AMERICAN PETROLEUM INSTITUTE - FIRES & BLAST DESIGN PRACTICE

          API Recommended Practice - 2001/2002

Challenge/Background

API RP2A Section 18 provides limited guidance for the design of fixed offshore structures for accidental loading including fire and blast. This guidance was published in 1997 and incorporated into the main body of the 21st Edition. For floating systems no similar guidance is available and, although recourse is often made to the UK Interim Guidance Notes (published in 1991), they also contain no explicit guidance for floating structures.

 

API has identified a need to replace the RP2A provisions, with a new Recommended Practice for ‘Design and Assessment of Offshore Structures for Fire and Blast’. In October 2001, MSL was commissioned by API to prepare this Recommended Practice for the protection of offshore structures against fires and explosions. This guidance, the first draft of which will be available Q1 2002, will cover new and existing installations and will encompass fixed platforms, FPSOs, semi-submersibles, SPARS and TLPs.

 

Scope of Recommended Practice

Recent and proposed major deepwater developments in the Gulf of Mexico and events elsewhere in the world have raised awareness of the importance of fire and blast safety assessments for new and existing installations. Section 18 provides some guidance on the assessment of fixed platforms for fire and blast. However, the Exposure Categories defined therein were developed for assessment of risks associated with environmental loads (hurricanes) and are not appropriate for accidental loading due to the inability to evacuate ahead of the event. Two matters therefore require coverage:

  • Re-definition of Exposure Categories for fire and blast, which provide for appropriate safety assessments of higher-risk installations without penalty to existing and future low-risk installations.

  • Detailed guidance for the protection of offshore structures against fire and blast loading that represents modern best-practice and is applicable to all offshore structures.

BP has agreed to release the MSL-prepared BP Guidance document in this area as the basis for the new API Recommended Practice. The BP Guidance covers assessment, risk classification, fire loads and response, explosion loads and response, analysis methods and the interpretation of the results of fire and blast consequence analyses.

 

Combined fire and explosion load cases are also considered. The risk classification follows an approach based on API RP2A. The base document will be expanded/augmented to:

  • Establish relevant Exposure Categories.

  • Cover a Recommended Practice for floating systems representative of modern best-practice.

  • Describe the background to and basis for the ‘Dimensioning’ explosion scenario.