Coker Safety And Reliability Lessons Learned

Coker Safety and ReliabilityLessons LearnedDale Wilborn2015 Coking.comConference 2015 Chevron

COKER SAFETY & RELIABILITYCurrent SituationThe Delayed Coker industryhas had many incidents withsevere consequences,including numerous fatalities.There has been greatprogress in the last 15 years toimprove Coker design toreduce personal exposure andimprove safety.Even with all theimprovement, Chevron hasexperienced some near missand operational reliabilityincidents. Current focus areasare metallurgy and Inspection.Near miss, Incidents and Lessons Learned Furnace OutletStart-up issuesLock out- tag out incidentErosion of thermowellErosion – Corrosion at elbowsErosion at velocity steam injection location Absorber- Stripper and DebutanizerTrace water causing reboiler corrosionTrace water causing vaporline corrosion PROCESS GAS SPONGE ABSORBERBLISTERINGHYDROGEN Delta Valve – 10 Year look back COKER Shutdown cleanup using RTIDesired Outcome Provide “lessons learned “ to raise awareness & increase focus on Coker safety and reliability. Highlight potential vulnerabilities, discuss inspection, training, and incident prevention. 2015 Chevron2

Coker Furnace Incidents Coker Startup Issues &Incident Furnace Pass Flow Meter Inadequate lock-out tag-out Furnace Outlet Barrel: OutletThermowell Erosion Furnace Transfer Line Erosion 2015 Chevron3

Coker Startup Issues & IncidentOVERVIEW* Charge pump cavitation* Loss of furnace flames 50% of burners1. Charge Coker with LCO, establish levels andpump circulation.2. Commission steam for Coker structure.3. Drain (multiple times) fuel gas linewith chemical cleaning liquid.4. Clean plugged furnace charge pumpsuction screens.5. During pump switch to electric,significant water hammer & pipingvibration. 2015 Chevronwater4

Coker Startup Issues & Incident6. Coke from piping caused furnace FCplugging; cleaned multiple control valves,establish flow control.7. Furnace warm-up, module circulation, feedin to coke drum.8. Furnace charge pump cavitation fromflashing seal flush.9. Low furnace pass flow, high furnace outlettemperatures, fuel gas TC closes; fuel gason new minimum flow.10.High CO and O2 in firebox; visualinspection of furnace shows multipleburners were not lit. Loss of flames withfuel gas into firebox is a HAZARDOUScondition. 2015 Chevron5

COKER XxXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 2015 ChevronxxxxxxXErratic control, large furnace temperature swings.XXXXXXXXX6

Coker Startup Issues: Corrective Action1. Cleaned furnace charge pump suction screens.2. Changed the charge pump seal fluid from FCC LCO (with heavygasoline being dropped to LCO due to refinery processing constraints)to HCGO pumparound.3. Drain liquid from fuel gas headers.4. Re-light burners. NOTE: Low pressure Safety InstrumentedSystem (SIS) fuel gas chop function DID NOT activate becausethe pressure sensors are upstream of the TC.5. With oil flow and furnace burners re-established, returned to minimumflow at desired furnace outlet temperature.6. Since resid below coking temperature entered the coke drum, feedcycle time extended to increase coking time. Also, increased steamstripping time. There were no tarry drum issues during quench, drain,or coke removal. 2015 Chevron7

Coker Startup Issues: Corrective ActionMAINTENANCE1. Disconnect fuel gas flanges / open bleeders at low points to verify dry afterchemical cleaning.2. Inspect coke drum vaporlines, column bottoms piping; clean if necessary.OPERATIONS1. Use heavy gasoil, not FCC LCO for startup charge to Coker.2. FURNACEa. Review fuel gas minimum flow guidelines, increase to maintain adequateburner header pressure for flame stability.b. Develop short term emergency procedure for low fuel gas burner header pressurein lieu of SIS trip.c. Correct SIS fuel gas pressure measurement location.3. STRUCTURE STEAM. Wait until drum inlet temperature is over 700 F beforeintroducing structure steam (minimize potential for condensed water in system). 2015 Chevron8

Furnace Pass Flow Meter - Inadequate LockOut – Tag Out Poor communication regarding location of isolation between operatorreleasing equipment and mechanic doing the work on resid orificepass flow meter plugged tubing. Resid sprayed from furnace pass flow orifice meter. Resid at 550 F,500 psig furnace discharge pump pressure. Resid “auto-ignition”estimated to be 650F. 2015 Chevron9

Furnace Outlet Barrel: OutletThermowell ErosionOriginal Outlet barrel configuration: Steam:airdecoking caused thermowell erosion. Residleaking into the conduit caused false outlet reading,higher furnace firing rate, accelerated coking rate.Thermowells replaced, furnace de-coked.Outlet barrel configuration can be a source of cokeaccumulation. 2015 Chevron10

Furnace Transfer Line ErosionCHALLENGES1. Furnace transfer line is prone to coke accumulation, increasedpressure drop, higher velocity.2. Furnace outlet transfer line (especially elbows) is vulnerable toerosion and through wall “loss of containment”. The first elbow aboveoutlet barrel is especially vulnerable.Discussion Topic: Furnace transferpiping configuration 2015 Chevron11

