Post on 06-Mar-2018
FABIG TECHNICAL MEETING REVIEW
Explosion Analysis of an Onshore Plant with Worked Examples, Quantitative Risk Analysis,
Probabilistic Explosion & MDOF Response Analysis
Pol Hoorelbeke
Total Petrochemicals
Bob Brewerton/Jerome Renoult
GexCon AS
For further information please contact:Pol HoorelbekeTotal PetrochemicalsTelephone: + 32 02 2883950Fax: + 32 02 2883152E-mail: pol.hoorelbeke@total.com
Jerome Renoult Bob BrewertonGexCon AS GexCon ASTelephone: + 47 55 574330 Telephone: + 44 (0) 1732 465465Fax: + 47 55 574331 Fax: + 44 (0) 1732 469735E-mail: rwb@natabelle.co.ukjerome@gexcon.com E-mail:
Vapour Cloud Explosion Hazards in Petrochemical onshore facilities
Pol HoorelbekeTotal Petrochemicals HSE
2 20050406, FABIG meeting
ExxonMobil
Shell
BP
Total
ChevronTexaco
ENIConocoPhillips
PDV
Gazprom
Non-OECD based
OECD based
Petronas
Qatar Petroleum
Pemex Saudi Aramco
Saudi Aramco
Adnoc
NIOC
Sonatrach
17%Exxon Mobil
Royal Dutch/Shell
BP
ChevronTexaco
Total
ConocoPhillips
ENI
Pemex
PDV
INOC
KPCAdnocPetrobras
Others NOC
Saudi Aramco
NIOC
OECD based
FSU
China
Non-OECD based
NNPC
Petronas
Libya NOC Sonatrach
Total Petrochemicals is part of the Total group
Oil producers
I.O.C.
N.O.C.
Gas producers
I.O.C.
N.O.C.
17%
Russiaand other
CIS
3 20050406, FABIG meeting
Total
47 Sites
40 Sites
179 Sites
214 Sites61 Sites
14 Sites
• 110,000 employees
• Turnover: 110 G€
• An energy company Exploration & Production
Gaz & Electricity
Refining & Marketing
Chemicals
555 high risk sites worldwide
4 20050406, FABIG meeting
Total Petrochemical sites
• Europe: Feluy
Feluy Research
FAO Antwerp
Antwerp Elastomers
Carling
Feyzin
Gonfreville
Notre Dame de Gr.
Lavera Naphta Chimie
Lavera APPRYL
El Prat
Stalybridge
• Middle East Umm Said
“Rass Laffan”
• Asia Sanshui
Singapore
Daesan
Ayutthaya
• USA La Porte
La Porte
Research
Carville
Cosmar
Bayport
Port Arthur
• Others Houston
Brussels
Paris
Lyon
Ets Lacq / Mont
Beijng
Agents
5 20050406, FABIG meetingTypical petrochemical onshore plant
6 20050406, FABIG meeting
Historical evidence of VCE hazards
• Offshore industry has a relatively recent vapour cloud explosion explosion history: The piper Alpha explosion on the 6th of July 1988 was one of the first
major devastating explosions in offshore. There were 226 people on theplatform at the time of the accident; only 61 survived.
• Onshore Hydrocarbon industry has a much longer vapour cloudaccident history: On the 29th of July 1943 a release occurred from a rail car in the BASF
works at Ludwigshaven. The rail car contained 16,5 te of a mixture of 80% butadiene and 20% of butylene. A vapour cloud formed and ignited. 57 people were killed and 439 injured. The explosion demolished a block 350 m x 100m;
On the 23th of March 2005 a devastating explosion occurred at the BP-Amoco refinery at Texas City. At least 15 people were killed and more than70 injured.
