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Title: Flowpath evaluation and reconnaissance by remote field Eddy current testing (FERRET)

Abstract

This document describes the design and development of FERRET (Flowpath Evaluation and Reconnaisance by Remote-field Eddy current Testing). FERRET is a system for inspecting the steel pipes which carry cooling water to underground nuclear waste storage tanks. The FERRET system has been tested in a small scale cooling pipe mock-up, an improved full scale mock-up, and in flaw detection experiments. Early prototype designs of FERRET and the FERRET launcher (a device which inserts, moves, and retrieves probes from a piping system) as well as the field-ready design are discussed.

Authors:
;
Publication Date:
Research Org.:
Westinghouse Savannah River Co., Aiken, SC (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10123845
Report Number(s):
WSRC-MS-93-612
ON: DE94006673; TRN: 94:002652
DOE Contract Number:
AC09-89SR18035
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: [1993]
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION; PIPES; IN-SERVICE INSPECTION; EDDY CURRENT TESTING; RADIOACTIVE WASTES; COOLING SYSTEMS; UNDERGROUND STORAGE; INVENTIONS; REMOTE SENSING; FLUID FLOW; 420500; 420200; 055001; MATERIALS TESTING; FACILITIES, EQUIPMENT, AND TECHNIQUES; TECHNICAL ASPECTS

Citation Formats

Smoak, A.E., and Zollinger, W.T. Flowpath evaluation and reconnaissance by remote field Eddy current testing (FERRET). United States: N. p., 1993. Web. doi:10.2172/10123845.
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Smoak, A.E., & Zollinger, W.T. Flowpath evaluation and reconnaissance by remote field Eddy current testing (FERRET). United States. doi:10.2172/10123845.
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Smoak, A.E., and Zollinger, W.T. Fri . "Flowpath evaluation and reconnaissance by remote field Eddy current testing (FERRET)". United States. doi:10.2172/10123845. https://www.osti.gov/servlets/purl/10123845.
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@article{osti_10123845,
title = {Flowpath evaluation and reconnaissance by remote field Eddy current testing (FERRET)},
author = {Smoak, A.E. and Zollinger, W.T.},
abstractNote = {This document describes the design and development of FERRET (Flowpath Evaluation and Reconnaisance by Remote-field Eddy current Testing). FERRET is a system for inspecting the steel pipes which carry cooling water to underground nuclear waste storage tanks. The FERRET system has been tested in a small scale cooling pipe mock-up, an improved full scale mock-up, and in flaw detection experiments. Early prototype designs of FERRET and the FERRET launcher (a device which inserts, moves, and retrieves probes from a piping system) as well as the field-ready design are discussed.},
doi = {10.2172/10123845},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Dec 31 00:00:00 EST 1993},
month = {Fri Dec 31 00:00:00 EST 1993}
}
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Technical Report:
View Technical Report (1.39 MB)
DOI:  10.2172/10123845
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  • The feasibility of detecting stress-corrosion cracks (SSC) using the Remote Field Eddy Current (RFEC) technique was demonstrated. The RFEC technique interrogates the entire thickness of the pipe and is applicable for in-line inspection. If it can be shown that the RFEC technique is effective in detecting SSC, then the technique is an ideal method for detecting the defects of interest. A defect detection model is proposed for explaining the mechanism for crack detection. For axially oriented, closed cracks, such as SCC, the conventional defect detection model proved to be too simplistic and not applicable. Therefore, a new detection mode thatmore » examines the flow of circumferential eddy currents was developed based on experimental results. This model, though not rigorous, provides a general understanding of the applicability of the RFEC technique for finding SSC. The data from the cracks and various artificial defects is presented in three formats: isometric projections, pseudocolor images and line-of-sight data. Though only two cracks were found, the experimental results correlate well with the circumferential eddy current theory. A theoretical analysis of the effects of motion on the output signal of the receiver is presented. This analysis indicates that inspection speed of simple implementations may be limited to a few miles per hour. Remote field eddy current inspection has excellent potential for inspection of gas transmission lines for detecting stress corrosion cracks that should be further developed.« less

