A Novel Method for Crack Detection of Oil Docks and Offshore Structures and Equipment through Insulation and Protective Coatings

One of the main problems in oil docks and offshore stuctures is the initiation of small cracks in fitting places. Maintenance engineers have always looked for a method to detect the crack at an early stage before crack growing and critical conditions initiate. Although several non-destructive testing methods have been proposed for the inspection of these structures, removing insulating layer and protective coating makes these methods inappropriate and expensive. In this paper, a new non-destructive pulse eddy current method is used to detect and characterize fine cracks under insulation layer without separating and removing the insulation from the structure. First, the theory of pulse eddy current method is briefly explainedand then the pulsed eddy current test is carried out on a steel plate having several simulated cracks with different depths. The results of the tests on the test plates with insulation layers and without insulation layers are presented and compared.