Benefits of Single Platform Lifting Lead to Design, Construction of New Giant Ship

Abstract

This article, written by Editorial Manager Adam Wilson, contains highlights of paper OTC 23169, ’Building a Giant for Single Platform Lifts,’ by Edward P. Heerema, Allseas Group, prepared for the 2012 Offshore Technology Conference, Houston, 30 April-3 May. The paper has not been peer reviewed. Copyright 2012 Offshore Technology Conference. Reproduced by permission. The ship described here was designed and is being built for single lifting of topsides of offshore platforms up to 53,000 short tons and jackets up to 27,500 short tons. The vessel will have a wide slot at the bow that fits around platform substructures and will be equipped with a hydraulically operated topside-lifting system. For installing or removing platform jackets, it will have a system of two tilting lift beams at the stern. The building of the vessel and equipment is in progress; the vessel is scheduled to be commissioned by the end of 2013. Introduction The ship described here was designed and is being built for single lifting of top-sides of offshore platforms up to 53,000 short tons and jackets up to 27,500 short tons. The vessel will have a wide slot at the bow that fits around platform substructures and will be equipped with a hydraulically operated topside-lifting system. For installing or removing platform jackets, it will have a system of two tilting lift beams at the stern. The building of the vessel and equipment is in progress; the vessel is scheduled to be commissioned by the end of 2013. Traditional Modular Lifting vs. Topside Floatovers Installing large offshore platforms so far has generally been performed with crane vessels. Large topsides have to be installed module by module to ensure that the lifts remain within the capacity of the cranes. This can lead to considerable offshore hookup costs to complete the topside, which are greater than when performed on land. However, by single lifting the offshore hookup, costs can be reduced significantly. If a topside structure is completed on land and installed in one piece, the making of all the connections between elements or modules—structural, electrical, hydraulic and piping—is faster and less costly. Removing a large topside by traditional crane vessels requires the topside to be removed module by module or by more time-consuming, hazardous, and expensive dismantling offshore in small pieces. When removing the topside in a modular way, every module must be cut loose from the surrounding modules, lift points must be reinstalled, and lift rigging must be attached. Platform walkways, escape routes, and safety plans must be adjusted several times during the removal process. Several make-safe campaigns are required offshore and onshore. At an early stage, the accommodation facilities will have to be removed because of their outside position and then will no longer be available to the dismantling crew.