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Refinery
CDU: Check valve failure. Crude back-flowed via Water Injection Pump into Wash Water Tank and then to sewer. BP
CDU: Start-up. Excess water that had not been drained from the pump-around circuit, entered the column and steamed. All trays damaged. RV lifted discharging oil. Ground fires. BP
CDU/VDU: Changeover of Desalted Crude Pumps increased feed rate and light ends to VDU. Loss of vacuum and VDU RV release to atmosphere. BP
CDU/ VDU: Corrosion under Ammonium Chloride/ Amine deposits in column top. Check - water draining in crude storage, good desalter, wash water in overheads system and amine injection. BP
CDU/ VDU: Unmonitored corrosion of hot Naphtha line. Alonized line failed near VDU column. Fire. BP
CDU/ VDU: Dead-leg corrosion, release and fire at Desalter RV discharge, VDU Reflux pump suction and Short Residue pump suction. Stagnant line sulfide corrosion in HX bypass and residue systems. BP
CDU/ VDU: Avoid temporary low grade piping patch work - using CS or ½ Mo pipe in 5Cr-½Mo piping. They are usually forgotten and never replaced until rupture, fire and explosion. BP
VDU: Vacuum residue pipe leak. Alloy pipe wrongly replaced by CS during maintenance
VDU: Incorrect MOC in column branch. Leak and fire. Column fell on HX train
VDU: Pool fire. Column collapsed over HX train. Missing passive fire protection of column skirt
VDU: Pyrophoric fire of coke deposited in a packed section caught fire. Keep coke deposits wet. BP
VDU: When air entered overheads system, explosion. LGO packing and HGO pump-around trays. BP
VDU: Severe mechanical damage to internals during start-up due to excessive water accumulation from leaking heater stripping steam connection. BP
VDU: Excess water entry into VDU feed drum during a feedstock change. RV discharged large vapor onto the main column, resulting in leakage at a transfer line flange. Fire. BP
VBU: Pump strainer maintenance. Block valve failed. Oil spill that auto-ignited and destroyed VBU. Fire spread by FW application
DCU: Improper metallurgy caused hot oil above its AIT leak at pump discharge. Fire. Fatality
DCU: Reverse rotation: On power failure, Delayed Coker feed pump reverse rotated due to discharge check valve failure under discharge pressure + 30 bar BFW injected to furnace coil to purge it. Pump and its motor damaged. Provide remote operated discharge valve for bigger pumps
DCU: Fire resulted from opening the top unheading valve of an active LP coke drum
DCU: Air was replaced with heated oil (cold weather) in the column. Air and oil vapor mixed. As vent valve was not open, pressure rose, heated up the explosive mixture. Detonation. BP
Fluid Bed Coker: CS piece inadvertently inserted in 5 Cr pipe. Erosion failure. Released liquids close to AIT. Fire. Additional pipes ruptured adding fuel
FCC: Expander vibration resulted in safe shutdown. Leaking slide valve on reactor to regenerator led to loss of catalyst barrier. Steam purge to push hydrocarbon into downstream column led to steam leak towards Expander. Steam flow was reduced that unfortunately resulted in Hydrocarbon backflow into the air/ flue gas side; ignited by ESP installed to reduce catalyst particle emission
FCC: Shut down for maintenance. Due to erosion, slide valve failed to maintain a +ive catalyst bed barrier between reactor and regenerator. Air from regenerator travelled via reactor to downstream pipes with HC. Explosion. Debris punctured an asphalt tank 60m away. Asphalt poured out and spread. Ignited. Smoky fire in CDU and FCC units
FCC: Shut down for maintenance. Fuel gas was injected downstream of fractionator to keep reactor under positive pressure and steam was injected into reactor to act as a barrier between fuel gas and air in regenerator. As the reactor was holding pressure, steam flow was mistakenly stopped. Fuel gas reached the regenerator as the slide valves were not gas tight and possibly ignited by hot coke/ catalyst. Explosion. 145 ton regenerator top blew up 15 m and fell 38 m away. BP
