Method and apparatus for monitoring a cathodically protected corrodible hollow member
AssigneeMobil Oil Corporation
InventorEarnest E. Nelson
Life of this patent
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Abstract
A cathodic protection system for a buried, fluid pipeline that has an electrical lead or coil electrically coupled between the pipeline and a sacrificial anode. As the anode deteriorates by electrochemical reaction with its environment, a current flows through the lead or coil, producing an electromagnetic field that permeates the pipeline. The strength of this magnetic field can be correlated to the condition of the sacrificial anode and/or the condition of a protective coating on the pipeline. An apparatus for detecting the strength of the electromagnetic field travels through the pipeline in a scraper or similar device, senses the magnitude of the field, and generates a signal indicative of the condition of the cathodic protection system.
Claims19
In a cathodic protection system for an elongate corrodible member routed through an electrolytic environment, said corrodible member having a longitudinally extending channel therethrough, said cathodic protection system including at least one sacrificial anode disposed within said electrolytic environment in spaced proximity to said elongate corrodible member, and connecting means for electrically connecting said sacrificial anode to said elongate corrodible member, an improved system for monitoring the condition of said cathodic protection system comprising:
- first means, responsive to electrical current flowing through said connecting means, for establishing an electromagnetic field within said channel of said corrodible member, said electromagnetic field being proportional to said electrical current flowing through said connecting means;
- and
- second means, positionable in said longitudinally extending channel of said corrodible member, for detecting the magnitude of said electromagnetic field established within said channel of said corrodible member and for supplying a signal representative of the magnitude of said electromagnetic field.
In a cathodic protection system including a cathodically protected corrodible member having an interior channel and at least one sacrifical metal anode, the improvement comprising:
- connection means electrically connected between said corrodible member and said anodes for establishing an electromagnetic field proportional to the current flow therethrough, said connection means being so positioned and oriented relative to said corrodible member as to cause said electromagnetic field to penetrate through said corrodible member into the interior channel thereof, and
- detection means for determining the field strength of said electromagnetic field in said interior channel, said detection means being positionable within said interior channel of said corrodible member.
A cathodically protected pipeline system comprising:
- a length of corrodible pipe routed through an electrolytic environment;
- at least one electrically continuous metallic conductor having a higher electromotive potential than the material forming said pipe, said conductor being routed through said electrolytic environment in spaced relationship with said length of pipe;
- a plurality of electrical coils, each of said electrical coils electrically connecting said metallic conductor and said pipe at predetermined positions spaced along the length of said pipe, each of said electrical coils being so positioned and so oriented relative to said pipe so as to establish an electromagnetic field within the interior of said pipe at the particular location of said electrical coil, said electromagnetic field being proportional to the current flow through said coil between said pipe and said metallic conductor;
- carrier means for traversing through the interior of said pipe, said carrier means being propelled by a fluid flowing through said pipe;
- means carried by said carrier means for supplying a signal representative of the strength of the electromagnetic field established by each of said electrical coils as said carrier means traverses past each of said predetermined positions;
- and
- means carried by said carrier means for conveying each of said representative signals to a predetermined remote location.
The method of monitoring the condition of a cathodic protection system that includes a cathodically protected hollow corrodible member, at least one sacrificial anode, and at least one electrical connection between said corrodible member and said sacrificial anode comprising the steps of:
- establishing an electromagnetic field in the interior of said hollow cathodically protected member that is proportional to the electrical current flowing through said electrical connection;
- and
- detecting the magnitude of said electromagnetic field within the interior region of said hollow member.
A method of monitoring the condition of a cathodic protection system for a fluid carrying pipeline, said system including a sacrificial anode and at least one electrical connection between said pipeline and said anode, comprising the steps of:
- establishing an electromagnetic field at a predetermined location in the interior of said pipeline that is proportional to the electrical current flowing through said electrical connection;
- conveying a device for detecting said electromagnetic field and generating a signal representative of the magnitude thereof through said pipeline;
- and
- generating a signal representative of the magnitude of said electromagnetic field as said device traverses past said predetermined location.
Dependencies are inferred from the claim text.