Page 30 - Energize November 2021

NEWS

The evolution of Pratley’s flameproof cast iron junction box

ratley has been manufacturing it is not that common in the industry, which is why we advocate the use of our junction
flameproof junction boxes since boxes together with our own Ex e Kwikblok terminals as an extra level of protection,” adds
Pthe 1960s. Over the years, it has Breedt. Another key differentiator of Pratley flameproof cast iron junction boxes is their
refined the design of these enclosures, IP68 rating, the standard being a minimum IP54 rating. The increased rating means that
making Pratley’s cast iron flameproof Pratley’s junction boxes are completely dust-protected and watertight with up to 2 m of
junction boxes well-known in the mining water head.
and petrochemical industries. “Should you not need a Zone 0 rating, we recommend our non-sparking end
With the recent IECEx approval of connectors, as these have a locknut to secure the connection so that they cannot vibrate
these junction boxes, Pratley has proven loose. Here a sleeve is also fitted on the outside as a means of insulation,” highlights
its commitment to world-class product Breedt.
development and innovation. One of “The important part to remember, if you are advising anyone on such an installation,
these innovations is to offer Pratley’s is that this termination is now suitable for Zone 0 applications, with minimal additional
unique increased-safety (Ex e) Kwikblok consideration,” he adds.
terminals as a termination option inside There is a separate zoning system for gases and dust. Zoning itself is based on a risk
the flameproof junction box, essentially assessment approach, meaning that Zone 0 is where there is a specific hazard, in relation
doubling the level of protection. to an explosive gas atmosphere, under all circumstances and normal operating conditions.
“By combining our flameproof That means it is either submerged in or nearby a source of explosive gas, such that the
junction box with our Kwikblok terminals, concentration is explosive for the entire duration of the equipment’s use.
we can prevent arcing or sparking Zone 1 is where the hazard is present only some of the time, such that in most normal
across the connections themselves,” operating conditions there is minimal risk of a hazardous vapour being present around
explains Pratley’s electrical research & the enclosure. Zone 2 is where it is unlikely that there is a hazardous atmosphere or
development manager Sven Breedt. In where there is an insufficient concentration that can be ignited under normal operating
addition, electrical current limitations conditions.
prevent those terminals from exceeding In terms of dust, Zone 20 is where there is an explosive dust atmosphere, such as dust
their service temperatures, together packed onto or around the enclosure, or suspended in the surrounding air, for the entire
with limiting creepage and clearance or duration of that enclosure’s use. Zone 21 references only a part-time hazard around the
tracking distance. This means that the enclosure, while Zone 22 refers to abnormal operating conditions only.
terminals are spaced such that there The Pratley junction boxes are manufactured from fine-grained cast iron for increased
can be no arcs or sparks across the strength, robustness and impact resistance. This is critical, as they are intended to
connections, adding a second dimension withstand extremely high explosion pressures, unlike Ex e enclosures which are intended
to the safety. to prevent an explosion inside the enclosure altogether. Flameproof enclosures can contain
Flameproof junction boxes are the explosive pressures and hot gases and allow the latter to exit the enclosure via a
specifically designed to house equipment precision-machined flame path.
that arcs or sparks, meaning that any
termination type can be fitted into these
enclosures. However, with the inclusion
of increased-safety terminals inside a
flameproof enclosure, the terminations
rating is pushed up to Zone 0 (two
independent levels of protection via EPL
Gb, per SANS/IEC 60079-14/26), meaning
it can now be installed in an environment
where there is a constant hazardous
environment.
Here a typical application would be
on the inside of a fuel storage tank with a
dip sensor or a pump power supply unit,
where the internal environment of the
tank poses a constant hazard in terms of
both oxygen and flammable vapour or
gas, that can be ignited.
“While this is a useful combination,

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