An industrial safety system is a crucial countermeasure in all dangerous plants, such as oil and gas plants and nuclear plants. They are used to protect human, industrial plants and the environment in case the process goes beyond the allowed control margins.
As its name implies, these systems are not intended to control the process itself, but rather to protection. Process control is performed by process control systems (PCS) and is interconnected by security systems so that immediate action is taken if the process control systems fail.
Security and process control systems are usually merged under a system called the Integrated Control and Security System (ICSS). Industrial safety systems generally use dedicated systems that have at least SIL 2 certification; while control systems can begin with SIL 1. SIL applies to hardware and software requirements such as cards, processor redundancy and voting functions.
Due to the closing of ESD valves in a process, there may be some trapped flammable fluids, and these must be released to avoid unwanted consequences (such as increased pressure in vessels and pipes). For this, emergency depressurising (EDP) systems are used in conjunction with ESD systems to release (to a safe and secure location) such trapped liquids.