Patent Application
20130088220
This disclosure relates to apparatus for use in non-destructive testing (NDT), more particularly, but not exclusively, for non-destructive testing using electromagnets. The invention also relates to methods of non-destructive testing (NDT) using electromagnets.
The term non-destructive testing (NDT) is used to describe methods of material analysis, in which the properties of material under test can be evaluated without causing damage to the material.
Magnetic particle inspection (MPI) is a specific form of NDT, wherein a magnetic field is induced in the material under test (e.g. a ferromagnetic material or alloy) and magnetic flux leakage is monitored, in order to identify surface or subsurface discontinuities in the material.
On a large scale, it is known to pass an electromagnetic device, commonly referred to as a pig, along the inside of a pipeline, for monitoring magnetic flux leakage in the walls of the pipeline. On a smaller scale, it is known to apply ferrous particles to a surface of a material under test, whereby the relative attraction of the ferrous particles on the surface of the material provides a visual indication of areas of magnetic flux leakage from the material.
Typically, small scale MPI testing is carried out in a laboratory, where there is suitable provision for generating the required magnetic field.
What is required is an MPI apparatus suitable for use in the field (i.e. away from the laboratory), more particularly for use difficult or restricted access locations, e.g. at points of elevation.
According to one aspect of the invention, there is provided an apparatus for magnetic particle inspection in accordance with claim 1.
According to another aspect of the invention, there is provided a portable MPI kit in accordance with claim 17.
According to a further aspect of the invention, there is provided a method of MPI testing in accordance with claim 19.
Other aspects and features of the invention will be apparent from the appended claims or the following description of exemplary embodiments, made by way of example only, with reference to the accompanying Figures, in which:
Referring firstly to
The belt 12 includes first and second pouches 22, 24 that are slidably mounted on the belt 12. The first pouch 22 is configured to house a power pack (not visible in
The first and second pouches 22, 24 are located next to one another on the belt 12, and may be combined as a single pouch in alternative embodiments.
A power cable (not visible in
The belt 12 includes a holster 34 for releasably carrying the MPI electrode on the belt 12. The holster 34 includes a buckle and belt type fastener 36 for releasably securing the MPI electrode in the holster 34.
The belt 12 further one or more holders 37, e.g. for carrying a container 38 of magnetic ink (for use in MPI testing) and a container 39 of contrast spray (for aiding visual identification of an area under test) on the belt 12.
Accordingly, there is provided apparatus 10 for MPI testing, which is portable for use by a single operative, and consists of a self-contained MPI electrode and power supply arrangement, which can be body worn by a single operative in the field, so as to carried ‘hands free’, e.g. in elevated locations, such as on ladders. Individual components such as the power supply and inverter are carried in compartments 22, 24 on the belt 12.
The MPI apparatus 10 includes a DC battery pack 40, which serves as the main power supply for the apparatus 10. The DC battery pack 40 is arranged in wired communication with an AC inverter 42 (via cable 41), which is in turn arranged in wired communication with an electromagnetic MPI electrode 44 (via cable 43, e.g. corresponding to cable 30 in
The MPI electrode 44 is shown schematically in
In exemplary embodiments, the poles 48, 50 are movable relative to one another, e.g. for vary the spacing between their free ends 49. In the illustrated embodiment, the poles 48, 50 are pivotably connected to the main body 46, via a pivot points 47.
In exemplary embodiments, the MPI electrode 44 includes an electromagnet (not shown) and an activation mechanism for selectively energising the poles 48, 50. In the illustrated embodiment, the activation mechanism is in the form of a trigger 52 (e.g. a switch, lever or button or the like on the main body 46) which can be operated to energise the poles 48, 50 on demand.
In exemplary embodiments, the battery pack 40 and inverter 42 are small enough to be belt mounted, e.g. for mounting in respective pouches or compartments on a waist-worn belt of the kind shown in
In exemplary embodiments, the body worn MPI apparatus 10 is configured to provide 110 volt 50-60 Hz AC current to the MPI electrode.
In exemplary embodiments, the power supply takes the form of a lithium polymer battery pack 40. In exemplary embodiments, the inverter 42 is configured for changing 12 volts DC to 110 volts 50-60 Hz AC. In exemplary embodiments, the inverter 42 generates a quasi-sine wave output 60, as illustrated in
In exemplary embodiments, the apparatus 10 is provided with an electrical socket configured to be compatible for connection and use with portable 110 volt equipment
In exemplary embodiments, the inverter 42 is configured to deliver a higher frequency output (i.e. beyond conventional UK 50-60 Hz mains frequencies). In exemplary embodiments, the inverter 42 is configured to deliver an output above 50 Hz and up to about 500 Hz.
Providing as high output frequency in conjunction with an MPI electrode 44 has the advantage of creating a heightened ‘skin’ effect during surface magnetisation of the object under test. This gives an improved particle migration and thus and improved defect indication.
