Cost-effectiveness analysis of tank and base foundation diagnostics without paintwork removal

The article describes the particular qualities of application of a cylindrical steel tanks' and base foundation technical inspection method without removal of a protective covering. The model is formed and the basic parameters of an estimation of economic efficiency of carrying out of diagnostics are determined. The economic efficiency of application of the modern method of vertical steel tank examination is estimated. The high economic efficiency of the new technological method is substantiated in comparison with the traditional method. It is established that the advantage of using the innovative diagnostic method in comparison with the traditional method is fully manifested when it is necessary to maintain a large fleet of tanks. It is calculated that, given the design parameters, the savings in the use of the method proposed by the authors in the long term are 1773.2 million rubles compared with traditional. The use of a new technological method - the technology of diagnosing vertical steel tanks without removing the protective coating, allows to reduce the total cost of conducting diagnostics with a discount of 8.7 times. Dependences were obtained of the discounted volume of expenses on acquisition of the equipment and the subsequent diagnostics of vertical steel tanks on the operation time of the vertical steel tanks

Modeling of storage tank settlement based on the United States standards

Up to 60% of storage tanks in operation have uneven settlement of the outer bottom contour, which often leads to accidents. Russian and foreign regulatory documents have different requirements for strain limits of metal structures. There is an increasing need for harmonizing regulatory documents. The aim of this study is to theoretically justify and to assess the possibility of applying the U.S. standards for specifying the allowable settlement of storage tanks used in Russia. The allowable uneven settlement was calculated for a vertical steel tank (VST-20000) according to API-653, a standard of the American Petroleum Institute. The calculated allowable settlement levels were compared with those established by Russian standards. Based on the finite element method, the uneven settlement development process of a storage tank was modeled. Stress-strain state parameters of tank structures were obtained at the critical levels established in API-653. Relationships of maximum equivalent stresses in VST metal structures to the vertical settlement component for settlement zones of 6 to 72 m in length were determined. When the uneven settlement zone is 6 m in length, the limit state is found to be caused by 30-mm vertical settlement, while stresses in the wall exceed 330 MPa. When the uneven settlement zone is 36 m in length, stresses reach the yield point only at 100-mm vertical settlement

Study of Deformations in a Large-Capacity Oil Storage Tank in the Presence of Subgrade Inhomogeneity Zones

Characteristics of a joint action of a subgrade and a large 50000 m3 capacity storage tank have been overviewed. The maximum allowable values of the RVSPK-50000 base immersion in the presence of the inhomogeneity zone have been determined given the stiffness of metal structures. To simulate the inhomogeneity zone we applied the Drucker–Prager model – a linear elastoplastic material implemented in the finite element software package ANSYS. The dependences of the maximum design value of the outer tank bottom contour immersion on the inhomogeneity zone sector length have been obtained (in the range of 10 to 95 meters). It has been found that 95% of all cases of uneven immersion occurring in practice fall within this range according to data on diagnostics of 40 vertical steel tanks

Analysis of the stress-strain state of the process pipeline to tank junction in case of subsidence

The article presents the developed finite element model of the emergency oil discharge system pipelines with a junction to the tank. Numerical modeling was carried out in the ANSYS software complex, with the help of which the model of the junction under consideration was created, considering the geometric and physical nonlinearity of the structure. A design model for the structure deformation is proposed in case the base subsidence develops. With the help of the tabulated function, it was possible to determine the value of subsidence at which critical stresses arise in the metal. Dependences of the maximum effective stresses in the metal structures of the wall to emergency discharge system pipeline junction on the RVS-20000 subsidence values are obtained. When the tank subsidence value is 144 mm, the limiting state in the wall and the junction to the pipeline occurs and the metal passes into the state of developing plastic deformations

Using Linear Spectral Method when Calculating Seismic Resistance of Large-Capacity Vertical Steel Tanks

The paper is aimed at determining the possibility of applying the simplified method proposed by the authors to calculate the tank seismic resistance in compliance with current regulations and scientific provisions. The authors propose a highly detailed numerical model for a common oil storage tank RVSPK-50000 that enables static operational loads and dynamic action of earthquakes to be calculated. Within the modal analysis the natural oscillation frequencies in the range of 0-10 Hz were calculated; the results are given for the first ten modes. The model takes into account the effect of impulsive and convective components of hydrodynamic pressure during earthquakes. Within the spectral analysis by generalized response spectra was calculated a general stress-strain state of a structure during earthquakes of 7, 8, 9 intensity degrees on the MSK-64 scale for a completely filled up, a half-filled up to the mark of 8.5 m and an empty RVSPK-50000 tank. The developed finite element model can be used to perform calculations of seismic resistance by the direct dynamic method, which will give further consideration to the impact of individual structures (floating roof, support posts, adjoined elements of added stiffness) on the general stress-strain state of a tank

