Industry glossary
Terms you will meet in the documents, systems and scenarios.
Safety case
The document a major hazard facility must have accepted by the regulator that identifies the major accident hazards and demonstrates the control measures that prevent and mitigate them.
Safe operating limit
The value of a process variable beyond which the plant is outside its demonstrated safe envelope and the abnormal situation procedure applies.
Double block and bleed
An isolation made with two closed valves in series and an open bleed between them so that any leakage past the first valve is visible and vented.
Spade or blind
A solid plate inserted between flanges to positively isolate a line, recorded on the blind list with a numbered tag.
Ullage
The empty space in a tank between the liquid level and the safe fill level, which determines how much product can be received.
Emergency shutdown system
The independent instrumented system that brings a unit to a safe state by isolating feed and heat and stopping equipment when a trip setting is reached or the operator activates it.
Process safety event
Any loss of containment, safety system activation, safe operating limit excursion or near miss that is recorded and investigated as an indicator of major accident risk.
Management of change
The formal review that assesses the hazards and safety case effects of any change to plant, process, chemicals, procedures or organisation before it is made.
Reflux
The portion of condensed overhead product returned to the top of a distillation column to maintain separation.
Muster point
The designated location, selected by wind direction, where personnel assemble and are counted when the site emergency alarm sounds.