Abstract

As the oil and gas production in the Gulf of Mexico began to extend into deeper water and larger and more congested topsides facilities became necessary, the US offshore Industry recognized the need for a Recommended Practice (RP) for design of these new facilities against fire and blast loading. This paper describes the background to the development of the RP, which has been put together with extensive contributions from industry experts with different areas of specialist knowledge. The paper discusses the consistency of the RP with recent work to update related standards, in particular the UKOOA/HSE initiatives in the UK.

The paper addresses the issue of blast load determination and discusses the nominal loads provided in the new RP and their application to design. It also considers alternative methods for the calculation of blast loads, in lieu of applicable nominal load cases, including a promising new methodology analogous to the derivation of earthquake loading. The paper stresses the importance of good practice for fire and blast design and discuss the guidelines for facilities layout and structural connection detailing.

The paper highlights the interface to other API documents that provide guidance on the implementation of safety and environmental management practices and hazard identification, event definition and risk assessment e.g. API RP 75 (1) and the API RP14 (2,3) series. It briefly outlines how the new RP incorporates hazard analysis output into the structural response assessment to determine whether the structure or its components meet the specified performance criteria.

Background

Deepwater developments to harness larger and deeper hydrocarbon deposits bring with them the need for larger and more complex topsides facilities. A key learning from explosion research over the past 10 years is that congestion as well as confinement can lead to high overpressures in an explosion. The increased size of facilities increases the porabaility of releases and the increased congestion of facilities increase the consequences in the event that the release ignites, particularly if the ignition is delayed and an explosion occurs. Much can be done to manage this risk. Prevent the releases occurring is clearly preferable but the cosnsequences in terms of possible life-safety, environmental and economic consequences can be reduced by establishing performance objectives and incorporating good practices.

Good practices have been developed in the industry and incorporation of thiose practices early in the design can significantly reduce the risks associated with fire and explosions. Hence one on the key objectives of this proposed RP was to capture those practices and share them with the rst of industry.

In December 2000, API issued the 21st Edition of RP2A (4). The document includes as Section 18, 'Fire, Blast and Accidental Loading' that provides, for the first time in API, a recommended practice for design of fixed steel offshore structures against fire and blast events.

In October 2001, API SC2 formed a Fire and Blast Task Group under the Chairmanship of BP's Patrick OConnor.

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