Process plants are operated with many sophisticated process control systems. These systems are inevitable for safe and reliable operation of the plant and address the safety functions such as process sectioning, fire detection, gas detection, process protection and blow down. The safety functions are often designed combining various E/E/PES (Electrical / Electronic / Programmable Electronic System) technologies and other external risk reducing devices. In addition, computer and software intensive technologies are increasingly being used as part of the system. A malfunction of these systems can lead to loss of life, damage to assets and impact to the environment. The Safety Integrity Level (SIL) is a risk indicator that can be used to identify the reliability requirements of Safety Instrumented Functions (SIF) and Safety Instrumented Systems (SIS).