Protection Paradigms in Explosive Atmospheres
A Technical and Economic Analysis of the Transition to Intrinsic Safety in WirelessHART Networks
The development of modern industrial processes demands an unprecedented integration of safety, efficiency, and connectivity. In sectors such as petrochemical, chemical, mining, and pharmaceutical, the presence of flammable substances in the form of gases, vapors, or combustible dusts creates a latent risk environment where any technical failure can result in catastrophic consequences. Protection engineering for explosive atmospheres, governed internationally by the IEC 60079 series of standards and in Brazil by the corresponding ABNT NBR standards, has evolved from purely mechanical methods to sophisticated electronic solutions. At the heart of this evolution lies the debate between two fundamental methodologies: explosion-proof enclosures (Ex d) and intrinsic safety (Ex i). With the rise of the Industrial Internet of Things (IIoT) and the consolidation of the WirelessHART protocol, the choice of protection method has become a determining factor not only for safety but also for the economic viability and operational agility of industrial plants.
Historical Evolution and Regulatory Context of Classified Areas
The need to protect electrical installations in hazardous environments dates back to the early days of industrial electrification and coal mining. Historically, the concept of "explosion-proof" arose from the need to contain flames inside lamps and motors, using the physical mass of the enclosure to cool the gases resulting from eventual internal combustion. As electronic instrumentation advanced, intrinsic safety emerged, a paradigm that focuses on the absolute prevention of ignition through the limitation of electrical and thermal energy.
Currently, the regulatory framework is led by the IEC (International Electrotechnical Commission), specifically by committee TC 31, responsible for the IEC 60079 series. In Brazil, compliance is required through INMETRO certification, which identically adopts international standards, and by the Regulatory Standards of the Ministry of Labor, such as NR-10, which establishes guidelines for electrical services, and NR-20, focused on safety with flammable and combustible materials. Area classification is the first critical step, dividing environments into zones (0, 1 and 2 for gases; 20, 21 and 22 for dusts) according to the probability of the presence of an explosive atmosphere.
Physicochemical Fundamentals of Ignition and Protection
Understanding risk in classified areas is based on the fire triangle, which requires the simultaneous presence of fuel, an oxidizer (oxygen), and an ignition source. In industrial processes, fuel and oxygen are often unavoidable, making the control of the ignition source the only variable manipulable by safety engineering. Ignition sources in electrical equipment include sparks produced by the opening or closing of contacts, short circuits, and heated surfaces that exceed the auto-ignition temperature of the substance present.
The classification of gas groups (IIA, IIB, and IIC) reflects the minimum ignition energy (MIE) required to ignite each substance. Hydrogen, belonging to group IIC, requires extremely low ignition energy, which imposes more stringent requirements on equipment design. The temperature class (T1 to T6) defines the maximum surface temperature that the equipment can reach, which must always be lower than the auto-ignition temperature of the gas in the environment.
Ex d Methodology - Containment Engineering
The concept of an explosion-proof enclosure, standardized by IEC 60079-1, is based on the principle that an internal explosion is permitted, but must be contained so as not to propagate to the external environment. The equipment is housed in a robust metal enclosure, designed to withstand the internal pressure of the explosion without deforming. The vital technical characteristic of Ex d is the flamepath, which consists of slots or threads machined with micrometric precision.
When internal ignition occurs, hot gases are forced through these gaps. The flame path is designed so that, as it travels this distance, the gas loses thermal energy by conduction to the mass of the enclosure, exiting to the outside at a temperature lower than that required to ignite the surrounding atmosphere. This method is indispensable for high-power equipment, such as large motors and electric actuators, where current and voltage limitation is not technically feasible. However, for field instrumentation, Ex d presents significant operational disadvantages, including high weight, the need for special tools, and the impossibility of maintenance with the circuit energized.
Ex i Methodology - The Engineering of Intrinsic Prevention
Unlike physical containment, intrinsic safety (Ex i), detailed in the IEC 60079-11 standard, acts to prevent ignition by limiting the electrical and thermal energy available in the circuit to levels below the minimum ignition energy of the fuel. The system is designed to be incapable of generating a spark or a hot spot sufficient to cause an explosion, even under severe fault conditions such as short circuits or line interruptions.
