Failsafe with standard IO

Is it possible to achieve a Category 3 or 4 circuit architecture by using standard (non-failsafe) IO modules in a rack with an F-CPU? I contend the only way this might be possible is by wiring each half of a dual-channel input device to separate input cards and evaluating those two signals in a 1oo2DI block in the safety program. Others believe that two channels on the same input card will suffice.

Hello Stevec;

To configure and program a Safety solution for the s7-1500, you need the additional paclage Simatic Safety (6ES7833-1FB16-0YA5, see the order list in the second post below)

https://support.industry.siemens.com/cs/ww/en/view/54110126

https://support.industry.siemens.com/cs/ww/en/view/109772968

Simatic safety F-Systems is approved up to SIL3 (CAT 4) applications, on condition that ypu resqpect the basic requirements, including the use of F-I/Os and F-communication blocks for all safeyty-related controls.

You can configure and use standard (non-safety) I/Os in your configuration and in your program, but only for non-safety controls. Using standard I/Os for safety applications will never receive approval for SIL3.

Have a look at the screenshot belw, taken from the Simatic safety manual proposed earlier.

Hope this helps,

Daniel chartier

An external 2-channel safety monitor wired into the F-IO of the F-CPU should do the job, but then you could just wire them directly into F-IO.

Or, you can use an external safety system, with safety controller, safety relays, and safety monitoring.

I think the point (from the above reply) is that standard PLC inputs cannot be coerced into a certifiable safety configuration (SIL-3/4).

Stevec&e

I do use the Safety Advanced software. My question is concerned with the validity of the circuit and standard components. I would certainly process the signals within the failsafe program, but can I justify a dual-channel circuit architecture with two distinct standard input modules? I think it may be possible. I am opposed to using two channels of the same standard input module, as this reduces the circuit architecture to one channel, as the standard IO module has a single processor, or only uses the 1oo2D processor of the F-CPU.