Technology Research For Leg Construction Of Jack-up Rig

Recent years, as offshore oil exploitation fever, jack-up rig requirements are increasing.Pile legs production and installation are also gradually become one of the important structure of the offshore industry. Many domestic enterprises also want to get access to legs building areas, but they are all conditioned by the technical level of the domestic. Some parts of legs must rely on import and some parts must pay a high cost if they want to product.This paper mainly studies four primary technical problems when pile leg of jack-up rig is built. Racks cut by traditional digital control flame cutting method can't meet the strict dimension requirement. Cutting machine, cutting parameter and workflow layout are optimized in order to cut rack plates with high precision. Chords are processed by heat pressing instead of cold pressing. Chords are heat treated and straightened to meet the requirement of mechanical property and dimension. Chords are heat pressed, quenched and tempered by temperature and procedure control. Large scale press machine is needed for cold pressing but chords are short, stress can't be released, and there are defects such as crack when welding. These problems can be solved by heat pressing to reduce time and cost.Dimension control is very important during leg fabrication process to meet the high dimension requirement. Dimension should be controlled and ensured to be within tolerance limits in main chord fabrication and elongation, leg segment construction and erection,and other links. Welding should be executed according to welding procedure strictly. Current,voltage and temperature should be controlled. Welding should be carried out in the right sequence and anti-deformation should be controlled and post welding treatment should be done. Meanwhile, suitable jigs are very necessary. Leg upper air erection and jacking system commissioning are carried out simultaneously by leg erection when hull and crane are both in floating. It solved the problems that long erection time, low efficiency, influence by sea state and high cost, etc..