How do Safety Instrumented Systems (SIS) differ from Basic Process Control Systems (BPCS)?

Safety Instrumented Systems (SIS) are specifically designed to enhance safety by taking actions to prevent accidents or mitigate the consequences of hazardous situations. Essentially, they are dedicated to performing safety functions such as emergency shutdowns, pressure relief, or other critical safety responses. On the other hand, Basic Process Control Systems (BPCS) focus on the control and regulation of normal process operations, such as temperature, flow, and pressure, to ensure optimal production efficiency.

The distinction lies in their primary objectives: SIS are implemented as a fail-safe to protect personnel, the environment, and equipment during abnormal situations or failures, while BPCS aim to maintain quality and efficiency in production under normal operating conditions. Therefore, understanding that SIS are dedicated to safety functions and separate from the routine functional control provided by BPCS is crucial in Process Safety Management (PSM).