Uncertainty Analysis of a Safety Operating Envelope for a Subsea Shuttle Tanker

Abstract

This thesis investigates the uncertainty of a safety operating envelope (SOE) for a subsea shuttle tanker (SST). The main focus of this work is on the jam-to-rise and jam-to-dive aspects of the accidental cases for the SOE. The SST is investigated using a pitch angle of 10- 15- and 20- degrees for rising and diving. The findings of the free-running simulations, which take into account two current directions and load instances of 0.5 and 1 m/s with 5% and 10% standard variation, while using the Gumbel fitting method, revealed increased recovery depth differences ranging from 0.97% to 21.44% for the jam-to-rise scenario, and 0.42% to 11.26% for the jam-to-dive scenario for the 15-degree pitch angle cases. The cases with 10- and 20-degree pitch angles show similar percent differences. Future studies may look at how differences in recovery depth caused by current directions coming from different angles, such as a 60- and 120-degree angle, might significantly affect the results. To estimate the possible recovery depth and compare it to the Gumbel values in order to get more accurate results, other statistical techniques might be utilized, such as the Average Conditional Exceedance Rate Method