Path Planning Methodology for Multi-Layer Welding of Intersecting Pipes Considering Collision Avoidance

SUMMARY The V-groove joint of thick wall intersecting pipes must be filled by multi-layer weld. The welding path of intersecting pipes is complicated, and hence multi-layer welds increase the complexity of the problem. This paper proposes a methodology for path planning of multi-layer weld of thick wall intersecting pipes. The methodology is based on measuring the electrode pose located in both side and front views of intersecting pipes. In order to compensate for the path deviation around the pipe circumference, the measured values are used to interpolate the path of each pass between two views. The methodology has been applied in a case study. Simulation results approve that multi-layer weld appropriately fills the V-groove joint space around the pipe circumference. In addition, collision avoidance between welding torch and pipes is considered by introducing a safety ring. While the robot wrist moves inside the safety ring, no collision occurs. Simulation results show the robustness of the proposed path planning method, introduced for collision avoidance.

Path Planning of Complex Pipe Joints Welding with Redundant Robotic Systems

SummaryIn this paper, a path planning algorithm for robotic systems with excess degrees of freedom (DOF) for welding of intersecting pipes is presented. At first step, the procedure of solving the inverse kinematics considering system kinematic redundancy is developed. The robotic system consists of a 6 DOF robotic manipulator installed on a railed base with linear motion. Simultaneously, the main pipe is able to rotate about its longitudinal axis. The system redundancy is employed to improve weld quality. Three different simulation studies are performed to show the effect of the robotic system kinematic redundancy to plan a better path for the welding of intersecting pipes. In the first case, it is assumed that robotic manipulator base and main pipe are fixed, and the path is planned only with manipulator joints motion. In the second case, only the robot base is free to move and the main pipe is fixed, and in the third case, the main pipe is free to rotate together with the base of the manipulator. It is seen that kinematic constraints according to the system’s redundancy will help to plan the most efficient path for the welding of complex pipe joints.

Cutting Technique of Welding Groove for Intersecting of Braces at Small Angle during Liwan 3-1 CEP Jacket Fabrication

This paper presents the method to perform cutting of welding groove for intersecting of pipes at small angle during Liwan 3-1 CEP jacket fabrication. The mathematical model of the intersecting pipes as well as the cutting method for transition section have been studied using the principle of geometry, which enables fabrication team to print out the full scale template drawing to guide cutting of welding groove for intersecting of braces at small angle. This method has been fully tested during LW3-1 jacket fabrication which indicated that the welding groove can meet the requirements of AWS D1.1 code and the method can be adopted for future jacket construction.

Stress Distribution in the Region Around Two Normally Intersecting Pipes due to In-Plane Bending Moments Using Finite Element Method

Numerically calculated stress in the region of two normally intersecting pipes due to in-plane bending moments using finite element program MECHANICA are presented in this paper. The computer results were processed and then presented in stress versus location (along several lines) diagrams. Other investigators’ results for similar problem are not easy to obtain due to differences in the problem, in modelling, in finite element program used and in methods of data presentation. Lock et al (1985) and Moffat et al (1984) works were the closest for comparison purposes.