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Method for the nondestructive testing of pipes

A non-damaging, magnetic flux leakage technology, applied in the direction of material magnetic variables, etc., to achieve the effect of reducing the base noise level

Active Publication Date: 2011-04-20
V&M DEUT GMBH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, this patent document gives no indication how to evaluate defect signals extending obliquely with respect to the inspection or magnetic field direction and how a defect differentiation of external and internal defects can be achieved

Method used

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  • Method for the nondestructive testing of pipes
  • Method for the nondestructive testing of pipes
  • Method for the nondestructive testing of pipes

Examples

Experimental program
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Embodiment Construction

[0043] figure 1 A pipe 1 to be inspected is schematically shown in the upper part, which has a defect 3 on the outer surface of the pipe, which defect is oriented along the pipe axis (longitudinal defect). In this case, the inspection unit is designed for longitudinal defect inspection, ie the magnetic field of the yoke, not shown here, is oriented perpendicular to the tube axis.

[0044]The inspection unit comprises here three inspection probes 2 , 2 ′, 2 ″ with a probe (Sondenlineal) with an induction coil (not shown in detail) arranged rotatably around the pipe, which are arranged parallel to one another in the axial direction of the pipe set in one plane.

[0045] For the inspection of longitudinal defects, the pipe 1 is moved forward in the longitudinal direction while the inspection unit rotates around the pipe 1, as indicated by the arrow 4, whereby a helical detection of the entire pipe surface is obtained in the detection direction indicated by the arrow .

[0046]...

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PUM

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Abstract

The invention relates to a method for the nondestructive testing of pipes made of ferromagnetic steel for flaws by means of leakage flux, wherein the pipe is magnetized by a constant field and the flaws present in the near-surface region of the outer or inner surface of the pipe cause magnetic leakage flux, which exits the pipe surface and is detected by probes of a test unit each for longitudinal and / or transversal flaw testing, wherein the association of the detected amplitude signals is performed on the basis of the amplitude height and / or the frequency spectrum with respect to an outer or inner flaw by external or internal flaw thresholds. To this end, prior to associating the detected amplitude signals with an external or internal flaw, the angular position of the flaw relative to the respective magnetic field direction is determined, and a correction of the signals is carried out by way of a previously determined corrective factor for amplitudes and / or frequencies.

Description

technical field [0001] The invention relates to a method according to the preamble of claim 1 for the damage-free inspection of tubes made of ferromagnetic steel by means of magnetic flux leakage. Background technique [0002] The known flux leakage inspection is used in tubes made of ferromagnetic steel in order to detect imperfections, such as cracks, in the vicinity of the longitudinally or transversely oriented surface viewed axially, which cannot be detected by other inspection methods or It can only be detected by other methods with great inaccuracy, high cost and time-consuming. [0003] For example, cracks extending at least about 0.3 mm from the surface of the tube are detected by the method described (Nondestructive Evaluation, A Tool in Design, Manufacturing, and Service, CRC Press 1997). [0004] In the measuring methods known from the prior art, a uniform magnetic field is used on the inside or outside of the tube to detect defects in the vicinity of the surfac...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N27/87
CPCG01N27/87
Inventor A·格鲁斯S·尼斯切
Owner V&M DEUT GMBH