China-Magnets-Source-Material.com | Best Magnetic Solution
The Magnetic Flux Leakage (MFL) of non-destructive inspections is the most
widely used detection method to detect a variety of flaws in oil or gas
pipeline. The MFL system consists
of magnetizing device, yoke and hall
sensors. Its working principle is (as below drawing): firstly, to magnetize
pipeline detection range by strong magnetic force from magnetizing device. The leakage
magnetic field will appear when there is flaw on the pipeline wall. Secondly,
to convert MFL signal collected by hall sensors into current to test the flaw size
and location.
Magnetizing is the first step for MFL
and determines whether pipeline test area can produce enough magnetic field
signals. Magnetizing device usually uses permanent magnet, such as ferrite,alnico, smco and ndfeb magnet, due to its different characteristics in high magnetic
energy product, small volume, light weight and no external power required.
Ferrite (ceramic) is cheap but low Br; AlNiCo is high Br but low coercive force;
rare earth magnet which includes samarium cobalt and neodymium iron boron is
high coercive force and remanence but expensive.
For different permanent magnets, the
magnetic circuit should be designed according to their magnetic properties,
give full play to its advantages, so that the magnetic circuit reaches to the
optimum. For high remanence and low coercivity magnetic material, it should
adopt an elongated magnet; but on the contrary, it should adopt stubby magnets.
If the magnetization effect cannot meet the requirements and coercivity cannot
increase, increasing the size of the permanent magnets (typically width and
thickness) can meet the requirement. Common grades for MFL magnet are N38, N42,N45 and N50M, sizes 40x20x10mm, 25x25x25mm, 40x25x10mm and 45x45x45mm and soon. We also manufacture arc (segment), ring, and cylinder type magnet formagnetic flux leakage testing.
China Magnets Source Material Ltd. hasmany years production experience for MFL magnets; the magnets have been appliedfor the detection of the Pacific seabed pipeline. If you have such requirement, please feel free to contact us.
