Introduction

The DeltaV SIS™ process safety system, part of Emerson’s smart SIS, ushers in the next

generation of Safety Instrumented Systems (SIS). This smart SIS approach uses the

power of predictive field intelligence to increase the availability of the entire safety

instrumented function.

Sequence of Events Capability

With DeltaV SIS process safety system, events are automatically generated as

function blocks are executed within a module scan. Events are time stamped 

with a resolution of <1 ms,and they are recorded in the sequence that they occur in the

Event Chronicle. When using standard function blocks such as input blocks,

|voter blocks, and cause and effect blocks, a standard set of events are

automatically generated without special configuration or programing required.

For example,I/O failures, trip limits, first outs, and other similar events are automatically

time stamped by function blocks and recorded in the Event Chronicle.

When a process variable exceeds the trip limit, DeltaV SIS records the event along

with the analog value and the trip condition.

In general, when there is a plant event that triggers anemergency shutdown from the SIS,

one input will exceed a trip limit on one scan and this will cause outputs to trip and

more inputs will then change state. Sequence of Events Recording has been

used to find that first input that caused the trip by looking at all of the inputs in the plant.

With the DeltaV SIS system, the operator simply filters the Event

Chronicle for first out trips, and the first-out is clearly visible.

If higher resolution is required for some channels then they canbe wired to both

the DeltaV SIS Logic Solver and also to a DeltaV Discrete Input Card for Sequence

of Events, which provides a resolution of 0.25 ms.