Inspecting finned ferromagnetic heat exchanger tubes using tube to tube through transmission technique.

摘要

n chemical processing and air conditioner heat exchangers, finned ferromagnetic tubes are used. Flaws which occur in the plain ferromagnetic tubes also occur in the finned tubes. Conventional electromagnetic methods can not be used to inspect the finned tubes because of the interference caused by the fins. In this thesis, a recently developed method Tube to Tube Through Transmission (T4) has been tried. As this method is new little theoretical or experimental explanation exists for it. A study of magnetic fields is done to determine the nature of eddy currents induced in this new method. It is shown that the induced eddy currents have the same form as in the remote field eddy current (RFEC) method. Hence equations used in analyzing the RFEC signal are applied here also. Signals from machined defects were analyzed using these equations and it was found that the defect depths can be estimated within