Safety and hazardous areas

What this track covers

Gas analysers are often chosen because a process is dangerous, and installed where the danger is. This track explains the hazards, the vocabulary of area classification and the limits of what an analyser can promise, including what it means when a supplier makes no SIL claim.

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).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.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.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).Intermediate3 min
5. Hazardous area gas analysers explainedA hazardous area analyser is built so it cannot ignite flammable gas.Intermediate4 min
6. 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).Advanced3 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.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.Beginner3 min

Next track: Process primers