Ethernet APL brings real-time communication into the field of process systems

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Ethernet APL brings real-time communication into the field of process systems

Process control devices have not only been able to perform their measurement tasks for years, they have also been able to provide additional information. In theory, this makes the installed base transparent and provides detailed device diagnostic information that can be used, for example, for preventive maintenance of the devices.

However, this added value can only be partially achieved with the current technology. The 4-20mA analog technology is suitable for process control tasks, for example, but not for further data access. The additional HART protocol, which is mainly used today to configure the devices, is simply too slow for comprehensive data access. Fieldbus technology, which has been known for many years, has improved this aspect, but is also still considerably slow. In addition, fieldbus technology has proven to be too complex for many users over the years and has therefore not been able to fully establish itself.

Worlds grow together

A look at other industries shows that Ethernet has not only become the standard in office environments, but is also used in industrial applications. The main advantage is the high speed and seamless integration into IT systems. “It is only in the process industry that the Ethernet specifications have not yet met the operators’ expectations,” says Benedikt Spielmann, Head of Marketing Industrial Communication at Endress + Hauser. “Ethernet is a fast way to transfer data, but all components need a separate power source. This means a lot of cabling and the associated higher costs. In addition, Ethernet has so far been limited to a cable distance of 100 meters, while process systems often extend up to 1,000 meters. Another problem is that the RJ-45 connectors are not designed for harsh field environments. And the best argument against the use of Ethernet in the process industry has so far been the lack of suitability for hazardous areas due to a lack of intrinsic safety. “

Benedikt Spielmann, Head of Marketing, Industrial Communication at Endress + Hauser

Leading manufacturers and user organizations joined forces a few years ago to eliminate these disadvantages. The APL Group has set itself the goal of being able to use the fundamental advantages of Ethernet technology in process plants and to make Ethernet fit for use at the field level in the process industry: power and data transmission over the same two-wire line, suitability for Ex zones, high Bandwidth and long cable runs.

The work on the specification has now been completed. The technology was released during the Achema 2021 virtual conference. “The introduction of the Ethernet APL technology during the Achema Pulse was an important milestone,” said Benedikt Spielmann. “All specifications and guidelines were completed on time. The presentation of the first Ethernet APL devices on the manufacturer-independent APL exhibition wall impressively demonstrated that all participating manufacturers are working on their APL portfolios. There was also knowledge of which customer applications would benefit from the new technology. “

APL project work packages

One of the main tasks of the working group was to ensure intrinsic safety, for which it was initially necessary to limit the power transmission. This requirement initially contradicted the desire for higher bandwidth, long cable runs and robustness against electromagnetic interference. Questions about cables and plugs or the type of connection also had to be answered. All challenges were successfully mastered. The solution is reflected in various working papers, standards and documents:

  • 10BASE-T1L: The IEEE802.3cg-2019 specification defines full duplex 10 MB data transmission over two-wire cables at distances of up to 1,000 meters. This is also the basis for the production of physical layer components (microchips for coding and decoding in Ethernet APL devices).

  • 2-WISE: This concept for two-wire intrinsically safe Ethernet (2-WISE) is based on the fieldbus intrinsically safe concept (FISCO). The migration to existing fieldbus installations is simplified by compatible Ex-i parameters and simple installation is guaranteed without extensive validation in Ex zones.

  • Port Profiles: Functional and electrical requirements with several energy concepts are defined in the APL Port Profile Specification. This enables different topologies such as the common trunk-and-spur concept with up to 1,000 meters on the trunk and 200 meters on the branch line. In addition, the specification contains installation guidelines such as approved cables, shielding and grounding as well as the definition of clamp connections and M8 / M12 connectors.

  • Configuration guide: This guide contains detailed information on planning, installing and commissioning APL networks.

  • Conformance Test Specification: To ensure the conformity of an Ethernet APL device with the specified specifications, a corresponding test specification is created. These tests form the basis for the certification of Ethernet APL devices by accredited test laboratories of the user organizations involved and thus ensure the interoperability of the Ethernet APL devices for the end user.

Practical experience

Even before the official introduction of the standards and specifications and the correspondingly designed devices, the APL technology was successfully implemented in real environments. In 2019, BASF installed APL prototypes from various manufacturers at the Ludwigshafen site. The tests ranged from installation and commissioning to data export parallel to the process control system. Automation providers in the process industry discussed the promising results at the 2019 NAMUR Annual General Meeting. In summary, they stated that Ethernet APL has the following advantages:

  • Connectors and different topologies enable simple and flexible installation.
  • Remote access and fast data transfer simplify and accelerate the commissioning of the system.
  • Ethernet via two-wire fieldbus cable ensures stable communication.
  • Via the “second channel”, data from smart instruments can be routed around the process control system in accordance with the NAMUR Open Architecture.

All of these are experiences that the field device manufacturer Endress + Hauser can confirm. “Ten years ago we brought a flow meter with Ethernet connectivity onto the market and since then we have gradually expanded the portfolio,” says Spielmann, looking back on the development. The response was extremely positive, especially from the food and beverage industry. “More process data and more diagnostic information create transparency and help to optimize work processes. This additional functionality in the sense of digitization is very popular with users, “reports Spielmann.

End-to-end Ethernet technology offers a multitude of advantages in terms of efficiency and simplicity, especially when it comes to device maintenance. Users benefit from an integrated web server that simplifies remote access to field devices for parameter configuration or error detection. Even firmware updates are possible via this remote access, including high bandwidth. The efficiency of Ethernet also promotes the use of standard applications such as the creation of measuring point reports or the uploading / downloading of parameter sets.

In the future, access to data in the field will be possible without problems of interpretation, since the information is available to digital services such as the Netilion ecosystem from Endress + Hauser. In theory, this connection also works with other protocols such as PROFIBUS or HART. However, Ethernet APL makes more data available – and faster. A typical example is predictive maintenance, which is controlled with real-time data from the field devices. “Although the algorithms are in the field devices, they also have to be processed in the cloud. With Ethernet APL, the data highway is available to make the data available. If all of this were done via HART, the network would be constantly overloaded and the data transfer would be unbearable, ”explains Spielmann.

Another aspect is that Ethernet APL also supports the modular approach currently used in many chemical plants. Any number of APL segments with the same design that is already used in other segments can be added. The topology is set up first; everything else, such as the assignment of names or the startup parameters using the example of PROFINET as the Ethernet protocol, is automatically transferred to the devices. “With the current 2-wire Ethernet approach, we are also attracting users in the chemicals, oil & gas, minerals and mining sectors who have the same requirements for digitization. We are now providing them with the portfolio they need, ”said Spielmann.

Endress + Hauser is working flat out on the development of the Ethernet APL product portfolio. With the completion of the APL specification and the availability of the PHY chips, the necessary pieces of the puzzle are in place. Ethernet APL measuring devices for flow, level, pressure and temperature will be launched in the first half of 2022 and liquid analysis, ”says Spielmann.

About the author


Frank Jablonski is a freelance journalist, mylk + honey, for Endress + Hauser.


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