Technology of Repairing the Active Main Pipeline Using Braze-Welded Couplings

Abstract

Background. During operation, the main pipeline needs to be repaired. During periodic diagnostics of the pipeline state defects are detected, some of which are unacceptable. The classic repairing method, that involves the shutdown of the pipeline with subsequent replacement of its defective spots, requires significant financial costs and is associated with a forced  pipeline outage and environmental violation.

Objective. The purpose of this article is to improve the technology of reinforcing sections of main high-pressure pipeline with welded couplings, which are filled with molten metal by allowing obtaining high efficiency of pipe strengthening of medium and small diameters.

Methods. Strength improvement of the active pipeline spots is realized by installing brazed-welded couplings on an active main pipeline. Strengthening the pipeline with the coupling consists in the redistribution of the load part from the pipe to the wall of the coupling, which leads to a decrease of the stress level in the pipe wall. The reinforcement efficiency of the pipeline could be evaluated by the degree of reduction of circumferential stresses in the fixed pipe wall.

Results. The article suggests a technique for strength improvement of pipeline spots using couplings filled with a molten metal that has a high elasticity modulus. The operations of formation of under-coupling layer with the parameters that provide achievement of the maximum value of the stresses reduction degree in the reinforced pipe are proposed, while ensuring an even load distribution between the wall of the pipeline spot being repaired and the coupling shell. An improved technology for fixing defective spots of the active pipeline has been proposed, designs for front seals have been proposed that facilitate the formation of under-coupling layer with optimal parameters. The proposed technique makes it possible to increase the efficiency of the pipe strengthening of small and medium diameters.

Conclusions. The article proposes an improved technology of the defective spots reinforcing of the active main pipeline using braze-welded coupling. The focus is on the design of mechanical seals that ensure the tightness of the under-coupling space during the formation of the coupling layer.

Further research would be performed in the direction of developing a mathematical model of the pipeline reinforced with braze-welded coupling, taking into account temperature changes during heating and cooling of the coupling structures during the formation of the under-coupling layer. Some research will be also performed to improve the coupling structures and methods of quality control of their mounting on the pipe.