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Measurement technologies for tricky applications – Part 2

World Cement,

Read part 1 of this article here.

Play it safe

Explosion protection and international approvals for level measurement in silos is integral to all industry sectors. Legal changes, new technologies and new research mean that explosion protection is a source of ongoing discussion among experts. Not using certified level indicators and level switches can place everyone involved in the industry at risk. Bulk and solid materials are constantly on the move. In DustEx areas, level indicators with housing protection ‘t’ are essential. Their proposal is based on the fact that no ignitable dust enters the interior of the device; should this protection not be in place, an explosion could occur via the unprotected network circuits, which may generate excessive heat or ignitable sparks. The paddle switch Rotonivo® offers total reliability in very dusty environments within a silo due to its enhanced dust protection. The measuring devices now include a shock resistance feature – a major challenge, particularly within the building industry. Compared to previous standards, the requirements for IEC 60 079 are far more stringent. All devices within the UWT Rotonivo® rotary paddle switch series and the Vibranivo® fork sensors meet these rigorous standards and they can therefore be used within hazardous dust zones.

When used in GasEx areas or combined dust and gas hazardous areas, the device must meet the protection requirements for dust and also those for gas. An option is the design factor "Intrinsic Safety (i)" whereby all circuits are power limited, and therefore cannot cause ignition. Another option is to supplement the safety measures with a "flameproof enclosure (d)", in which any internal explosion triggered within the device will be contained within the housing. The UWT series Rotonivo® and Vibranivo® are well-suited for this. These series are also the first products to conform to RoHS (Restriction of Use of certain Hazardous Substances). The European Guideline 2002/95/EC (RoHS 1) regulates the use of hazardous substances in electrical and electronic equipment. The objective is to ensure that all UWT products are RoHS compliant.

Level switches require FM and CSA approvals in the North American and Canadian market. The principles of explosion prevention are equal to the European system, although the names are different (e.g. "Dust Ignition Proof (DIP)" for dust protection). The Eastern European market in turn requires its own certificates. Exportation of devices into Russia for use in hazardous areas requires a GOST-R certification in addition to the RTN Ex approval. In Ukraine, a declaration of conformity from the Institute TCC ExE is necessary. The most recently acquired certificate is the Brazilian EX-Protection Certification INMETRO. UWT technicians are constantly working to meet these approvals and to ensure that the company’s portfolio conforms to regulations for use in hazardous areas across the world.

Adapted from press release by

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