SafetyNET p

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SafetyNET p is a standard for Ethernet-based fieldbus communication in automation technology . Due to the real-time behavior with cycle times of up to 62.5 µs, SafetyNET p is suitable as a drive bus. It can be used in safety circuits up to and including category SIL 3 in accordance with the standard requirements from EN 61508 and EN 61511 .

Emergence

SafetyNET p is a registered trademark of Pilz GmbH & Co. KG and was presented to the public for the first time in 2006. The aim was to enable fieldbus communication on Ethernet in real time and, at the same time, to provide data communication in terms of machine safety. SafetyNET p combines safety and automation: it is both a safety and an automation fieldbus and thus the successor to SafetyBUS p .

The SafetyNET p technology was administered by the umbrella organization Safety Network International eV.

commitment

In addition to its use as an Ethernet-based fieldbus, one focus is the use of SafetyNET p in the communication of data with safety-related content. SafetyNET p is used wherever the time and content consistency of communicated data is required to protect against hazards. The dangers can be a threat to life and limb, but also the protection of assets.

A second area of ​​application is the communication of data in real time. With bus cycle times of up to 62.5 µs, SafetyNET p can be used even in extremely time-critical areas.

Typical areas of application are:

  • Factory automation (e.g. automobile production, presses)
  • Transport technology (e.g. cable cars, rides)
  • Drive technology (e.g. sensor-actuator control loop in drives or industrial robots)

In general, all automation and process technology applications are possible.

technology

SafetyNET p is based on Ethernet . There are two different, mutually compatible versions for SafetyNET p.

RTFN

RTFN (Real time frame network) uses conventional Ethernet IP frames for communication . The mechanisms for security and real-time are located on OSI levels  3 and higher. A producer-consumer model is used as the communication principle. A central process control ( PLC ) is not required. Among other things, this enables concepts such as modular mechanical engineering .

SafetyNET p RTFN is fully compatible with all IP-based Ethernet protocols and can be used mixed with these on the same medium. Conventional switches, routers and wireless access points can also be used.

Due to possible competing services, a system cycle time of around 1 ms can be achieved. If a higher performance is required, SafetyNET p RTFL can be used.

RTFL

RTFL (Real time frame line) uses Ethernet MAC frames for communication . A producer-consumer model is also used at the logical level for RTFL. In order to achieve the required performance, communication takes place in optimized Ethernet MAC frames. For this purpose, the first participant in the logical line sends an Ethernet MAC frame to its logical neighbor. This fills its part of the frame and forwards the frame along the logical line to its nearest neighbor. So all participants fill the frame one after the other. The last participant in the line sends the filled frame back to the first participant via the same route (through all participants). The individual participants can take the required data in the passage of the frame.

The achievable system cycle times are in the range of 62.5 µs. Other, IP-based traffic can be packaged by the SafetyNET p participants as part of the real-time communication within an RTFL frame.

Technical specifications

The framework data of SafetyNET p determined by the technology are as follows:

  • Compatible with Ethernet IP protocols
  • Networks can be set up in line, star or tree topology
  • Networks with changing participants are possible through a continuous topology scan
  • The maximum distance between two participants corresponds to that of conventional Ethernet (when using copper cables, this is 100 m)
  • With RTFN, the number of bus participants is only limited by the IP address space
  • With RTFL, 512 bus participants per segment are possible
  • Guaranteed system cycle times of up to 62.5 µs can be achieved
  • Suitable for applications according to SIL 3 of IEC 61508

The port number 40000 is entered for SafetyNET p in the IANA's "list of assigned port numbers" .

organization

The user organization Safety Bus p Club International eV , in which the manufacturers and users of SafetyBUSp have come together, has existed since 1999 . The organization was renamed Safety Network International eV in 2006 . In addition to the international organization, there are two other regional organizations: Japan, founded in 2000, and the USA, founded in 2001.

literature

  • Winfried Gräf: Machine safety. Hüthig GmbH & Co. KG, Heidelberg 2004, ISBN 3-7785-2941-2
  • BIA working paper: Test principles for safe bus systems.
  • EU machinery directive: 98/37 / EG
  • Safety Network International: SafetyNET p system description version 2.0