Case study

Quantifying risk and operability for offshore design

The challenge

The orientation and layout of equipment can profoundly influence the operability and safety of an offshore platform. Ensuring safe operation is paramount and quantifying risks at the design phase is a key step in achieving this.

Dispersion modelling is a means of quantifying the interaction of concentrated sources with prevailing winds around an asset. The wind acts to dilute and disperse smoke, gas and hot exhaust plumes which can either increase safety or drastically diminish it. The challenge lies in designing assets that utilise wind dispersion to increase safe operation. To this end, we perform dispersion modelling to aid safe helicopter and cranes operation around hot gas turbine exhaust plumes, detection of hydrocarbon leaks prior to ignition and design of safe escape routes and secure refuges in the event of fire.

Our involvement

We perform both near and far-field dispersion predictions to evaluate the safe operation of asset designs using Quantitative Risk Assessments (QRA) and safety cases. Building on our knowledge of far-field Atmospheric Dispersion Modelling (ADM) techniques that account for meteorological conditions and thermal properties of plumes we use Computational Fluid Dynamics (CFD) to predict dispersion around congested offshore assets. This technique produces detailed models of decks and equipment that enable development teams to quantify temperatures, toxicity and visibility levels and any location.

We have worked closely with EPCs and Operators to produce safe designs and safety cases for fixed jackets, floating platforms and FPSOs.

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Figure 2: Hydrocarbon gas dispersion at an onshore terminal.
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Figure 3: Fire modelling on an offshore platform.

Added value

At Frazer-Nash we provide our clients with the added value and insight from our wide ranging expertise and experience. This enables safe designs to evolve quicker and ranges from blast and explosions modelling, blast resistant design, fire modelling and detailed mechanical design.

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Figure 1: Hydrocarbon gas dispersion modelling on an FPSO.

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