RESEARCH OF VERTICAL FILTER’S BODY’S WELDED JOINTS CRACK’S AND DEFECT’S CAUSES

Abstract

Results of research of vertical filter’s welded joints crack’s and defect’s causes at the stage of manufacture are shown in this paper. One of the main causes of the shape’s deformation and cold cracks are significant internal stress in welded joints. In accordance with this changes in ovality of welded body at different stages of manufacture was analyzed. The experiments were carried out at the real existing production’s structures in the field. For housings vessels and equipment, which work under pressure one of the criteria of manufacturing quality is accordance of the geometric parameters to requirements of federal regulations. Among the main controlled parameters in accordance with GOST R 52630-2006 is a relative roundness of the apparatus. In these regulatory documents maximum level of internal stresses is not regulated. Thus, manufacturers try to reduce all means relative roundness, often creating a critical design loads that result in the formation of cold cracks on the design stage of manufacture, or in first months of operation. One of the manufacturing operation affecting the roundness of the housing unit is the process of welding the fitting to the sidewall, while the larger diameter welded fitting, the greater the deviation. In this paper, the technology of manufacturing the filter housing is welded to the two opposing tube, the total diameter greater than the diameter of the filter housing. The paper provides an analysis of the existing manufacturing technology used in the production, said method is used to reduce welding deformation. The absence of mandatory requirements for reducing internal stresses in such structures leads to the creation of constructions with high level of internal stresses, that fact significantly increases the probability of cold cracking. The appearance of the stress-strain state induced by this operation is described in many research projects. However, this fact is not taken in the account in real manufacture. Results shown in this paper demonstrates the influence of welding processes for possible deviations of the geometric shape of the hull unit and allows to provide at the stage of process development compensatory measures.