1. Introduction
2. Hydrostatic Test
2.1 Definition and Procedure
2.2. Analysis of the Cause of Deformation and Establishment of Analysis Scenarios
3. Possibility of Damage to Tank Considering Water Filling Situation
4. Deformation Analysis of Tank Outer Wall
4.1 Modeling and Boundary Conditions
4.2 Loading Conditions
4.3 FEA Results and Discussion
5. Theoretical Estimation of Deformation of the Tank Outer Wall
6. Summary and Conclusion
The focus was placed on the problem of occasional deformations during the process of hydrostatic testing after installation of a tank. It was assumed that such deformation is caused by overpressure resulting from the air inside the tank, which may occur during a hydrostatic test.
It was inferred that the causes of overpressure during a hydrostatic test were low air pipe performance, diameter difference between the inlet pipe and air pipe, and fast water filling rate above the appropriate level.
To confirm that deformation occurs because of the overpressure of the internal air during hydrostatic testing of the tank, the difference in diameter between the inlet pipe and the air pipe was considered using the Bernoulli equilibrium equation in terms of flow rate. Using this example, the possibility of a pressure rise was mathematically verified.
Six deformation analysis scenarios were established using the water filling level and the air pipe performance as the variables, and FEA was conducted for the urea water storage tank. The analysis showed a large deformation of up to 37 mm.
As a result of FEA, the stress results exceeded the allowable stress of the material in the deformation analysis scenarios of cases 3, 5, and 6. In these cases, a fracture of the structure can occur. In case 3, the deflection limit was not exceeded in terms of deformation. However, it was confirmed that permanent deformation can occur as a result of plasticity in terms of the yield strength of the material.
The maximum deflection that can occur was calculated using beam theory. It was demonstrated that overpressure may actually be a cause of deformation by verifying that the approximation of the deformation obtained through FEA is included in the resulting solutions of the maximum deflection calculation.