Ethernet-APL will accelerate digital transformation throughout the process automation industry, because it combines high-speed digital communications with support for the unique needs of industrial installations. By Sean Vincent, Fieldcomm Group
Change comes slowly in the process automation industry. And a corollary to this is that the excitement levels about new technologies are similarly muted. With facilities built for 30+ year operational lifecycles, and the significant expenses associated with turnovers, operators and engineers have little opportunity to embrace all the latest and greatest new technologies. For this reason, many plants still rely heavily on 4-20mA and HART instruments along with a smattering of higher-bandwidth fieldbus devices to implement their core process control systems.
A notable exception bucking the generally blasé attitude towards new tech is that the process automation industry is uniformly excited about a new Ethernet-based physical layer named Ethernet-APL. Users, suppliers, OEMs, integrators, and standards organizations are eager to take advantage of the benefits promised by Ethernet-APL for accelerating digital transformation. What is Ethernet-APL and how should users begin to deploy it?
Ethernet-APL basics and benefits
Standard Ethernet media has been widely adopted for industrial networks and automation communications. However, users, suppliers, and component manufacturers have long realized that for high-speed Ethernet communication to work at the field level for process automation instruments, a new physical layer would need to be developed to support unique industrial requirements. Principal amongst these needs is two-wire power using common cable types, data communications over those same two wires, long cable lengths, and the ability to deploy in hazardous environments.
A consortium of standards organization and suppliers formed, specifications were written, and chip manufacturers began developing silicon. By 2021/22 the initial work was completed, the technology launched, and products are now entering the market.
Ethernet-APL is a 10 mbit/sec Ethernet physical layer that can be deployed in hazardous areas using well known FISCO installation procedures. Existing two-wire fieldbus cabling may be used to connect Ethernet-APL instruments to networking infrastructure. Ethernet-APL is NOT an automation protocol, rather it is an Ethernet network supporting many Ethernet automation protocols like HART-IP, PROFINET, and EtherNet/IP.
The specifications define three specific components of an Ethernet-APL network: instruments, field switches, and power switches. A special class of device, known as a powered field switch, is also defined. A wealth of detail on Ethernet-APL can be found at the FieldComm Group website or the dedicated Ethernet-APL website.
Ethernet-APL promises to speed the digital transformation of process automation in several key ways:
- Higher speed communications means that more data can be transmitted, more functionality and intelligence can be built into instruments, leading to better predictive maintenance and operational efficiency improvement.
- Ethernet based communication means that a workforce of technicians and installers trained in IT technologies like TCP, UDP, IP, and similar will be able to install and maintain automation networks. This will lower costs and allow highly trained automation protocol specialists to focus more effort on better control and automation and less on maintaining the network.
- Using Ethernet as the network communications transport enables non-traditional Ethernet-APL enabled devices to share the same cabling infrastructure with field instruments. Imagine for example, a video camera on the same network as a pressure transmitter.
A big challenge for end users will be to begin to imagine the possibilities presented by Ethernet-APL technology.
Getting started with Ethernet-APL
Today’s process control architectures generally consist of instrumentation, connected to remote I/O modules which in turn use Ethernet backhaul to interface with core process controllers as well as asset management and engineering systems. Often there is a firewall between the process control network and other enterprise systems. For simplicity we’ve omitted this distinction in Figure 1.
Figure 1 (above) shows a typical plant network along with some ideas for deploying Ethernet-APL. On the diagram there is a multi-port powered Ethernet-APL field switch, a remote I/O unit that supports Ethernet-APL and field instrumentation. The deployment is intentionally located in a “mildly” hazardous area, Zone 2 Div 2, and would be a good first step for testing out Ethernet-APL infrastructure.
The powered field switch sits at the junction between the non-hazardous and hazardous area and performs two roles. The first role is to convert plant Ethernet—which might be a fibre optic cable carrying gigabit level traffic—to 10 mbit/sec intrinsically safe Ethernet-APL. The second role is to inject power into the Ethernet-APL physical layer so that the remote I/O and instrumentation can be powered.
The remote I/O module is installed in the hazardous area with power and signal supplied by the Ethernet-APL cable, which can be up to 1,000 meters long, connected back to the powered field switch. One of the roles of the remote I/O module is to convert standard 4-20ma HART field instrument signals to high-speed HART-IP for transport over the Ethernet-APL cable.
This configuration offers a fairly simple way to get started with Ethernet-APL by installing two cables and two pieces of expandable infrastructure. As Ethernet-APL field instruments become commercially available they may be connected to open ports on either the powered field switch or the remote I/O unit.
A note about cabling
One objective of an end-user Ethernet-APL deployment team may be to reuse existing FOUNDATION Fieldbus and PROFIBUS-PA Type A cables. The intention would be to more easily facilitate the transition of common existing installations over to Ethernet-APL.
But users are cautioned about reuse of existing cabling, and the Ethernet-APL technical guidelines lay out specific requirements for cable electrical characteristics to meet the link maintenance and data rate specifications of the technology at the specified maximum distance. In these cases, cable testing will be needed, and it is helpful to work with suppliers and qualified installation professionals to plan a successful deployment.
Accelerating digital transformation
Even within the disciplined process automation industry, it is possible for new technologies to spark excitement. Ethernet-APL is a prime example. Users, suppliers, OEMs, and integrators already rely on standard Ethernet when designing their systems. By allowing those digital architectures to seamlessly extend all the way out to field devices, while including the power, wiring, and safety characteristics needed for industry, Ethernet-APL is positioned as the technology of choice for both new and retrofit digital transformation projects.
All images supplied by FieldComm Group
About the Author
Sean Vincent is director of technology programs of the FieldComm Group. His career is dedicated to development, testing, and support of protocols and tools for the process industry. He currently leads the development of new technologies and tools within FieldComm Group and in collaboration with other organizations. Sean holds an Electrical Engineering degree from the University of Texas at Austin.