FCC: Debutanizer outlet didn’t open during a start-up while receiving from upstream Deethanizer. Operators routed Debutanizer Over-Head Drum flow to Wet Gas Compressor Inter-Stage Drum (ISD). On ISD LAHH, compressor tripped venting to flare. High liquid levels in Flare KOD, made worse by operators routing ISD liquids directly to flare. Flared gas + liquid broke an elbow. Vapor Cloud Explosion (VCE). Flare KOD pumps didn’t start on LAH
FCC: Depropanizer overhead piping corrosion in elbow. C3+HC release. VCE. Blast toppled the fractionator and damaged FCCU and other units. Elbow downstream of ammoniated water injection point. Localized corrosion. Similar more incidents under Piping
FCC: During shutdown oil was drained from a vessel used to separate heavy oil and solid catalyst. Vessel was steam purged. Hot oil was introduced before steam condensate (water) was drained. Led to rapid expansion, rupturing vessel and igniting oil
FCC: Unstabilized gasoline pump tripped. Liquid routed to unit Flare KOD via RV on high level. KOD liquid was drained to OWS (CBD route was defunct). Vapor cloud ignited by FCC furnace
FCC: Continuous HC liquid flow to a column with blocked outlet led to relief flooding unit Flare KOD. Entrained liquid in the flared gas led to liquid hammer that ruptured KOD’s corroded outlet elbow. HC release, fire and explosion. Plant modification routing KOD liquids back to inlet instead of Slop Tanks as originally designed; Poor alarm rationalization and management
FCC: C3/ C4 gas recovery unit pipe rupture. VCE. Gas and FCCU destroyed
FCC: Pump casing weld failure in C3= Splitter unit. C3= release. Explosion. Damage to FCCU
FCC reactor: Air used to purge the instrument connections accumulated locally in the reactor head resulting in the formation of coke by partial combustion of hydrocarbons. 1.5 m thick soft coke accumulated in the top head. Further air accumulation ignited the coke. Explosion. BP
RFCC CO Boiler: Aqueous ammonia/ urea solution sprayed to convert NOx into N2 + H2O (SNCR - Selective Non-Catalyst Reduction process) caused external corrosion/ thinning of boiler tubes, as the solution did not vaporize as expected; dripping liquid droplets caused wet CO2 corrosion. Based on spray test, the spray nozzles were extended to avoid liquid dripping
Gas Treatment: Loss of lean oil resulted in low temperature (-) 48°C in an LPG heat exchanger. Shell embrittlement and rupture. Gas ignited by a fired heater. BP
H2: CO2 from shift reaction was absorbed by Potassium Carbonate solution. During maintenance, carbonate solution was withdrawn from its tank, resulting in H2 flow from the absorption tower into the tank. High tank pressure. Explosion and Fire. Failure to isolate and/or purging the tower with N2
H2: SS pipe bypassing HTS converter - no flow pipe - ruptured. Water and KOH (from K promoter in SMR catalyst) accumulation in low point. SCC. Fire. SS replaced with 1¼Cr-½Mo
HCU: Faulty level instruments. Gas blowby from HP Sep to LP Sep, whose relief valve was sized for fire only. LTs of LC and LAHH/LALL should track each other and give discrepancy alarm. Size RVs for gas blowby, if applicable
HCU: Stage 2 Reactor 3 outlet piping ruptured. High temperature ~ 760°C. Hot spot in bed 4. Reactor was not shut down and depressurized after crossing 427°C. Poor temperature inputs/ monitoring
HCU: 2” H2 line at 208 bar failed at weld. Resulting flame impingement on reactor skirt. Reactor collapsed. Similar, H2 leak and fire. Damaged the main reactor. Similar, CS elbow rupture released H2 + HC. Explosion. HC release from column with extensive damages to HCU, HDS and H2 units
HCU: Spent catalyst sucked up by vacuum with a hose by a 'diver' inside the reactor. As the spent catalyst may ignite on contact with O2 in air, the reactor was first filled with N2, an asphyxiation agent. The diver entered with a breathing air helmet. Catalyst movement buried him. Air released from his helmet ignited the catalyst. Consider the 4 risks - suffocation, falling, burial, and burns with limited escape and rescue options. Do NOT use the diving method
HCU: RV malfunctioned and opened. To reseat it, operators tried to close its 6” inlet valve. Unable to reach, they closed its lower rated 20” outlet valve. Valve failed. H2 + HC release. Fire and explosion. CSB
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