DeltaV SIS™ has a dedicated network to provide safety communications. The SISNet is a counter-rotating fiber optic ring network that provides communications between SIS nodes with very high reliability. Messages on the bus are sent via black channel communications protocol, which provides protection against the effects of transmission errors. The DeltaV SIS power supplies, communication channels, hardware, and real-time operating systems are completely independent of the DeltaV BPCS, maintaining the separation required by IEC 61511.

In addition to sharing input values between logic solvers, the SISNet secure communications can be used to implement logic across multiple SIS modules. This enables extending the control strategy, or can provide advanced warning of a decision to shut down in one plant area due to a process trip in a different area.

The SISNet provides online expandability, as additional DeltaV SIS nodes can be added to a running system without shutting down the process. SISNet Domains provide increased flexibility and scalability, providing improved support for large projects, easier expansion of existing systems, and easier isolation of separate SIS applications.