Hendelse på FPSO Alvheim, januar 2009 TEKNA Prosessikkerhet Event on Alvheim FPSO jan 2009, TEKNA Process safety

Alvheim FPSO Topside: 2 trinns separasjonstog 2 rekompresjonstog 2 eksporttog TEG tørketårn 140 000BPD olje 2 MSm3/d gass Topsides 2 stage separation train 2 compressor trains 2 export trains TEG drying tower 140mbd oil 2 MSm3/d gas

Hva gikk galt? Overfylling av fakkeldunk fra kjøler (sjøvann) Med påfølgende unormal fakkling og ”fallende” flammer fra fakkeltårn Fakkeldunk beskyttet i henhold til normal designpraksis Hvorfor gikk det galt? What went wrong? Overfilling of flare drum from cooler (Sea water) With subsequent abnormal flaring And ”falling” flames from flare stack Flare drum protected as per normal design practice Why did it go wrong?

Systemoversikt System overview

Systemer involvert i hendelsen Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Kjøler overtrykks beskyttelse Vann/gass strømmer til fakkel Water/gas flows to flare Sprengblekk ryker ved 4barg Downstream disc set at 4barg Designtrykk fakkel 14barg Flare design pressure 14barg Volume between discs normally full of air at 0barg. Upon burst disc activation, seawater will flow to flare Segment mellom disker er normalt fullt med luft 0barg, ved sprengblekk aktivering vil sjøvann/gass strømme til fakkel. Pressure trasnmitter installed to detect bursting disc failure caused by overpressure Upstream burst disc SP – 18barg Trykktransmitter for deteksjon av sprengblekk aktivering som følge av overtrykking Sprengblekk ryker ved 18barg Cooler design pressure 18barg Designtrykk kjøler 18barg

Fakkeldunk beskyttelse Nivåtransmitter initierer PSD3, settpunkt 42,1% Level transmitter initiates ESD2, set at 91.7m Level transmitter initiates PSD3, set at 42,1% Nivåtransmitter initierer ESD2, settpunkt 91,7% (2,8m) Level transmitter for level control Nivåtransmitter for nivåkontroll To flare for burning Pressure blowdown lines from topsides Til fakkeltårn for brenning Trykkavlastnnigslinjer fra topside 15m x 4m

Hendelsesforløp Incident events

During normal production on 16th Jan Under normal produksjon 16. januar 16.01.09 20:33:42 Flare During normal production on 16th Jan Feilaktig PSD3 Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Spurious PSD3 activation on HP flare drum high level Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Kjølere isoleres 20:33 16.01.09 Coolers isolated Flare M Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Coolers isolated Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Utløpsventiler stenger 5s senere for å unngå: Kjølere isoleres 16.01.09 20:33 Flare Utløpsventiler stenger 5s senere for å unngå: Innestengt trykk Vannhammer Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Sea water outlet valves close 5s later to avoid Shut in pressure waterhammer Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Alarm aktiveres, høyt trykk i kjøler 20:33 16.01.09 20:33 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In Gas Out XV LST 0132 LST 0133 LT 0135 Flare Meter Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press Alarm activated – high pressure in cooler Operator does not notice alarm -Lacking alarm filtering/grouping, hundreds of alarms upon PSD3 -Lacking alarm text, little description To Closed Drain Sea Water Lift Pump (cooling) Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV Operatør legger ikke merke til alarm: Mangelfull alarm filtrering/gruppering, flere hundre alarmer aktiveres ved PSD3 mangelfull alarm tekst, lite beskrivende

påfølgende aktivering av sprengblekk 20:33 Termisk utvidelse med påfølgende aktivering av sprengblekk 16.01.09 20:33 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Thermal expansion bursts bursting disc Thermal expansion protection undersized and unreliable Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Termisk trykkavlastning underdimensjonert, og lite pålitelige Filter XV

Kjøler innløpsventil stenger Heat transfer to cooling water causes thermal expansion and pressure increase Varmeoverføring til kjølevann med påfølgende termisk ekspansjon og trykkoppbygning Sprengblekk ryker Burst disc breaks Cooler inlet valve closes Kjøler innløpsventil stenger Alarm Cooler outlet valve closes Boxed in sewater is heated and expands. Alarm not noticed and thermal expansion protection (PSV) does not work -> burst disc breaks. Kjøler utløpsventil stenger

Ingen ESD 2 blir aktivert 16.01.09 20:33 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) No ESD2 activated Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Ingen ESD 2 blir aktivert Filter XV

