Abstract
Passive Fire Protection (PFP) materials applied to offshore facilities form one of the major risk reduction measures which are used to directly protect platform personnel and the asset from the major hazard of fire. Many commonly used PFP materials on which current performance standards are based have been in service for a number of years. The original materials were specified to satisfy prescriptive legislation rather than being specified through any risk-based approach, and have subsequently sustained damage through weathering and general duty. Verifying that these materials satisfy their current performance requirements is proving one of the major challenges for operators of ageing assets.
Recognising that information on the performance of weathered PFP containing anomalies is scarce, a Joint Industry Project (JIP) was undertaken which developed acceptance criteria for PFP materials containing anomalies.
A significant exercise has been undertaken for an offshore installation to ensure that the PFP effectively manages the fire risks, and satisfies the platform performance standards which define the PFP requirements in terms of coverage and fire resistance properties. This paper describes the process undertaken to make this demonstration.
The PFP installed on the installation under assessment was originally specified to protect steelwork exposed to a cellulosic fire of 60 minutes. PFP samples were removed from the installation and jet fire tested in order to understand how the actual PFP installed would perform under produced hydrocarbon jet fire conditions. The resulting test data combined with the JIP results enabled the establishment of survivability criteria, and the required condition of the PFP (in terms of thickness and bonding to the substrate) in which this survivability would be applicable.
Structural analysis was undertaken in which the platform was subjected to a significant programme of non-linear fire collapse analysis to determine the time at which local failure of the platform would occur under a series of fire scenarios. The analysis established where PFP was required to ensure that the platform performance standard for structural and TR (Temporay Refuge) integrity was satisfied. The survival times under fire loading for various structural elements of the platform (protected in their current state, unprotected, and with upgraded PFP protection), formed input to the platform Quantitative Risk Assessment (QRA) to confirm the impact of removing, leaving, upgrading, or adding PFP.
The structural collapse model was also used to minimise the risks during the actual PFP replacement activities by analysing the impact of removing sections of material on the likelihood of a structural collapse mechanism developing under jet fire impact.
A robust and detailed assessment process has been carried out, which has led to defining a PFP scheme which is fit for purpose to manage the installations Major Accident Hazards (MAHs), and which has been achieved with the risks during replacement activities being minimised throughout the offshore campaign