Furnace Transfer Line Erosion 2011 – furnace outlet pipingerosion at outside of elbow after4 years. Coke in line increaseddownstream velocity. OPSdiscovered after spall, isolatedimmediately. 2013 – elbows flanged forremoval to clean, with stellitehard facing on inside.Furnace geometry: Outlet changed to maintainupward flow, no outlet barrel. 2015 Chevron12

Furnace Transfer Line Erosion Quench steamadded to furnaceoutlet from 6:00position. Lowersoutlet temperatureduring online spall.2015: Through wallerosion at 12:00position, slightlydownstream after 3-7years.Coke build-up on sidewalls results in highervelocity. 2015 Chevron13

Coker Distillation Incidents Absorber – Stripper Debutanizer 2015 Chevron14

Stripper CorrosionReboilerReturnChimney Tray 1 with corrosionfrom chlorides Corrosion – outside of reboiler (processside) tubes and shell 2015 ChevronChimney tray 1 afterrepairs15

XXXX.Stripper Repairs &PerformanceSHUTDOWN REPAIRS1. Replace tube bundles2. Repair reboiler shells.3. Add stainless steel over floor of total draw traythat feeds reboilers.XXXXCurrent Operation1. Gap control for absorber – stripper side waterdraw tray. Tray removes water, verypredictable. H2O removal from tray 13.2. Intermittent water from stripper bottoms todebutanizer.3. ISSUE: Determining if water is “trapped” belowH2O draw tray. Water vaporized leaves behindcorrosive chloride salts.XX 2015 Chevron

Debutanizer Condition Debutanizer tray 33, “Prussian blue” cyanide saltdeposits.Cause: Trace water in stripper bottoms was notbeing removed in debutanizer OH reflux drum.Water was being refluxed. After going down anumber of trays, the water was vaporized, leavingdeposits at the tray where vaporization occurred.Prior to shutdown, experienced column OH piping loss of containment.Corrosion from ammonium bisulfide accelerated by presence of cyanides. 2015 Chevron17

COKER SPONGE ABSORBERHYDROGEN BLISTERINGHISTORY1. Long history, no major issues.2. Water circulation with ammonium polysulfide (APS) injection is usedupstream of Sponge absorber.3. Additional nitrogen, increased ratio of APS per MBPD resid.4. Wet H2S service, but unexpected problem discovered in shutdown. 2015 Chevron18

Coker Sponge Oil Absorber Hydrogen Blistering Discovered Hydrogen blistering withcracks in the steel. Wet H2S andpossibly cyanides are root cause.No tray issues. Floating valve caps 2015 Chevron19

Coker Sponge Oil AbsorberRepairReplaced top 8 feet of Sponge Absorber.Maintained upstream sour watercirculation with APS to remove cyanidesfrom Coker tail gas.Discussion Topic: Determining if allcyanides in Coker tail gas have beenremoved. 2015 Chevron20

Automatic TOP and Bottom Unheading with DeltaValves – 10 Year Look back 2015 Chevron21

The old coke drum unheadingwas a SAFETY risk withpotential for personalexposure, and injuriesoccurred during mechanicaltop and bottom unheading. 2015 Chevron22

Bottom Unheading The new system hasrevolutionized the industry;there has been a dramaticimprovement in Coker Safety.CHEVRON EXPERIENCE – 10 Years14 coke drums 2015 Chevron No Loss ofContainment incidents. No SAFETY incidentsassociated with valveoperation.23

Top UnheadingAuto-switch cutting toolCut nozzle (2)Bore Nozzle (4)Delta Valve, fully automated, remoteoperation, no manual labor. 2015 Chevron24

Coker Shutdown Clean-Up with RefinedTechnologies Incorporated (RTI) 2015 Chevron25

Coker Shutdown Clean-Up with RefinedTechnologies Incorporated (RTI) Extensive pre-shutdownequipment installed toallow steam andchemical to be routed toall desired locations. Introduces trippinghazards. 2015 Chevron26

Upper Section Main FractionatorColumn entry with appropriate personalprotection equipment 2015 Chevron27

Coker SHUTDOWN CLEANUPTunnel column by removing tray deckmanways to allow inspection. Columncondition was very good, trays were veryclean. 2015 Chevron28

Coker SHUTDOWN CLEANUPSome coke and sludge onbottom HCGO chimneydraw tray 2015 Chevron29

Coker STARTUP ISSUEnNnnnnXXXXXXXXXXXXXXXXXXXXXXUpon startup, the overhead fin fan cooling performance wassignificantly worse.Lesson Learned: Column chemical cleaning needs to have OHXXXXXXXXXXXXXXXXXXexchanger cleaning to follow. 2015 Chevron30

Coker Safety and ReliabilityLessons LearnedQUESTIONS ? 2015 Chevron

significant water hammer & piping vibration. 4 OVERVIEW * Charge pump cavitation . Coker Sponge Oil Absorber Hydrogen Blistering Discovered Hydrogen blistering with . CHEVRON EXPERIENCE – 10