  • This report describes experimental application of the RFEC technique for crack detection in gas transmission pipelines. Crack data from three pipe samples are presented. A total of eight stress corrosion cracks were detected ranging in depth from 25 percent of wall thickness to completely through-wall. An improved defect detection model is presented that explains the interaction of the remote electromagnetic field with axial cracks as well as other defects such as metal loss and circumferential cracks. The investigation of the through-wall crack helps illustrate this model and also indicates RFEC has potential for detection and location of leaks from cracks.more » Many regions with crack depths less than 25 percent and lengths less than one inch were investigated, but dejection was unsuccessful. Data from artificial defects are presented to describe the relative sensitivity and characterization capability of the RFEC technique to longitudinal and circumferential planar (crack-like) defects as well as volumetric (metal loss) defects.« less

  • Heat exchanger tubes can be examined for metal loss using remote field eddy current (RFEC). RFEC is an electromagnetic technique that produces a fast, economical, and thorough heat exchanger tube assessment. With RFEC services available, damaged tubes can be found and plugged, keeping heat exchangers operating near peak efficiency and reducing the risk of an unplanned shutdown. The technique is becoming well recognised in industry. RFEC uses a low-frequency field to penetrate ferromagnetic tube walls which are not practical to inspect with conventional eddy current. Internal and external metal loss is detected with nearly equal sensitivity. RFEC data from themore » field are presented with examples of different types of metal loss signals.« less

  • The Remote Field Eddy Current (RFEC) technique is ideal for inspecting unpiggable pipelines because all its components can be made much smaller than the diameter of the pipe to be inspected. We reviewed the technique, and used demonstrations from prior work by others in presentations on the technique and how we plan to develop it. Coils were wound; a jig for pulling the coils through the pipe was manufactured; defects were machined in one six-inch diameter, ten-foot long pipe; and the equipment was assembled. After completing first crude pullout test to show that RFEC inspection would work, we repeated themore » experiment with a proper jig and got excellent results. The test showed the expected behavior, with the direct field dominating the signal to about two pipe diameters from the drive coil, and the remote field dominating for greater separations between the drive coil and the sensing coils. Response of RFEC to a typical defect was measured, as was the sensitivity to defect size. Before manufacturing defects in the pipe, we measured the effect of defect separation and concluded that defects separated by 18 inches or 1/3rd of the pipe diameter did not interfere with each other. We manufactured a set of 13 defects, and measured the RFEC signals. We found a background variation that was eventually attributed to permeability variations in the seamless pipe. We scanned all thirteen defects and got satisfactory results. The two smallest defects did not show a signal, but these were much too small to be reported in a pipeline inspection. We acquired a ten-foot seam welded pipe that has much less background variation. We are measuring the sensitivity of RFEC signals to mechanical variations between the exciter and sensing coils.« less

  • ;
    The Remote Field Eddy Current (RFEC) technique is ideal for inspecting unpiggable pipelines because all of its components can be made much smaller than the diameter of the pipe to be inspected. For this reason, RFEC was chosen as a technology for unpiggable pipeline inspections by DOE-NETL with the support of OTD and PRCI, to be integrated with platforms selected by DOENETL. As part of the project, the RFEC laboratory facilities were upgraded and data collection was made nearly autonomous. The resulting improved data collection speeds allowed GTI to test more variables to improve the performance of the combined RFECmore » and platform technologies. Tests were conducted on 6-, 8-, and 12-inch seamless and seam-welded pipes. Testing on the 6-inch pipes included using seven exciter coils, each of different geometry with an initial focus on preparing the technology for use on an autonomous robotic platform with limited battery capacity. Reductions in power consumption proved successful. Tests with metal components similar to the Explorer II modules were performed to check for interference with the electromagnetic fields. The results of these tests indicated RFEC would be able to produce quality inspections while on the robot. Mechanical constraints imposed by the platform, power requirements, control and communication protocols, and potential busses and connectors were addressed. Much work went into sensor module design including the mechanics and electronic diagrams and schematics. GTI participated in two Technology Demonstrations for inspection technologies held at Battelle Laboratories. GTI showed excellent detection and sizing abilities for natural corrosion. Following the demonstration, module building commenced but was stopped when funding reductions did not permit continued development for the selected robotic platform. Conference calls were held between GTI and its sponsors to resolve the issue of how to proceed with reduced funding. The project was rescoped for 10-16-inch pipes with the intent of looking at lower cost, easier to implement, tethered platform applications. OTD ended its sponsorship.« less