Lower cost alternative to Ex d indicators celebrates fifth birthday with further improvements
To satisfy a requirement for lower cost flameproof loop powered 4/20mA indicators, in 2020 BEKA introduced two new IECEx and ATEX certified instruments which are drop-in alternatives to Ex d flameproof indicators. Using a novel combined explosion protection technique, not only are these indicators less expensive than Ex d indicators, they feature very large easy to read displays, operator push buttons, and eliminate the need for expensive Ex d cable glands. What’s not to like?
Alternative design
This alternative design uses three different types of explosion protection, Increased Safety Ex e, Encapsulation Ex m, and Intrinsic Safety Ex i. The resulting Ex eb Increased Safety indicators have an Increased Safety enclosure that provides impact and IP66 environmental protection for the display assembly, and the Ex e field terminals. Energy limiting components are protected within a certified Encapsulated Ex m assembly which powers the Intrinsically Safe display and push buttons, as shown in Fig 1.
Unlike conventional intrinsically safe 4/20mA indicators, this alternative design has no entity or cable parameters at it’s input terminals, just a maximum input voltage. The indicator may be safely connected in series with almost any 4/20mA loop located in Zone 1 or 2, with any type of explosion protection, including Flameproof Ex d, but not Intrinsic Safety.
Field proven
The BA304SG which has four 34mm high digits, and the BA324SG which has five 29mm high digits plus a 31 segment bargraph, have now been in successful worldwide use for more than five years.
Following customer feedback, and to further increase applications, both models have recently been updated. The maximum voltage drop that both models introduce in a 4/20mA loop has been reduced to 2.9V, and to 5.8V when fitted with an optional loop powered backlight. North American AEx certification has been added, and a stainless steel enclosure is now available as an option.