Redundancy

The redundant SLS 1508 Logic Solver modules are connectedto the field at the redundant

terminal block. No control strategy configuration is required to take advantage

of SLS 1508 Logic Solver redundancy, as the system’s auto-sense capability

automatically recognizes the redundant pair of Logic Solvers.

An integrity error alarm in a redundant SLS 1508 Logic Solver pair will notify

the operator of a failure. Both SLS 1508 Logic Solvers in a redundant pair

are monitored for integrity alarms at all times.

Events that can cause integrity alarms include:

• Hardware failure within a SLS 1508 Logic Solver

• Communications failure between a SLS 1508 Logic Solver and the SISNet

• Communications failure between a redundant pair of SLS 1508 Logic Solvers

• Communications failure between a SLS 1508 Logic Solver and an DeltaV Controller

• Removal of a SLS 1508 Logic Solver from the carrier