What is the purpose of a Safety Instrumented System (SIS) in a hydrogen production plant?

The purpose of a Safety Instrumented System (SIS) in a hydrogen production plant is to provide a layer of protection against process hazards by automatically taking the plant to a safe state when predefined critical process parameters deviate from their normal operating range. A SIS is a dedicated safety system that is separate from the basic process control system (BPCS). It consists of sensors, logic solvers, and final elements, such as shutdown valves or emergency vents, that are designed to detect hazardous conditions and take pre-defined actions to mitigate the risk. For example, if the temperature in a reactor exceeds a safe limit, a SIS might automatically shut down the feed flow to the reactor and activate a cooling system. The SIS is designed to operate independently of the BPCS, providing a backup layer of protection in case the BPCS fails. SIS are designed and implemented to achieve a specific Safety Integrity Level (SIL), which is a measure of the system's reliability and effectiveness in preventing hazardous events. By providing automatic safety functions, the SIS reduces the risk of accidents, protects personnel and equipment, and minimizes environmental impact. Therefore, ensuring automatic response to hazardous conditions is the purpose of an SIS.