7 20050406, FABIG meeting
Cracker experience (1975 – 2003)Number of crackers in operation (2002)
78
56
56
37
20
17
6
270
0 50 100 150 200 250 300
Asia
Western Europe
North America
Eastern Europe
Latin America
Middle East
Africa
TOTAL
5564TOTAL
98Africa
191ME
342LA
917EU
1270NA
1288Asia
1458WE
# cracker.yearsRegion
# of major accidents in WE region: 7 Major explosion: 4.8 E-3 per cracker.year
Vapour Cloud Explosions : a real risk in Petrochemicals
8 20050406, FABIG meeting
• Total Petrochemicals Data Analysis on PE units
ATEC database : 853 PE units in the world
Experience 1987-1996 : 4.979 reactor-line.years
# accidents: 3
99% confidence interval: 7.05 E-5 → 2.29 E-3 per reactor-line.year
Average: 6.25 E-4 per reactor-line.year
• Total Petrochemicals Data Analysis on Low pressure PE reactor-line
experience 1975 – 2003: 6 131 reactor-line.years
3 « Pasadena like accidents » have been identified in this period
99% confidence interval: 5.51 E-5 → 1.79 E-3 per reactor-line.year
Average: 4.89 E-4 per reactor-line.year
Vapour Cloud Explosions : a real risk in Total Petrochemicals
Total Petrochemicals : one VCE every 80 years
9 20050406, FABIG meeting
Some characteristics of petrochemical onshore installations in relation to VCE hazards
• Large congested areas. A typical congested volume of a large steam cracker could be 150 m x 80 m x 15 m
• Large quantities of flammable materials. A typical major vapour cloud can contain 10 – 50 tons of flammableproducts
• Several zones with dense congestion
10 20050406, FABIG meeting
Some characteristics of petrochemical onshore installations in relation to VCE hazards
11 20050406, FABIG meeting
Some characteristics of petrochemical onshore installations in relation to VCE hazards
12 20050406, FABIG meeting
VCE approach in onshore industry
• The major concern for onshoreinstallations has been the offsite risk;
• Seveso legislation put emphasis on accident prevention (for onsite andoffsite people) and effect mitigation for off site people
• Simple methods (TNT equivalent, ME, Baker Strehlow, etc.) allow goodpredictions for damage potential in thefar field
Offsite property damage cost
of Toulouse accident is
currently estimated at 1,8 G€
33
31
13 20050406, FABIG meeting
Simple methods(TNT equivalent, ME) give a goodidea for the far fieldblast load potential
Overpressure-distance for case "a" and case "b"
(ME method & TNT equivalent)
10
100
1000
10000
100000
10 100 1000
Distance (m)
Ov
erp
res
su
re (
mb
arg
)
ME-5a ME-5b ME-7a ME-7b ME-10a
ME-10b TNTa TNTb FLACS
14 20050406, FABIG meeting
BP-Amoco Refinery Texas City explosion23th of March 2005
1
10
100
1000
0 100 200 300 400 500 600 700 800 900 1000
Distance from Cloud Epicentre (m)
Calc
ula
ted
Bla
st
Overp
ressu
re (
mb
arg
)
ME curve 5
ME curve 6
ME curve 7
ME curve 8-10
15 20050406, FABIG meeting
Conclusions
• The situation till say 5 years ago was:
Simple methods allowed to cope with the main concerns (i.e.offsiterisk assessment)
Onshore hydrocarbon process industries did not make the sameprofits as offshore facilities and advanced technologies (3D modelling) were expensive
• Even today there is still an important gap between explosion research (theoretical and experimental investigations) andapplication of this research in the plants
• Accidents like Skikda clearly demonstrate the necessity to:
Use advance technology for onshore plants;
16 20050406, FABIG meeting
Vision of Total Petrochemicals
• Accidents like Skikda clearlydemonstrate the necessity to perform risk assessments ofexplosion effects in the nearfield;
• The near field can only bestudied by means of advancedtechnologies
Technology
Investment
Advanced
modelling
Simple
empirical
correlations
Computational
Fluid Dynamics
• The results of extensive research that has been done over the last 30 yearsshould be applied in the field.
• There is a enormous amount of data and knowledge available but large parts of it remain within a select group of experts;
17 20050406, FABIG meeting
Skikda, Algeria, Jan 20, 2004
Damage:
23 workers were killed.
9 were missing.
74 were injured.
$800,000,000 (U.S.) estimated property damage.
Quote from LNGWM Alert,
Jan 22, 2004
“The fact that the boiler explosion caused damage to the nearby process equipment raises questions about separation distances in this 1970s vintage process facility”
1 FABIG Technical Meeting – 6th and 7th of April 2005
FABIG Technical Meeting – April 2005
Probabilistic Explosion Analysis
in an Onshore Plant
Presented by Pol Hoorelbeke,
Jérôme Renoult & Robert Brewerton
2 FABIG Technical Meeting – 6th and 7th of April 2005
GexCon is...
