High-strength type-B sleeve for pipeline girth weld repair and its key application technology

Abstract

In recent years, the repair technology of type-B sleeves has been widely used for the hazard control of pipeline girth welds. However, the prominent problems such as the unreasonable geometrical dimension of sleeve and the delayed cracking of fillet weld are exposed in the girth weld defect repairing of high-strength pipelines with type-B sleeves. In order to solve the problems faced in the application of type-B sleeves and meet the requirements of girth weld defect repair in high-strength pipeline, the design method for geometric dimension of type-B sleeves and the recommendations on value of key parameters were proposed after research. Meanwhile, X65/X70 type-B sleeves were developed through the research on special composition design and processing technology, with the weight about 20%?30% lighter than the traditional Q345R sleeves. Besides, the technical requirements, including the welding conditions (pipeline transportation pressure and flow rate of medium), preheating temperature, welding mode and post-weld heat treatment, were provided, and the selection scheme of welding material for X70 type-B sleeves was put forward. Considering the delayed cracking of sleeve fillet weld, it is suggested to cancel the root welding and the inter-layer magnetic particle detection, add the ultrasonic phased array detection after welding and the magnetic particle detection 48 hours after welding. The reliability of X65/X70 type-B sleeves has been verified by full-scale laboratory test and field application demonstration, and the sleeves have been successfully applied to the repair of girth weld defects of X80 high-strength pipelines.

Keywords

• high-strength pipeline
• girth weld
• x65/x70 type-b sleeves
• welding procedure
• nondestructive examination