Capítulo 1
Como se formam as atmosferas explosivas
Publicados
- What is an explosive atmosphere? Fire triangle, explosion pentagon and why ATEX exists
An explosive atmosphere is a mixture of flammable gas, vapour, mist or dust with air, at atmospheric conditions, in which a flame spreads through the whole mixture after ignition. The definition, fire triangle, explosion pentagon and why ATEX rules exist.
- ATEX explained: the two EU directives 2014/34/EU and 1999/92/EC in plain language
ATEX is two EU directives. 2014/34/EU sets what manufacturers must prove before Ex equipment is sold; 1999/92/EC sets what employers must do where explosive atmospheres can occur. Duties, CE marking, the EPD and national adoption explained.
- Ignition sources in hazardous areas: the 13 ignition sources and how to control them
EN 1127-1 lists 13 types of ignition source, from hot surfaces and sparks to static, lightning, radio waves, ultrasound and exothermic reactions. How each one ignites an explosive atmosphere and the practical controls used in Ex areas.
- Explosion protection strategy: avoid the atmosphere, avoid ignition, limit the effects
Explosion protection follows a fixed order: prevent the explosive atmosphere, avoid effective ignition sources, then limit the effects of an explosion. Primary, secondary and constructive measures, examples for each and how the risk assessment chooses them.
- Static electricity as an ignition source: charging, discharges and bonding
Static electricity ignites solvents, gases and dusts when charge from flowing liquids, powders or people discharges as a spark, brush, propagating brush or cone discharge. How charge builds up, which discharges ignite what, and how bonding and flow control prevent it.
- Hybrid mixtures: when flammable gas and combustible dust are present together
A hybrid mixture of combustible dust with flammable gas or vapour can explode when each is below its own lower limit, and ignites more easily. Why, where it happens (solvent drying, coal mines, fumigated grain) and what it means for zoning and Ex marking.
- Deflagration, detonation and overpressure: what happens in a gas or dust explosion
Most gas and dust explosions are deflagrations: flames slower than sound whose pressure depends on confinement and congestion. A detonation is a shock-driven flame at about 1,800 to 2,000 m/s. Flame speed, overpressure effects, vapour cloud and dust explosions, and BLEVEs.