Clients
ProcessSafety Dept
International, independent Analyst Alliance Established through Research Institute CMI 1970s Experienced consultants within ATEX/Seveso II, QRAs, EPAs, hazid/hazop and other diciplines Development, sale and support of advanced CFD software with world-wide distribution Protective equipment & system testing and certification
SimulationSoftware
R&DDept
GasExplosion &
Fire Consulting
Dept
Xafe AS(Stavanger)
Lilleaker Consulting
(Oslo)
Associated partnersGexCon AS
A company that offers complete services towards process industries on explosion safety and fire
3 FABIG Technical Meeting – 6th and 7th of April 2005
GexCon provides...• First class competent consultants and project managers
– Cross-diciplinary and fundamental background and approach
– Reputable and in-depth competence – expert level
• Oil and gas safety assessments– QRAs for Topsides, incl. FPSOs/FSOs
– CFD and qualitatively based risk assessments - onshore installations incl. transport systems
– Design Accidental Load (DAL) analysis
• Dust fire and explosion risk– ATEX Explosion Protection Services
– Design Accidental Load
– Area Classifications
– CFD based and qualitative Risk assessments for process facilities and transport systems
• Simulation Software– CFD code FLACS – ventilation, dispersion, explosion/fire, analysis (gas, aerosols, explosives)
– CFD code DESC – ventilation, dispersion, explosion/fire, analysis (dust)
• Experiments & testing (2005)– EU- and JIP-backed activities on gas dispersion, LNG and Hydrogen
– Testing of tools for ’hot work’ in potentially explosive atmospheres
– Independent small to large scale testing of new mitigation principles/systems - certification
4 FABIG Technical Meeting – 6th and 7th of April 2005
The problem
Existing unit
Future unit
What is the risk of escalation in the
future unit in case of an explosion
occurs in the existing unit?
5 FABIG Technical Meeting – 6th and 7th of April 2005
Step by step
The probabilistic explosion analysis is performed based on
advanced CFD simulations using the FLACS code developed by
GexCon. The main steps in the analysis are:
- Build a 3D geometrical model
- Ventilation simulations
- Dispersion simulations
- Explosion simulations
- Explosion risk based on a time dependent ignition model
Structure response analysis
Blast or pressure exceedance curves
6 FABIG Technical Meeting – 6th and 7th of April 2005
Building a 3D model in FLACSBy importing a CAD model (Microstation or PDMS)
7 FABIG Technical Meeting – 6th and 7th of April 2005
Building a 3D model in FLACSFrom drawings and/or photographs
8 FABIG Technical Meeting – 6th and 7th of April 2005
Building a 3D model in FLACSUsing the Anticipated Congestion Method developed by GexCon
9 FABIG Technical Meeting – 6th and 7th of April 2005
Building a 3D model in FLACS
10 FABIG Technical Meeting – 6th and 7th of April 2005
FLACS dispersion simulations
There is an infinite number of possible leak scenarios.
Assumptions need to be made in order to reduce the study to a
limited number of representative scenarios. ≈ 300 simulations are
performed.
Following assumptions are made:
- Ventilation conditions
- Gas composition
- Leak locations
- Leak directions
- Leak rates
- Segment sizes
11 FABIG Technical Meeting – 6th and 7th of April 2005
Ventilation conditionsWind direction frequency
0
5
10
15
20346-015
016-045
046-075
076-105
106-135
136-165
166-195
196-225
226-255
256-285
286-315
316-345
36.5%
22.2% 23.3%
Total = 82%
12 FABIG Technical Meeting – 6th and 7th of April 2005
B HGFEDC QPNML R
Leak locations
13 FABIG Technical Meeting – 6th and 7th of April 2005
B HGFEDC QPNML R
DF402
DF702
R401
E733-S
C701
E733-T
DC301DF401 DF303AE734-S
E309-S
G302A
D723
C301
C401
G722
R202 R201
R200P601A
P301
C302
P702
P705
G720
D720
BE503A
C501
P501
BE705A
D302
G301A
P302
DF201A
Leak locations
14 FABIG Technical Meeting – 6th and 7th of April 2005
B HGFEDC QPNML R
DF402
DF702
R401
E733-S
C701
E733-T
DC301DF401 DF303AE734-S
E309-S
G302A
D723
C301
C401
G722
R202 R201
R200P601A
P301
C302
P702
P705
G720
D720
BE503A
C501
P501
BE705A
D302
G301A
P302
DF201A
Leak locations
15 FABIG Technical Meeting – 6th and 7th of April 2005
46%4%
13%
11% 13% 13%
Leak locations and frequencies
16 FABIG Technical Meeting – 6th and 7th of April 2005
Leak rates and frozen cloud assumption
96 kg/s> 64 kg/s
48 kg/s32 – 64 kg/s
24 kg/s16 – 32 kg/s
12 kg/s8 – 16 kg/s
6 kg/s4 – 8 kg/s
3 kg/s2 – 4 kg/s
1.5 kg/s1 – 2 kg/s
0.75 kg/s< 1 kg/s
Repr. Leak rateLeak rates
Simulated
Estimated
17 FABIG Technical Meeting – 6th and 7th of April 2005
Dispersion simulations
Flammable gas cloud
18 FABIG Technical Meeting – 6th and 7th of April 2005
Dispersion simulations
Flammable gas cloud
19 FABIG Technical Meeting – 6th and 7th of April 2005
FLACS explosion simulations
There is an infinite number of possible explosion scenarios.
