1 / 16

SAFETY DISTANCES: COMPARISON OF THE METODOLOGIES FOR THEIR DETERMINATION M. Vanuzzo , M. Carcassi.

SAFETY DISTANCES: COMPARISON OF THE METODOLOGIES FOR THEIR DETERMINATION M. Vanuzzo , M. Carcassi. Università di Pisa. Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione (DIMNP), University of Pisa. CONTENTS. Definition of Safety and Separation distances

damon-meadows
Download Presentation

SAFETY DISTANCES: COMPARISON OF THE METODOLOGIES FOR THEIR DETERMINATION M. Vanuzzo , M. Carcassi.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SAFETY DISTANCES: COMPARISON OF THE METODOLOGIESFOR THEIR DETERMINATION M. Vanuzzo,M. Carcassi. Università di Pisa Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione (DIMNP), Universityof Pisa ICHS 2011 - San Francisco, USA - September 12 -14

  2. CONTENTS • Definition of Safety and Separation distances • Standard and Regulation inherent to hydrogen safety distances • Risk- Informed approach • Comparison of NFPA and ISO methodologies for the determination of safety distances • Consideration about the choice of the leak diameter • Conclusion ICHS 2011 - San Francisco, USA - September 12 -14

  3. CONSIDERED STANDARD AND REGULATIONS • Regulation NFPA 2 “Hydrogen technical code” (United States) - • EIGA IGC Doc 75/07/E “Determination of Safety Distances” (EU) • Standard ISO 20100 “ Gaseous hydrogen Fuelling stations “ • Regulation-Draft of “Technical rules for distribution and the transport of hydrogen in pipelines” (Italy) • Regulation "Approval of the technical rule of fire prevention, construction and exercise of hydrogen fueling station“(Italy) ICHS 2011 - San Francisco, USA - September 12 -14

  4. DEFINITION OF SAFETY AND SEPARATION DISTANCES • EIGA: “the safety distance is the minimum separation between a hazard source and an object (human, equipment or environment) which will mitigate the effect of a likely foreseeable incident and prevent a minor incident escalating into a larger incident”. • SANDIA: “Separation or safety distances are used to protect the public and other facilities from the consequences of potential accidents related to the operation of a facility. Separation distances are also used to reduce the potential that a minor accident at one portion of a facility propagates to another part of the facility thus increasing the resulting consequences.” (SAND 2009-0874) • ISO (ISO/DIS 20100): the same definition of EIGA • NFPA 2 NO DEFINITION but refers to SANDIA report ICHS 2011 - San Francisco, USA - September 12 -14

  5. RISK RELATED (INFORMED/BASED) NFPA2 introduces a new methodology for the determination of hydrogen safety distances, the risk informed process. The definition of “risk-informed” is presented in the Sandia’s report : “Risk-informed is a methodology that utilizes risk insights obtained from quantitative risk assessments (QRAs) combined with other considerations to establish code requirements. “ “Risk-basedis a methodology that utilizes risk obtained from quantitative risk assessments (QRAs) compared with a specific acceptance risk criteria. “ RISK INFORMED = RISK BASED + OTHER CONSIDERATIONS ICHS 2011 - San Francisco, USA - September 12 -14

  6. RISK INFORMED SPECIFICATION { Statistical Analysis (leak frequencies) Quantitative Risk Assessment Accident Scenarios (jet / flash fire) Risk Criterion (risk guideline) What are the “other consideration”? Uncertainties (statistical analysis, ignition probabilities, harm criteria etc..) Parametric Assumption (pressure, system size, system category etc..) ICHS 2011 - San Francisco, USA - September 12 -14

  7. NFPA METHODOLOGY • Hydrogen-specific component leak frequencies • Harm criteria • Cumulative probability to determine which range of leaks represents the most likely leak size • The risk resulting from different leaks sizes was also evaluated for four standard gas storage configurations • The choice of the leak dimensions is based on risk reasonably close to 2x10-5. On the basis of the previous considerations Leak area = 3% of the flow area ICHS 2011 - San Francisco, USA - September 12 -14

  8. ISO METHODOLOGY • Hydrogen-specific component leak frequencies • Harm criteria • The safety distances are defined for different types of hydrogen systems forming a well identifiable physical module • Introduction of a definition of leak likelihood for every physical module. This level of leak likelihood is assumed to be reflected by the value of the Leak Probability Indicator (LPI) for that system. • Choice of the leak dimension’s risk lower than 10-5/year for the public, 10-4/year for customers. On the basis of the previous considerations The leak diameter varies according to the type of system that is considered ICHS 2011 - San Francisco, USA - September 12 -14

  9. COMPARISON OF NFPA AND ISO METHODOLOGIES ? ICHS 2011 - San Francisco, USA - September 12 -14

  10. UNCLARITY IN THE ISO METHODOLOGY Statistical analysis for determination of component release frequencies The reason for shifting the frequencies of one order of magnitude ? (www.hydrogensafety.info/2010/aug/separationDistances.pdf) ICHS 2011 - San Francisco, USA - September 12 -14

  11. COMPARISON OF NFPA AND ISO METHODOLOGIES SAME METHODOLOGY BUT DIFFERENT LEAK SIZES CONSIDERED DIFFERENT CONSIDERATIONS ICHS 2011 - San Francisco, USA - September 12 -14

  12. CHOISE OF LEAK DIAMETER NOTABLY DIFFERENT ICHS 2011 - San Francisco, USA - September 12 -14

  13. LEAK DIMENSION EVALUATION 0.10% - 1% Range considers by ISO { 1.0E+01 ? 1.0E+00 Leakage Frequency (/yr) 1.0E-01 GAP 1.0E-02 1.0E-03 1.0E-04 1.0E-05 Minor leaks Ruptures Medium leaks Major leaks 1.0E-06 3% considered by NFPA 1.0E-07 0.01% 0.10% 1.00% 10.00% 100.00% Leakage Area (% Flow Area) ICHS 2011 - San Francisco, USA - September 12 -14

  14. CONCLUSIONS { METHODOLOGY SAFETY DISTANCE DETERMINATION PROCESS CONSIDERATIONS LEAK DIMENSION SAFETY DISTANCE VALUE For this reason is important to clearly define for which purpose the safety distances should be used ? to prevent escalation and protect targetsfrom more probable small releases (ISO) to prevent escalation and protect targets from great releases (NFPA) or ICHS 2011 - San Francisco, USA - September 12 -14

  15. THANK YOU. Contact Author: Matteo Vanuzzo (UNIPI-ITALY) matteo7785@libero.it Presented by: Marco Carcassi (UNIPI-ITALY) carcassi@ing.unipi.it

  16. DEFINITION OF SAFETY AND SEPARATION DISTANCES • ITALIAN REGULATION FOR HYDROGEN FILLING STATION defines three kind of safety distances: • Protection safety distance: “the least value of horizontally distances among the plant’s perimeter and every dangerous element of the activity; • Internal safety distance: “the least value of horizontally distances among the various dangerous elements of an activity; • External safety distance: “the least value of horizontally distances among every dangerous element of an activity and the perimeter of the nearest external building. ICHS 2011 - San Francisco, USA - September 12 -14

More Related