Fully integrated pipeline bundles are built and tested onshore. The bundlesare towed to the field using the Controlled Depth Towing Method (CDTM). Recently this method was used to tow a very long bundle (6.7 km) to the Piperfield in the British sector of the North Sea.
Time domain simulations were carried out to predict the bundle behaviour indifferent situations. A discussion of the numerical model will be presented. Several parts of the bundle configuration were model tested and full scalemonitoring was performed during the tow at sea. Bundle tow in still water andsurvival sea states is discussed as well as the impacts of failure modes on thebundle behaviour.
Fully integrated pipeline bundles are built and tested at the productionsite. After completion the bundle is launched and towed to the field. Often itwill be necessary to cross other pipelines located on the tow route from theproduction site.
To achieve clearance with these other pipelines it is essential to perform asafe tow. To this extent a dynamic analysis of the tow is carried out.
The importance of having reliable numerical methods to predict the dynamicbehaviour of towed pipeline bundles is given by the fact that it is extremelydifficult to carry out model tests on these systems due to their immenselengths.
The numerical model presented in this paper is based on a lumped massapproach, allowing flexibility with respect to modelling of differentconfigurations. Model tests were carried out to gather information aboutessential items of the tow. Full scale monitoring was carried out to validatethe numerical model for future projects.
In principle CDTM involves the transportation of a pipeline bundle suspendedbetween two tugs, the Leading Tug (LT) and the Trailing Tug (TT), Figure 1. Tomaintain control during tow, the bundle is designed and constructed withinspecific tolerances with respect to its submerged weight.