Assumptions need to be made in order to reduce the study to a
limited number of representative scenarios. ≈120 simulations are
performed.
Following assumptions are made:
- Gas composition
- Gas cloud sizes
- Gas cloud locations
- Ignition locations
20 FABIG Technical Meeting – 6th and 7th of April 2005
B HGFEDC QPNML R
Gas cloud and ignition locations
7 gas cloud sizes:
4%, 7%, 15%, 22%, 36%, 50% & 100%
21 FABIG Technical Meeting – 6th and 7th of April 2005
Explosion simulations
Pressure
22 FABIG Technical Meeting – 6th and 7th of April 2005
Explosion simulations
Pressure
23 FABIG Technical Meeting – 6th and 7th of April 2005
Explosion simulations
Flame
24 FABIG Technical Meeting – 6th and 7th of April 2005
Ignition modelling
• Ignition sources
– Two types of source: continuous and discrete
• Continuous ignition sources will ignite the flammable gas cloud as soon as it reaches the source.
• Discrete ignition sources can ignite a combustible gas cloud at any moment.
– Centre and end ignitions
• Continuous ignition sources are associated to end ignitions only.
• Discrete ignition sources are associated to both centre and end ignitions (50/50).
25 FABIG Technical Meeting – 6th and 7th of April 2005
Ignition modelling
• Ignition intensitiesContinuous Adjustment Factors for Ignition Source Categories # items or sq. meter Adjust Continous
Gas Age Maintenance Manning Technology Overall Module Total
Hot work (# hours per 365*24h) 1.83E-02 1.83E-02
Pump 9.60E-05 Pump 24 0.459 1.06E-03
Compressor 2.30E-03 Compressor 9 0.459 9.50E-03
Generator 3.50E-03 Rotating machinery 0.9 0.85 1 0.6 0.459 Generator 0 0.459 0.00E+00
Electrical equipment * 2.60E-06 Electrical eq. 0.9 0.9 1 0.6 0.486 Electrical eq. * 3000 0.486 3.79E-03
Other equipment * 2.60E-06 Other eq. 0.9 0.9 1 0.6 0.486 Other eq. * 3000 0.486 3.79E-03
Other * 1.30E-06 Other 1 1 1 1 1 Other * 3000 1 3.90E-03
Personnel * 3.00E-06 Personnel 1 0.95 0.6 1 0.57 Personnel * 3000 0.57 5.13E-03
* per m2 exposed to gas SUM 4.54E-02
Discrete Adjustment Factors for Ignition Source Categories # items or sq. meter Adjust Discrete
Gas Age Maintenance Manning Technology Overall Module Total
Pump 2.10E-07 Pump 24 0.459 2.31E-06
Compressor 5.10E-06 Compressor 9 0.459 2.11E-05
Generator 6.20E-06 Rotating machinery 0.9 0.85 1 0.6 0.459 Generator 0 0.459 0.00E+00
Electrical eq. * 2.70E-08 Electrical eq. 0.9 0.9 1 0.6 0.486 Electrical eq. * 3000 0.486 3.94E-05
Other equipment * 2.10E-09 Other eq. 0.9 0.9 1 0.6 0.486 Other eq. * 3000 0.486 3.06E-06
Other * 1.70E-08 Other 1 1 1 1 1 Other * 3000 1 5.10E-05
Personnel * 4.00E-08 Personnel 1 0.95 0.6 1 0.57 Personnel * 3000 0.57 6.84E-05
* per m2 exposed to gas SUM 1.85E-04
26 FABIG Technical Meeting – 6th and 7th of April 2005
Ignition modellingProbability of exceedance – Sensitivity cases
– Offshore philosophy for shutting down ignition sources
• Gas detection = low alarm 15s after leak start, high alarm 30s after leak start
• ESDV = closed 60s after detection
• Continuous ignition sources start to shut down on gas detection, and are closed
2min after gas detection
• Discrete ignition sources reduced to 25% (pump, comp. and equip.) and 50% (elec.) on high alarm, personnel evacuated 30s after high alarm
– Onshore philosophy for shutting down ignition sources
• ESDV = closed 120s after detection
• Continuous ignition sources are not shut down, except for hot work (120s after
leak start) and personnel (120s after leak start)
• Discrete ignition sources: see model
27 FABIG Technical Meeting – 6th and 7th of April 2005
Ignition modelling
Offshore philosophy "
Onshore philosophy " No reduction, except for hot work and personnel
Reduction of continuous ignition sources
0
0.2
0.4
0.6
0.8
1
1.2
0 30 60 90 120 150
Time (s)
Re
du
cti
on
fa
cto
r (-
)
Rotating Machinery
Electrical eq., other eq., personnel
28 FABIG Technical Meeting – 6th and 7th of April 2005
Ignition modellingReduction of discrete ignition sources
0
0.2
0.4
0.6
0.8
1
1.2
0 15 30 45 60 75 90 105 120 135 150
Time (s)
Red
ucti
on
facto
r (-
)
Rotating machinery
Electrical eq. & other eq.
