments. It must be remembered that if a portable vacuum cleaner is used, although it sucks in at one end it will blow out the other. This air exiting the 

Control rooms housing electrical equipment should be pressurized with clean filtered air and entrances should preferably be fitted with two sets of interlocked doors to seal the factory environment, with only one operable door at a time. All electrical cabinets and consoles should be pressurized with fan units fitted with filters and due care should be taken to ensure that there is sufficient air available to remove excess heat from the cabinets. 

---

To minimize the risk of ignition by particles generated by frictional effects or impacts, all modem standards for explosion protected electrical equipment restrict the content of aluminium, magnesium and titanium as enclosure materials to a level considered as totally excluding the risk of ignition (e.g. clause 8 in IEG 60079-0 and EN 50014). 

TGL Technische Gute- und Lieferbedingungen, Technical Regulations for Quality and Delivery) have defined the classification of hazardous areas (TGL 30042) and the requirements for construction and testing of explosion protected electrical equipment (mainly TGL 19491). 

Part B Explosion protected electrical equipment - Group II Austria BVFA... 

The state of the art - the second edition (and following editions) of the European Standards (EN) (see Table 3.5) - is considered to form an appropriate basis for construction and testing of explosion protected electrical equipment. Other aspects of safety may require revision of established standards. 

Explosion protected electrical equipment for zone 1 (Group II, category 2 G) and the classical firedamp-proof apparatus for coal mines (Group I, category M2) are covered by the B module (EC-type examination) and by the C module (conformity to type) or the E module (product quality assurance). Alternatively, with respect to the B module, the notified body issues an EC-type examination certificate (in German EG-Baumusterpriifbescheinigung), whose marking mainly includes ... 

For explosion protected electrical equipment manufactured, type tested, certified and commissioned under the ATEX 100a Directive, the marking described in Table 5.2 shall be added by the marking code given in Table 5.3. The Ex in a hexagon has been taken from the old article 100 directives, whereas the B, C, D or E marks for the generation of Harmonized Norms have been deleted. 

The majority of the type tests listed above refers to electrical apparatus in general, i.e. these tests are valid for non-explosion protected electrical equipment as well. 

Financial considerations - selecting explosion protected electrical equipment 459... 

Circuit Breaker - A device used to interrupt or break an electrical circuit when an overload condition exists usually installed in the positive circuit used to protect electrical equipment. 

Thermal and overspeed cutout devices are coimnonly used to protect electrical equipment (and thus the operator). A thermal cutout is simply a temperature-sensitive switch with a preset limit designed to interrupt power when the temperature exceeds a certain value. As its name implies, an overspeed switch operates when it senses that a motor or other device is operating at too fast a speed. Obviously, excessive speed may create dangerous conditions and indicate failure of equipment. The overspeed switch operates to shut down an overspeeding device by interrupting power to it. 

The Regulations provide a range of means for assessing conformity. However, as far as electrical equipment is concerned, conformity assessment through a notified body will be the norm, following much the same EC type examination processes and procedures that have been used in the past. There are, however, additional requirements for product quality control and third party audits. In the UK, the Electrical Equipment Certification Service (EECS) and SIRA Test and Certification Ltd already provide conformity assessment services, basing their assessments on the harmonised standards that already exist for explosion-protected electrical equipment the main standards are identified in Chapter 15. 

Protected electrical equipment Yes/No Type. 7. Special ventilation requirements Yes/No Specify ... 

The part played by fuses, MCBs, RCDs and RCBOs in protecting electrical equipment, circuits and people is discussed in Chapter 3 of Basic Electrical Installation Work 8th Edition. In this chapter we are looking at their operating principles. 

---