Hvorfor ingen deteksjon? Designsvakheter: Scantime for transmitter spesifisert på SCD til 100ms Installert trykktransmitter har en responstid på 530ms Trip node satt til 1s scantime Deteksjonsloop ikke rask nok til å detektere trykkpuls som følge av termisk ekpansjon After 530ms a 4 barg input pressure would give an output value of 2,15barg What if pressure pulse only last for up to 100ms? Input signal; Pressure in pipe Output signal; 4-20ma Design weaknesses Scan time for transmitter specified as 100ms Installed transmitter has response time of 530ms Trip node on 1s scantime Detection loop not quick enough to detect pressure pulse from thermal expansion

Prosessen tilbakestilles og normaliseres PSD nivåtransmitter Inhibiteres 16.01.09 20:35 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Process reset and returned to normal PSD level transmitter inhibited Problems with level transmitters Many spurious trips Operator does not always believe reading Type of level measurement no longer recommended Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Problemer med nivåstransmittere (Radar): Mange feilaktige aktiveringer Operatør stoler ikke alltid på nivåvisning type nivåmåler ikke lenger anbefalt Filter XV

Isoleringsventiler åpnes Prosessen tilbakestilles og normaliseres Isoleringsventiler åpnes 16.01.09 20:39 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Process reset and returned to normal Isolation valves opened Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

20:39 Fakkel fylles med vann ~500m3/h 16.01.09 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Flare system fills with water ~500m3/hr Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Fakkel fylles med vann ~500m3/h Filter XV

da transmitter er inhibitert PSD nivå (42%) nås, men ingen aksjon da transmitter er inhibitert 16.01.09 20:42 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) PSD trip level reached but no shutdown due to trip being inhibited Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Alarm høy ved 85% 20:52 16.01.09 High level alarm at 85% Flare M Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) High level alarm at 85% Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Noen ventiler lukkes manuelt 20:53 16.01.09 20:53 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Some valves closed manually The operators do not know which cooler is flowing to flare, as there has been no alarm/trip from burst disc failure. Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV Operatør vet ikke hvilken kjøler som evt. strømmer til fakkel, da ingen sprenblekk aktiveringer har gitt alarm/nedstenging.

lukker resterende ventiler ESD2 aktiveres og lukker resterende ventiler 16.01.09 20:53 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press Fylling av fakkeldunk opphører To Closed Drain Sea Water Lift Pump (cooling) ESD2 activates and closes remaining valves Filling of flare drum stops Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Trykkavlastning av topside initieres som følge av ESD2 16.01.09 20:54 Flare Trykkavlastning av topside initieres som følge av ESD2 Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Topsides blowdown due to ESD2 Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

ESD nivåtransmitter og ”tvinger” noen ventiler åpne 20:56 Operatør inhibiterer ESD nivåtransmitter og ”tvinger” noen ventiler åpne 16.01.09 20:56 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Operator inhibits ESD transmitter and ”forces” some valves open By inhibiting the ESD transmitter, the operator can drain the flare drum and it frees up other valves for operation Onshore had asked for the coolers to be able to ”breathe” upon shutdown; SW outlet valves opened to avoid thermal expansion Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Ved å inhibitere ESD transmitter får operatør mulighet til å drenere fakkeldunk, samtidig frigjøres andre ventiler for operasjon Filter XV Onshore har bedt om å la kjølerne ”puste” ved stans; utløpsventiler ønskes åpnet for å unngå termisk ekspansjon

Fakkel fylles ytterligere 16.01.09 20:56 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Flare drum fills with more water Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Fakkel fylles ytterligere med vann Filter XV

Trykkavlastning avbrytes manuelt 16.01.09 20:57 Flare Trykkavlastning avbrytes manuelt Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Blowdown manually aborted Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Fakkel nivå går utover ESD-sensorens måleområde 16.01.09 20:56 – 21:05 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Flare drum level goes outside ESD sensor range Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Fakkel nivå går utover ESD-sensorens måleområde Filter XV

sprengblekk trykksensor aktiveres og initierer ESD2 16.01.09 21:05:08 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Backpressure means that burst disc pressure switch activates ESD2 Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Baktrykk medfører at sprengblekk trykksensor aktiveres og initierer ESD2 Filter XV

ESD 2 stenger bare noen ventiler da noen ventiler er 16.01.09 21:05 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) ESD2 only shuts some valves as some are manually overriden Gas In Gas Out F Distribution Compressor Suction Cooler (typical) ESD 2 stenger bare noen ventiler da noen ventiler er overstyrt manuelt Filter XV

Trykksensor inhibiteres 16.01.09 21:05:18 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Pressure switch overridden Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Trykksensor inhibiteres Filter XV

sprengblekk trykksensorer på kjøler 2 aktiveres og initierer ESD2 16.01.09 21:07:37 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Pressure switch on cooler 2 bursting discs activates ESD2 Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Overstyrte ventiler lukkes manuelt 21:07 Tilførsel av vann til 16.01.09 21:07 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Overridden valves closed manually Flow of water to flare drum stops Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Tilførsel av vann til fakkeldunk opphører Filter XV

