SIL certificate for passive component like Terminal Unit
Since carrying out maintenance job is not easy with 3-Layer TU; our maintenance department proposed to replace it by single layer TU. But contractor is telling that they do not have any single layer TU for SIL-2 application.
Please advice: "Is the SIL certificate is also required for passive component like Terminal Unit or we can use any non-SIL certified Terminal Unit?"
The available TU units for S800 High Integrity I/O modules are given in this data sheet ... http://www05.abb.com/global/scot/scot400.nsf/veritydisplay/5496308a113ed06bc125
Im not sure what you mean by "3 layer". Do you mean the number of rows of terminal screws at the bottom of the TU ? All the TU's have more than one row. The "extended" MTU's are wider and slightly easier to work on but still have 3 rows of terminals. However, they will require more cabinet space.
Another option is to use a TU812 which has a 25 pin D-Sub connector. You can then connect this ( via a pre-made cable ) to a much larger single row of temination modules.
Generally "passive" components are not SIL certified (terminals, wires, sockets/boards - everything without "electronic"), because there is implemented solution to prevent issues from this side (like wire break detection, design - shut down in case of lost voltage in the safety loop, several measurements with voting logic in case of "critical" measurements, etc.).