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Storage Tanks
Plugged PG may not indicate residual pressure. Plugged vent line blew-off tank lid, when workers attempted to open it. Fatalities. Inspect regularly lines and equipment that may plug
45% Chloro Acetaldehyde (CAA) polymerized when heated by a failed tank tracing. Plugged and ruptured vent pipe. HCl cloud release
Lightning: API discounts lightning as a low probability event. A few accidents in storage tanks, usually escalate to adjacent tanks
Lightning: Impact on power supply can cascade
Lightning: Vent gas caught fire. Still happens
Lightning: Oil on top of OWS caught fire and the fire spread
Lightning: PDA unit fuel oil tank with propane. Lighter propane had flashed. Fire and explosion. BP
Lightning: On lightning strike, an Ethyl Acrylate and Butyl Acrylate tanks exploded. Tanks were properly grounded; perhaps an internal part was not bonded to the tank, generating a spark. Grounding and bonding all parts is a must
Lightning: MTBE. Cone roof tank with internal floating roof. After repair/ maintenance, the tank was brought to service - blinds were opened with isolation valves still closed awaiting fresh supply. MTBE in external piping leaked via gate valves into the tank, evaporated forming an explosive mixture. On lightning strike, internal explosion sheared off the cone roof. Remember: All valves leak. BP
Earthquake: Failed tanks and pipe breaks can result in dyke overflow. Cracked dykes cause subsoil/ aquifer contamination. Dykes may have holes
Tsunamis: or hurricanes can wash away tank foundations, electrical system damage, break pipe connections and debris impact
Floods: can spread oil in SWD around the plant; damage transformers located at low levels with resultant fires
Solar: Thermal input caused RVs on 1,000s of C3= cylinders pop that caught fire, launching the cylinders as missiles. Usually partially filled or ‘empty’ cylinders heat up fast
Ambient Temperature: Low ambient temperature, crystallized cyclohexane that ruptured a tank area pipe. Butadiene condensed, creating vacuum and collapsed the tank
Ambient Temperature: Gas liquified. Vacuum. Tanker collapsed. Add N2 padding
Ethanol tank fires require higher amounts of foam than oil fires. Design foam and water systems suitably. These fires produce very little smoke and sometimes the flames are invisible. BP
Bulk chemical shipment drums/ containers look alike but may carry a wrong chemical due to mix-up
Consider the impact of water weight/ head stored in one of the compartments, on the adjoining empty compartment. It has broken ships; tilted tanker cars. BP
Ammonia: Though molecular weight < air, forms low level dense clouds. High LEL 16%. Hi auto-ignition temp 650°C. Still it can explode, though LEL is high, UEL is 25%. WWW
Ammonia: Backflow of warm liquid NH3 resulted in ‘rollover’. High pressure. Tank lifted off. NH3 release ignited. Toxic N2O cloud. Avoid backflow. Add temperature control to alarm rollover; design tank to fail at roof than at bottom
Ammonia: Storage tank overfilled. Both LAH and LAHH had failed
Ammonia: Regularly overfilled. 99% Vs 53% max. Tanker truck exploded, releasing 22 tonnes of anhydrous NH3 - dense ammonia cloud. 129 died and 1,150 injured. In liquified service, over filling leads to over-pressurization and stress
Ammonia: Road tanker. Plant air was used to speed up NH3 unloading. The compartment split open, flooding the area with liquid NH3. Diluted with water spray. Caution: Heat of NH3: H2O reaction can speed up NH3 vaporization. BP
Ammonia: Refrigerated tank moved 25 m sideways, leaving its floor behind. 7,000 tonnes of NH3 was released. Fire. Water application, aggravated the fire. On stopping water, fire went out. BP
Urea: Liquid urea storage tank. Vertical riveted seams replaced by horizontal welded plates. Poor welding and inspection led to tank failure releasing 2 million gallons of liquid ammonium nitrate
Tanker: Wrong lining for the monomer shipped. Reacted with iron, polymerized and exploded
Tanker: While cleaning out bottom sludge, grinding work was done on discharge chute. Flammable mix in the chute flashed back. Fatality. Caution: Sludge may contain HC. BP
Tanker: Truck moving without first disconnecting the supply hose has led to many accidents. Add physical barriers to prevent the tanker moving without ensuring hose disconnection
Tanker: While connecting the loading arm of a tanker, its insulating flange was bypassed with a strap/cable, possibly to guard against static electricity. This provided a continuous electrical path. As the tank's vapor return loading arm came in close contact with the tanker’s pipe manifold, a spark occurred. Static charge generation is a concern during product loading. Stray currents can occur while connecting and disconnecting the loading arms. BP
Tanker: Unloaded using compressed air into storage tank. Air leak via a tanker manhole, resulted in backflow of liquid, as liquid was at a higher level at the destination. Add a check valve in the transfer line. Monitor unloading. BP
Tanker: While transferring asphalt into barrels, workers heated the tanker to loosen and drain residual asphalt. Tanker exploded under high vapor pressure
Tanker: Unloading pump started before opening top manholes. Vacuum. Tanker collapsed. BP
Dikes: Inspect for spills and leaks. Pump out rainwater promptly from dikes. Dikes filled with rainwater can’t contain spills
Carbon bed adsorbers for emission control. Heat generated by adsorption ignited flammable vapor in the adsorber that ignited the attached tank. Account for heat generation. Add flame arrestor at adsorber inlet
Poor purging led to gas holder damage. BP
Noded Spheroid: Emptied of oil. Then filled with water to purge oil and gas via top vent for inspection. Water drained with air entering from top vent. Oil and gas trapped in top parts was ignited by FeS. Low grade internal explosion that pushed out water, forming vacuum. Spheroid collapsed. The pushed out water leapt over a fire wall and damaged an adjoining floating-roof tank. Gas test thoroughly all nooks and corners. Add vents in likely trap points at allow air to avoid pulling in vacuum. BP
Tanks were being converted to unleaded gasoline. Leak from a gasoline tank drain line resulted in an explosion near the diesel generator outside tank farm. Firefighters tried to locate the leaking valve at the bottom of the tanks, while wading through a water-foam-hydrocarbon mixture. Burn injuries. BP
Tank overfilled. Ignition. Explosions and Fire. Firefighters fought the fire while standing in a mixture of water, foam and oil to locate a valve in a naphtha storage tank feeding the fire. Fatality. CSB
Diesel Generator: Tank was overfilled, due to a faulty LG, diesel reaching up its vent line. When a worker removed the faulty LG, diesel sprayed out and ignited by hot DG exhaust. No LAH or SDV. BP
Caution: In handling radioactive level gauges
While recuing a worker who fell into a tank with residual Toluene, assuming Toluene was toxic, a hole was cut in the tank side wall. Explosion. Additional fatality and injury. BP
Heat Exchangers
Refrigerated LPG Absorption: Hot lean oil was stopped but cold rich oil flow was continued. Transient condition resulted in lower than MDMT. When hot lean oil flow was started, thermal stress caused rupture and release. Ignited by a heater 170m away. Jet fire. Identify such issues during design
Tube leak led to HC in return Cooling Water to Cooling Tower. Fire and explosion during welding in ‘water service’ Cooling Tower. Tubes are thinner than pipes. Can leak on minor corrosion that is difficult to spot in tube bundle. Expect HC in Cooling Water network. Have HC detectors on Cooling Tower top
Usual to keep HP process fluid on tube and LP seawater on shell. May lead to corrosion of CS tube sheets behind titanium cladding on the shell side. HC release/ explosion. Go for seawater on tube side
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