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PROFINET and PROFIsafe
PROFlsafe functional safety communication profile plan
PROFlsafe is a functional safety communication profile proposed by PI International that is loaded on the PROFIBUS and PROFINET communication protocols and complies with IEC 61508 functional safety international standard. In 2023, the total number of PROFIsafe nodes installed worldwide has exceeded 25.6 million.
Compared with traditional safety systems, PROFIsafe has the following characteristics:
Standard fieldbus technology and fail-safe technology are "combined into one system, that is, fail-safe communication and standard communication coexist on the same cable; PROFlsafe fail-safety is based on a single-channel communication system, and safety communication does not reach its purpose through the cable: Compared with standard PROFIBUS, standard communication components such as cables, dedicated chips, DP-stack software, etc., remain unchanged; Fail-safe measures are enclosed in the terminal module (F-Master, F-Slave), and patented SIL monitors are used to achieve extremely high safety: The highest fail-safe integrity level is SIL3° (IEC61508); It can be used for both low-energy (Ex-i) process automation and fast-response manufacturing automation.
Well-known Beckhoff°, Rexroth, FESTO, WAGO, Phoenix Many well-known manufacturers such as Contact°, Sick, Banner, and Turck have also launched many related products that support PROFIsafe. On December 16, 2015, the China National Standardization Administration officially approved GB/T20830-2015 "Functional safety communication profile based on Profibus DP and Profinet 10--PROFlsafe" as a recommended national standard. This is the first functional safety communication profile in China. The release of the safety communication standard will promote the rapid development of my country's manufacturing industry towards a safer, more intelligent and fully automated direction.
Introduction to PROFlsafe
PROFINET and PROFIsafe are different technologies. PROFINET is an open industrial Ethernet standard that provides real-time data exchange while maintaining openness for flexible plant and machine concepts. In addition to standard features, each PROFINET device has some optional features to provide additional functionality. PROFlsafe is such an optional feature that extends the standard PROFINET communication protocol to meet strict safety standards in order to meet the unique requirements related to functional safety. PROFINET is an industrial Ethernet solution and an application that defines cyclic and acyclic communication between components, including diagnostics and alarms. PROFIsafe is an additional software layer that is added to the bus of the PROFINET (or PROFIBUS) standard protocol network to provide the functional safety part of the communication, ensuring the integrity of the fail-safe signals transmitted between safety devices and safety controllers to comply with relevant safety standards for industrial networks
'PROFIlsafe and Ethernet-APL
Since Ethernet-APL can cooperate with PROFINET and is called PROFINET over APL, the cooperation between Ethernet-APL and PROFlsafe is natural and reasonable, so we can also call it PROFINET/PROFIsafeover APL.
PROFINET over APL extends the application to functional safety, because a single network technology can be used for control systems and safety instrumented systems, which increases the flexibility of factory design and reduces the requirement for inventory spare parts. In addition, the information of the same field device can be used for safety and non-safety functions, which will improve maintenance efficiency. Safety communication is not achieved through redundant cables, which not only saves costs in terms of wiring and variety, but also facilitates future system transformation. The process industry will eventually be able to have a unified Ethernet architecture, not only for non-explosion-proof field device information from the field to the cloud, but also for explosion-proof field devices that meet intrinsic safety requirements. The APL field device on the upper left of Figure 24 runs a safety application to provide measurement values for the safety application running in the safety control system on the right. Data sent to the network by the safety application in the field device first passes through the PROFIsafe layer that ensures safe communication, for example, by adding additional checksums, serial numbers and other additional information to the data packet. The data then runs through the PROFINET protocol stack and enters the APL field switch directly below the figure through the Ethernet-APL connection. After the field switch processes the data, it sends the data to the 100Mbit/s Fast Ethernet on the right of Figure 24. After passing through the PROFINET protocol stack, it enters the PROFIsafe layer to run the data, check the safety integrity and pass it to the safety application in the safety programmable logic controller (SPLC°). In this way, the safety control system can run safety functions in combination with Ethernet-APL field devices.
Figure 24 Communication between PROFIsafe and PROFINET/Ethernet-APL.
Figure 25 shows the parallel operation of the safety infrastructure and the control infrastructure. The right side of Figure 25 shows the control system of the DCS. The control system uses PROFINET as the communication protocol and uses media redundancy (ring redundancy). The APL field instruments are connected to the controller via the APL field switch. This topology only requires the configuration of the APL field switch to allow the control system and the APL field instruments to communicate directly without any interface or data conversion.
Figure 25 Safety system application parallel to the control system
Figure 25 shows the controller of the safety system on the left, which shows an APL field instrument certified for safety applications (indicated in amber), an APL field switch, an industrial switch, and a safety system (SPLC) based on PROFINET/PROFIsafe combined with Ethernet-APL. In addition to these components, Figure 25 also shows a dedicated engineering station and an asset management system. Obviously, both can communicate directly with APL field devices, which simplifies the maintenance and testing process of the safety system, especially the safety field instruments. When repeated tests of APL safety field instruments are required, they can be initiated and recorded by the asset management system. Figure 25 shows the structural separation between the control system and the safety system, which has advantages in terms of availability and safety. When information exchange is required between the control system and the safety system, the two systems can be connected using OPC UA server-to-server communication (see the red line in the upper middle)