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PRCI PR-70-54/TR-72-50
- Magnetic Flux Leakage of Small Defects in Line Pipe
- Report / Survey by Pipeline Research Council International, 10/01/1972
- Publisher: PRCI
$348.00$695.00
L00972e
Automation Industries
Need: The basic principles of magnetic flux leakage have commonly been demonstrated and used in magnetic particle testing for cracks. A suitable sensor can also detect the same leakage field that produces a crack indication in magnetic particle testing by attracting the particles. Voids, inclusions, and corrosion can also produce leakage fields. In pipeline testing, the technique consists of applying a magnetic field along the axis or circumference of the pipe and detecting any leakage field present. Hopefully, any leakage field is somehow related to a defect. It is a basic characteristic of the technique that a defect on one side of the wall produces a leakage field on both sides. This means that in buried pipeline testing, both ID and OD defects such as corrosion could be detected from the inside of the pipe with a suitably instrumented pig.
Result: It is the purpose of PRCI PR 70-54 to evaluate the MFL technique in detecting pipeline defects. This involves obtaining data on the leakage fields produced by a wide variety of defects and evaluating the effects of uncontrolled variables that may affect the leakage field. The program was divided in two parts, program 1 and program 2. Program 2 was completed first. It's main objective was to develop a method to calculate the MFL for defects common to buried pipelines. To accomplish this, a series of Fortran time-sharing computer programs were written to model the MFL phenomena. The programs can model the MFL produced by inclusions, voids, cracks, corrosion and hard spots, the computer programs were verified successfully by comparing experimental MFL signature to the results obtained using the computer model.
Benefit: The MFL method proved to be sensitive to all-important defects modeled. A major limitation should be noise due to magnetically nonhomogeneous or anis tropic material due to processing effects. Discrimination between types of defects such as inclusions and corrosion should prove to be difficult.
Automation Industries
Need: The basic principles of magnetic flux leakage have commonly been demonstrated and used in magnetic particle testing for cracks. A suitable sensor can also detect the same leakage field that produces a crack indication in magnetic particle testing by attracting the particles. Voids, inclusions, and corrosion can also produce leakage fields. In pipeline testing, the technique consists of applying a magnetic field along the axis or circumference of the pipe and detecting any leakage field present. Hopefully, any leakage field is somehow related to a defect. It is a basic characteristic of the technique that a defect on one side of the wall produces a leakage field on both sides. This means that in buried pipeline testing, both ID and OD defects such as corrosion could be detected from the inside of the pipe with a suitably instrumented pig.
Result: It is the purpose of PRCI PR 70-54 to evaluate the MFL technique in detecting pipeline defects. This involves obtaining data on the leakage fields produced by a wide variety of defects and evaluating the effects of uncontrolled variables that may affect the leakage field. The program was divided in two parts, program 1 and program 2. Program 2 was completed first. It's main objective was to develop a method to calculate the MFL for defects common to buried pipelines. To accomplish this, a series of Fortran time-sharing computer programs were written to model the MFL phenomena. The programs can model the MFL produced by inclusions, voids, cracks, corrosion and hard spots, the computer programs were verified successfully by comparing experimental MFL signature to the results obtained using the computer model.
Benefit: The MFL method proved to be sensitive to all-important defects modeled. A major limitation should be noise due to magnetically nonhomogeneous or anis tropic material due to processing effects. Discrimination between types of defects such as inclusions and corrosion should prove to be difficult.
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