Process and factory automation differ in virtually all key features. In the process industry, the paths are longer, the environments are harsher, the requirements for continuous operation are higher, and explosion protection with intrinsic safety is required. This also results in a very strong need for extremely rugged technologies and products. Ethernet-APL has been specifically developed for process plants.
Ethernet specifically for the process industry
SPE describes a physical transmission path for Ethernet, for example, based on 10-BASE T1L with a 10 Mbit transmission rate. The advantages of SPE include the reduced number of wire pairs, as only one is required for communication. The transmission technology therefore supports all Ethernet-based protocols, which enables continuous communication from the cloud to the sensor in the factory automation, and in the process industry as well, with Ethernet-APL.
For the power supply, Ethernet-APL offers defined, broadly differentiated performance classes in IEC standards, which can also be used in hazardous areas for long cable routes with the associated voltage drop in the cable. Explosion protection via intrinsic safety and very rugged installation technology is also included.
A two-wire cable, plug-in terminals and devices with reverse polarity protection ensure ease of use and installation. Compliance testing, which manufacturers submit to as part of device certification, guarantees a high degree of inter-operability. The switch transmits the power supply and communication through point-to-point connections. This topology has a simple design and is therefore easy to use and maintain. The network infrastructure is highly resistant to interference, even during connection and disconnection processes, which are often required when performing maintenance or replacing devices.
Protection for hazardous areas
The intrinsic safety type of protection is an integral part of Ethernet-APL. This makes it ideal for safely operating measuring instruments and other field devices, such as sensors and actuators.
Ethernet-APL borrows the FISCO concept from fieldbus technology, but allows higher power and greater distances between the switch and the field device. A chapter has been added to the established IEC standard (IEC 60079) which details the methods used to verify intrinsic safety. This intrinsic safety concept for Ethernet-APL connections is known as 2-WISE, which stands for “two-wire intrinsically safe Ethernet”.
The legally required verification of intrinsic safety is very simple for users. The designer selects the devices according to the desired zone, takes care to use a suitable cable (up to 200 metres long) and documents the installation. Time-consuming calculations to prove intrinsic safety are no longer required. Suitable devices show the 2-WISE marking and the explosion-protection class for which the Ethernet-APL device is approved.
Clear network structures
The FieldConnex Ethernet-APL rail field switch provides the transition by establishing the connection to the instrumentation, translating the data transparently and without barriers from fast Ethernet or Gigabit to Ethernet-APL. The switch protects the field devices from unnecessary data traffic as they have very little power available for computing power.
The expected traffic determines the design of Ethernet networks. The instrumentation in the process plant represents a large number of participants, each of which only needs to transmit very small amounts of data, such as the measured values, diagnostics and alarms. These prerequisites enable network architects to plan clear structures.
This means that an APL network never has to withstand a 500 MB download from Singapore, for example. Definitions from leading industrial protocols for implementation, such as PROFINET over APL and EtherNet/IP over APL, take these special requirements into account.
End-user expectations
The promise of a network in the field of processing plants, with Ethernet-APL as the underlying technology, is raising high expectations among users. They expect a network in the field of processing plants to be the platform of the future, and the basis for digitalisation and the seamless integration of all plants into a single system. End users want to simplify device diagnostics and integrate functional safety, all to create a good user experience when using complex devices. Plant engineers are looking for cross-system data migration to help them link the actual device tags to the master tag list, thereby increasing the speed and quality of loop checks. Exchanging devices is now easier than with the current best-practice solution of 4-20 mA and HART technologies.
Ethernet-APL is the physical layer, or data highway, to the field of process plants. It is based on over 30 years of experience in digital communication, combined with today’s most modern digitalisation and explosion-protection concepts. This provides users with what is currently the most powerful tool for modern plants.
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