Patent ID: 7541817
Filing Date: 2009-06-02
Classification: G01N

Abstract:
1. A method of diagnosing corrosion risk of a pipe or a pipeline buried in soil due to DC stray currents and/or AC voltages induced in the soil, comprising: i) providing a two-part metal probe including a first probe part having a first metal element of a first size and a first specific resistivity R ii) burying said two-part metal probe in said soil; iii) electrically connecting said two-part metal probe to said pipe or pipeline; iv) measuring an AC current flowing between said pipe or said pipeline and said two-part metal probe while said pipe or said pipeline and said two-part metal are electrically connected; v) electrically disconnecting said two-part metal probe from said pipe or pipeline; vi) measuring an AC voltage between said pipe or pipeline and said two-part metal probe while said pipe or pipeline and said two-part metal probe are disconnected from one another; vii) measuring a spread resistance based on said AC current determined in step iv) and said AC voltage measured in step vi) according to Ohm's Law; viii) passing a first excitation current through said first probe part and determining the voltage generated by said first excitation current across said first probe part for measuring the resistance of said first probe part according to Ohm's Law while said pipe or pipeline and said two-part metal probe are disconnected from one another; ix) passing a second excitation current through said second probe part and determining the voltage generated by said second excitation current across said second probe part for measuring the resistance of said second probe part according to Ohm's Law while said pipe or pipeline and said two-part metal probe are disconnected from one another; x) storing said measurements provided in steps iv), vi), vii), viii), and ix); xi) repeating said steps iii) through x) periodically, xii) determining an actual corrosion of said first probe part based on the measurements performed in steps viii) and ix) according to a mathematical corrosion algorithm; and xiii) diagnosing the risk of corrosion of said pipe or pipeline based on an empirical combination of the actual corrosion of said first probe part, said spread resistance determined in step vii) and said AC voltage measured in step vi).