Ian Verhappen raises quite a few good points in his recent opinion piece on Ethernet-APL ["Ethernet-APL: Potential vs. possible," Feb '21, p. 16]. I’d like to comment on a couple of these.
First and foremost is the idea of the killer app. Perhaps as instrument architecture evolves to take advantage of the much greater bandwidth of Ethernet-APL, a killer app that hasn’t been identified before now will emerge. But in the meantime there are plenty of applications for plant data that are presently underutilized because of the “friction” associated with getting at the instrument data. Predictive maintenance, enterprise-wide analytics, and process optimization come to mind immediately.
Remember that Ethernet-APL is simply a physical layer. A high-speed, IP-based, two-wire physical layer that has the advantage of supporting intrinsic safety. In the last paragraph, I spoke of friction. One of the major advantages of Ethernet-APL is the potential to remove a significant part of the friction associated with moving data all the way from the instrument to the enterprise without multiplexers, gateways, protocol translators and the like. For engineers, particularly new engineers familiar with IP networking, Ethernet-APL will be much simpler to install and configure than current plant architectures.
On top of Ethernet-APL lies an application protocol, like HART-IP, which essentially is old reliable HART encapsulated in an IP packet. HART-IP is used in many HART multiplexers. Now, two-wire Ethernet-APL with power enables HART-IP to be directly deployed on instruments. And since most plant engineers are familiar with HART and every major asset manager or DCS supports the HART protocol, support for HART-IP enabled Ethernet-APL devices is already available.
On the plant software side of the brownfield application, EtherNet-APL instruments can easily be absorbed. But what about the enterprise software and analytics? How are they handled? Until a single application protocol can extend from instrument to enterprise there will still be a gateway in the chain to supply information to the enterprise. Fortunately, the software specification to bridge the gap between OT protocols like HART-IP and IT protocols like OPC UA already exists in the form of a standard for a Process Automation Device Information Model (PA-DIM). Commercial products supporting PA-DIM will be available in 2021.
Lastly, let’s address the greenfield vs. brownfield topic from the physical side. Yes, a goal of Ethernet-APL is to reuse existing cabling, and no doubt some companies will do just that. But by and large, users are not ripping out instruments and are frankly pretty satisfied with their existing HART 4-20mA installations. So, like WirelessHART before, a large opportunity for Ethernet-APL lies in expansion of existing facilities to incorporate additional sensing points. For a good primer on these opportunities, review the NAMUR Monitoring + Optimization (M+O) concept, which itself is part of the NAMUR Open Architecture (NOA) model.
Finally, as the technology gets some mileage underneath it, users will better understand the advantages, become more trusting, and begin expansion of their installations beyond M+O and into supervisory and even regulatory control.
Paul Sereiko
Director – Marketing and Product Strategy
FieldComm Group
