Pratley, well-known for its innovative electrical termination products, has developed and launched a ground-breaking new product, the Flameproof Ex d Envirobox®. This is claimed to be a world first: a polymeric, corrosion-resistant, direct-entry, flameproof junction box.
Pratley’s new Flameproof Ex d Envirobox® junction box in an underground mining application.
Sven Breedt, Electrical Research & Development Manager at Pratley, says: “It’s a new product unlike any other in the world and one of Pratley’s most innovative electrical inventions.”
Flameproof equipment is designed to prevent internal ignition within a flammable atmosphere from transmitting outside the protective enclosure. However, all traditional direct-entry flameproof junction boxes made from steel, cast iron or aluminium materials can be prone to corrosion over time and when used in very harsh environments. Special attention needs to be given not only to the overall climatic conditions of the area where the enclosures are installed, but also to the material and design of the equipment.
Pratley’s new Flameproof Ex d Envirobox® junction box, made from a specially formulated, robust engineering polymer, is designed to withstand severe environmental conditions. This makes it ideal for use in areas where there is a high risk of corrosion, such as on offshore oil platforms, in underground mines, and in petrochemical plants.
“The need for a lightweight and corrosion-resistant flameproof junction box is evident in the current, ever-changing mining environment,” Breedt says. “Over a decade’s worth of research and development went into the design and development of this junction box.”
The specially formulated, robust engineering polymer is unique to Pratley. The material has exceptional mechanical properties: in strength, stiffness, creep, dimensional stability and more. These attributes ensure that the Flameproof Ex d Envirobox® can withstand 2x 20-joule impact tests in a -40°C environment – and it has been third-party tested to a 4 000-kilopascal internal pressure. Additionally, it is IP66/68 certified for continuous underwater depths of up to 300 m; this means it is water- dust- and gastight.
The flame path in the lid and base is accurately machined. Breedt notes, by contrast: “The flame path surface of traditional Ex d junction boxes is coated or greased to prevent corrosion. However, this is not a long-term solution as the coating can wear off and greases would need to be reapplied periodically.”
The engineering polymer of the Envirobox® ensures that the flame path, with its machined surface, is completely corrosion resistant. This renders the junction box safe, easy to use and maintenance-friendly in surface and underground mining applications. The lid is fastened down with eight stainless steel A2-70 Allen head screws, also contributing to the corrosion resistance of the junction box, and it carries Pratley’s signature red Ex identification band for quick Ex equipment identification.
The junction box is supplied standard with 4 x M25 entries but can be supplied with M20 entries or smaller entries on request. The box can accommodate Pratley Ex d flameproof cable glands and accessories. It is thus particularly versatile. Each box is supplied as a standard two-way box with 2 x flameproof blanking plugs.
It can safely accommodate terminals, connectors, relays, and any other non-energy storing devices. The internal bosses are drilled and tapped to provide an earthing point for terminal mounting rails or earth lugs. These are electrically connected to the box entries providing complete earthing continuity.
Boxes can be fitted with an N35 terminal rail, a Pratley patented Cranked rail, an inverted Cranked rail, or Piggyback rails. Pratley Kwikblok® terminals and pre-cut lengths of cable with glands can also be factory fitted to customer requirements.
It has an optional external earthing point and is supplied with 4 x M6 nuts and washers as well as a 1 x M6 spring washer. The box has threaded mounting M5 holes and can accommodate an indexable mounting plate that can be purchased separately if required.
The Flameproof Ex d Envirobox® is fully certified to SANS, EN and IECEx Standards for use in surface and underground mining applications (Ex db I/IIB+H2 T6..T5 Mb Gb, Ex tb IIIC T85..T100 Db) in Zones 1, 2, 21 & 22 and an ambient temperature range of -40°C to +55°C.
Pratley’s Flameproof Ex d Envirobox® sets a new standard in junction boxes in the electrical industry.
“I am confident that what Pratley has produced is a product that meets our policy statement of producing products that outperform all others on the world market. Our goal was to produce the only direct-entry junction box that is corrosion-resistant, and the new Pratley Flameproof Ex d Envirobox® certainly achieves that goal. It is a world first, and I see it marking the future of electrical termination products for explosive atmospheres,” Breedt says.
For more information visit: www.pratleyelectrical.com
