Method for determining average wall thickness for pipes and tubes using guided waves
First Claim
1. A method for measuring changes in an average wall thickness for a longitudinal section of pipe from a single location comprising the steps of:
- directing interrogating mechanical waves into a wall of said pipe at said single location;
receiving a multifrequency return signal, said multifrequency return signal resulting from a dispersion of said interrogating mechanical waves throughout said longitudinal section of pipe;
analyzing said return signal by determining the ratio of wave group velocity at a first selected frequency to wave group velocity at a second selected frequency, said first and second selected frequencies being discrete frequencies offset from a cut-off frequency, said cut-off frequency being a frequency range over which said return signal is significantly attenuated due to the original geometry of said pipe;
comparing said ratio of wave group velocities with a baseline ratio for said pipe; and
correlating a change in said ratio with a respective change in said average wall thickness for said longitudinal section of pipe.
1 Assignment
0 Petitions
Accused Products
Abstract
A method for determining changes in the average wall thickness or the mean radius of a pipe or tube using ultrasonic and/or magnetostrictive wave probes by analyzing the dispersive behavior of waves traveling in the tube wall volume. The method examines certain wave propagation modes and identifies a cut-off frequency that is characteristic for a particular wall thickness or tube diameter. This method permits the rapid and accurate inspection of a length of pipe or tube from a single location on the inside diameter of the pipe and permits a comparison of data gathered with similar data for the structure in its original condition. Changes in the cut-off frequency, indirectly determined by the method of the present invention are inversely related to changes in the wall thickness and/or the mean radius for the cylindrical structure. In this manner the method of the present invention provides a mechanism for determining the remaining service life for such pipes and tubes.
64 Citations
8 Claims
-
1. A method for measuring changes in an average wall thickness for a longitudinal section of pipe from a single location comprising the steps of:
-
directing interrogating mechanical waves into a wall of said pipe at said single location; receiving a multifrequency return signal, said multifrequency return signal resulting from a dispersion of said interrogating mechanical waves throughout said longitudinal section of pipe; analyzing said return signal by determining the ratio of wave group velocity at a first selected frequency to wave group velocity at a second selected frequency, said first and second selected frequencies being discrete frequencies offset from a cut-off frequency, said cut-off frequency being a frequency range over which said return signal is significantly attenuated due to the original geometry of said pipe; comparing said ratio of wave group velocities with a baseline ratio for said pipe; and correlating a change in said ratio with a respective change in said average wall thickness for said longitudinal section of pipe. - View Dependent Claims (2, 3, 4, 5)
-
-
6. A method for measuring changes in an average wall thickness for a longitudinal section of pipe from a single location on said longitudinal section of pipe, comprising the steps of:
-
directing interrogating mechanical waves into an inside wall of said pipe; receiving a multifrequency return signal, said multifrequency return signal resulting from a dispersion of said interrogating mechanical waves throughout said longitudinal section of pipe; analyzing said return signal by determining a shift in a cut-off frequency identified within said return signal, said cut-off frequency being a frequency range over which said return signal is significantly attenuated due to the original geometry of said pipe; correlating said shift in said cut-off frequency with a respective change in said average wall thickness for said longitudinal section of pipe. - View Dependent Claims (7, 8)
-
Specification