Computer Vision System for Welding Inspection of Liquefied Petroleum Gas Pressure Vessels Based on Combined Digital Image Processing and Deep Learning Techniques.

Yarens J Cruz,Ramón Quiza,Marcelino Rivas,Rodolfo E Haber,Gerardo Beruvides

doi:10.3390/s20164505

Abstract

One of the most important operations during the manufacturing process of a pressure vessel is welding. The result of this operation has a great impact on the vessel integrity; thus, welding inspection procedures must detect defects that could lead to an accident. This paper introduces a computer vision system based on structured light for welding inspection of liquefied petroleum gas (LPG) pressure vessels by using combined digital image processing and deep learning techniques. The inspection procedure applied prior to the welding operation was based on a convolutional neural network (CNN), and it correctly detected the misalignment of the parts to be welded in 97.7% of the cases during the method testing. The post-welding inspection procedure was based on a laser triangulation method, and it estimated the weld bead height and width, with average relative errors of 2.7% and 3.4%, respectively, during the method testing. This post-welding inspection procedure allows us to detect geometrical nonconformities that compromise the weld bead integrity. By using this system, the quality index of the process was improved from 95.0% to 99.5% during practical validation in an industrial environment, demonstrating its robustness.

Highlights

Pressure vessels are closed containers, tanks, or pipelines designed to receive and store a fluid at a pressure greater than outer ambient pressure conditions
For dealing with the aforementioned shortcomings, this paper proposes an integrated system for pre-welding and post-welding inspection, based on computer vision techniques, for industrial applications
In the welding stage of liquefied petroleum gas (LPG) pressure vessels analyzed, most defects were related to butt joint misalignment and incorrect weld bead geometry

Summary

Introduction

Pressure vessels are closed containers, tanks, or pipelines designed to receive and store a fluid at a pressure greater than outer ambient pressure conditions. They are used in a large number of industries, such as power generation, chemical, petroleum, petrochemical, and nuclear industries. The fluids contained in pressure vessels may have specific characteristics, such as volatility, compressibility, flammability, or radioactivity. Cylindrical vessels are generally preferred, because they present simpler manufacturing problems and make better use of the available space [1]. Demands, and to achieve higher profits; industries that produce pressure vessels are not the exception. If the defects originating during the manufacturing process are not detected, the vessel can break during operation. A ruptured pressure vessel can be hazardous, possibly leading to poison gas leaks, fires, or explosions, which may cause significant losses of human

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