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Safety Instrumented Systems (SIS)

Last updated: October 30, 2017

What Does Safety Instrumented Systems (SIS) Mean?

A Safety Instrumented System (SIS) is composed of sensors, logic solvers, and final control elements for the purpose of taking a process to a safe state when predetermined conditions are violated.

The function of the SIS is to monitor the process for potentially dangerous conditions (process demands) and to take action when needed to protect the process.

Safeopedia Explains Safety Instrumented Systems (SIS)

An SIS is designed to reduce the frequency or the severity of an identified emergency event. This will protect personnel, equipment, and the environment.

It is critical that the three elements of the SIS—a sensor, logic solver, and final control element—function as designed in order to safely isolate the process plant in the event of an emergency.

An SIS is one of the layers of protection in a complex system after plant design, in a Basic Process Control System (BPCS), and also in alarm/operator intervention.


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