Redundant PLC used as SIS for SIL-2


Thread Starter

Benjamin Tsai

I need to find a PLC consists of I/O modules,CPU,power supply and communication modules which shall be all redundant. I shall emphasize that I/O modules shall be redundant. This redundant PLC will be as SIS for SIL-2. I had found some SIL-2 certificated PLCs, but I can't find the PLC be with output modules redundant.

Bob Peterson

My guess is you are looking to meet a spec of some sort. I would just ask the end user what they want and go with that.

The Simatic S7-400FH from Siemens have al you mentioned and can also have redundant failsafe I/O (F-DI / F-DO / F-AI and even F-DI EXi).

See the handbooks on under
ID 2201072; ID 1186523; ID 12488248 (just type the numbers by the manual search).

When you search only for SIL2 equipment, you can use a CPU 315F or CPU 317F or when those are not big enough then a CPU 416F. When this have to be also redundant then you need the S7-400FH (CPU 414FH or CPU 417FH).

With the S7-400FH you can built up a system with 2 powersuplys(or 4), 2 CPU's, 2 or 4 ethernet (redundant) communication processors and several ways to built up the I/O redundant.

This system is certified up to SIL3 and this is also available on the page by Siemens.

When you need the pdf-files and the certificate, please give me your email address.

Best regards,
You have a choice between a Triconex PLC or an ICS Triplex PLC... As far as I'm concerned the ICS Triplex is the Lexus of PLCs hands down, especially if you require TMR...

Benjamin Tsai

Hi, Lowiek:

Thanks for your information. I need the pdf files, would you please email to me. Thank you again.

Best regards,
You have many options available in TMR & QMR range. They are ICS Triplex, Triconex, Hima, FSC etc.. Among all these ICS Triplex is top of the range of PLC for safety applications.

One more point I'd like to make is that the SIL number for controllers is from input card to output card. It doesn't take into account the field devices. ie if you want a SIL-2 loop, the controller may need to be SIL-3, to satisfy the loop requirements.