Intrinsically safe equipment is classified into protection levels: "ia", "ib", and "ic". Level "ia" is the most stringent, guaranteeing safety even in the event of two independent and simultaneous faults, and is therefore the only method permitted for installation in Zone 0 (environments where the explosive atmosphere is permanent or frequent). Implementing Ex i requires a detailed analysis of the entity parameters: Maximum Voltage (V), Maximum Current (C), Maximum Power (P), Internal Capacitance (C), and Internal Inductance (I). For wired systems, the inclusion of Zener barriers or galvanic isolators is necessary to limit the energy sent from the safe area to the classified area.
The Emergence of WirelessHART in Industrial Automation
Wireless technology has revolutionized automation by eliminating the physical barrier of cabling, which represents one of the biggest costs in industrial projects. WirelessHART, formalized by the IEC 62591 standard, was the first open wireless communication standard designed specifically for the critical needs of the process industry. It operates in the 2.4 GHz band using the IEEE 802.15.4 standard, but adds essential layers of robustness for the factory environment, such as Time Division Multiple Access (TDMA) for determinism and frequency hopping (Channel Hopping) to avoid interference and mitigate the effects of signal fading caused by metallic structures.
A WirelessHART network is structured as a mesh, where each sensor acts not only as a measurement point but also as a router that forwards data packets from other nodes. This characteristic gives the network a self-organizing and self-healing capability: if a path is blocked by a physical obstruction or temporary interference, the system automatically finds alternative routes to ensure that the information reaches the Gateway and, consequently, the control system. The data reliability of a well-designed WirelessHART network can exceed 99.9%, making it suitable for monitoring and, in certain cases, process control.
Smar Philosophy - Technical Strategy for the WirelessHART Line
Smar has adopted the intrinsically safe (Ex i) philosophy as the standard for its WirelessHART transmitter line. This strategic decision is based on the intrinsic nature of battery-powered wireless devices: as they are very low-power devices and do not have external cabling that could introduce dangerous energies in case of failure, the Ex i concept is technically the most suitable and efficient.
Unlike conventional 2-wire transmitters, where safety depends on external barriers installed on the panel, Smar's WirelessHART devices are "self-sufficient" in terms of protection. All the energy required for measurement and radio transmission comes from appropriate internal batteries, whose circuit is designed to limit current and voltage internally, guaranteeing Ex ia certification. Smar's philosophy in opting for Intrinsically Safe safety was to prioritize safety, "preventing internal ignition," rather than "containing the explosion within the enclosure."
Simplified Maintenance and Reduction of Operational Risks
Maintaining assets in classified areas is one of the most critical and bureaucratic processes in an industrial plant. According to the guidelines of NR-10 and NR-20, any intervention on Ex d equipment requires the complete de-energization of the circuit or the issuance of a Work Permit (PT) for "hot work," which often requires a partial shutdown of the process and continuous monitoring of the atmosphere with explosimeters.
The choice of intrinsic safety in Smar's WirelessHART line transforms this operational reality. Because the equipment is Ex ia certified, maintenance, including battery replacement, can be performed with the instrument in the field, without the need to de-energize the network node or obtain special safety permits. Battery replacement is a simple and safe procedure, drastically reducing intervention time and technicians' exposure to hazardous areas.
Impact on Global Efficiency and Asset Management (IIoT)
Adopting the intrinsically safe WirelessHART is not just a safety decision, but a cornerstone of operational excellence within the IIoT concept. Modern automation aims to minimize downtime for corrective maintenance and optimize the use of labor. Smar transmitters provide continuous diagnostics that can be accessed remotely via Gateway.
This visibility allows the maintenance team to adopt a predictive approach, monitoring battery health and sensor status without needing to physically go to the field for clipboard rounds (manual inspection rounds). The ability to perform remote diagnostics and configurations via the HART 7 protocol on a wireless infrastructure accelerates commissioning and allows process deviations to be identified before they cause unplanned downtime.
Complementing this strategy, Smar offers the AssetView solution, an intelligent asset management platform that integrates data from WirelessHART devices in real time. With AssetView, it is possible to view the status of instruments, receive fault alerts, monitor performance trends, and plan interventions based on reliable indicators. This approach strengthens predictive maintenance and increases plant availability, bringing actual production closer to nominal capacity.
Total Cost of Ownership (TCO) Analysis
Although the capital expenditure (CAPEX) of a WirelessHART transmitter may be higher than that of a traditional 4-20 mA transmitter, a Total Cost of Ownership analysis reveals overwhelming savings. In Ex d wired installations, the cost of the infrastructure (galvanized steel conduits, shielded cables, cable trays, sealing units, and heavy assembly labor) often exceeds the value of the instrument itself.
