Welding of Large Diameters Pipes
Explosive and Thermochemical Welding of Pipes Having Large Diameters
Tech Area / Field
- OTH-BIT/Building Industry Technology/Other
8 Project completed
Senior Project Manager
Ryzhova T B
VNIIEF, Russia, N. Novgorod reg., Sarov
- Dynamic Materials Corporation, USA, CO, Boulder
Project summaryGoal of the Project is development of technology for explosive and thermochemical welding of pipes having large diameters.
In spite of the fact that welding of metal constructions has been used already for a long time in industry and engineering, and for today there are several its variants (arc, contact, gas, cathode-ray, and other types of welding), this technological process is constantly under improvement. New types of welding are looked for. It can be explained, since welded joints are strongest, practically feasible, they provide leakproofness of a joint, etc., in comparison with all variety of variants of one-piece joint of metal constructions. So, welding is the only possible variant of pipelines joint for huge branches, which are the main means of transportation basic energy raw materials of the contemporaneity - oil and gas.
When forming pipelines, a consecutive welding of pipes is performed in accordance with constructing of all branch. Pipelines are often located in regions having complicated geographical and climatic conditions, sometimes pipelines have to intercross reservoirs on their bottoms. In such cases the traditional welding process with application of expensive equipment requiring energy power supplies becomes much more complicated.
Therefore efforts on introduction of untraditional methods of welding (for example, by explosion) are recently undertaken. However, for welding pipes of large diameter, new welding technologies require improvement of the key moments (for welding by explosion, this is prevention from deformation and reduction of diameter of loaded object; for thermochemical welding, it is necessary to produce seam resistant to corrosion).
In RFNC-VNIIEF a rich experience in development of explosive technologies and introduction of them in industry is accumulated as a result of conversion activities. RFNC-VNIIEF buildings and test sites are traditionally used for explosive efforts (detonation of charges of high explosives (HE) with weights of several tens kilograms). The equipment-methodical complex is constantly employed for recording dynamic parameters of physics of short-time processes (detonation characteristics of HE, velocities of plates launching, pressure pulses at their collisions, etc.).
In particular, reliable joint of pipes having diameter less 0.5 m without their deformation was made during experimental studies of processes of welding by explosion.
A series of formulations of thermochemical mixtures adequate to various temperatures of oxidation-reduction reaction and various final components of this reaction.
Under the Project framework it is suggested to study processes of explosive and thermochemical welding of metals and to develop technology of explosive and thermochemical welding of pipes having large diameters. Both in the first and in the second cases, the preliminary estimations of the process will be carried out for optimization of experimental efforts. The following characteristics will be in the experiments:
– optimum composition of HE charge intended for launching of layer to be welded to the joint of two pipes. Optimization of HE charge is necessary for its minimization (reduction of unloading and deformation effects on objects);
– optimum filler of pipes cavities aimed to exclude their deformation at pulse loading;
– optimum formulation of thermochemical mixture (in temperature and reaction velocity, in final product if reaction).
At the final stage a series of control tests will be performed on explosive and thermochemical welding of pipes having diameters ~ 1.5 m. Control over quality of welded seam will be made by the methods of acoustic and metallographic analysis.
The Project efforts will help to use potential of high-skilled scientists and engineers earlier involved in weapon development for development of new advanced industrial technologies. Thus, two basic objectives of the ISTC will be reached:
– reorientation of scientific potential of weapon scientists and engineers;
– raising of the level of industrial technologies.
Within the Project framework the following efforts will be performed:
1. Review of current status of studies in application of technologies of explosive and thermochemical welding of pipes having large diameters.
2. Numerical-experimental studies for selection of optimum formulation of HE charge and material of filler of pipes cavities.
3. Experimental verification of explosive welding of pipes having large diameters.
4. Numerical-experimental studies for selection of optimum thermochemical mixture.
5. Experimental verification of thermochemical welding of pipes having large diameters.
6. Analysis of results obtained during the Project efforts. Stating of technology for explosive and thermochemical welding of pipes having large diameters.
The program of experimental studies will be discussed and coordinated with the foreign collaborators. It is planned to discuss results obtained during the Project efforts at workshops with participation of the foreign collaborators.
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