Endress + Hauser outlines the usefulness of Ethernet in process industry
Ethernet in process plants
At first glance, Ethernet may seem out of place in the process industries. With its high data rate and large bandwidth, Ethernet is a stark contrast to established process Fieldbus protocols such as Profibus PA, HART and Foundation Fieldbus H1.
In reality, industrial Ethernet will not likely replace process Fieldbuses directly. Rather, it will augment their functionality by providing seamless integration into a high-capacity backbone network based on the same standard Ethernet as used in the rest of a company’s network infrastructure.
Profibus International (PI) has recognised the need to bridge this gap with Profinet by launching a multi-pronged initiative to first identify the specific needs of process users and then adapting Profinet to address these needs.
Existing industrial networks are typically special purpose networks designed to address specific requirements.
Controls suppliers support open remote I/O networks such as Profibus and DeviceNet, while field instruments are typically networked using Profibus PA, HART or Foundation Fieldbus.
The typical plant is thus saddled with many disparate communications solutions that give the user integration headaches. Industrial Ethernet addresses users’ requirements with just one cable.
However, for Ethernet to establish itself as the basis for plant-wide communication, it has to satisfy specific automation requirements.
Profibus PA is PI’s preferred solution for networking process field devices. Compatible with the international Fieldbus standards IEC 61158, Profibus PA meets requirements for intrinsic safety in explosive environments and provides power over the bus to devices.
PA-devices normally connect to a host such as a PLC/DCS via Profibus DP, but due to the development of gateways, PA segments can be connected directly to Profinet, meaning that Profinet can serve as a plant-wide backbone network.
This brings industrial Ethernet one step closer to the level of the instrumentation network by allowing a single Profinet segment to connect multiple PA clusters.
Profinet’s connectivity to legacy networks will allow existing DeviceNet, Profibus DP and Profibus PA, HART and Foundation Fieldbus networks to connect seamlessly to a Profinet backbone network.
Profibus PA offers communication to process field instruments in applications that require a different network medium, for example, for networking intrinsically safe devices in explosive environments. Via a network coupler, PA devices can communicate seamlessly with other devices on both Profibus DP and Profinet. This allows all communication to take place seamlessly through a single network architecture, leaving the choice of the physical layer to the end-user.
Many existing plants already use process networks such as Profibus PA or Foundation Fieldbus.
For retrofit or migration projects in existing plants, significant value can be achieved by modernising the industrial network infrastructure with a solution that adds functionality while preserving investments in legacy systems. This is the main driver behind PI’s initiative to adapt Profinet to the needs of process users.
To meet process industry requirements, PI is developing Profinet interfacers not just for Profibus PA, but also for all other technologies including HART communications protocol and Foundation Fieldbus.
Using standard Ethernet with industry-specific enhancements has helped countless manufacturers increase data transparency, shortened start-up time, lower downtime and maintenance costs and increased productivity.
While Ethernet can greatly enhance data gathering from the plant floor, this becomes especially useful if the data are effectively evaluated using applications such as plant asset management (PAM).
More details are available at Endress Hauser.
9-Oct-2007