I use my process control system for all automation requirements. So what is so special about a SIS?

Many people are unsure of the the difference between a safety instrumented system (SIS) and your process control DCS (BPCS). Both have inputs and outputs connected to field devices and both provide the ability to control them. Both will scan inputs, perform calculations, both are fast enough and it may seem they have the same hardware and software quality. There is also not that much difference in the cost of the I/O.

 This perceived commonality has led many companies to use the DCS for implementation of their safety requirements. There are, however, many differences which might not be apparent at first glance, some of which are detailed in the below comparison:

So which system, the BPCS or the SIS, would you use for your dedicated safety functions?

Maybe you will allow safety functions up to SIL 1 to be implemented in your BPCS and safety functions with higher SIL requirements to be engineered in your SIS?

The takeaway question:

How are you designing your safety functions and into what automation technology as of right now? If you want to find out more, contact us or post a comment.