Asset type: Floating Liquefied Natural Gas (FLNG)
Project scope: Cryogenic Risk Analysis (CRA) using 3D numerical tools
We have established the basis of a methodology to use 3D numerical tools in the Cryogenic Risk Analysis of Floating Liquefied Natural Gas (FLNG) to improve the risk picture and the cryogenic spill protection.
What is FLNG?
FLNG is the term used for producing, processing, storing and offloading natural gas at sea. The revolutionary technology unlocks remote offshore gas fields which previously were too costly to develop and this allows the world’s growing energy demand to be met efficiently and sustainably through more use of gas, the cleanest fossil fuel.
Why are we doing this project?
A significant risk of FLNGs is the presence of cryogenic hazards, which pose a risk to both offshore personnel and assets. The most common approach to estimate the associated risks is to carry out a Cryogenic Risk Analysis (CRA) using analytical tools (2D) rather than advanced numerical tools (3D).
The CRA couples the hazard zones estimated with analytical tools (2D-based) with cryogenic frequencies to estimate the risks to both personnel and assets. However, analytical tools (2D-based) are not suited to highly congested / confined offshore installations and strong conservative assumptions are required to overcome modelling limitations (e.g. cryogenic flow interacting with the structures).
A new service for Cryogenic Risk Analysis for FLNGs
Lloyd’s Register has established the basis of a new service for Cryogenic Spill Protection Optimisation and Cryogenic Personnel Risk using advanced numerical tools. We foresee the need for a more physically inclusive method to estimate Cryogenic Risks in FLNGs.
The Cryogenic Structural Collapse Analysis (CSCA) numerical framework requires the solution of the cryogenic fluid flow problem, heat transfer and structural integrity analysis. The overall goal of the new method is to predict the failure of the structural element due to brittle fracture and assess if the remaining structural members are able to prevent the collapse of the module structure.
The method consists of:
- Cryogenic flow modelling: 3D analysis of cryogenic accidental events using Computational Fluid Dynamics and temperature mapping to the structures.
- Cryogenic heat transfer: 3D cooling of the main load bearing structure in contact with the cryogenic leak..
- Structural integrity analysis (Phase3): 3D non-linear structural collapse of main load bearing structure with Finite Element techniques and structural redundancy assessment.
The CSCA is oriented towards Cryogenic Asset Integrity Risks and Cryogenic Spill Protection Optimisation, but can be used to give input into Cryogenic Personnel Risk estimations (PLL, loss of escape).
What are the benefits?
Basing the cryogenic risk analysis on 3D analytical tools will remove much of the uncertainties and limitations that inherently follow the use of simplified 2D analyses, e.g.:
- The recommendations following a CRA with 2D analytical tools (e.g. Cryogenic Spill Protection) could lead to an increase in the risks levels of other accidental risks (e.g. Explosion) and compromise the overall FLNG risk picture.
- Over conservative assumptions tend to increase the CAPEX and OPEX of the FLNG design, with extensive structural coverage with cryogenic spill protection. Such large coverage might be unnecessary.
The Cryogenic Structural Collapse Analysis (CSCA) utilising advanced 3D numerical methods aims at increasing the accuracy of the cryogenic risk modelling, optimize and potentially reduce the Cryogenic Spill Protection needs and give better input to Personnel Risk.