Personnel
Offshore philosophy "
# Onshore philosophy
Reduction of discrete ignition sources
0
0.2
0.4
0.6
0.8
1
1.2
0 300 600 900 1200 1500 1800 2100 2400 2700 3000
Time (s)
Re
du
cti
on
fa
cto
r (-
)
Other sources
Personnel
29 FABIG Technical Meeting – 6th and 7th of April 2005
Explosion frequenciesFrequency of ignited gas clouds
1.00E-09
1.00E-08
1.00E-07
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1 2 3 4 5 6
Gas cloud category (-)
Cu
mu
lati
ve f
req
uen
cy (
n/y
)
Leak 1
Leak 2
Leak 3
Leak 4
Leak 5
Leak 6
Total
30 FABIG Technical Meeting – 6th and 7th of April 2005
Probability of exceedance
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
0.00 0.10 0.20 0.30 0.40 0.50 0.60
Pressure (barg)
Pro
ba
bilit
y (
n/y
)
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20
0.25
0.00 0.20 0.40 0.60 0.80 1.00 1.20
Time (s)
Pre
ss
ure
(b
arg
)
31 FABIG Technical Meeting – 6th and 7th of April 2005
Example of projectsFeluy (Total) – Polymers
Kollsnes (Statoil) – Gas treatment
Snøhvit (Statoil) – Liquified natural gas
Gonfreville (Total) – Petrochemicals
Page 1
1 Fabig seminar Jan 2005
1) MDOF Explosion response analysis of large refinery plant
By R W Brewerton (GexCon) and C Izatt ( Ove Arup & Partners). April 2005
•Large pressure vessel on high saddles•70m high multi-Loop Reactor •More complex equipment: (future)
www.gexcon.com
2 Fabig seminar Jan 2005
2) The problem
Existing unit
Future unit
What is the risk of escalation in the future
unit in case of an explosion occurs in the
existing unit?
Page 2
3 Fabig seminar Jan 2005
3) Selected equipment
Raised Vessel 11.5m longx 3.3m dia(MDOF)
Loop reactor 70m high(MDOF)
?
4 Fabig seminar Jan 2005
4) Pressure vessel 11.5m x 3.3m dia: Meshing for DYNA analysis
Concrete part
Steel part
Page 3
5 Fabig seminar Jan 2005
5) Saddle and shell elements for NLFEA
6 Fabig seminar Jan 2005
6) DLM* Method for explosion loading on large obstacles
• DLM = Direct Load Monitoring
• Dominant loading is often like inertia component of wave loading on submerged structures.
Source: HSE OTO 1999-046 ch 6 and FABIG TN8.
Page 4
7 Fabig seminar Jan 2005
7) Selection of explosion loading
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
0.00 0.10 0.20 0.30 0.40 0.50 0.60
Pressure (barg)
Pro
bab
ilit
y (
n/y
)
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20
0.25
0.00 0.20 0.40 0.60 0.80 1.00 1.20
Time (s)
Pre
ss
ure
(b
arg
)
8 Fabig seminar Jan 2005
8) Loading Method
501 502
503 504
505
506•Select deterministic load case(s), in this example
for 10-4 return event
•Select upstream and downstream monitor points
(X & Y loads)
•Find pressure at each point (in time domain)
•Calculate differential pressure (eg 504-503, 502-
501) and 506-505
•Decide on pressures on saddle supports
Page 5
9 Fabig seminar Jan 2005
9) Point pressure-time histories
•Evaluation of other factors: reflection possibility, saddle
loads, attached pipes, what load factor (1.0, 1.5?)
