A Methodology to Assess the Downtime of a Multi-Phase Offshore Floating Bulk Transshipment Operation

Abstract

Operators who want to im- or export bulk (coal, iron ore, scrap, etc.) by means of offshore bulk transshipment often want to determine the operability of their bulk transshipment configuration in an early stage to assess if offshore floating bulk transshipment is a feasible option for im- or export of the commodity. The downtime of such offshore (un)loading operations may be unacceptably large. The operational windows may become limited. This implies insufficient im- or export volumes, which may result in large and expensive storage capacity onshore. In this paper a methodology is proposed to assess the operability of offshore floating bulk transshipment. Offshore bulk transshipment is a multi-phase operation. For offshore operations consisting of multiple phases, persistency of the environmental conditions has to be considered. Persistency analysis allows for multiple operational phases, individual phase duration and shift of sea states during the operation. The proposed methodology shows that using persistency data of the waves (wind and current are not considered yet), the downtime of an offshore floating bulk transshipment operation can be estimated more accurately. Compared to persistency analysis, scatter analysis (using wave scatter diagrams) resulted in an optimistic estimate of the downtime. Persistency analysis is better in demonstrating the influence due to each consecutive step on the total operability. This methodology could be further extended to other multi-phase offshore operations.

Technical and economic feasibility study for offshore transshipment operation

“…For WANG et al (2016), the development of a greenfield port or the expansion of an existing port involves a high gestation period and high costs, noting that it is not always possible to expand ports, as the available areas are decreasing. In view of this, to keep up with the worldwide demand for bulk cargo, transshipment offshore is used as a solution to problems such as vessel size restriction, operating time and flexibility if there is a need to change the location of the operation.…”