An analytical model for the eddy current inspection of broken prestressing windings in prestressed concrete pressure pipe.

摘要

Prestressed concrete pressure pipe (PCPP) has proven to be a reliable and rugged form of water conveyance around the world for nearly sixty years. However, as many of these original pipes are nearing the end of their anticipated operational lifetime, their imminent failure leading to service disruptions and the looming exorbitant cost of replacement demand new techniques in the integrity testing arsenal. An electromagnetic nondestructive testing technique recently developed by the Applied Magnetics Group (AMG) of Queen's University in collaboration with the Pressure Pipe Inspection Company (PPIC) exploits low frequency eddy currents induced in the conducting components of the pipe in order to gauge their condition. Specifically, as broken prestressing windings are a major cause of pipe failure and rupture, a sensitive method has been developed to inspect for them. As this research is still in the developmental stage, a reliable, quantitative model is required to account for the numerous factors present in the application of this technique. This study presents a simple model whereby the actual, detector inspection signals arising from a 1.52 m diameter embedded cylinder pipe, a standard pipe size, are calculated for many different inspection arrangements and pipe properties. This simple procedure may be extended to many more cases. Although no opportunity exists at present to test the accuracy of the present model, favourable agreement is made with a previous theoretical model.