Week 8 Flashcards
what does hazardous area classification focus on?
Any cause that leads to a flammable atmosphere / ignition prevention.
What defines an explosive atmosphere?
Flammable substances present in the form of gases/vapours/mists or dusts.
Oxygen is present.
Concentration within explosivity limits.
What does the ATEX directive require?
Places that have explosive atmosphere are classified into hazardous and non hazardous areas.
what are the three pillars (objectives) of hazardous area classification?
Identify - areas of the plant where explosive atmospheres are present.
Classify - areas by probability of explosive atmosphere.
Specify - equipment based on classification.
what are the three pillars (objectives) of hazardous area classification?
Identify - areas of the plant where explosive atmospheres are present.
Classify - areas by probability of explosive atmosphere.
Specify - equipment based on classification.
Why are dusts dangerous to explosive enviromnents.
Dusts that are not removed settle out into layers.
They can form explosive clouds / Ignite on hot surfaces and create overheating via insulation.
what is the lethal dose curve?
The lethal dose curve shows the percentage of people affected against the does.
The LD50 is the dose resulting in 50% deaths.
What are the hazardous zones?
Zone 0 - area in which explosive atmosphere is present for continuously long periods
Zone 1 - an area which explosive atmosphere is likely to occasionally occur in normal operation
Zone 2 - Area in which explosive atmosphere not likely to occur
What are the hazardous zones?
Zone 0 - area in which explosive atmosphere is present for continuously long periods
Zone 1 - an area which explosive atmosphere is likely to occasionally occur in normal operation
Zone 2 - Area in which explosive atmosphere not likely to occur
What are the fundamental questions a hazardous area classification should aim to resolve or showcase?
Where could explosive atmospheres be present in my plant
How often will an explosive atmosphere be present
How do i control the ignition to make explosion improbable.
What are some precautions to avoid workspace exposure?
Substitution of hazardous chemicals
MInimization of inventory (toxic chemicals stored in the process)
Increase mechanical handling instead of people handling chemicals
Process change
Suppression of vapour or dusts.
Segregation of toxic chemicals
Containment of toxic chemicals and ventilation
What are factors affecting dispersion?
Dispersion
Height of release
ground conditions
Atmospheric stability
Momentum and bouyancy
