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Safety Variables to MODBUS/TCP

A chemical facility had Safety Variables connected to the SIS (Safety Instrumented System) and they wanted to add those variables to their MODBUS Host. The safety variables they wanted to share were from HART devices: Functional Safety HART Temperature Transmitters.

The HES HART to Ethernet Gateway System  is the ideal multichannel HART-to-MODBUS converter, but it cannot be connected to the safety loops directly as that would negatively affect the customer’s loop reliability per IEC 61511 guidelines.

Safety Variable to MODBUS TCP
Download the PDF file

To each safety loop, the SSX HART Functional Safety Isolator is added to provide air-gap isolation between the safety loop and the HART-to-MODBUS converter. The exida® approved, SIL 3 capable SSX is certified for use in Safety Functions. The isolator is designed such that the HART digital signal crosses the air-gap isolation.

The output of each safety isolator can then be wired to three of the four channels on the HES HART-to-MODBUS converter. The HES reads the HART dynamic variables and diagnostic data of the STZ Temperature Transmitter and maps them to MODBUS registers awaiting the communication request from the MODBUS Host.

The SSX safety isolator is a powerful tool to get more functionality from safety systems.

Key Attributes:

  • HART-to-MODBUS conversion with the HES
  • Isolation from SIS with SIL-3 capable SSX Isolator
  • All dynamic variables and diagnostics are safely delivered from the temperature transmitters in the safety loop to the SCADA System via MODBUS/TCP

Download HES Data Sheet or SSX/SST Data Sheet