Safety IO, optical bus on copper
We have a old fire and gas system where the end user wants to use the old copper cables. And complie to SIL 2 requirements.
Is it possible to use a converter from optical bus to copper in an High integrety system ?
You mean the ModuleBus between IO Clusters ?
This isnt even a HI issue. The ModuleBus is an optical bus. There is no convertor for "copper". ( Except obviously the TB820, but thats just for connecting to the IO Cluster Backplane )
However, I'm not sure that I understand exactly what copper cables your customer wants to reuse. The modulebus is a short distance bus between the IO clusters and normally wont extend more than a few tens of meters.
Your question is little confusing since there are two points in it.
As per the first statement, I understood that customer wants to use existing field cables of copper (metal/conductor) to connect field instruments to AC 800M HI S880 modules. If yes, the existing field cables can be used to connect the field instruments. This will not effect the SIL, Safety Integrity Level of the safety function(s) or SIS.
From the second statement, I assumes that, you want to extend the module bus (Optical bus) to remote IOs in different location to connect S880 IO modules? If yes, you can exetend the module bus using TB826/TB825 module. With this, the communication between IO cluster will be on optical and field instruments will on copper connected to S880 IO modules.