Pepperl + Fuchs releases the safety relays KFD2-RSH

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  Pepperl + Fuchs releases safety relay KFD2-RSH

30. May 2018 – The safety relays KFD2-RSH from Pepperl + Fuchs combine diagnostic function, line error transparency and double redundancy in a 1oo3 (one to three)) architecture. Each switching operation automatically checks the function of the switching contacts. The relays are immune to test pulses and thus compatible with digital output cards for all common control panels.


The 1oo3 architecture with dual redundant switch contacts forms the core of the modules. For DTS applications (de-energized to safe) there are three serial contacts. For ETS (energy-to-safety) signal circuits, there are two groups of three contacts arranged in parallel. The safety function is also guaranteed if up to two contacts in a group fail

The integrated diagnostic function shifts the three contacts with a time delay after each switching operation. In ETS applications, all three relays of both contact groups are initially closed with three consecutive switching operations. During the delay time, the device checks if this contact closes the circuit and detects faulty circuits.

DTS device diagnostics occur during the reboot process. Initially, two relay contacts are closed simultaneously, then the third contact closes after a time delay. The idea is that no current will flow before the third contact closes, otherwise this relay will be defective because it will not disconnect the circuit. Another relay is checked every switching cycle

After switching three times, the relay module is fully tested once without additional effort. The diagnostic results are provided:

  • via the LED on the module
  • as collective error message at the infeed module
  • by evaluation of the test pulses from the control panel
  • at the additional relay output [19659010] The KFD2-RSH safety relays offer a line fault transparency. As a result, short circuits and line breaks can also be detected on the field side via the digital output card (DO card) of the control system and assigned to a specific signal circuit. An additional wiring is not required.

    DO cards on control panels often provide built-in diagnostics. The module input filters the test pulses coming from the DO card. This prevents unintentional switching of the field device due to a diagnostic measure or the unintentional display of a line fault in the control panel

    The single-channel devices are certified to ATEX / IECEx Zone 2 and UL standards and are suitable for DTS and ETS applications up to IEC61508 SIL 3. The DTS modules are also suitable for applications according to EN ISO 13849 PL e


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