• Level 1: Emergency shutdown and depressurisation of the overall plant
• Level 2: Emergency shutdown for a process unit within the plant
• Level 3: Process shutdown for a process unit within the plan
• Level 4 Process train shutdown within a unit
• Level 5: Shutdown of Individual equipment and utilities
Level 1 Shutdown – Emergency shutdown and Depressurisation of the Overall Plant
Level 2 Shutdown – Emergency Shutdown for a Process Unit within the Plant.
Level 3 Shutdown – Process Shutdown for a Process Unit within the Plant
A Level 3 shutdown shall be initiated by major process or utility failure that may affect all trains within a unit.
A Level 3 shutdown will shutdown common equipment for the unit in which the abnormal condition occurs and initiate audible and visual alarms at the CCR.
Level 4 Shutdown – Process Train Shutdown within a Unit
A Level 4 shutdown will shutdown the entire process train in which the abnormal condition is occurring and initiate audible and visual alarms at the CCR, where there is no expected potential for the abnormal condition to propagate to a parallel train
Typical examples include high-high levels in vessels, where carry-over of liquid can have adverse consequences on downstream equipment.
Level 5 Shutdown – Shutdown of Individual Equipment and Utilities
A Level 5 shutdown will shutdown the piece of equipment required to bring an abnormal situation under control and initiate audible and visual alarms at the CCR, where the situation has a low potential for escalation. A typical example isa ‘low-low’ level in a process vessel, which shuts an ESD valve in the vessel outlet line to prevent gas blow by to a lower rated vessel downstream.