An Application of Fabrication Method to Control Welding Distortion Regarding a Pressure Vessel
- Jong Min Kim (Hyundai Heavy Industries Co., Ltd.) | Ha Keun Kim (Hyundai Heavy Industries Co., Ltd.) | Dong Ju Lee (Hyundai Heavy Industries Co., Ltd.) | Hee Tae Lee (Hyundai Heavy Industries Co., Ltd.)
- Document ID
- International Society of Offshore and Polar Engineers
- The 29th International Ocean and Polar Engineering Conference, 16-21 June, Honolulu, Hawaii, USA
- Publication Date
- Document Type
- Conference Paper
- 2019. International Society of Offshore and Polar Engineers
- pressure vessel, angular distortion, production method, transverse shrinkage, Welding distortion, STEM
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- 11 since 2007
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An effective design method to control the welding distortion of a pressure vessel constructed by HY-80 steel, especially thick plate, have been established using experiment, measurement data and FE analysis. It is found that the major factors affecting the distortion of the pressure vessel are angular distortion and transverse shrinkage. To estimate these factors, predictive equations have been derived by several experiments and the results are embedded in simplified thermo-elastic method(STEM)(Park et al., 2001) for FE analysis. Based on the results, proper quality control methods have been proposed to meet the allowance criteria without additional mechanical constraint of pressure vessel during fabrication.
Welding technique is typically used for structures requiring water-tight or pressure-tight conditions such as pressure vessels. However, in case of welding, thermal deformation occurs due to heat input of welding unlike other fabrication methods. Such deformation of the structure causes an excessive gap or misalignment in the process of joining or installation of the manufactured structures. In addition, recently, as the operation conditions of large structures such as pressure vessels become severer and the thickness used becomes thicker. This increases the demand for quality control. A proper distortion control method is becoming an important issue, and it is the most efficient way to establish an appropriate production planning through the distortion assessment.
In this study, the weld distortion assessment and control methods of an end-bulkhead of pressure vessel have been established to satisfy the accuracy of fitness. The welding distortions were identified with STEM and the validity of the predictions was verified by the data measured during the fabrication stage of the product.
HEAT INPUT MODEL
The temperature distribution, heat affected zone(HAZ) size and welding distortion were measured through the welding experiments in order to determine the optimal heat input model for FE analysis of the welding. Nonlinear thermal elasto-plastic analysis technique was used in the FE analysis. The heat transfer and thermal stress were analyzed individually. The lower surface of the welded member was assumed to be on the surface plate condition to constrain the reverse distortion caused by the welding heat input. The material was assumed as isotropic, temperature dependent and yield point was defined according to von-Mises yield stress.
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