Safety Alerts 18

Petrochemicals

• EO: Ammonia leaked past several check valves + positive displacement pump RV into Ethylene Oxide tank. Tank ruptured and EO cloud exploded

• EO: Cycle fatigues resulted in a hairline crack in the welded seam of Level Indicator (LI) on Aldehyde Column. Minor EO leak that formed PEG that accumulated in the mineral wool insulation. During repairs to LI, on removing insulation metal sheath, air contacted the insulation soaked with PEG. Auto-oxidation and ignition heating the LI piping. Decomposition of EO within the piping propagated to the column that then exploded

• Explosion in final purification column of EO plant. Decomposition of contents led to rapid over-pressurization

• PO: Wastewater tank storing Propylene Oxide and Styrene plant wastes. N2 Blanket Compressor was under maintenance. Tank Oxygen contents was monitored by a temporary O2 analyser to purge with N2, if required. Peroxides and caustic in waste. O2 build up from peroxides decomposition was not detected by the O2 analyser in a dead zone. On restart, the tank Off Gas Compressor sucked in flammable vapor that was ignited and flashed back to the tank. Tank exploded killing 17. Ignorance of peroxide presence and its decomposition + poor location of O2 analyser + stopped N2 purging. AIChE CEP

• Liquid phase oxidation of butane. Insufficient purging of reactor when it was down resulted in an explosion releasing reactor’s contents. VCE

• Poor vapor freeing: Reactor with C3= and a layer polypropylene granules was purged with Nitrogen six times. But it released C3= held among the granules when filled with water. WWW 

• PVC: 24 identical reactors. While trying to empty wash water from an isolated reactor, operator forced open drain valve of another reactor in service. Flammable VC release and explosion. Interlock override by mistake without cross checking + poor or no communication + no running status display near the valve

• PVC: Similar. Mechanic removed top manhole cover of an autoclave and went down to the floor below to remove manhole at bottom. By mistake opened the manhole of the adjoining autoclave. Vinyl Chloride and Nitrogen at pressure blew off the cover. 3 fatalities. WWW 

• Acrylic Polymerization: Batch process. Monomer + solvent added in steps, heated with steam in jacket to a specified temperature. Then heating is switched off and initiator added. Hot solvent vapor from heat of reaction cooled in overhead condenser and sent to the reactor to keep it cool and then further monomer/ initiator added over an extended period. When the full batch was added in one go, heat output was high. Flammable vapor and explosion

• Butadiene: Known to form Popcorn Polymer that blocked PSV inlet and HX. Piping/ equipment rupture on rapid growth/ expansion. Unstable Pyrophoric Polymers and explosive Polyperoxides. Many incidents. Minimize air ingress. Inhibit. Popcorn accumulation and expansion in dead legs led to line rupture, Butadiene release, explosion and fire. Identify and eliminate dead legs

• Acrylic Acid: Intermediate tank provided between 2 columns purifying AA. Feed to downstream column was stopped for test runs. AA accumulated in the tank. Cooling coils at tank bottom was not effective to cool accumulating top layers. Dimerization heat led to polymerization. Tank exploded and fire

• Batch / Runaway Reaction: Agitator failure led to poor mixing in an exothermic reactor. Chemical continued to be added. On starting the agitator, unreacted chemicals reacted, led to higher temperature which the cooler was unable to handle. Chemicals vented via relief valve impacting nearby residents

• Batch / Runaway Reaction: On rising temperature, the batch was overcooled leading to unreacted components accumulation. Resultant runaway reaction blew and propelled off the reactor. Overcooling can damage too

• Styrene plant: During Benzene unit restart, a flange gasket burst releasing H2. Explosion. Instead of spiral-wound gasket, only compressed asbestos fiber (CAF) gaskets were in use

• Improper and prolonged storage of hazardous chemicals can result in large explosions

LNG

• LNG Tank roll-over or water boil off in oil storage tanks. Rupture/ fire

• Fire inside empty LNG storage tank. Pressure hike lifted its concrete dome which then collapsed down inside the tank. Multiple fatalities

• Closed blowdown valve resulted over-pressurization of an LNG plant HX that exploded

• Low FD Stack intake height can lead to leaking hydrocarbon suck-in with air. Destroyed many heaters and boilers. LNG Train exploded

• Poor Isolation: N2 header block valve not closed after completing LNG defrosting operation. Natural gas back flowed via N2 header into a control room where smoking was allowed. Explosion

• Start-up warming up of a LNG line led to thermal expansion in a blocked-in piping. As its PSV was isolated, line ruptured; released LNG ignited resulting in BLEVE, vapor cloud explosion, a fireball, a small secondary pool fire. Poor isolation and car seal procedures. Failure of temperature indicator alarms

• Leaking LNG, extremely cold, has caused fractured metal supports / plates in several incidents