The World's Largest Single Point Mooring Terminals: Design And Construction Of The SALM System For 750,000 DWT Tankers

Abstract

ABSTRACT This paper will discuss the design, fabrication and installation of two (2) identical Single Anchor Leg Mooring (SALM) Terminals which serve as crude oil export terminals. Both are designed to safely moor and load tankers as large as 750,000 DWT in environmental conditions that will be occasionally severe. The determination of mooring forces via calculation and model tests and the design and fabrication of the components which transfer these loads will be discussed. Of particular interest is the design and fabrication of the "heart" of the systems, the fluid swivel assemblies which include several innovative features with respect to operation and maintenance. These fluid swivels are the largest ever built for SPM applications and are designed to transfer crude oil and bunker fuel oil simultaneously and to absolutely preclude the possibility of commingling of the two fluids. Model tests that were conducted on the fluid swivel/loading hose system will be discussed. The foundation design and the optimization of this design with respect to available offshore construction equipment will be outlined as will the installation methods employed. INTRODUCTION The safe, efficient and economical transportation of crude oil from typically remote producing areas to the consuming areas of the World presents several difficult problems. Solutions to any of these problems offer attractive cost savings for crude oil feed stocks. A major step in optimizing crude oil transportation has been the development of the Very Large Crude Carrier (VLCC). Unfortunately, the development of the VLCC has threatened to outpace the development of terminals suitable for loading/unloading these giant, deep draft vessels. One solution to this problem that has gained wide acceptance in recent years is the Single Point Mooring (SPM) or "monobuoy" type of terminal. The SPM terminal solves several problems that are inherent to other types of tanker loading/unloading facilities (harbors, jetties, sea islands, multiple buoys and fixed towers):It can be readily placed far offshore in the deep water necessary to accommodate deep draft tankers.It can operate efficiently in rough seas and is not sensitive to directional changes of wind, waves and currents. With the tanker moored via bow lines only to a single buoy, the tanker is free to "weathervane" about the buoy and stay head-on to the weather, thus reducing mooring forces and increasing terminal utilization.It reduces operational dependency on support vessels such as tugs.It is generally less expensive to construct and/or operate than the other types of loading/unloading facilities. This paper describes the ARAMCO - Ju' Aymah SALM Terminals (Arabian Gulf) which are the largest export SPMs ever built, and discusses the unique design features that were incorporated into these systems to make them safer, more efficient and more economical to operate than previous SPM designs.