SLS 1508 hardware and DeltaV SIS software is used to install, configure, and operate a system to implement a safety instrumented system in conjunction with sensors and final elements to take a process to a safe state when hazardous conditions occur. Safety instrumented functions are implemented in DeltaV SIS software using SLS 1508 logic solver cards that are installed on DeltaV I/O interface carriers.
Each Logic Solver card (that appears in the I/O configuration in DeltaV Explorer) is associated with a Logic Solver (that appears in the SIS Network configuration in DeltaV Explorer). Throughout the SLS 1508 documentation logic solver refers to either of these depending on the context. Logic solver card always refers to the physical card. Logic solvers are where the safety configuration is created. Logic solver cards are where the configuration is downloaded and run.
DeltaV SIS components are physically separate from, but integrated with, the DeltaV distributed control system (also known as a basic process control system or BPCS). The SLS 1508 logic solver cards mount on standard DeltaV I/O interface carriers but they are powered separately from the BPCS power supplies. Each logic solver executes up to four SIS modules that perform the safety instrumented function. Safety instrumented functions are configured in one or more SIS modules using the DeltaV engineering tools—DeltaV Explorer and Control Studio. SIS modules are downloaded to run in Logic Solvers.
In some cases data needs to be shared between SIS modules as the SIF cannot be completely implemented in a single module. This data is shared between SIS modules through the use of Secure Parameters and Secure Parameter References. Each logic solver can publish up to 16 Secure Parameters. These are Boolean with status values that the SIS module can write to and can be referenced by any other SIS modules in the same logic solver or in a different logic solver on the same node. For larger SIS applications, SIS modules running in logic solvers on different nodes may also need to access these secure parameters. This is accomplished using SIS Network domains.
The simplest SLS 1508 system consists of the Logic Solvers on a single node. In DeltaV Explorer these would be configured in the default SIS Network domain folder. For SIS applications that require communication between nodes, larger SIS networks become necessary. The larger networks are configured as one or more fiber optic rings containing multiple SIS Network domains. To allow their Secure Parameters to be seen by Logic Solvers on other controllers these Logic Solvers must be configured as Global Publishers. Logic Solvers can be configured as either Domain or System Global Publishers which define their scope.
For information on the capacities of secure parameters in a DeltaV SIS Network refer to the System Capacities topic.