Industrial safety system
An industrial safety system is a countermeasure crucial in any hazardous plants such as oil and gas plant sand nuclear plants. They are used to protect human, plant, and environment in case the process goes beyond the control margins. As the name suggests, these systems are not intended for controlling the process itself but rather protection. Process control is performed by means of process control systems (PCS) and is interlocked by the safety systems so that immediate actions are taken should the process control systems fail. Process control and safety systems are usually merged less than one system, called Integrated Control and Safety System (ICSS). Industrial safety systems typically use dedicated systems that are SIL 2 certified at minimum; whereas control systems can start with SIL 1. SIL applies to both hardware and software requirements such as cards, processors redundancy and voting functions
Types of industrial safety systems
There are three main types of industrial safety systems in process industry:
Process Safety System or Process Shutdown System, (PSS).
Safety Shutdown System (SSS): This includes Emergency Shutdown-(ESD) and Emergency Depressurization-(EDP) Systems.
Fire and Gas System (FGS).These systems may also be redefined in terms of ESD/EDP levels
SSS
The safety shutdown system shall shutdown the facilities to a safe state in case of an emergency situation, thus protecting personnel, the environment and the asset. Safety Shutdown System shall manage all inputs and outputs relative to Emergency Shut Down (ESD) functions (environment & personnel protection). This system might also be fed by signals from the main fire and gas system
FGS
The main objectives of the fire and gas system are to protect personnel, environment, and plant (including equipment and structures). The FGS shall achieve these objectives by: Detecting at an early stage, the presence of flammable gas, Detecting at an early stage, the liquid spill (LPG and LNG),Detecting incipient fire and the presence of fire, Providing automatic and/or facilities for manual activation of the fire protection system as required, Initiating signals, both audible and visible as required, to warn of the detected hazards, Initiating automatic shutdown of equipment and ventilation if 2 out of 2 or 2 out of 3 detectors Initiating the exhausting system.
ESD
Emergency Shutdown-(ESD) systems are aimed at isolating (closing) any hazardous valves in a process due to abnormal conditions.
EDP
Due to closing ESD valves in a process, there may be some trapped flammable fluids, and these must be released in order to avoid any undesired consequences (such as pressure increase in vessels and piping). For this, emergency depressurization (EDP) systems are used in conjunction with the ESD systems to release (to a safe location and in a safe manner) such trapped fluids.
PSV
Pressure safety valves or PSVs are mechanical devices and are usually used as a final safety solution when all previous systems fail to prevent any further pressure accumulation and protect vessels from rupture due to overpressure
