Safe Evacuation From Offshore Petroleum Installations
Authors: Woolgar Reeni , Ré António Simões , Veitch Brian , Pelley Dean 
Published: October 2008

Marine evacuation systems used on offshore petroleum installations have been investigated using a series of model experiments in a large test facility. The performance of a conventional twin-falls davit launched lifeboat system was evaluated during launching, clearing, and sail-away phases of the evacuation process from a bottom fixed installation. Performance was examined as a function of weather conditions, from calm water up to Beaufort 8. Based on the results, some guidance is given concerning the rational design of evacuation system configurations.

Introduction

The work reported here is part of a larger study on offshore evacuation system performance and safety. The main aim of the work is to evaluate lifeboat evacuation capabilities as a function of weather conditions. In particular, the aim is todetermine how performance capabilities deteriorate with degrading weather conditions. Secondly, the work aims to establish measures of capability, or performance, which have practical utility for design and regulation purposes. These aims are motivated by the trend away from prescribed specification standards in favor of goal-setting regulatory regimes.

This paper focuses on the quantitative effects of weather on lifeboat evacuation system performance. Observed and measured experimental results are presented and discussed. A set of evacuation zones is defined, which, together with the empirical results, lead to a method for configuring an evacuation system arrangement that can reasonably be expected to fulfill an explicitly defined role.

The scope of the work reported here is limited to evacuation by twin-falls davit launched lifeboat, or totally enclosed motor propelled survival craft (TEMPSC). Evacuation starts with the lowering and splash-down of the boat, and ends with sail-away to a rescue zone. Escape and rescue phases of the escape, evacuation and rescue (EER) process are not dealt with here.

Evacuation during emergencies must necessarily be done in prevailing weather conditions. The performance of evacuation systems in rough weather is not well known. Experience under emergency conditions is fortunately limited: it is also not controlled in the experimental sense. Further, testing with full-scale manned equipment is prohibitively dangerous and testing with unmanned equipment is expensive.

The approach taken to investigate evacuation system performance in rough weather was to conduct model scale experiments, which overcame the problems noted above (e.g. Crossland et al. 1992, pp.19-20). There are limitations to model testing in this context, and some of these have been discussed by Simões Ré & Veitch (2001). For example, no attempt was made to model the reliability of the equipment, nor account for the role of maintenance. Further, it was impossible to account for human factors.

Test Setup

The tests were done in the Offshore Engineering Basin (OEB) at the National Research Council of Canada, Institute for Marine Dynamics (NRC/IMD). The OEB has a working area of 65m×26m. Individual wave maker segments cover two adjacent sides of the basin.