Safety Alerts 5

Storage Tanks

• Static Electricity: Naphtha filling. As filling hose got switched from one tanker to another, air was routed to the tank and accumulated on top. Static Electricity accumulated in the non-conducting naphtha. A metallic float measuring the level, while oscillating broke the earthing. Spark and explosion. Tank farm destroyed. Uncommon in volatile gasoline as it produces a rich mixture. Less volatile naphtha, C6, C7 and BTX produce flammable mixture. Normal earthing may not be enough. Avoid loose metal floats

• Static Electricity: Spark between a steel weight used to keep a top filling hose and Ethyl Acetate tank. Tank was grounded but flow thru non-conductive hose generated static and top filling caused vapor generation in top. Ground and bond all equipment + avoid top or free fall filling (Inert gas padding avoids air) + Use conductive materials

• Static Electricity: Spark around an internal floating roof of a gasoline tank

• Static Electricity: Reformate transfer to a gasoline tank for blending. Static discharge due to high pumping rate and temperature changes caused inbreathing/ flammable atmosphere. Mild internal explosion that distorted tank roof. BP

• Static Electricity: Diesel routed to floating roof tank that had contained gasoline earlier. Gasoline:air accumulation above diesel. High velocity diesel transfer resulted in static charge and explosion. Keep low velocities and extra care on switch-loaded tanks. BP

• Static Electricity: MTBE tank was cleaned and a high pressure rotating water nozzle was introduced thru tank top manhole for jetting out. Static discharge from high speed fine water mist. Internal explosion. Manhole blown off. BP

• Static Electricity: CO2 jet from extinguishers contain small solid CO2 particles. A charge may accumulate. CO2 was used to inert a naphtha tank and it exploded. Similar, CO2 used in a jet fuel tank. Similar, high pressure water jets used to clean supertankers. WWW

• Corrosion: Used up Oxygen in an isolated tank and it collapsed; persons who entered such tanks have fainted. WWW

• Floating Roof: Collapse or sinking. Pontoon buckling. Sank on excessive rainwater accumulation. Pushed oil to roof via vacuum breaker/ vent. Avoid closed roof drain valve, frozen drain, debris/fouling the drain. Ensure rainwater draining capacity

• Floating Roof: Primary and secondary seals were separated from a tank wall, to avoid heat damage while the wall was cut to add an access door. Oil that had accumulated in the seal spaces drained out. No internal inspection was done before starting the welding. Fire. In addition to gas testing, visual inspection to check for oil, sludge or wax is a must. BP

• Floating Roof: While repairing a single deck floating roof, its emergency drain was replaced by a longer pipe. Emergency drain was to route rain water into the tank if the normal roof drain is closed or clogged, to prevent overloading the roof. After a heavy rain, excess rain water on the roof and its weight forced Jet A1 to flow up through the emergency drain and flood the roof. Avoid emergency drains on single deck floating roofs. Go for good sized rainwater drains with outlet valves kept opened. BP

• Floating Roof: Rim seal fire escalated quickly to a full surface fire when vapours in the leaking pontoons exploded. Regularly gas test pontoons to eliminate vapour build-up in the pontoons. BP

• Gasoline tank roof seal changed from liquid filled type to gastight spring loaded type. Bumpers under the roof (that hit the tank shell when the seal is fully compressed) were also modified. New bumpers were closer to the tank shell and made contact more often, deforming the pontoon welds over the years. The roof finally sank and three pontoons were flooded. Regularly gas test the pontoons. BP

• Internal roof collapse: Tank was emptied, cleaned and inspected. When firefighters tested its foam systems, the internal roof, not designed to withstand the weight of water collapsed. BP

• Earthquake: Liquid sloshing resulted in rim-seals damage and crude oil overflow. Metal-metal contact between floating roof and side wall resulted in sparks that ignited the overflow

• Earthquake: Damaged the roof of a naphtha tank. Foam applied as a preventive measure. Continuous dripping of water and foam onto the naphtha surface - static discharge and fire. BP

• Isolation: Swinging spec blind or hammer blind. Valve passing led to gasoline leak/ flashing and accumulation in tank pit. Operator overcame by fumes. VCE. Similar incident in an LPG plant. Use buddy system

• Styrene polymerized, an exothermic reaction, due to - higher temperature in top layers, CS rust particles in an unlined tank, lack of inhibitor inside stalactites on tank roof, improper O2 level to help inhibitor, lack of refrigeration and poor liquid mixing/ stagnation without mixers - and pressurized storage tank. Under sized vents and atmospheric venting instead of flaring led to toxic cloud release. Must measure temperature along the liquid height and in vapor space

• Plugged tank 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 plug

• 45% chloro-acetaldehyde (CAA) in tank polymerized when heated by a failed tank tracing. Plugged and ruptured vent pipe. HCl cloud release

• Lightning: Tank vented gas caught fire. Low probability as per API. Still happens. Oil on top of OWS caught fire and the fire spread

• Lightning: Fire and explosion in a PDA unit fuel oil tank with propane. Lighter propane had flashed. BP

• Lightning: On lightning strike, an Ethyl Acrylate and Butyl Acrylate tanks exploded. While the tanks were properly grounded, perhaps an internal part was not bonded to the tank, that could have generated an internal spark. See above - Ethyl Acetate incident. Grounding and bonding all parts is a must

• Lightning: MTBE service. 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. All valves leak. BP