Safety Switch Configuration

[TISM]

My application involves measuring the temperature in a furnace. I need to provide a hardwired High temperature safety switch which I was going to activate via a 4-20mA signal from a close coupled "puck" type transmitter wired to the K-Type. I also want to provide operators with an indication of this temperature via their SCADA. Is it OK to loop the 4-20mA signal from the transmitter through a PLC AI card as well as the high integrity switch? It would seem to be OK as the switch is fail safe in case of signal loss but I am not sure whether a frozen PLC would corrupt the signal to the switch. While a separate temperature element would appear to be the logical solution, access to the furnace is very limited.
I look forward to comments from those with more experience than me, and if you can cite a standard or accepted text regarding this point that would be even better.

Thanks you in advance

TISM