Hvordan redusere mengden isolasjon NKF Bransjeseminar. Petroleumstilsynet, Stavanger. 03.06.2006 Odd Egil Overskeid Senior Engineer Process June 10, 2016 Slide 1
Fakkelsystem og prosess Teknisk sikkerhet Strålingskrav Lekkasjerate [kg/s] q [w/m²*k] n Isentropisk T1 Fordampningsvarme T2 JT Temperaturer Prosess Material n Boiling liquid June 10, 2016 Slide 2
Brannområder og prosessutstyr Evakuering Eskalering 10 2 Økonomisk verdi Seksjonalisering Prioritering t=? 100 kw/m² Akseptkriterier 350 kw/m² > 2 kg/s q 250 kw/m² 0.1-2 kg/s? LQ P June 10, 2016 Slide 3
Akseptable lekkasjer Det må utarbeides spesifikke kriterier for den aktuelle plattformen Statoil sine standardkriterier: Lekkasjerate beregning Brudd etter 4 min Raten til fakkel er cirka 10 000kg/h=2,78kg/s Orifice er 343mm² Dvs 2,78/343=0,008 kg/(s*mm²) Arealet til 10 rør 3,14*52,48²mm²=2754mm² Lekkasjeraten=0,5*2754*0,008=11kg/s Maks 10 kg/s, dvs øke trykkavlastningsraten. Dersom brudd kan forsinkes til etter 5min Er det akseptabelt med 50kg/s Hvilke belegg kan utsette brudd med 1min? June 10, 2016 Slide 4
Fakkelsystemet - fakkelmodell 450 000 kg/h 125 kg/s 200-300m/s Sonic tip June 10, 2016 Slide 5
UTS kurver og varmekapasitet - bruddstyrken til stål June 10, 2016 Slide 6
Temperaturer i brann og styrken til metall Poolbrann: Global 100 100 kw/m², lokal 150 kw/m2. T=800ºC Liten Jetbrann: Global 0 kw/m², lokal 250 kw/m². T=1000ºC Stor Jetbrann: Global 100 kw/m², lokal 350kw/m². T=1155ºC Fra Scandpower Guideline: June 10, 2016 Slide 7
Brann på hydrokarbonfylt segment - Bruddberegninger T? q P? Fra scandpower guideline: A~D^2 UTS PD^2 D^2-d^2 Ingen sikkerhetsfaktorer June 10, 2016 Slide 8
Von Mises with Lame Theory (rupture stress kriterie) Ductile burst pressure, strainrate June 10, 2016 Slide 9
Temperaturstigning i stål Tilført energi 224 kw/m2 * 0.86 m² * =193 kj/s 0.5 kj / kg*k 26.4 kj/k 193 / 26.4 7 C/s Cirka 420 grader på 1 minutt 1 m 0.86 m² 52.7 kg 10 DD20 103.4 barg 224 kw/m² Dupleks halv vekt i forhold til CS. Dobblet så rask oppvarming. Ikke dobbel styrke. Må øke tykkelsen for å få bruddmargin. June 10, 2016 Slide 10
Trykkavlastning med brann Trykk, temperaturer, faselikevekt Kokende væske, isentropisk gass Varmeovergangstall, veggtykkelser June 10, 2016 Slide 11
Trykkavlastning med brann June 10, 2016 Slide 12
Bruddberegninger June 10, 2016 Slide 13
Bruddberegning rapport June 10, 2016 Slide 14
10 rør 600# (103.4barg design trykk). Tre typer brann June 10, 2016 Slide 15
Løsninger og usikkerhet Varighet Fakkelkapasitet Akseptabelt Isolasjon Modellering Materialdata Scenario June 10, 2016 Slide 16
Konklusjoner Mengden brannisolering reduseres best ved å gjøre et godt fakkeldesign med bruddberegninger og samarbeid med Teknisk sikkerhet Brannisolering bør være et av de siste tiltakene for å tilfredstille akseptkriterier. Degradering av brannisolering Bruddberegninger som viser integrasjon med fakkelkapasitet og rømningsfilosofi bør foreligge eller bør etableres. Nybyggdesign er komplekst Kontinuerlig arbeid med prosss og prosessikkerhet Brannisolering kan ikke fjernes uten videre Ved bruk av bruddberegninger er det vanskelig å snakke om hvor mye isolasjon som er spart, hva skal man sammenlikne med? Sett over 10års perioder er omfanget helt klart redusert. June 10, 2016 Slide 17
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