Shutdown logic diagram

 Schematic of shutdown logic

A shutdown logic diagram (also known as an ESD logic diagram) shows the shutdown level hierarchy within a plant or platform. The shutdown logic diagram starts by telling the big picture of the shutdown level, usually the level starts from 0 and continues with a higher number (1, 2, …). A lower number represents a more critical shutdown. The following sheets continue with a hierarchy of details for each process unit.

A trip logic diagram describes the 'cause' that can trigger a trip and the effect that can occur after the signal is activated. This diagram also shows the action such as time delay, start inhibit, reset that will be performed for each action.

The location of each instrument acting as a trigger/cause must be clearly specified.

Reference document: SAFE Chart, philosophy

The SAFE table lists the required safety devices for each process device. The SAFE table must ensure that all safety requirements have been met and what executive actions the safety device must perform.

The philosophy provides the narrative and the engineer translates it into cause and effect interaction so that the plant works as the intended philosophy.

Purpose of the Shutdown Logic Diagram

The shutdown logic diagram can be used as a reference when preparing a cause and effect diagram.