Replace hardwired safety I/O's with redundant system?

[intools]

The existing plant has the CLX 1756-L62 (4MB), 1756-CNB (controlnet), 1756-ENBT (ethernet ip 10/100), 5x1756-IF16 (analog input), 3x1756-OF8 (analog output).

Other remote I/O's are via the single media controlnet.

The safety (ESD) I/O's are hardwired to the local 1756-IF16, 1756-OF8 cards in the MCC building where the 1756-L62 processor is located.

The new plant will be a copy of the existing plant.

Can we upgrade the system to be redundant (2x 1756-L62, 2x1756-CNBR, 2x1756-ENBT) ?

1. How reliable is the new redundant system? Will it be SIL-2 rated/certified or the Guardlogix system has to be used?

2. The safety I/O's account for 10% of total I/O's in the plant. Can the safety and non-safety tasks be handled in the same pair of redundant processors? Or the third processor has to be added?

3. The additional costs of the redundant controlnet media, processor, SRM and EBNT cards may be offset a little bit by eliminating the multipair home-run cables from local junction boxes (they can be wired to the remote I/O's via redundant controlnet media).

 

[OZEE]

I believe that, technically, the 1756-L62 isn't "Safety Rated", so you can't do anything with it that is SIL-2 rated. By code (at least in the US), "safety" must be done in either hardware or a "safety rated" PLC (e.g., GuardLogix), so what you have now would not be considered "safe"...

 

[Honga]

GuardLogix can handle your normal code and safety code in the one processor. Although a GuardLogix processor takes up 2 slots.

Not sure if this helps or not.

 

[Honga]

May be worth reading the safety standards, hard wired analog IO for safety doesn't seem very safe.

I'm sure if you contacted your local Rockwell Distributor they'd have a safety specialist willing to have a chat.