Autor: Georgii Feodoridi

            Kseniia Feodoridi

Abstract: Industry 4.0 initiatives are extending Ethernet and IP connectivity from supervisory layers toward field devices. In hazardous areas, however, network design must satisfy both automation requirements and explosion-protection constraints. This paper discusses how intrinsically safe Ethernet can support IIoT and cyber-physical systems, why bandwidth headroom matters for bounded latency, and how Time-Sensitive Networking (TSN), Ethernet-APL, and IEC 60079/62443 practices fit together in hazardous-area deployments. The central argument is that line rate alone does not deliver determinism; determinism is achieved by combining adequate bandwidth, switched architectures, traffic separation, TSN mechanisms, and security zoning. In current hazardous-area field deployments, the practical standards-based path is typically Ethernet-APL over 10BASE-T1L, while 1 Gbit/s and 10 Gbit/s remain highly relevant at control, aggregation, and backbone layers [1]-[9], [12].

Key Words: hazardous areas; intrinsic safety; industrial Ethernet; Ethernet-APL; TSN; IIoT; OT security.

DOI:  10.5281/zenodo.19555333

Intrinsically Safe Industrial Ethernet for Hazardous Areas

Industrial plants increasingly rely on continuous operational data for control, diagnostics, asset management, and analytics. NIST describes operational technology (OT) as systems and devices that detect or cause direct changes in the physical environment, while IEEE 802.3 remains the base Ethernet family spanning many speeds and media types [1], [2]. A key architectural trend is reducing gateway layers and moving Ethernet/IP closer to field devices. For hazardous areas, this shift must coexist with intrinsic safety requirements from the IEC 60079 series [7]-[9], [14]. Ethernet-APL has emerged as the standards-based way to extend Ethernet to process-field devices over a two-wire, long-reach, power-and-data medium built on 10BASE-T1L [3], [4].

Why bandwidth headroom still matters

Bandwidth does not by itself make a network deterministic, but it reduces serialization delay and provides headroom for mixed traffic. This matters where control traffic shares a network with diagnostics, configuration, logging, firmware transfer, or sensing streams. Lower utilization generally shortens queue occupancy and lowers the probability of congestion-related delay. However, bounded latency still depends on switched topologies, quality-of-service enforcement, traffic policing, synchronization, and TSN scheduling rather than speed alone [2], [5], [6].

It is important to distinguish between where these rates are used. In hazardous-area process automation, the field-access segment currently standardized for intrinsically safe Ethernet is typically 10 Mbit/s Ethernet-APL over 10BASE-T1L, with long reach over simple two-wire cabling. Gigabit and 10 Gigabit Ethernet are therefore most relevant at controller, aggregation, historian, edge-compute, and backbone layers, where multiple lower-speed field streams converge [3], [4].

Hazardous areas and intrinsic safety

Hazardous areas are a special case because communication infrastructure must not become an ignition source. IEC 60079-11 defines protection by intrinsic safety "i", IEC 60079-25 covers intrin-sically safe electrical systems, and IEC 60079-14 governs the design and installation of Ex elec-trical systems [7]-[9]. In practical terms, intrinsic safety limits the electrical energy available in field circuits. That energy-limited approach is why intrinsic safety is often preferred when plants need maintainability and straightforward hazardous-area installation philosophy. For Ethernet deployments, this is valuable because modern field devices are no longer single-variable instruments; they increasingly behave as diagnosable, networked nodes with remote parameterization, event logs, and multi-channel data exchange [1], [4], [7], [8].

Where the certified concept is correctly implemented, damaged or disconnected field wiring connected to an intrinsically safe interface is assessed within the energy-limitation framework of the Ex system rather than treated as ordinary low-voltage networking hardware [7]-[9]. 

Media choices in the field

Optical fibre offers galvanic isolation and very high bandwidth and is often preferred for long, high-capacity backbone paths. Wireless is useful where mobility, temporary coverage, or diffi-cult routing make cabling unattractive, but NIST notes that industrial wireless must contend with interference, latency, reliability, and security challenges specific to industrial environments [10], [11]. NIST testing has also shown measurable degradation of industrial wireless performance in the presence of Wi-Fi interference [10]. For hazardous-area process instrumentation, copper single-pair Ethernet with Ethernet-APL is attractive because it preserves an Ethernet/IP archi-tecture while using a two-wire medium familiar to process plants and engineered for hazard-ous-area deployment [3], [4].

For applications where communication loss is unacceptable, guided media remain easier to en-gineer for predictable performance because the transmission path is physically controlled, whereas radio channels are affected by interference, multipath, and local spectrum conditions [10], [11].

Determinism, cybersecurity, and resilience

Modern hazardous-area networks must be resilient not only to process faults but also to cyber events and electromagnetic disturbance. IEEE 802.1 TSN defines deterministic services over IEEE 802 networks, including bounded low latency and low packet delay variation, and IEC/IEEE 60802 selects TSN features and defaults for industrial automation profiles [5], [6]. On the security side, NIST SP 800-82 Rev. 3 emphasizes OT-specific security measures that preserve reliability and safety, while IEC 62443-3-2 formalizes partitioning systems into zones and conduits as the basis for risk assessment and target security levels [1], [12].

The engineering implication is that real-time flows should be segmented from management, maintenance, and enterprise traffic, and that security controls should be placed in ways that do not introduce unbounded jitter into critical paths. In other words, safety, determinism, and cy-bersecurity have to be engineered together rather than treated as separate layers of after-thought [1], [6], [12].

Why IIC certification matters

Gas-group selection is not a labeling detail; it is part of the technical basis for equipment selection in hazardous areas. ISO/IEC 80079-20-1 provides the material-characteristics framework used for gas and vapour classification, while IEC 60079-0 defines Group II sub-group markings such as IIA, IIB, and IIC, and IEC 60079-11 applies the corresponding intrinsic-safety design and assessment requirements to equipment [7], [13], [14].

For intrinsically safe Ethernet, this means the device, associated apparatus, and overall system design must be evaluated against the applicable equipment subgroup and installation rules ra-ther than treated as ordinary networking hardware. Where the classified atmosphere requires IIC equipment, specifying appropriately certified components provides deployment flexibility on-ly when the final selection also matches the actual zone classification, gas or vapour present, and approved installation concept [7]-[9], [13], [14].

Conclusion

Intrinsically safe industrial Ethernet is best understood as a layered architecture problem. Ethernet provides the common transport, TSN and industrial profiles provide deterministic behavior, IEC 60079 provides the explosion-protection framework, IEC 62443 and NIST guidance provide cyber resilience, and Ethernet-APL provides the currently practical field-level physical layer for hazardous-area process plants [1]-[9], [12].

The near-term opportunity is therefore not simply "10 Gbit/s in the hazardous field" but a coher-ent end-to-end design in which intrinsically safe Ethernet reaches the field at 10BASE-T1L/Ethernet-APL while higher-capacity 1 Gbit/s and 10 Gbit/s links serve controllers, aggregation nodes, historians, edge compute, and backbones. That layered architecture aligns plant safety, maintainability, and digital-transformation goals more convincingly than either low-speed legacy buses or unconstrained enterprise Ethernet transplanted directly into hazardous areas [2]-[9], [12].

Reference

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