Ethernet-APL Unlocks the Benefits of Digital Communication for the Process Industry

Summary

They hang on the wall in orderly rows. Neatly wound cables run from each instrument to a corner of the room where they disappear into a thick bundle. What’s peculiar about this picture is that none of the flow, pressure or temperature instruments is connected to a pipe in accordance with the actual purpose it serves. But what appears unusual to the outside observer is routine for engineers at BASF. After all, pipes filled with media are superfluous in the BASF electrotechnical test lab in Ludwigshafen. In this room, the engineers are focused on evaluating and testing field instrument communication technologies.

Hanging on the walls–for virtually every measurement principle–is also an instrument from Endress+Hauser that utilizes the new Ethernet-APL communications standard. APL stands for advanced physical layer and refers to Ethernet’s physical communications layer. This standard was developed especially for the requirements of the process industry. The goal was to implement process-like frameworks such as safe operation in Ex zones and communications over long distances with a single 2-wire cable for power and communications signals–and at speeds of up to 10 MBit/s.

Data highway enables new functions

In practice, these new characteristics make it possible to implement applications such as predictive maintenance. To do that, edge devices send instrument data direct from the field into a cloud network such as the Netilion IIoT ecosystem from Endress+Hauser. Netilion then runs various analyses and returns the results to the user in the form of information and recommendations for action.

The application possibilities and frameworks for a new communications infrastructure sounded appealing to the automation specialists at BASF in Ludwigshafen from the very start. BASF engineers began working on the details of Ethernet-APL as far back as the NAMUR general meeting in 2016, a little more than 10 years after digital communication with Profibus PA and Foundation Fieldbus first found its way into industrial plants.

To gain practical experience with the new approach as quickly as possible, five years ago the BASF engineers organized instruments from various manufacturers after the NAMUR workshop and tested them. The idea was to then test the interaction of the regulation and control technology, frequency converters, network distributors, actuators and measurement and analysis instruments. For this purpose they set up a larger, stand-alone test lab in March 2019 with prototypes from leading process technology manufacturers.

The components support PROFINET as a common industrial Ethernet protocol. This protocol has been utilized in factory applications for many years and with the completion of the final version of the communications-independent PA-Profile V4.0, a major step was taken toward the suitability of PROFINET for use in process automation systems. As a consequence, Endress+Hauser also made its field instrument prototypes available with PROFINET.

Benefits of the new technology

The cost and effort associated with new hardware and software and the corresponding extensive testing, are offset by the concrete benefits the technology is expected to yield. While many in the industry view Ethernet-APL as a way to utilize the services and functions of future digital offerings, the technology has present-day tangible advantages as well. Lab testing shows that data can be rapidly uploaded to the sensors. And in the reverse direction, trouble-free downloading of the data from the instruments is possible at high speeds as well.
Network and instrument diagnostics are simple to retrieve. Malfunctions are easy to detect and, as a result, faster to rectify. Together with the system and media redundancy, this leads to efficient maintenance and high plant availability. New applications are significantly easier to bring on line and configure. The tests at BASF, which ranged from installation and commissioning to unlocking of data parallel to the process control system, demonstrated that compared to analog 4–20mA technology, Ethernet-APL makes it possible to utilize the basic advantages of Ethernet technology and digital fieldbuses in process engineering production environments as well.

Explosion protection and functional safety

It goes without saying that BASF also installs instruments in the test lab that are suitable for use in explosive atmospheres. Although this still currently relates to the Ex ic protection level, in the near future the plan is to test intrinsically safe instruments for use in zone 0 (Ex ia). This was made possible by designing 2-WISE (2-wire intrinsically safe Ethernet) explosion protection for intrinsically safe 2-wire fieldbus systems on the basis of the Fisco concept (fieldbus intrinsically safe concept, IEC 60079-11 and -25) together with Dekra Exam GmbH. Ethernet-APL also utilizes a power approach that differs from the “power over data line” concept.

Furthermore, the standard safety controls utilized by BASF are already furnished with a PROFINET communications module that is directly connected to the APL field switches. In the future that means the same technology can be used for both the safety and control system applications. The advantages of consistent use of Ethernet-APL technology are introduced and explained in detail in a white paper titled “Ethernet-APL in the Field for Highly Available Safety Applications." Among other things the authors recommend using the investments in Ethernet-APL for process automation to address the requirements of functionally safe applications. This streamlines market entry and avoids subsequent investments.

Running through the scenarios

Whether the user is dealing with frequency converters, motor controls or analysis instruments, only one communications ring cable is required to connect all the different components in the field, an advantage when setting up the system. This scenario was repeatedly rehearsed in the test center. What’s also important for the operator, and a frequent occurrence in the real world, is the replacement of a network component. If a measurement instrument fails, for instance, in the future it will only require disconnecting the faulty device and connecting the replacement, which is then powered and downloaded with all the necessary information from the process control system. There is no need to configure the instrument or set any parameters.

The MRP (media redundancy protocol), which provides the overall high degree of fault tolerance, helps to quickly detect interruptions and reconfigure the network. And thanks to the S2 system redundancy feature in PROFINET, during a controller outage the redundant controller automatically takes over the communication.

Flexible and future-proof

The test lab already features a fiber optic connection. The PROFINET backbone can also be connected via this high-speed link. Another aspect of the flexibility is that 4-wire instruments can be connected, although it’s not mandatory with the new technology. Given that all of the network devices are equipped with virtual proxy servers, a further advantage is that in addition to APL PROFINET field instruments, PROFINET-PA devices can be installed.

After testing and confirming all of these characteristics, the BASF test center and the suppliers are ready for the arrival of the first series of products. While these devices will be put to the acid test before being employed in the “real” world, this step toward production will happen quickly. Thanks to the extensive testing of prototypes, the BASF team is well prepared to install Ethernet-APL technology in a pilot plant at a European location as soon as next year.