Introduction

Winnik, S.

doi:10.1016/b978-0-08-100714-3.09976-5

Cited by 1 publication

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“…Corrosion under insulation (CUI) refers to corrosion on the external surface of piping and vessels underneath the insulation layer, and is one of the leading failure mechanisms for insulated pipe infrastructure. Breaks in the weather shield can lead to the ingress of water, which in combination with (cycling) processing heat leads to corrosion at the pipe surface [ 2 ]. According to an Exxon Shell study, the highest incidence of leaks in the refining and chemical industries is due to CUI and adds up to about 10% to total plant maintenance costs [ 3 ].…”

Section: Introductionmentioning

confidence: 99%

Eddy Current Testing with Giant Magnetoresistance (GMR) Sensors and a Pipe-Encircling Excitation for Evaluation of Corrosion under Insulation

Bailey

Long

Hunze

2017

Sensors

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This work investigates an eddy current-based non-destructive testing (NDT) method to characterize corrosion of pipes under thermal insulation, one of the leading failure mechanisms for insulated pipe infrastructure. Artificial defects were machined into the pipe surface to simulate the effect of corrosion wall loss. We show that by using a giant magnetoresistance (GMR) sensor array and a high current (300 A), single sinusoidal low frequency (5–200 Hz) pipe-encircling excitation scheme it is possible to quantify wall loss defects without removing the insulation or weather shield. An analysis of the magnetic field distribution and induced currents was undertaken using the finite element method (FEM) and analytical calculations. Simple algorithms to remove spurious measured field variations not associated with defects were developed and applied. The influence of an aluminium weather shield with discontinuities and dents was ascertained and found to be small for excitation frequency values below 40 Hz. The signal dependence on the defect dimensions was analysed in detail. The excitation frequency at which the maximum field amplitude change occurred increased linearly with the depth of the defect by about 3 Hz/mm defect depth. The change in magnetic field amplitude due to defects for sensors aligned in the azimuthal and radial directions were measured and found to be linearly dependent on the defect volume between 4400–30,800 mm3 with 1.2 × 10−3−1.6 × 10−3 µT/mm3. The results show that our approach is well suited for measuring wall loss defects similar to the defects from corrosion under insulation.

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Section: Introductionmentioning

confidence: 99%