Profinet Features for Process Automation

By David Humphrey

Category:
ARCView

Summary

dhs1.JPGIndustrial networks are the “highways” of the digital plant and key enablers for every company’s digital transformation. Highly performant Ethernet-based industrial networks, like Profinet, are already well established in automation architectures and will continue to support and drive digital transformation in industry. However, for the process industries, these networks have traditionally lacked some specific features and refinements needed for process automation.

Siemens, a leading supplier of process automation solutions, has addressed these requirements by enhancing and expanding its portfolio of distributed IO systems for process automation to extend the benefits of Profinet down to the field level.

Digitizing the Last Mile

The process industries have been relatively slow to replace traditional analog 4-20 mA technology with digital process fieldbuses. Special requirements for using a fieldbus in hazardous and explosive environments greatly limited speed and bandwidth of the network’s “last mile” (to borrow a phrase from the logistics world), creating a bottleneck for digitalization. While existing networks like Profibus and Profinet (based on standard Ethernet) provide a “backbone” network in modern plants, these networks have been deployed mostly at the peer-to-peer level, or are used like master-slave networks for connecting IO devices in normal environments. Connecting to field devices in harsh or explosive environments still requires interfaces to slow, non-Ethernet-based fieldbuses.

The market for process automation equipment includes large end users in industries ranging from bulk chemicals to refining to oil & gas exploration. All industries require time-critical performance, but “real-time” is defined differently by industry and even by application. While high-speed machine control has the most demanding performance requirements, in the process industries, the priority is on high equipment availability for nonstop, round-the-clock operation. Equipment suppliers often use availability levels as a parameter in their service level agreements. To ensure the appropriately high levels of availability, process industry owner-operators require device-level features like simple integration, hot-swapping, configuration in run, and scalable redundancy.

Profinet for the Process Industries

Profinet, an industrial network based on standard IEEE 802.3 Ethernet, was developed by member companies of Profibus and Profinet International (PI). PI, an industrial consortium, manages and oversees the portfolio of industrial networks that also includes Profibus DP and Profibus PA. In the spirit of “one cable for everything,” PI has enhanced Profinet to address a wide variety of industrial user requirements.

Features for Process Users

Siemens, a founding member of PI, recently announced new products that expand and enhance the features and capabilities of Profinet for process industry users. Process automation requirements dictate that continuous processes may not be interrupted, even when hardware errors occur, a device is replaced, or an existing hardware configuration is changed. These features take advantage of capabilities in the Profinet IO profile. These include support for system (S1, S2, R1, R2) and media redundancy, time synchronization and stamping, and configuration in run (CiR) - all available in new distributed IO products.

Based on the Siemens ET 200SP IO system, the new, compact SIMATIC ET 200SP HA (high availability) distributed IO system adds new features that specifically address process automation requirements, including network and IO module redundancy. Two interface modules for Profinet can be used to achieve network redundancy, and both IO modules and terminal blocks can be installed in redundant configurations. In addition, users can replace defective modules (hot-swapping) and add new IO modules to an existing configuration under power, if needed. Once new hardware is installed, the new configuration is loaded from the engineering station without stopping the process (configure in run).

Siemens’ new “smart field distributor,” the SIMATIC Compact Field Unit (CFU), complements the distributed IO in process applications. The CFU is essentially a marshalling island for devices installed in harsh or explosive environments that communicate via Profibus PA. The CFU provides a central location to connect all Profibus PA cables, which then communicate with the DCS via Profinet.

Siemens’ Strategy for Distributed IO for Process Automation Employs Both Built-in Profinet Networking and Enhanced Hardware dhs2.JPG

 

Like the ET 200SP HA distributed IO system described above, the SIMATIC CFU allows for quick, smart device configuration. When a device is added or replaced, the system verifies whether it supports the appropriate standard Profibus PA profile already defined in the engineering configuration. If so, standard communication can begin immediately and the installation is finished. These generic profiles are similar to universal drivers in the IT world and are the basis for plug & play in automation, commonly called “plug & produce.”

Finally, the CFU is an attractive option for migration projects in which the control system and engineering stations are modernized, but much of the IO and field instruments are left in place and reused. A CFU can reduce wiring in the field by marshalling Profibus PA devices at a single point, then transferring data to the controller at high speed via Profinet.

To fulfill stricter process automation requirements, Siemens has extended environmental parameters, including the temperature range (now -40 to +70 °C), added conformal coating, and certified the devices for installation in hazardous areas up to Ex-zone 2-22. Finally, the products adhere to NAMUR Recommendation NE21, which covers immunity to interference.

To configure IO and field instruments on Profinet in process applications, Siemens offers standalone software and diagnostic tools as well as tools built into the company’s SIMATIC PCS 7 process control systems.

Recommendations

Based on ARC’s research and analysis, we make the following recommendations:

  • For process equipment suppliers: Industrial networking and fieldbuses are gaining importance in process automation, especially to support initiatives like Industrie 4.0 and IIoT. As you evaluate automation suppliers to partner with, consider the role the network plays in support of digitalization initiatives as well as the key automation requirements of process industry end users.

  • For end users: When discussing your process automation requirements with your suppliers, be sure to take into account the role the industrial network will play, not only for supporting future data requirements, but also in reducing wiring costs and shortening commissioning and maintenance times.

     

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Keywords: Profinet, Process Industries, Oil & Gas, Chemicals, Industrial Ethernet, Digitalization, DCS, SIMATIC PCS 7, ARC Advisory Group.

 

 

 

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