Design of Protection Structures Off and Onshore and Role of FLACS

Transcription

1 Design of Protection Structures Off and Onshore and Role of FLACS By Bob Brewerton Inoventech Ltd

2 Design of Protection Structures Off and Onshore and Role of FLACS Existing applications of protection structures in oil & gas Offshore blastwalls Explosion relief panels Offshore escape tunnels Future applications Explosion and fire resistant containment systems for Li-ion batteries for cars and other applications Acknowledgements: GEXCON AS for dispersion and explosion simulations Booth Industries Ltd (Bolton) for hardware pictures Arup Advanced Technology Group for Non Linear FEA

3 Piper alpha July 1988

4 Basic causes 167 Fatalities on UK N Sea s largest production platform (1988) Initiating event was failure of wrongly installed small PSV Consequence exacerbated by: 1. Proximity of process module to control room and weak Durasteel panel blastwall. 2. Inflated loss of life due to lack of SSIV,s to isolate Piper Alpha from incoming / outgoing pipelines which had more than 200mmscf of gas inventory. 3. By 1981 SSIV s had been perfected but Occidental did not install them. The DoE had not asked for them. Major changes to offshore safety regime followed from public enquiry, with eventual worldwide effect (e.g. ISO )

5 Advantages of stainless steel for protection structures subject to explosion and fire Strength Ductility Fire resistance Corrosion resistance and durability

6 Stress-strain curves for stainless steel and carbon steel % strain (Euroinox guide)

7 Full scale crushing test on 4mm thick duplex stainless blastwall components shows ductile behaviour without rupture. (height 1.2m) (Chapman Dowling - Imperial College 1991)

8 Strength retention of carbon and stainless steels at elevated temperature. (Ref 3 Advances in the use of high strength carbon and stainless steels offshore, Fabig TM ) Conventional operating area for fire resistant structures and bulkheads Zone of interest for the products presented as designs ensure that none are load-bearing during a fire

9 Stainless steel blastwalls Guidance: FABIG TN4 Explosion Resistant Design FABIG TN5 Stainless Steel Blastwalls FABIG Newsletter 68 Developments in Blastwall Layout Design and Assessment

10 Multiple fixed platforms - Buzzard development in UK North Sea, 6 main blastwalls and much other cladding. All stainless steel PS Gas sweetening Drilling risers & wellheads Accommodation & utilities

11 The role of FLACS Tool to provide usable loading information for design of protection structures.

12 Example: part of an onshore chemical plant: FLACS geometry model for explosion analysis (a siting study for a chemical plant expansion)

13 Animation of dispersion of a gas cloud

14 Explosion animation flame growth

15 Pressure wave animation

16 Decay of explosion pressure in far-field (to establish design loadings on buildings and plant)

17 Positions of blast and fire barriers in a typical large offshore process topsides Note red barriers are blast and fire resistant

18 Stainless steel blastwalls in an offshore module Note, structural connection of stainless steel to carbon steel is by welding

19 LSDYNA model for a non-linear analysis of a 9m high duplex SS wall, supported at top and bottom only (Von-Mises Stress)

20 Close-up of upper part showing grade S355 compliant top support and mesh refinement in NLFEA model (principal stress)

21 Definition of elastic and ductile response behaviour of a structure

22 Local buckling failure mode for normal trapezoidal corrugation with b/t ratio 60 (elastic response behaviour)

23 Patented arch profile blastwall improves post-elastic buckling performance Much used for stainless & carbon steel blastwalls UK, Norway, Australia & Azerbaijan.

24 Typical Duplex SS arch profile blastwall keeps resistance up to ductility ratio 4

25 Arch profiles for 3 bar blastwalls destined for offshore Azerbaijan, note fabricated panel on right

26 Explosion relief panels (ERPs): Guidance: FABIG TN2 Explosion Mitigation Systems EN Explosion Venting Devices ATEX FABIG Research Doc R598 Full scale explosion tests on explosion relief panels

27 Explosion relief panels (ERPs): Stainless steel explosion relief panels installed on a gas compressor building in France

28 Transverse section through wall ERP shows how they open in an explosion

29 ERPs viewed from inside. Note, alu foil & chicken wire covered high density rockwool insulation for sound reduction & fire resistance.

30 7.2m long prefabricated roof cassettes for explosion relief of a gas compressor enclosure (UK)

31 Use of FLACS for ERP systems To verify venting efficiency for enclosed spaces To obtain rate of pressure rise during opening and peak pressure building and roof have to resist. NFPA 68 can work where equipment congestion is low but needs generic verification with FLACS (e.g. GdF) Typical Av/Vol =

32 Kollsnes ERPs: full wall coverage

33 Explosion Relief panel before full scale explosion test. (and video of front view showing congested test module)

34 Explosion Relief panel after explosion test to 0.5bar. And video of side view

35 Offshore escape tunnels Guidance: None

36 Offshore escape tunnels, type 1: With type 1 overall strength comes from truss, insulated from SS outer carcass. Inner liner (SS) Ceramic fibre insulation truss Outer carcass is blast & fire resisting Internal view showing liner

37 Type 2 offshore escape tunnel on a 240m long FPSO: Overall strength comes from SS outer carcass (stressed skin). Internal truss is for carcass support to prevent sagging in jet fire after an explosion Escape tunnel 2 3 bar resistance on inboard side

38 Prefabricated Type 2 escape tunnel section This FPSO example has extra width for internal control panels serving nearby external process equipment. The ring frames at supports are thick-wall carbon steel RHS. Note access door.

39 New applications, lithium ion battery containment for: hazards of use Lithium ion batteries can burn/explode if physically damaged or heated. More hazardous than other battery types. Can ignite accidentally due to control failures Once ignited cannot be extinguished in less than 30 mins 1hr, needs 25tonnes of water. Can reignite or explode in the following 24 hours (problem for removal of a car after a crash?) Poisonous acrid smoke given off affects casualties & people nearby Difficult to cope with casualties in a burning wreck High voltage electrocution risk for rescue people first responders to EV fires have to be firemen Lack of experience or proper collated accident data available for training of emergency crew.

40 Tesla S fire at a recharging station in Norway There have been fatalities with electric vehicles (EV s) in accidents due to damage to battery containment.

41 A potential solution, based on minimising risk and consequence uses SS Relief panels, venting downwards, because battery is located just below vehicle occupants in EVs

42 Battery containment function is to reduce consequence from a cell failure or severe crash Provides separation of cells, Explosion relief for internal explosion Resistance for fire and explosion in an adjacent cell. Perforated plate protects against impact from beneath battery set without impeding venting This containment concept has been used in large scale for explosive handling facilities. FLACS version needed to simulate Li-Ion battery explosions Research proposal has stalled due to lack of industry interest.

43 Conclusions 1. FLACS has had a significant historic role in explosion protection design in oil and gas industries. 2. Past major accidents have lead to regulatory and design changes that reduced subsequent fatalities and loss. 3. Electric vehicles are inadequately regulated and currently have major inherent problems that need designing out. 4. GexCon s FLACS research proposal is designed to assist LI-Ion battery containment in a major way but, 5. Just as has been the case in the past, no one appears to be interested in committing research funds to investigating potential major accidents until large numbers of fatalities have occurred.