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Show -2- maint~ined at all. times to burn the waste gas, we do not have a flare. What we have IS a vent pipe - where unburned heavy hydrocarbons or other combustible gase~ can descend to grade level and become ignited to produce a flashback, a fire, and possibly a catastrophic explosion. B~fore we d.iscuss design calculations, testing, installation and service of inspiratlng flare pilot burners, which differ from regular furnace or boiler inspirating pilot burners mainly by mixture-tube length and by severe "open environment" application conditions versus the controlled environments of furnaces and boilers, let's consider state-of-art designs for flare burner tips and seals. Flare Burner Tips and Seals In the 1940s and '50s, density-differential seals were developed for elevated flares. Positioned below refractory-lined flare burners, these massive "seals" (also called labyrinth or molecular seals) consume vast amounts of expensive purge gas; but they are only partially effective. Because these seals do not prevent air intrusion, the flare burner tips employed with this obsolete technology must be refractory-lined to extend tip life and delay the inevitable and very dangerous burn-back and burn-thru conditions. Burning inside a refractory-lined flare tip causes quick failure of the refractory, which is also subjected to temperature/expansion cycling. Refractory failure then leaves the upper portion of the flare burner unprotected from searing flames that further accelerate damage to the flare tip. Pieces of refractory accumulate in the base of the massive seal, where they can interfere with waste gas/offgas flow, building up pressures that are sufficient to "burp refractory" from an elevated stack. Spalled refractory will also plug the drain in the base of a mole seal, accelerating corrosion and the very dangerous burn-thru conditions. Burn-thru in a flare tip and down inside a mole seal allows explosive gas/air mixtures to penetrate a flare system - with cata-strophic results. Frequent refractory maintenance, frequent flare-.tip replacements, and cut~ing out corroded sections of a mole seal, then welding on patches create senous safety problems. Explosive gases may surround a flare stack in a refinery, gas plant, offshore platform or chemical/petrochemical processing facility. Dangerous Trade-Ofts for Short-Term Profits Maintenance expenses average nine p.ercent .in refineries and large chemical/ petrochemical plants. To improve profit margins, some plant managers are |