SIL certification For Terminal Unit
We are in process of installing the ABB 800xA system with AC800M Hi controller & S800 I/O. The system will be used for SIL-2 application. For I/O we have used AI880, AO815, DI880 and DO880. All I/O are proposed with 3-layer TU (Terminal Unit). (AI880 with TU834; AO815/DI880/DO880l with TU830).
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?"
Voted best answer
Contractor is right: there are no single-row terminal units available for your I/O modules.
Please refer to the 3BSE020924 document (S800 I/O Modules and Termination Units) to get information about I/O modules and TU compatibility and their SIL certification.
About the maintenance with 2 and 3-row TU: this is not difficult at all. Just start connect wires from bottom row to upper.