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Lars Petter Blikom, DNV GL OIL AND GAS: Process safety and availability of Floating Liquefaction topsides
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Lars Petter Blikom, DNV GL OIL AND GAS: Process safety and availability of Floating Liquefaction topsides

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Lars Petter Blikom, Segment Director - Natural Gas, Marketing and Business Development, DNV GL OIL AND GAS delivered this presentation at the 2013 FLNG Forum in Perth. The two day conference brings …

Lars Petter Blikom, Segment Director - Natural Gas, Marketing and Business Development, DNV GL OIL AND GAS delivered this presentation at the 2013 FLNG Forum in Perth. The two day conference brings attendees key insights into the technology and concepts that will unlock Australia’s stranded gas reserves. This event brings together case studies, keynote and technical presentations from the experts at the forefront of the Floating LNG projects. For more information about the forum, please visit the event website: http://www.informa.com.au/flngforum2013

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  • 1. Safety gaps and gas leak consequences FLNG Forum, Fraser Suites,Perth Lars Petter Blikom 4th December 2013
  • 2. DNV and GL Merger: Creating a global leader 1. Worldwide local presence and premium quality 2. The world’s leading provider of marine assurance & advisory services 3. The world’s leading provider of pipeline verification, validation, verification and asset integrity services 4. The world’s leading provider of technology qualification and risk advisory services 5. A comprehensive set of offshore standards and service specifications 6. Leading technology and innovation capability. © Det Norske Veritas AS. All rights reserved. 2
  • 3. Outline  The effects of gas leaks with varying safety gap sizes  Ventilation influence on gas cloud volume  Explosion over pressures with varying safety gap sizes © Det Norske Veritas AS. All rights reserved. 3
  • 4. Simulating heavy gas leaks  Previous studies show that heavy gas leaks create large clouds, spreading across modules.  More ignition sources exposed  The explosion mitigating effect of the safety gap is reduced  Aim: Quantify build-up of gas clouds onboard the FLNG, and compare maximum gas clouds and ventilation rates at different safety gap sizes FLACS v10.1, gexcon.com © Det Norske Veritas AS. All rights reserved. 4
  • 5. Gas leak simulations: Module configuration SG SG SG Forward SG SG • Five identical high risk modules, simulate heavy gas jet from one leak point © Det Norske Veritas AS. All rights reserved. 5
  • 6. Gas leak simulations: Different safety gap dimensions SG1 2/3 x SG1 5/3 x SG1 4/3 x SG1 • Four different safety gap sizes • In each configuration, same safety gap size is used between the five high risk modules, and location of other modules and the FLNG size is adjusted accordingly © Det Norske Veritas AS. All rights reserved. 6
  • 7. Gas leak simulations: Four environmental cases Case 1 Case 2 Case 4 Case 3 © Det Norske Veritas AS. All rights reserved. 7
  • 8. Case 1 • Cloud size is reduced around 15 % with around 9 % increase in ventilation rate, and vice versa • Approximately same behaviour for both safety gaps larger than SG1 © Det Norske Veritas AS. All rights reserved. 8
  • 9. Case 2 • Head-on wind creates wakes and recirculation patterns, the ventilation is poor and mitigating effect of safety gap is not obtained © Det Norske Veritas AS. All rights reserved. 9
  • 10. Case 3 • Cloud size is reduced around 10 % with 4 % increase in ventilation rate • Same reduction in maximum gas cloud size for both safety gaps larger than SG1, suggests an optimal gap size exists © Det Norske Veritas AS. All rights reserved. 10
  • 11. Case 4 • Cloud size is reduced around 35 % with 11 % increase in ventilation rate • Unexpected smaller cloud size for safety gaps both smaller and larger than SG1 – due to longitudinal staggering of modules © Det Norske Veritas AS. All rights reserved. 11
  • 12. Comments  Different gas cloud patterns seen for different wind directions  Measures to improve ventilation could be taken such that the ventilation effect is maximised, i.e. take advantage of the most commonly occuring wind directions/FLNG headings. © Det Norske Veritas AS. All rights reserved. 12
  • 13. Why is this important?  Larger safety gaps lead to increased ventilation  Increased ventilation leads to smaller flammable gas clouds  Smaller flammable gas clouds will expose less ignition sources and generate lower overpressures  In probabilistic explosion risk analyses (ERA), it has been seen that the cloud size is a main driver for the dimensioning accidental load (DAL)  Even a moderate decrease in the average gas cloud size may cause significant decrease in DAL, i.e. lower risk - 10 % average decrease in cloud size -> 25 % decrease in DAL © Det Norske Veritas AS. All rights reserved. 13
  • 14. Mitigation of explosion pressures with safety gaps  Configuration of two neighbouring modules, the source module and the target module. Safety gap Source Target  Leak occurs and gas cloud is ignited in source module  What are the resulting overpressure loads in the target module, for varying safety gap? © Det Norske Veritas AS. All rights reserved. 14
  • 15. Mitigation of explosion pressures with safety gaps Configuration 1: Configuration 2: SG0 2.5 x SG0 • Clouds of various volumes ignited in source module – measure overpressure on 4x4 m2 panels on deck in target module. © Det Norske Veritas AS. All rights reserved. 15
  • 16. Example: Cloud of 16920 m3 - fills parts of target module for configuration 1 Configuration 2, 2.5 x SG0 Configuration 1, SG0 © Det Norske Veritas AS. All rights reserved. 16
  • 17. Flame Front Acceleration in Congested regions (modules) Deceleration in safety gaps  Trheshold value equivalent to the DDT (Deflagration to Detonation Transition – Explosion. © Det Norske Veritas AS. All rights reserved. 17
  • 18. © Det Norske Veritas AS. All rights reserved. 18
  • 19. © Det Norske Veritas AS. All rights reserved. 19
  • 20. Example: Cloud of 4230 m3 – restricted to source module Configuration 2, 2.5 x SG0 Configuration 1, SG0 © Det Norske Veritas AS. All rights reserved. 20
  • 21. Maximum overpressures in target module Configuration 1, SG0 Configuration 2, 2.5 x SG0 • Comparing configurations 1 and 2, in the larger gap configuration a cloud of a fixed volume gives smaller overpressures in the target module • Large overpressure reductions ocurr for cloud volumes below 10000 m3, which are restricted to the source module regardless of the safety gap size © Det Norske Veritas AS. All rights reserved. 21
  • 22. Summary  The advantage of safety gaps is two-fold: - Reduce gas cloud size - Reduce explosion overpressures  There should be an optimal safety gap configuration reducing the risk to a minimum at a feasible cost JIP FLNG REVDesign © Det Norske Veritas AS. All rights reserved. 22
  • 23. Safeguarding life, property and the environment www.dnv.com © Det Norske Veritas AS. All rights reserved. 23