Safety Alerts 3

Separators/ Vessels

• Nitrobenzene column start-up. Damaged trays led to poor separation and abnormally high nitrobenzene concentration in bottoms. Explosion. Plant damage and fatalities

• Confined space: Welds in a tall reactor were inspected by stain detection. Liquid solvent was used to wipe off excess red dye. Solvent fumes in the confined space, made the inspector faint. BP

• Quick Opening Doors may fail on repressuring. Refer to manufacturer's procedure for fastening method. Stay clear of doors when repressuring. If possible, avoid Quick Opening Doors

• Opening filter doors before fully venting have caused a number of incidents. Interlock doors

• Vent, drain, RV inlet and PG were blocked polymer and decomposition materials. Unaware of internal pressure, when the half the bolts of the cover were removed, internals blew out. BP

• Vents and drains: of a vessel was plugged with polymer. There was internal pressure as a result of decomposition. While unbolting a cover, the cover and internals blew out as missiles. BP

Storage Tanks

• Storage tank incidents are more in refineries (61%), followed by petrochemical plants (34%) and oil fields (5%). External floating roof > inner floating roof. Loading/unloading operations > grounding > static electricity

• Rapid filling: Crude Oil Tank didn’t overflow but excess vapor vented was ignited by uninsulated hot piping. Piping manifold failure released additional oil to fire. F&G. Regulate tank filling rate

• Blending: Calculation error - excess Butane was blended with gasoline. Light ends vapor lifted and tilted the roof generating static or metal - metal sparks. Fire. Blending agitation may also generate static sparks in tanks. Poor control of blending operation has resulted in multiple floating roof sinkings. Blending in a closed circuit piping system under pressure is recommended. BP

• Light ends sphere filled with low RVP natural gasoline instead of straight run gasoline. When it was pumped out at a higher rate, not enough vapor was generated in the sphere. Vacuum developed and sphere collapsed as it was not vacuum rated. BP

• LPG: Tanks fed from a refinery via a pipeline. Inlet pipe ruptured. Poor relief on inlet pipeline, congested LPG tank layout and poor town planning with many nearby homes. Gas cloud ignited by ground flare. BLEVEs of 4 spheres and 48 bullet tanks. Extensive fatality and loss

• LPG: Sample valve frozen. Leak and BLEVE. Add DBB in sample point

• LPG: Route drain pipes away from the sphere. Keep 600mm minimum distance between valves. Check for icing while draining. First valve should be ROV/ ESD. Insulate or mound the sphere. Add deluge water. Slope the ground below. Add a BDV

• LPG: Water was drained from an LPG sphere. LPG in the drained fluid vaporized, chilled and the froze downstream drain valve. The first valve got plugged by hydrate. While trying to fully open the first valve, its handle came off. Leaking LPG cloud was ignited and LPG pool below the sphere caught fire. Uncooled sphere top burst, knocking down an adjacent sphere, that also burst

• LPG: Similar, LPG sphere RV failed to open. Operators opened its drain valve, not realizing that vapor pressure on top would be the same. Drain valve froze. LPG ignited. BLEVE

• LPG: Similar, sphere over-pressurized and its RV did not lift. Inlet line ruptured. Resulting flame heated the sphere. BLEVE. More spheres and tanks on BLEVE. WWW

• LPG: Internal ball float came loose and blocked RV inlet in tank top. Tank deformed. If the ball can block any top branches, protect with a metal cage or go for a different type level indicator. WWW

• LPG: Butane/ Butadiene low boilers condensed and pulled in vacuum when the ambient temperature was below 0°C. Design the tank for vacuum and/or recycle warm gas. WWW

• LPG: Liquid butane brought to a lab, thermally expanded, bursting the container. Flash fire. BP

• LPG: Truck loaded with gas venting. Vent line became red hot as air: LPG mixture was ignited by pyrophoric iron sulfide. BP

• LPG: Fire below a sphere under-construction. Polyurethane cold insulation + combustible materials