Fakkeldunk er overfyllt ESD2 initierer trykkavlastning 16.01.09 21:08 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Fakkeldunk er overfyllt Flare drum is overfilled ESD2 activates blowdown Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Trykktransmittere viser 6 barg hvilket indikerer væskemedrivning i fakkelrør Personell observer unormale flammer 16.01.09 21:08 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Pressure transmitters on flare drum outlet shows 6barg which demonstrates liquid carry over to flare boom Operators notice unusual flare patterns With some liquid in base of drum there is less frequent spurious level trips. Normal level about 30% Maximum pressure in process in second blowdown was 15barg. Flare design pressure is 14.5barg. Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV Ved noe væske i bunn av tank er det erfart en lavere frekvens av feilaktig aktivering. Væskenivå i fakkeldunk normalt omtrent 30% ~20m3 Maks trykk i prosessen ved andre gangs aktivering av trykkavlastning var 15barg, fakkel designtrykk er 14,5barg.

Prosessen trykkavlastes Sjøvannpumpen stoppes Nivå i fakkeldunk dreneres Sprengblekk skiftes Prosessen normaliseres 16.01.09 21:08  Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Process is blown down Seawater pump stopped Level in flare drum drained down Bursting disc changed Process returned to normal Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Hvorfor gikk det galt.........noen av grunnene Prosess design Mangelfullt design av termisk trykkavlastningsventil for kjøler Manglende indikasjon for aktivering av sprengblekk (for treg respons) med manglende ESD-aktivering som følge Scenario ikke tilstrekkelig behandlet i HAZOP Nivåinstrumentering upålitelig (mange feilaktiveringer) Alle tre nivåinstrumenter på fakkeldunk er av samme modell Alarmpresentasjon i kontrollrom Mange feilalarmer gir liten tillit til alarmsystemet Manglende eller dårlig alarmtekst Høyt antall alarmer Inhibitering av nivå- og trykktransmittere og overstyring av isoleringsventiler Inhibiteringer foretatt uten tilstrekkelig risiko analyser Lett tilgang til inhibiteringer Manglende etterlevelse av prosedyrer Manglende forståelse av risikobilde Sikkerhetskultur Why did it go wrong....some of the reasons Process design Poor design of thermal expansion PSV on cooler Poor design of burst disc failure indication (too slow) and it did not activate ESD on burst disc failure Scenario not thought about properly in HAZOP Level instrumentation unreliable (many spurious failures) All 3 level instruments on the flare drum were of same type Alarms in control room Many spurious alarms led to little faith in alarm system Missing or bad alarm descriptions Many alarms Inhibiting of level and pressure transmitters and manual use of isolation valves Inhibits put in place without associated risk assessments Easy access to inhibits Procedures not followed Poor understanding of risk overview Safety culture

Potensial i hendelsen Potential of event

Faktisk konsekvens Ingen skade på personell eller materiell Unormal fakkling, overstrømning av hydrokarbon væske til fakkeltårn Produksjonstap Actual consequence No people hurt and no damage to equipment Abnormal flaring, carryover of hydrocarbon liquid to flare tower Production loss

Potensial I forhold til omstendighetene ved hendelsen Potensial for større mengde flytende hydrokarboner ut av fakkel Potensial for eskalering på grunn av brann på dekk Større materielle skader og langt produksjonsavbrudd Potential In line with the circumstances of the event Potential for more hydrocarbon liquid from flare tip Potential escalation due to fire on deck More serious equipment damage and long production outage

Potensial ved hendelsen I verste fall… Dersom trykkavlasting av anlegget med fullt produksjonstrykk skjer samtidig som flammedunken er overfylt og deler av fakkelsystemet er væskefyllt, kan lokale transiente overtrykk oppstå som er høyere enn designtrykk for fakkelsystemet Kan føre til hydrokarbonlekkasjer andre steder enn ved fakkelutløp Kan gi antennelse/eksplosjon Større materielle skader og langt produksjonsavbrudd Potential of incident In the worst case... If the topsides blowdown from full pressure happens at the same time as the flare drum is overfilled and parts of the flare system are liquid full, local transient overpressures could lead to pressures above flare system design Could lead to hydrocarbon leaks at locations other than just the flare tip Could lead to ignition/explosion More serious equipment damage and long production loss

Lignende hendelse Alvheim (uken etter) Similar incident on Alvheim (the week after)

