Installation of an Internally Clad Pipeline Using the J-Lay Method

ABSTRACT A J-lay system for deep and shallow water application was built by HeereMac and used on SSCV Balder to install a 316 L internally clad pipeline in the Maui field offshore New Zealand. The paper describes investment justification, concept development, system specifications, as well as Maui project welding process selection and offshore experience gained with the system. INTRODUCTION HeereMac operate four of the five large Semi Submersible Crane Vessels (SSCV'S) which are sailing the world's seas. Their employment is basically limited to the super heavy lift market, of which the total volume, worldwide, is not sufficient to ensure an optimum utilization level of these vessels, and therefore HeereMac seek enhy to other market segments. At the same time HeereMac look for participation in the deepwater developments which start to emerge around the world. Deepwater construction projects require deepwater lift capability, and deepwater pipeline installation equipment, and HeereMac are preparing to offer this in a total package centered around its SSCV Balder. In 1991 HeereMac built and commissioned the world's first J-lay system, designed to the requirements of all deepwater projects which can be envisaged for the next decade. In addition, the system can handle SIUJ1OWwater pipelines, for the reason that Balder is to be bid for total constructionprojects involving heavy lift and pipelay work in remote areas all around the world, including those in shallow water (see figure 1). The J-lay system was first used only recently on the Maui B to Maui A pipeline installation project offshore New Zealand, which presented three technical c.q. managerial hurdles :Constructing the J-lay system in a very tight schedule, with little room for experiments or mishaps.Applying the J-lay system in swell-dominated shallow water, which is the most difficult from an operational viewpoint.Welding 316 L internally clad carbon steel pipe in the 6G position. Having to face these problems, and bearing in mind that the J-lay system was to be seen as a long term investment adequate for all the ext decade's projects, required a high level of quality and reliability incorporated in the design and construction. With specific rules for design and construction of such equipment lacking, HeereMac chose to have Lloyd's certify the system along the lines of the Code for Lifting Appliances, As far as the selection c.q. development of the welding procedures and equipment were concerned, the focus was mainly on reliability and quality reproducibility rather than on welding speed. This was permitted by the length of the Maui pipeline being only 15 km. A description of the system development and specifications, development of the welding procedure and equipment, as well as operational experience from the Maui B pipeline project are now presented. CONCEPT DEVELOPM17NT OF THE J-LAY SYSTEM HeereMac's market approach philosophy, as stipulated in the introduction, led to two stringent design requirements to be incorporated in the J-lay system: