engleski

The analysis of causes for a change in material properties in the pressure vessel during exploitation

Classical approach in pressure vessel analysis includes the comparison of stresses present in characteristic section and stresses that are characterized by behaviour of the selected material. Yield stress is a material property that is used the most in design. The second approach includes toughness and the possibility of crack appearance throughout the useful life, as well as the change in material properties during exploitation. This knowledge can be easily used in determining vessel thickness, but also helps in the material selecftion process. The analysis of causes for a change in material properties from manufacturing all the way to the removal from exploitation was performed on over fifty vessels in oil processing. A special attention was given to a reactor vessel that operates under heavy operating conditions (operating pressure of 15.5 MPa, operating temperature of over 450 oC, and with a complex catalytic chemical process using hydrogen). The vessel body is made out of low-alloyed steel ASTM A 387 Gr.D, and is reinforced on the inside with a 4-mm thick layer of stainless austenite steel AISI 347. Another problem is present when determining further usage of this vessel, that is, after observing certain changes in chemical and material properties of the vessel body material during exploitation. Based on the analysis of causes for a change in material properties, it is a possible to improve the design of these types of vessels. It is also possible to determine its useful life more accurately.

pressure vessel; analysis; material; exploitation

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