Non-Destructive Inspection ATLAS

Example of FSM - Inspection with removable instruments

mark Tank bottom plate

1. Details of examination

- It is desirable to inspect, detect and quantify plate thinning while a tank is in operation.

- It is desirable to confirm tank bottom condition without stopping the operation.

- The quality of tank content is likely to be oxidized when a tank is opened.

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- Some method to inspect a tank bottom plate without opening the tank is requested.

Details of examination

2. Inspection and analysis procedures

①. Sensing-pins and electrodes are placed on an annular plate around a tank.

②. Potential differences (PD) between each paired sensing-pins are measured bi-directionally.

③. PD in a sound condition is calculated by using finite element method (FEM).

④. PD change rate is calculated using PD obtained from ② and ③.

⑤. In order to solve the simultaneous equation, PD change rate of each lattice is obtained.

⑥. PD change rate of each lattice is collated with the mastering curve. Thereby, the thickness distribution is obtained.

Inspection and analysis procedures

Example of result

Result of EPD Method

Finally, the simultaneous equations are solved by using the result of bi-directional measurements and the plate thickness distribution is inferred as shown in the figure below.

Verification of accuracy

Verification of accuracy

Tank bottom plate 1

Tank bottom plate 2

Tank bottom plate 5

Tank bottom plate 4

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