There's a question that comes up time and again during instrumentation projects in classified locations: do we really need flameproof Ex d enclosures for every indicator on this loop?
For decades, Explosion Proof (Exd) — or flameproof — has been a popular choice for field-mounted process indicators in Zone 1 and Zone 2 hazardous areas. It works. It's familiar. But it comes with a set of trade-offs that are increasingly hard to justify when there's a better option available.
The BEKA SG range of 4/20mA loop powered indicators — certified Ex eb (Increased Safety) and Ex tb (dust ignition protection by enclosure) — offers a compelling alternative: lower cost, lighter weight, a larger and clearer display, and now with Class I Zone 1 North American certification, a solution that works on both sides of the Atlantic.
The Problem with Flameproof for Simple Indication
Flameproof Ex d enclosures are engineered to contain an internal explosion and prevent flame propagation to the surrounding atmosphere. That's the right tool when you're housing switching equipment, relays, or components that could produce an arc or spark.
But a 4/20mA loop indicator? It draws its power directly from the signal loop. It inherently does not produce sparks or arcs as it doesn’t contain switching elements or moving contacts that can spark (e.g., switches, relays, or contactors). The heavy, threaded, cast-aluminum or stainless steel housing of a flameproof unit isn't just unnecessary for this application — it's a cost and a burden.
When you specify flameproof protection for indicators throughout a facility, you could be missing a potential significant cost saving opportunity not to mention a much easier installation regime.
Enter the BEKA SG Range: Increased Safety, Simplified
The BA304SG, BA304SG-SS, BA324SG, and BA324SG-SS are field-mounting, loop powered 4/20mA indicators built around the Ex eb (Increased Safety) and Ex tb protection concepts. Rather than containing an explosion, Increased Safety engineering eliminates ignition sources through robust construction, tighter tolerances, and enhanced protection against faults. The result is a unit that is certified for the same Zone 1 and Zone 2 (and Zone 21/22 for dust) locations — without the flameproof premium.
What Makes the SG Range Stand Out
A genuinely cost-effective solution. The SG range is priced as a direct alternative to flameproof indicators, not as a premium product. For projects involving multiple field indicators across a large installation, the savings are significant — without any compromise in certification or safety.
Lighter weight, easier installation. The GRP (Glass Reinforced Plastic) and stainless steel enclosures are substantially lighter than cast flameproof housings. That means simpler mounting, reduced structural loading on instrument stands and pipework, and faster installation on-site.
Bigger, clearer displays. This is perhaps the most prominent advantage. The BA304SG features a 4-digit display with figures 34mm high. The BA324SG adds a 5-digit display plus a 31-segment bargraph. Both offer a very wide viewing angle and high contrast that puts most flameproof indicator windows to shame. In practice, an operator can read the process value from further away and in more difficult lighting conditions.
Drop-in replacement capability. The SG indicators connect into any 4/20mA Zone 1 or Zone 2 loop with basically any type of explosion protection — flameproof Ex d, pressurized Ex p, encapsulated Ex m, or increased safety Ex e — without any need for Zener barriers or galvanic isolators. Obviously if the loop is intrinsically safe, you must use an intrinsically safe certified alternative indicator, also available from Beka. Replacing an existing Ex d indicator on a current installation is straightforward.
IP66 rated. Both GRP and stainless steel variants carry IP66 protection, suitable for outdoor and wash-down environments, with an operating temperature range of -40°C to +60°C.
No extras charge for factory calibration. All SG indicators can be supplied pre-configured and calibrated to your specified range, with scale and tag marking included at no additional cost — reducing commissioning time on-site.
Now with Class I Zone 1 North American Certification
For projects and facilities operating under North American electrical codes, we're pleased to confirm that the BEKA SG range now carries Class I Zone 1 North American certification (ETL listed).
This is significant. Historically, the Ex eb protection concept has been more widely adopted in IECEx and ATEX-governed markets. The addition of North American certification means the SG range is now a fully viable option for US and Canadian sites operating under NEC/CEC Zone classification — not just offshore or international projects.
For operators managing assets across both North American and international locations, or running greenfield projects under Zone methodology, this opens the door to a single standardized indicator solution across the entire facility footprint.
The Four Models at a Glance
|
Model |
Enclosure |
Display |
|
BA304SG |
GRP, field mount, IP66 |
4 digits, 34mm high |
|
BA324SG |
GRP, field mount, IP66 |
5 digits, 29mm high + bargraph |
|
BA304SG-SS |
Stainless Steel, field mount, IP66 |
4 digits, 34mm high |
|
BA324SG-SS |
Stainless Steel, field mount, IP66 |
5 digits, 29mm high + bargraph |
All models carry IECEx, ATEX, UKCA, and North American (ETL) certification for Zone 1, Zone 2, Zone 21, and Zone 22 locations, and are backed by BEKA's three-year guarantee.
Optional accessories include a loop or separately powered backlight, dual isolated alarms, and pipe mounting kits. An engraved stainless steel legend plate is also available for the SS variants.
The Bottom Line
If your project calls for field-mounted 4/20mA indication in a non-IS Zone 1 or Zone 2 installation, the case for specifying flameproof Ex d as the default is weaker than it has ever been. The BEKA SG range delivers the same certified safety performance with a lighter enclosure, a larger display, a lower price point, and — now — the North American approvals to support projects across the full range of global jurisdictions.
It's the kind of engineering decision that looks good in the budget, on the instrument schedule, and out in the field.