Electricity: measuring and testing – Magnetic – Magnetic sensor within material
Reexamination Certificate
2000-02-29
2001-08-28
Snow, Walter (Department: 2862)
Electricity: measuring and testing
Magnetic
Magnetic sensor within material
C324S227000
Reexamination Certificate
active
06281678
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to testing equipment and, more specifically, to testing equipment for eddy current tube analysis. The present invention, a triple-action heat exchanger tube probe, is an electromagnetic probing device attached to a long flexible extension means which is, in turn, connected by electrical wiring running therethrough, to an analyzing device. The purpose of this type of device is to provide a means of probing and detecting defects within non-ferrous heat exchanger tubing material. This can be accomplished by providing an electromagnetic transmitting coil within the probe that can induce eddy currents through some distance within the tubing material in order to produce a corresponding magnetic field therein that will indirectly cause an induced output current to be produced within a receiving coil in the probe that may then be transmitted to analyzing equipment. Thereupon the input/output currents are compared with calibrated standards and algorithms used by specialized diagnostic software programs running on test equipment for a determination of the defect condition of the material under test. Because of limitations in computer technology test probes have been limited to using one the of electromagnetic coil pair per test.
Recent advances in computer technology, however, have lead to the development of test equipment with multiple input/output signal generating and processing capability allowing for the support of multiple-coil pair use in test probes. This breakthrough technology now yields more information per test than was possible with previous testing techniques. This is accomplished by focusing on the advantages of each coil pair and ignoring the disadvantages. The results of this technique yield great benefits. The preferred embodiment of the present invention, the Tri-Tip Probe, is a prime example of the new technology that provides a unique assembly of 3 distinct coil pair types.
The first coil pair in the assembly is known as the AC3 coil pair. They specialize in electronically erasing all gradual geometry changes and detect large defects within these areas. It is positioned first in the probe assembly in order to be effective in testing through the end of the tube.
The middle coil pair, known as the Differential coil pair, excel at detecting small defects and making accurate depth determinations on both the inside and outside of the tube but cannot be used to determine overall wear patterns.
The last coil pair in the Tri-Tip Probe assembly is known as the x-axis coil pair. X-axis coil configuration is excellent at detecting overall wear patterns on both sides of the tube because it faithfully follows the tube geometry. The composite radiation pattern results in a large lobe of energy that can be rotated to further troubleshoot located defects.
Each of these coil pairs adds data missed by the others and the composite effect removes all the disadvantages inherent in each pair separately. With its unique combination of coil pairs, The Tri-Tip Probe can provide more information from a single test then was previously possible from any other probe or series of individual tests.
2. Description of the Prior Art
There are other eddy current probing devices designed for eddy current tube analysis. Typical of these is U.S. Pat. No. 5,270,647 issued to Robert Beissner and Takashi Kikuta on Dec. 14, 1993.
Another patent was issued to Valentino S. Cecco et al. on Aug. 17, 1993 as U.S. Pat. No. 5,237,270. Yet another U.S. Pat. No. 4,855,677 was issued to William G. Clark et al. on Aug. 8, 1989 and still yet another was issued on Sep. 17, 1991 to Valentino S. Cecco et al. as U.S. Pat. No. 5,049,817.
Another patent was issued to William G. Clark on Nov. 26, 1991 as U.S. Pat. No. 5,068,608.
U.S. Pat. No. 5,270,647
Inventor: Robert Beissner & Takashi Kikuta
Issued: Dec. 14, 1993
A pipe electromagnetic field simulation apparatus used to simulate a current produced by flaw in a pipe when the flaw is subjected to the electromagnetic field of a transmitting coil. The apparatus includes a system for determining an electromagnetic field distribution of a represented pipe without a flaw, a system for determining an equivalent current source of a represented flaw in the represented pipe, and a system for determining the electromagnetic field distribution of a represented pipe with a flaw. The apparatus may also include a system for determining a signal received by a detector which indicates a flaw.
U.S. Pat. No. 5,237,270
Inventor: Valentino S. Cecco and Jon R. Carter
Issued: Aug. 17, 1993
Eddy current probes for ferromagnetic tubes of relatively small diameters are disclosed. A probe housing is made of non-ferromagnetic material and shaped to be introduced into a tube for inspection. The probe housing includes at least two eddy current measuring assemblies either of these assemblies includes magnetic field generators for producing a maximum magnetization at a predetermined area of the tube and a minimum magnetization at a diametrically opposite area of the tube. At least on eddy current measuring coil is associated with each magnetic field generator to measure the eddy current generated in the tube and which has a relatively high sensitivity to an anomaly at the maximum magnetization area. Further the current measuring assemblies are spaced apart axially with the housing and are rotated about its central axis by a predetermined angle so that each assembly differs in sensitivity to an anomaly depending upon their location within the housing.
U.S. Pat. No. 4,855,677
Inventor: William G. Clark, Jr. and Michael J. Metala
Issued: Aug. 8, 1989
An improved eddy current probe system and method for simultaneously detecting different types of flaws at different depths within a metallic wall, such as a section of Inconel tubing, is disclosed herein. The system comprises a current generator for generating alternating currents of substantially different frequencies, a probe head including first, second and third concentrically arranged coils in separate communication with a the current generator, shielding material disposed between the coils for preventing cross talk between the coil and the pulsating magnetic field of the coils adjacent to it, and a detector circuit which may include an inductive bridge for providing an electrical output representative of the impedance changes in the respective coils. In operation, each of the coils conduct currents having substantially different frequencies, the highest frequency being conducted by the smallest-diametered coil and the lowest frequency being conducted by the largest-diametered coil. The different levels of magnetic field penetration provided by the coils as it is helically moved around the inside surface of a section on Inconel tubing not only allows the probe system to detect diverse kinds of flaws such as cracks, pits, or regions of thinning, but also flaws located at different depths throughout the tube wall. In the method of the invention, a computer is used to adjust the frequencies of the alternating currents conducted through the coils during the scanning operation in order to maximize the impedance changes in each coil, thereby maximizing the resolution of the probe system.
U.S. Pat. No. 5,049,817
Inventor: Valentino S. Cecco and F. Leonard Sharp
Issued: Sep. 17, 1991
Eddy current probes for detecting internal defects in a ferromagnetic tube are disclosed. The probe uses a plurality of eddy current measuring means, each being operated at a different operating point on the impedance diagram. By operating more that one such eddy current measuring means simultaneously, noises by, for example, permeability variation of a ferromagnetic material and internal magnetic deposit, can be made less influential.
U.S. Pat. No. 5,068,608
Inventor: William G. Clark, Jr.
Issued: Nov. 26, 1991
Both a system and a method for determining the length of a discontinuity such as a crack or other fault in the interior wall of a steam generator heat exchanger tube is disclosed here
Kroll Michael I.
Snow Walter
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