Ethernet-APL

Ethernet-APL (Advanced Physical Layer) is a physical layer specification designed to bring Ethernet technology into the field level of process plants, including hazardous areas. Based on IEEE 802.3cg (10BASE-T1L) and extended for the requirements of the process industry, it enables high-speed, two-wire Ethernet communication with integrated power supply over long distances.
For operators, this means seamless connectivity from the control room to field devices, greater access to process and diagnostic data, and simplified integration into plant networks.

Key benefits of Ethernet-APL

Single two-wire cable for both power and data
Long cable reach: up to 1000 m for trunk lines and 200 m for spur lines from field switch to field device.
High data rate of 10 Mbit/s
Intrinsic safety for installation in Zone 0/1/2 and Division 1/2 areas
Compatible with standard Ethernet-based protocols such as PROFINET over APL

What is Ethernet-APL?

Ethernet-APL extends the 10BASE-T1L single-pair Ethernet standard with specifications tailored for process automation. These include intrinsic safety concepts, long cable lengths, and robust operation in harsh environments. Using a trunk-and-spur network topology, it connects field switches to devices over spurs while maintaining a powered backbone for extended distances.

Power and communication share the same two-wire shielded cable, reducing installation effort and enabling the reuse of suitable existing fieldbus cabling. Although APL allows for true two-wire field devices, it is also possible to use it with an additional power supply in a four-wire field device. This makes Ethernet-APL particularly suitable for brownfield upgrades as well as new installations.

Hazardous area operation

APL graphic — Ethernet-APL enables high-speed Ethernet connectivity directly into hazardous areas, meeting intrinsic safety requirements.

A key feature of Ethernet-APL is its ability to supply both power and high-speed data to instruments in hazardous areas while meeting intrinsic safety requirements. Devices can be installed directly in Zones 0, 1 or 2, and Divisions 1 or 2, simplifying plant design and reducing the need for additional protective equipment. The intrinsic safety approach used in Ethernet-APL is defined to be interoperable across compliant devices and infrastructure.

Protocols and integration

Today, Ethernet-APL enables the direct use of PROFINET at the field level, supporting advanced diagnostics, parameterisation, and integration with process control systems. Its Ethernet foundation means it can also support other protocols, paving the way for future adoption of OPC UA and other IIoT-oriented data exchange models. This aligns with NAMUR Open Architecture (NOA) principles for parallel data access.

Advantages for operation and engineering

Compared with legacy 4–20 mA/HART or fieldbus systems, Ethernet-APL provides:

Increased data availability, including multi-variable and diagnostic information
Faster commissioning and simplified network configuration
Standardised Ethernet infrastructure for IT/OT convergence
Easier lifecycle management through remote updates and configuration
Reduced complexity by consolidating power and data cabling

KROHNE implementation

The first KROHNE device to feature Ethernet-APL will be the OPTIMASS X400 with the MFC 400 converter. This implementation will be introduced first in the EMEA region, followed by Asia and the US. With Ethernet-APL, the OPTIMASS X400 will offer direct Ethernet connectivity for process automation, enhancing integration with plant networks and enabling advanced diagnostics in hazardous area installations.

Although in comparison to 4-20mA, the power budget of APL allows for an extended two-wire portfolio, it is insufficient to cover the complete range of applications, including the largest diameters and most challenging fluids. Therefore, in a first step, KROHNE has extended its high-end four-wire xFC 400 converter range with APL first, starting with MFC 400.