In Smar's WirelessHART Ex i model, the infrastructure is virtually non-existent. Installation is limited to the mechanical mounting of the support, eliminating costs associated with complex cables and electrical connections. Furthermore, operational costs (OPEX) are reduced due to ease of maintenance and the absence of plant shutdowns for simple instrument interventions. Installation savings are estimated to range from 50% to 90%, depending on the distance and complexity of the environment.
Regulatory Compliance and INMETRO Certification
Smar's WirelessHART line holds certifications from renowned international bodies such as Underwriters Laboratories (UL), and the mandatory INMETRO certification in Brazil.
Compliance with the ABNT NBR IEC 60079-11 standard requires the manufacturer to submit the PCB (printed circuit board) design to trace spacing analyses (creepage and clearance), verification of foolproof components, and spark tests.
For battery-powered equipment, such as the LD400WH and TT400WH, the standard also imposes stringent requirements on the safety of lithium cells, ensuring that they do not overheat or rupture in the event of an internal short circuit. Smar uses appropriate batteries, configured to provide the necessary autonomy while maintaining the total intrinsic safety of the system. Obtaining the INMETRO seal is the ultimate guarantee for the user that the equipment will operate safely in the most critical areas of the plant.
Conclusion
The Prevention Paradigm as the Basis of Industry 4.0
The transition from Ex d protection to Ex i intrinsic safety in WirelessHART networks represents more than a technical change; it's an evolution in industrial safety philosophy. By adopting Ex ia for its wireless line, Smar not only meets the most demanding safety standards (allowing use in Zone 0), but also unlocks higher levels of productive efficiency.
The superiority of the Ex i concept for low-power instrumentation is indisputable from the perspectives of safety, installation, and maintenance. While Ex d remains vital for power machines, the agility demanded by modern digital automation finds its ideal partner in Ex io. By eliminating the risks associated with the mechanical integrity of heavy enclosures and enabling simplified, live maintenance, Smar positions itself at the forefront of the IIoT, offering solutions that protect people, assets, and the environment, while driving financial results through operational excellence.
Bibliographic References
- Sensycal. "Intrinsic Security (Ex i): What it is, how it works, and strategic advantages."
- Shield System. "Classified Areas and NR 20: Risk Management with Flammable Materials".
- Nova Smar / Luís Henrique Camargo. "Explosion-Proof and Intrinsically Safe Installations: Technical Differences for WirelessHART".
- Former Reg. "Protection Concepts Explained: Deep Dive into Ex d, Ex e and Ex i".
- Extronics . "Standards Governing Hazardous Areas and IEC TC 31 Overview".
- EletroAlta / Meromed. "Regulatory Framework: Classified Areas, NR-10 and NR-20 integrated into the PGR".
- Industrial Monitor Direct/Zero Instrument. "Hazardous Area Instrumentation Selection Guide: Ex d vs Ex i".
- Smar / ABB. "IIoT and Industrial Automation: Productivity and Operational Safety".
- Sabo Miya Hassan et al. (ResearchGate). "Application of Wireless Technology for Industrial Control: A WirelessHART Perspective".
- FieldComm Group/Smar. "WirelessHART Technology: Mesh Networking and Industrial Reliability".
- Pepperl+Fuchs / LX Antenna. "Wireless Communication and Antenna Requirements in Hazardous Locations".
- ABNT NBR IEC 60079-11 / ISO/IEC 80079-34. "Equipment Protection by Intrinsic Safety 'i' and Quality Management".
- ABNT NBR IEC 60079-17. "Explosive Atmospheres: Inspection and maintenance of electrical installations".
- UL / INMETRO. "Mandatory Certification for Equipment in Explosive Atmospheres".
- Tractian / SafetyCulture. "Maintenance and Inspection of Assets in Classified Areas: Practices and Checklists".
- ByteSnap Design. "Intrinsically Safe PCB Design and Battery Testing Requirements (IEC 60079-11)".
- Smar Technical Portfolio. "WirelessHART Transmitter Line: LD400WH, TT400WH, TP400WH and DT400WH".
ADRIANO MARCELO CORTEZE
NOVA SMAR S/A
20/MAR/2026
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