• Local Shut-Down (LSD) – From local switches or from detection of abnormal conditions in a non-essential unit or where sparing of equipment is employed. This will cause the shut-down of a single piece of equipment.
The safety shut-down system of an installation, consisting in a set of safety loops and devices, comprises different sub-systems organised as complementary barriers to the Process Control System, as represented in the following schematic (§ Figure 5.2.1).
For each installation, an ESD/PSD logic shall be defined and represented in an ESD/PSD Logic Diagram.
The ESD/PSD Logic Diagram shows the top-down hierarchy of ESD and PSD levels, all their causes and actions in the form of a block logic diagram