• caused a rapid escalation of the fire to the top of the sphere. BP

• LPG: Truck RV discharged into the enclosed rear compartment. Fire and explosion. BP

• LPG: Leak in pressurized C3/C4 storage area. Fire. 9 tanks damaged

• LPG: Overfilled tanks ruptured on solar thermal expansion - 1948. Tank Car with DME (Dimethyl Ether) 200 fatalities + 4,000 injuries. 1978 - Propylene 217 + 200

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

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

• Flame Arrestor: Fine gauze FA choked with sand and corrosion products, created vacuum and tank partially collapsed on product withdrawal. Check of FA regularly. Avoid fine gauze in FA. BP

• Choked Vent: Tank pulled vacuum and collapsed when its vent was covered with plastic bag for painting or by honeycomb or solidified wax from hot paraffin liquid or a plugged flame arrestor. Inspect vent before filling or emptying a tank

• Choked Vent: Air blown into a high melting point liquid. Tank Blown off. WWW

• Hydrotest: Fast filling with undersized vent, tank blew it’s top. Remember: Tank filling takes a long time. No short cut. Air can’t get out as fast as water can be pumped in

• Hydrotest: Tanks on soft reclaimed soil collapsed

• Hydrotest: LPG spheres collapsed due to CUI (Corrosion Under Insulation) of its legs. Legs were coated with fireproof concrete. Salt water sprays at periodic intervals. Legs had severely corroded under the fireproofing. Add inspection windows on insulation to monitor CUI. Apply first coatings on the legs. Repeat of a similar incident 28 years ago. BP

• Corrosion: An insulated tank was emptied when corrosion holes were found on the roof. A severe gale, funneled between other tanks, caused the rusty tank to collapse. BP

• Corrosion: Rust in a buoyancy chamber resulted in low O2. On entering 2 persons asphyxiated. BP

• Corrosion: Weld in a tank containing C3 at (-) 44°C failed. Wave of liquid propane swept over the dikes and inundated process area before igniting. Failed weld was a repair on a weld failure a year earlier. Suspect: Microbiological SRB (sulphate reducing bacteria) from hydrotesting with sea water

• Corrosion: Used up O2 in an isolated tank. Tank collapsed. Persons who enter such tanks have fainted. WWW

• Water entry into a hot heavy oil tank, resulted in steam generation and overpressure. Explosion and fire. A number of ‘water explosion’ incidents are due to poor rundown temperature control, disturbance to bottom water layer. BP

• Water entry into Hot Oil Expansion Vessel led to boil off/ rupture/fire. Drain water at all low points drains during start-up. Potential source of water - one of the heat exchangers where the drain valve was not at the bottom. Consider oil as hydrotest medium to keep water out

• Water or light ends entry into hot Bitumen tank resulted in violent boil off/ rupture and fire. Resulted in hot bitumen spray when a tanker truck with water was filled with hot bitumen

• Roll-Over or Froth-Over: Refinery recovered oil storage tank. Internal floating roof. Fed with ballast water and water heated by steam coil. Automatic heating control changed over the years to manual control. Local TG + hand felt tank shell temperature controlled steam flow. An emulsion layer floating on top of water acted as a good insulator to the oil on top. Local TG malfunction set off 6 vertically arranged control room temperature alarms. As the alarms were considered unreliable, steam flow was maintained. The emulsion broke, heating oil resulting in vapor release. H2S and LEL alarms in tank farm

• Froth-Over: Steam heating system left running for several days in an Long Residue tank - that had water. Trapped water vaporized. Froth over. Tank damaged. Hot oil sprayed over a large area. BP

• Froth-Over: Hot Vacuum Oil accidentally transferred to a Slops tank with water and oil. Froth-Over sank the internal floating roof and roof ruptured under internal pressure. BP

• Slops Tank: Steam heating coil. At 100°C, water-oil emulsion separation + released light ends. VCE. BP