Using Linear Spectral Method when Calculating Seismic Resistance of Large-Capacity Vertical Steel Tanks

The paper is aimed at determining the possibility of applying the simplified method proposed by the authors to calculate the tank seismic resistance in compliance with current regulations and scientific provisions. The authors propose a highly detailed numerical model for a common oil storage tank RVSPK-50000 that enables static operational loads and dynamic action of earthquakes to be calculated. Within the modal analysis the natural oscillation frequencies in the range of 0-10 Hz were calculated; the results are given for the first ten modes. The model takes into account the effect of impulsive and convective components of hydrodynamic pressure during earthquakes. Within the spectral analysis by generalized response spectra was calculated a general stress-strain state of a structure during earthquakes of 7, 8, 9 intensity degrees on the MSK-64 scale for a completely filled up, a half-filled up to the mark of 8.5 m and an empty RVSPK-50000 tank. The developed finite element model can be used to perform calculations of seismic resistance by the direct dynamic method, which will give further consideration to the impact of individual structures (floating roof, support posts, adjoined elements of added stiffness) on the general stress-strain state of a tank

Analysis of the stress-strain state of the process pipeline to tank junction in case of subsidence

The article presents the developed finite element model of the emergency oil discharge system pipelines with a junction to the tank. Numerical modeling was carried out in the ANSYS software complex, with the help of which the model of the junction under consideration was created, considering the geometric and physical nonlinearity of the structure. A design model for the structure deformation is proposed in case the base subsidence develops. With the help of the tabulated function, it was possible to determine the value of subsidence at which critical stresses arise in the metal. Dependences of the maximum effective stresses in the metal structures of the wall to emergency discharge system pipeline junction on the RVS-20000 subsidence values are obtained. When the tank subsidence value is 144 mm, the limiting state in the wall and the junction to the pipeline occurs and the metal passes into the state of developing plastic deformations

Modeling of storage tank settlement based on the United States standards

Up to 60% of storage tanks in operation have uneven settlement of the outer bottom contour, which often leads to accidents. Russian and foreign regulatory documents have different requirements for strain limits of metal structures. There is an increasing need for harmonizing regulatory documents. The aim of this study is to theoretically justify and to assess the possibility of applying the U.S. standards for specifying the allowable settlement of storage tanks used in Russia. The allowable uneven settlement was calculated for a vertical steel tank (VST-20000) according to API-653, a standard of the American Petroleum Institute. The calculated allowable settlement levels were compared with those established by Russian standards. Based on the finite element method, the uneven settlement development process of a storage tank was modeled. Stress-strain state parameters of tank structures were obtained at the critical levels established in API-653. Relationships of maximum equivalent stresses in VST metal structures to the vertical settlement component for settlement zones of 6 to 72 m in length were determined. When the uneven settlement zone is 6 m in length, the limit state is found to be caused by 30-mm vertical settlement, while stresses in the wall exceed 330 MPa. When the uneven settlement zone is 36 m in length, stresses reach the yield point only at 100-mm vertical settlement

Modeling of storage tank settlement based on the United States standards

Up to 60% of storage tanks in operation have uneven settlement of the outer bottom contour, which often leads to accidents. Russian and foreign regulatory documents have different requirements for strain limits of metal structures. There is an increasing need for harmonizing regulatory documents. The aim of this study is to theoretically justify and to assess the possibility of applying the U.S. standards for specifying the allowable settlement of storage tanks used in Russia. The allowable uneven settlement was calculated for a vertical steel tank (VST-20000) according to API-653, a standard of the American Petroleum Institute. The calculated allowable settlement levels were compared with those established by Russian standards. Based on the finite element method, the uneven settlement development process of a storage tank was modeled. Stress-strain state parameters of tank structures were obtained at the critical levels established in API-653. Relationships of maximum equivalent stresses in VST metal structures to the vertical settlement component for settlement zones of 6 to 72 m in length were determined. When the uneven settlement zone is 6 m in length, the limit state is found to be caused by 30-mm vertical settlement, while stresses in the wall exceed 330 MPa. When the uneven settlement zone is 36 m in length, stresses reach the yield point only at 100-mm vertical settlement

Study of Deformations in a Large-Capacity Oil Storage Tank in the Presence of Subgrade Inhomogeneity Zones

Characteristics of a joint action of a subgrade and a large 50000 m3 capacity storage tank have been overviewed. The maximum allowable values of the RVSPK-50000 base immersion in the presence of the inhomogeneity zone have been determined given the stiffness of metal structures. To simulate the inhomogeneity zone we applied the Drucker–Prager model – a linear elastoplastic material implemented in the finite element software package ANSYS. The dependences of the maximum design value of the outer tank bottom contour immersion on the inhomogeneity zone sector length have been obtained (in the range of 10 to 95 meters). It has been found that 95% of all cases of uneven immersion occurring in practice fall within this range according to data on diagnostics of 40 vertical steel tanks