Safety and hazardous areas

What you will be able to do

• Use flammability limits and LOC correctly
• Read a zone, gas group and temperature class
• Tell protection concepts apart
• State what SIL does and does not mean for an analyser
• Recognise oxygen enrichment and deficiency hazards

Follow these lessons in order

1. Flammability, explosive limits and gas safety basicsA flammable gas burns only when fuel, oxygen and an ignition source are present and the fuel-air mixture lies between the lower and upper explosive limits (LEL and UEL).Why gases burn.Beginner3 min
2. What is limiting oxygen concentration (LOC)?The limiting oxygen concentration (LOC) is the oxygen level below which a flammable vapour or dust cannot sustain a flame.Safe by removing oxygen.Beginner3 min
3. Inerting and purging: how they work and how to prove themInerting keeps a vessel's oxygen below the limiting oxygen concentration by filling it with nitrogen or another inert gas.How inerting is done and checked.Intermediate3 min
4. Hazardous area classification: zones, gas groups, T-ClassesArea classification says how likely an explosive atmosphere is (Zone 0, 1 or 2 for gas), what gas it could be (group IIA, IIB or IIC) and how hot equipment may get (T1 to T6, 450 to 85 C).The classification vocabulary.Intermediate3 min
5. Protection concepts: flameproof, intrinsic safety, purgingHazardous-area equipment avoids ignition in one of three ways: contain an explosion (flameproof, Ex d), prevent sparks and heat (increased safety Ex e, non-sparking Ex n or ec, encapsulation Ex m), or limit energy (intrinsic safety Ex i), or keep the gas out (pressurised or purged enclosures, Ex p).How equipment is made safe.Advanced3 min
6. Hazardous area gas analysers explainedA hazardous area analyser is built so it cannot ignite flammable gas.Putting an analyser in a zone.Intermediate4 min
7. What SIL means for gas analysers, and what it does notA safety integrity level (SIL 1 to 4) states how reliably a safety instrumented function does its job on demand.What a safety integrity level is.Advanced3 min
8. Oxygen enrichment and oxygen deficiency hazardsToo much oxygen makes materials ignite more easily and burn fiercely; above about 23.5 % is commonly treated as oxygen-enriched.The hazard at both ends of the scale.Beginner3 min

Stuck on a real problem while you learn? Ask an engineer. Every lesson is checked against the figures in our catalogues.