Use of a higher frequency output makes it possible to produce lighter, easier to use MPI electrodes. For example, it is possible to provide an MPI electrode 44 of reduced specification (e.g. in terms of the number of coils and laminations), whilst maintaining an adequate magnetising effect on the surface of the object under test suitable to undertake an MPI test operation. Hence, it is possible to reduce the size and weight of the MPI electrode 44, if the electrode is powered by an inverter 42 with a high output frequency (e.g. 500 Hz).
In exemplary embodiments, the apparatus 10 includes stand-by circuitry for controlling on/off operation of the electrode 44 without the need for a dedicated on/off switch for the power supply. An example of such stand-by circuitry is shown schematically at 50 in
The stand-by circuitry 50 is configured to operate a stand-by mode in which only a small current (e.g. in milli amps) is supplied from the battery 40 (i.e. via the inverter 42) to the MPI electrode 44 when the MPI electrode is inactive.
When the trigger 52 is operated, the stand-by circuitry 50 is configured to recognise an imbalance, indicative that there is a demand for power to the electrode 44. In response, the circuitry 50 automatically switches the inverter on, so that full current can be supplied to the electrode 44. Similarly, the stand-by circuitry 50 is configured to detect when the electrode 44 returns to an inactive state (e.g. when there is no demand for power to the electrode 44 via the trigger 52), in order to return the inverter 42 to the stand-by mode.
The stand-by circuitry 50 prolongs the life of the battery 40. It also avoids the need for disconnection of the electrode 44 from the inverter when the electrode is not in use, and obviates the need for a dedicated on/off switch for the inverter 42.
The stand-by circuit is particularly advantageous for the portable, body worn MPI apparatus 10, since the operative is able to use or stow the electrode 44 without operating multiple switches to turn the apparatus on/off between testing operations. This is particularly advantageous for elevated testing operations and the like, where the operative may require 3 points of contact on a ladder or other support.
In exemplary embodiments, the apparatus 10 includes safety circuitry indicated at 54 in
An exemplary method of operation of the apparatus 10 by a lone operative at a remote testing location will now be described, e.g. for use in detecting cracks or other surface breaking discontinuities/defects in a weld bead in a pipe line.
Firstly, the operative puts on the belt 12, so that the battery pack 40, inverter 42 and MPI electrode 44 are carried by the belt and the operative is able to move ‘hands free’ in relation to the apparatus 10. The operative is thus able to ascend a ladder or the like, in order to reach an elevated test location, unhindered by the apparatus 10.
Typically, a section of material or component under test will then be sprayed with a contrast spray 39 (to aid visualisation of the area under test), e.g. as carried in one of the holders 38 on the belt 12. A conventional micro-fine iron oxide fluid suspension or other such magnetic ink 38 (e.g. as carried on the belt 12) is also applied to the surface of the area under test.
If not already removed, the operative removes the electrode 44 from the holster 34 and positions the poles 48, 50 of the electrode 44 in contact with the material under test. The trigger 52 is operated, whereby the standy-by circuit switches to the normal operation mode, in order to allow the electromagnet to become energised, for inducing a magnetic field in the material under test.
Dependent upon the orientation of the electrode 44, one side of any local crack or other surface breaking discontinuity in the material will serve as a north pole and the other side of said crack or discontinuity will serve as a south pole, with the effect that any leakage or “extraneous” field will loop out from any significant crack/discontinuity in the surface under test. Ferrous particles in the magnetic ink will be attracted to “build up” or aggregate in the region of any crack/discontinuity in the material, thereby providing a visual contrast to the surrounding area, in order to highlight cracks and other discontinuities in said area.
The use of an AC power supply for the electrode (via the AC inverter) is particularly advantageous for generating AC magnetic fields capable of finding finer surface breaking discontinuities (e.g. fine cracks) in a test area of a ferrite material/component than is possible using conventional portable DC devices. This is because AC magnetisation tends to be greatest at the surface of a material or component under test. Moreover, the continually reversing polarity of AC magnetisation serves to shuffle and agitate the micro ferrous particles in the magnetic ink, which aids migration of the particles to areas of leakage.
Although the illustrated embodiment shows a belt-mounted MPI apparatus, the MPI apparatus may alternatively be mounted on a body worn harness or other arrangement intended to be worn by a single operator, so that the single operator is able to use the apparatus in the field, e.g. in elevated locations, such as on ladders. In each case, the power supply, inverter and electrode are intended to be carried on the body worn arrangement, together with the magnetic ink and contrast spray in exemplary embodiments.
The result is a self-contained and portable AC MPI system configured to be body worn for field inspection of surface breaking defects in ferrite materials, such as in weld beads in pipelines.
Although described with particular reference to MPI testing apparatus including a portable, hand-held electromagnetic MPI electrode, the concepts described herein may be applicable to operation of other hand held devices, such as drills, branding irons, industrial hair shearing devices.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1117266.5 | Oct 2011 | GB | national |
