Automation networks in hazardous process automation facilities have a multitude of challenges. For example, process applications often demand 24/7 operation and reliability while managing a gazillion signals. In addition, hazardous environments, such as extreme temperatures or flammable/explosive conditions require specialized precaution strategies.

Hazardous environments require intrinsically safe technologies. Therefore, process automation facilities use intrinsically safe technologies like Profibus PA, Hart, Wireless Hart, and Foundation Fieldbus to provide communication. However, there has long been a desire to bring Ethernet technology to field devices in hazardous areas. However, Ethernet is NOT intrinsically safe. The good news is that the quest for the deployment of high-speed, Ethernet-enabled instrumentation has taken a step forward with the introduction of Ethernet-APL.

What is Ethernet-APL?

Ethernet-APL (Advanced Physical Layer) is a new physical layer (PHY). PI North America, a non-profit trade organization, defines Ethernet-APL as follows:

APL is a new physical layer. The goal of APL is to bring Ethernet down to field-level instruments in hazardous areas. Ethernet at the field level will make digitalization for process industries a reality. Ethernet adds its universality and speed to existing field device installations.

Ethernet-APL limits the current and voltage in the PHY to intrinsically safe levels for Zones 0 and 1/Div. 1. (For reference, see the European Union and North American classifications below.) The physical connector is a rugged two-wire connection and will exceed the 100 meter limit of 100BASE-TX Ethernet networks, making it suitable for manufacturing facilities.

As a reference, the intrinsic safety requirements for the European Union and North America are described below:

European Union Classification

Zone 0 Hazardous Area – Flammable atmosphere present continuously or for long periods

Zone 1 Hazardous Area – Flammable atmosphere likely in normal operation or frequently due to repair, leakage, etc

Zone 2 Hazardous Area – Flammable atmosphere unlikely in normal operation and, if it occurs, will exist only for a short time

European Union Classification

North America Classification

Division 1 – Ignitable concentrations of hazards exist under normal operating conditions or where a hazard is caused by frequent maintenance, repair work, or equipment failure.

Division 2 – Ignitable concentrations of hazards are handled, processed, or used, but which usually are in closed containers or systems. They can only escape through accidental rupture or breakdown of such containers or systems.

North American Classification

Ethernet-APL: A Bit of History

In 2018, “The APL Project” was established by major industry-standard development organizations (SDOs) FieldComm Group, Profibus & Profinet International, ODVA, and OPC Foundation—as well as twelve leading process automation suppliers to meet the following Ethernet-APL goals for the industry:

  • To establish current/voltage limitations to be intrinsically safe in Zones 0 and 1/Div 1
  • To ruggedize a two-wire connection
  • To power over the two-wire connection
  • To provide wired segments longer than the 100-meter limit
  • To use the same, established  industrial Ethernet protocols, running over this new PHY 

On June 15, 2021, The APL Project launched the new Ethernet-APL technology at the ACHEMA Pulse Digital Fairs. Dr. Jorg Hahniche, chair of The APL Project, states:

We’re very pleased to release the carefully crafted technology specifications and engineering guidelines to enable Ethernet-APL technology to start to transform the field of process plants. The high level of cooperation across multiple standards development and vendor organizations within the APL Project has resulted in one future-oriented Ethernet physical layer for process automation. This technology launch is a key progress marker, and the development journey will continue now with products in the pipeline from significant industry partners.

What does Ethernet-APL offer?

Ethernet-APL comes with user-friendly deployment support, such as: .

Multiple Protocol Support

Ethernet APL supports higher-level protocols, such as EtherNet/IP, HART-IP, OPC UA, and Profinet. 

The APL Project has also taken the following support steps:

  1. The project has teamed up with semiconductor manufacturers to offer the chips needed for 10BASE-TL PHYs for Ethernet-APL.
  2. The twelve APL Project industry partners are putting the final touches on the development of new products. They recently digitally displayed these products during the ACHEMA Pulse fair in Karlsruhe, Germany, highlighting the multiple product options that Ethernet-APL will offer shortly.

Familiar Topology

Ethernet-APL supports trunk-and-spur installations and has redundancy concepts that are similar to Fieldbus practices. In addition, the Ethernet-APL protocol defines two general types of segments: “Trunk lines that carry high-level power and data for distances up to 1,000 meters (m), and spur lines that carry power and signals with optional intrinsic safety for distances up to 200 m. Anchoring the trunks are APL Power Switches, each of which provides up to 60 W of power and communications for as many as 50 devices. Anchoring each spur, in turn, is an APL Field Switch that provides IS power and communications to the field devices themselves.

In addition, Ethernet-APL requires IEC 61158 Type A shielded, twisted-pair cables, which are also in keeping with standard Fieldbus protocols. Per Michael Browne, executive director at PI North America:

From the very outset, the ability to reuse existing single, twisted-pair Fieldbus cabling was a requirement for APL due to the high installation costs involved. For example, the Type A cabling used by Profibus PA should work just fine for APL.


Why should you be interested in Ethernet-APL?

The bottom line: Ethernet-APL is the future of process automation and has numerous benefits:

  • Simple engineering and maintenance
  • Speeds-up deployment
  • Redundancy mechanisms for high availability
  • Asset optimization
  • Open technology
  • Powerful integration technologies
  • Risk reduction
  • Intrinsically safe explosion protection option


The next steps for Ethernet-APL will include the release of field devices from select vendors. Paul Sereiko, director of marketing at FieldComm Group:

Where FOUNDATION Fieldbus and Profibus PA are currently used, we don’t believe that end users will start ripping out field instruments to install APL. We doubt a refinery unit will consider upgrading until their existing assets are at end of life. Early adopters are much more likely in more flexible process applications, such as life sciences, and food and beverage.”

With the recent launch of Ethernet-APL, there is a new single Ethernet physical layer that enables cable distances of up to 1,000 meters, intrinsic safety, and support for maximum productivity. In addition, products with conformance testing certification will soon be available. To learn more about Ethernet-APL, you may want to sign-up for the Ethernet-APL 2021 Virtual Workshop. 

Planet Technology USA is a US-based distributor of Planet Technology, Inc. Our versatile networking products include standard switches, PoE switches, and Industrial switches. If you are interested in any of our state-of-the-art products, contact us today.