•Decide whether negative phase to be included: look at the
deflection response for this:
10-4 blast pressures on PP4 - D302
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20
0.25
0.75 0.80 0.85 0.90 0.95 1.00 1.05Time [s]
Pre
ss
ure
[b
ar]
Point 501
Point 502
Point 503
Point 504
Point 505
Point 506
10 Fabig seminar Jan 2005
•Judge movements particularly in relation to pipe
flexibility and stresses.
10) Response: deflections (positive loading phase only)
Page 6
11 Fabig seminar Jan 2005
11) Response: Stresses and deflections
12 Fabig seminar Jan 2005
•Max Von Mises stress 103
MPa, UF approx 0.4 hence
OK.
•Obtain force plot and:-
•Code check the support
bolts eg to EC3 (hand calcs)
•Code check concrete and
foundation eg to EC code or
ACI
12) Response: Saddle stresses
Page 7
13 Fabig seminar Jan 2005
13) Concrete saddle supports
Moment range for D302 support
14 Fabig seminar Jan 2005
14) Loop reactor model
Page 8
15 Fabig seminar Jan 2005
15) Explosion Loading on medium - small obstacles (DLM or drag Method)
Source: HSE OTO 1999-046 ch 6.
• The monitor points are far from the obstacle .
• Either: use smaller control volumes at the obstacle or use drag method
• In far-field include blast overpressure impulse (with reflection effect)
16 Fabig seminar Jan 2005
16) Drag Coefficients CD
Source: Baker, W E, Cox, P A Westine, P S, Kulesz J J and Strehlow R A (1983)
Explosion Hazards and Evaluation, Elsevier Scientific Publishing Company.
•“Drag” pressure = 0.5 V2.
•Pipe design load = 0.5 CD V2 * D
where D is pipe diameter including insulation.
Page 9
17 Fabig seminar Jan 2005
•Drag varies with height
•Use CD value of 1.2
17) Drag pressure – time histories
18 Fabig seminar Jan 2005
•Peak overpressure is twenty times as high as drag pressure
at this distance (much more equal in near field)
•Treat as Zero-rise-time impulse, with shock reflection factor
of 2.0 and clearance times according to “Explosive shocks in
air” by Kinney and Graham (Springer Verlag Berlin, New York).
18) Explosion overpressure time histories
Fieldpressure
Net force applied to member,(positive phase only)
duration depends on member size
Page 10
19 Fabig seminar Jan 2005
•Natural period 1.4 secs therefore response is in “Impulsive”
regime.
•Low DLF for primary: secondary modes will be important.
19) Response: deflections
20 Fabig seminar Jan 2005
•Plot max value from dynamic
simulation.
•Assess member resistance.
•Member is a large (hot) coaxial
pipe in steam jacket and both
are structural.
•Nodes are full-strength
gussetted H beam to steam
jacket spool - good for ductility
as in seismic design.
20) Response: Beam forces (max)
Page 11
21 Fabig seminar Jan 2005
A201 concrete columns - Moment-axial force demand interaction
--- Bending-axial demand
--- Bending-axial ultimate capacity
21) Response: Concrete column resistance & UF (max)
22 Fabig seminar Jan 2005
22) Tank and support structure: relative displacements (important for interconnecting pipes)
•15.5mm max
Page 12
23 Fabig seminar Jan 2005
23) Response animation: deflections x 50
24 Fabig seminar Jan 2005
24) Response animation: deflections (x50) & beam forces
Page 13
25 Fabig seminar Jan 2005
25) Response: deflections (x50) & beam forces at tank
26 Fabig seminar Jan 2005
26) Future study: 60 pipe pipe-rack pipe forces: drag
or overpressure dominating?
?
Page 14
27 Fabig seminar Jan 2005
27) Recommendations & discussion points
• MDOF analysis is the most reliable method for complex plant.
• Response is like seismic response. Dynamic resistance will not happen on its own: it needs to be built in at early design stage.
• Loading needs careful definition.
• For avoidance of unacceptable domino effects criteria such as10-4
return have to be used carefully.
• Maintain load factor >1.0 (eg 1.5) through design. Only allow 1.0 for final design and ALARP decisions.
• Implement load factor through difference between assessed probable loading and specified design resistance.