Laboratory Scale Experimental Simulation of a Pipe Rested on a Saddle Supporting System for Verification of Numerical Modeling

The paper presents results of preliminary experimental and numerical tests over research and development of the numerical, FEM (Finite Elements Method) based method of pipeline strain/stress condition assessment with the use of data possessed from inline inspection tool. At the beginning, the research is focused on an example of a typical flaw which may be detected in oil or gas transporting pipeline by Geometry Measuring Pipeline Intelligent Gauge (Geo-PIG) during inline inspection. Such a typical flaws are dents and folds in the pipe which rests on a supporting concrete block or other type of saddle supporting system. The research method is based on numerical simulation and analysis. But it must be verified experimentally. For the needs of experimental verification of the numerical method tests were conducted at laboratory scale. Artificial dents, folds, and ovalizations were created with the use of material strength testing machine for samples of weldless thin walled pipe rested on specialized stand, simulating a saddle supporting system. The process of buckling during the three-point bending test took place close to the middle support with visible local buckling in the pipe wall. The experiment was conducted under the strict control, enabling measurements of deformations and strains in selected points located on external surface of the pipe wall. Since the Military University of Technology (MUT in Warsaw) itself is not a provider of inline surveys with the use of Pipeline Intelligent Gauge PIG), the substitutive equipment was used for deformation measurements on tested pipes with so called “digitizing arm” which was the analogue of the real inline inspection tool. The use of 3D digitizing arm was successful. The data collected with the use of this tool are coherent and may be used for verifications of FEM modeling. The preliminary numerical test models for the experiment simulation are also presented. The only disadvantage of laboratory tests was that they do not allow to conduct investigation on pressurized pipe for technical as well as for safety reasons. Experimental research on deformations and strains conducted for bent pipes will allow verifying strains and stress distributions obtained from numerical calculations. This will allow improving methods of numerical simulations.