During normal production on 22nd Jan Under normal produksjon 22. januar 22.01.09 14:00 Flare During normal production on 22nd Jan Feilaktig PSD3 Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Spurious PSD3 Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Under normal produksjon 22. januar 22.01.09 14:00 Flare PSD nivåtransmitter inhibiteres Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) PSD transmitter inhibited Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Sjøvannspumpe stopper Strømkutt 23. januar 23.01.09 15:16 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) SW pump stops and activates PSD3 Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV Sjøvannspumpe stopper og initierer PSD3

PSD3 isolerer kjølerne 15:16 23.01.09 PSD3 isolates coolers Flare M Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) PSD3 isolates coolers Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

En kjøler deisoleres 16:14 manuelt 23.01.09 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) One cooler de-isolated manually Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Sjøvannspumpe startes 23.01.09 16:52 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) SW pump started Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV Sjøvannspumpe startes

Vannhammer slår igjennom sprengblekk 16:52 Blir ikke detektert 23.01.09 16:52 Flare Blir ikke detektert Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Water hammer breaks bursting disc. This is not detected on transmitter Flare drum starts to fill with water ~1200m3/hr Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV Fakkeldunk begynner å fylles med vann ~1200m3/h

16:53:44 PSD nivå nåes, men er inhibitert 23.01.09 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) PSD level reached but it is inhibited Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV PSD nivå nåes, men er inhibitert

16:58:52 ESD nivå nåes 23.01.09 ESD level reached Flare M Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) ESD level reached Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV ESD nivå nåes

ESD2 isolerer kjølerne 16:59 En av ventilene feiler 23.01.09 16:59 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) ESD2 isolates coolers One of valves fails partially open, but shows closed Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV En av ventilene feiler i delvis åpen posisjon, men viser stengt

Nivået i fakkeldunk fortsetter å stige, men med en lavere rate 23.01.09 16:59 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Level in flare drum continues to rise, but at a lower rate due to partially closed valve Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV Nivået i fakkeldunk fortsetter å stige, men med en lavere rate pga. delvis stengt/åpen ventil

ESD2 aktiverer trykkavlastning Personell observerer dråper fra fakkel 23.01.09 16:59 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) ESD2 activates blowdown Operators observe drops from flare tip Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Operatør stenger manuelt pumpen, og stopper fylling av fakkeldunk 23.01.09 16:59 Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Operator manually stops SW pump and flare drum filling stops Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV Operatør stenger manuelt pumpen, og stopper fylling av fakkeldunk

Common cause failure Flare M Dehydration Inlet Cooler HP Flare KO Drum Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Common cause failure Flare M Dehydration Inlet Cooler HP Flare KO Drum Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Common cause failure Flare M Dehydration Inlet Cooler HP Flare KO Drum Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Design oppfyller ikke krav til to uavhengige barrierer Flare Sea Water Return XV Thermal Relief Burst Discs PST 0147 ESD Shell Press PT 0106 Flare Header 0151 PST PST 0152 PSD ESD M Sea Water Return Gas In LST 0132 LST 0133 LT 0135 Flare Meter Gas Out XV Dehydration Inlet Cooler Thermal Relief 0158 LT HP Flare KO Drum XV Burst Discs PST 0381 ESD Low Point Level PT 0306 Shell Press To Closed Drain Sea Water Lift Pump (cooling) Design does not meet requirement for two independant barriers Gas In Gas Out F Distribution Compressor Suction Cooler (typical) Filter XV

Forbedringer Ny instrumentering for deteksjon av sprengblekk aktivering (samt nedsatt settpunkt) Oppgradering av nivåinstrumentering Funksjonelt forskjellige instrumenter for PSD og ESD SIL3 krav til ESD nivå nedstenging ESD nivå aktivering stenger sjøvannspumper direkte Etablering av uavhengig sekundær barriere Stor oppgradering av kontrollsystem; alarmfiltrering, alarmbeskrivelser, bildepresentasjon etc. Økt fokus på kompetanseheving og bygging av sikkerhetskultur Improvements New instrumentation for detection of bursting disc failure (also reduced set point) Upgraded level instrumentation Functionally different instruments for PSD and ESD SIL3 required for ESD level shut down ESD activation stops SW pump directly Establishing independant second barrier Big upgrade of control system; alarm filtering, alarm descriptions, picture layouts etc Increased focus on competence building and building safety culture

Erfaringsoverføring Passing on the learnings

Erfaringsoverføring Tilsvarende hendelse allerede kjent i industrien -Similar event already known in industry -Event could have been avoided if lessons had been transferred Hendelsene kunne ved erfaringsoverføring vært unngått

Hendelse på FPSO Alvheim i januar 2009 TEKNA Prosessikkerhet