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Screening Inspection of Pipes
Example1 Pipe through tank dike
When conducting thickness measurement by UT (Ultrasonic Testing) or RT (Radiographic Testing), not only does it require taking down a tank dike, but also it costs a lot of money to build a temporary dike in the meantime.
In recent years, it has been tried to inspect a tank without demolishing its dike, for example, by means of a guided wave detection technique.
Still, there were many places where accurate examination was unavailable by the technique because guided waves are likely to be affected by external conditions on pipes such as corrosion proof tapes.
In contrast, AEPD testing ensures an inspection unaffected by external conditions on pipes or internal fluid nor requiring the demolition of a dike.
In AEPD testing for penetrating pipes of a dike, sensing pins are spaced in the measurement section evenly and parallel to the direction of the impressed electric currents.
Furthermore, sensing pins for comparison will be placed at a regular interval on somewhere healthy outside the dike.
Comparing electrical potential differences between sensing pins in the measurement section and those in the reference section, it is possible to understand if corrosion is present or not and its severity, if any.
Example 2 Convection tube
In recent years, there have been cases where wall thinning, which is presumed to be high-temperature sulfide corrosion occurring in the heating furnace convection tube, has progressed over the years. When it is needed, screening tests in AEPD are being utilized.
Similar to the oil barrier penetration pipe inspection, the potential difference between the measurement section and the reference section is compared to evaluate the presence or absence of corrosion and the scale.
Arrangement sectional view of measuring tube
Minimum wall thickness value (mm) by FSM
