What is a SIS( Safety Instrumented System)?

A SIS is a Safety Instrumented System .It is designed to prevent hazardous events by taking the process to a safe state. A SIS is composed of sensors, logic solver and final elements. Other common terms for SIS system are: Safety Interlock Systems, Emergency Shutdown Systems(ESD), Safety Shutdown Systems(SSD).

can any one mention IEC standards for SIS

these are the IEC standards for Safety instrumented System

IEC 61511 / ISA 84