Andy Smith
MIne-action specialist
 

Metal-detection

 

 

What follows is the PowerPoint presentation named "Metal-detection", formatted as a scrolling webpage.

 

Humanitarian Demining

Part 2: Metal detection

 

This presentation introduces metal-detection in humanitarian demining, NOT mine detection. The use of dogs and other means of detection that may be used to find explosives are introduced elsewhere.

Most Humanitarian Demining is done manually, using metal-detectors as a primary detection tool. For detailed procedures actually used in the field, see Chapter 6 of the Generic SOPs or Metal-detector setup.

 

This detector is a Schiebel AN-19.

The Schiebel AN-19 was once the industry standard metal-detector.

The old Schiebel was still in use in Lebanon in 2003. In easy soils and looking for the right mines, it still has its uses - and many commercial companies retain their old detectors for use when possible - keeping newer models for more difficult areas.

While the old Schiebel AN-19 and its Mod7 version are still widely used - they are not robust and not appropriate to search for minimum metal targets. This picture shows broken Schiebels in Africa - all of which are uneconomic to repair. Cables and head-hinges have broken and the surface of the head has worn against the ground exposing the coils.

The length of the detector that is favoured varies dramatically, and depends on how the tool is used. A detector that has a battery that must be worn on a belt can make it impractical to use a one-man drill. (In a one-man drill, the man with the detector also kneels down and excavates any signals he gets.) The man on the left is using a Vallon, the one on the right, an Ebinger.

Some use a detector that can only be used standing - which does not always mean that they use a two-man drill.

The Afghans attached the Schiebel AN-19's battery to the detector shaft so that they could use a one-man drill.

The detector is placed behind him while he excavates.

This Vallon has the battery attached to the handle and an expandable pole. Most modern detectors allow the length to be adjusted.

This man is also engaged in a one-man drill. He has propped a long detector beside him as he investigates a reading.

Others prefer to work kneeling all the time, even while detecting. In this case, the detector is held vertically. There is some evidence that the angle of the detector head to the shaft can alter some detectors' performance.

The detector in the last slide was an Ebinger 420SI. This is an Ebinger 420GC, but it looks the same. What seems to be a side-handle is actually a speaker. In GC mode, this particular model of detector's ability to detect at depth may be significantly reduced.

Short detectors may also be used standing. This deminer is using an Ebinger 420 under power lines. The effect on performance of electromagnetic disturbance from power lines, substations or radio broadcast facilities can be profound. So can the proximity of one detector to another during use.

The detector was the popular Ebinger 420 - more popular for its robust reliability than its great performance. That said, models of detector without a ground-compensating capability can sometimes be used in areas with electromagnetic soils. They may signal continuously, but the signal may vary where there is a ground anomaly such as a lump of metal - or even the presence of a buried non-metallic itemů. although the latter should never be relied on. If a check is made using the anticipated target in the difficult ground and the deminer can understand the detector's varying signal - it may be appropriate to use the detector anyway.

There may be other reasons to use a long detector. For example, this is in Cambodia - and the deminer is using his detector among bamboo. This is because the bamboo has a value for the local people so must not be cut. Ground conditions and the angle of an incline may also dictate working in an upright position.

The deminer in the bamboo was using a MineLab and in this picture I am being trained to use the MineLab detector in Cambodia. This model had an effective ground-compensating feature but real design weaknesses so that it was too easy to break. The later MineLabs have overcome these problems.

The MineLab F1A4 could also have the battery box attached to the detector shaft.

The MineLab F3 is a very different looking beast - and much easier to work with. Its handle expands easily and snap-on colour-coded endcaps adjust sensitivity. There is evidence that it is the best detector in terms of its ability to "compensate" out the sound of electromagnetic disturbance in difficult ground without a significant reduction in search depth. It is the detector that I have bought for use in any country - its only downside is that iit uses more battery power than some other detectors.

This is a modern Foerster Minex and the old Schiebel side by side - showing how the ergonomics has moved on. The electronics inside have sometimes changed just as much. I have had personal experience (in Angola) that the Foerster Minex's build quality is not robust, with hundreds of models unusable after a few months of use - and no advice directly available from the manufacturer despite the request being made through UNDP.

This is the Schiebel ATMID, Schiebel's updated offering.

And below is the Guartel. Their Guartel MD8 was interesting, but many people did not understand the effect of using a large head to find shallow targets in difficult soils, or the advantages and disadvantages of its "double D" head. Some had high hopes of the Guartel Mini-8 (A4 sized), but I have never seen one in use. [An A4 sheet is around the same size as a US letter-size sheet of paper.] Small is attractive - because it means less weight - but the detector must still be robust and able to find the mines.

Minelab have achieved this with their small F3 detectors, the picture shows one folded and one partly expanded. They can be used at any length and their construction is robust.

F3 detector folded and partly expanded

There are many models of detector, with MineLab and Vallon apparently leading the field with their latest models that are able to detect at depth in electromagnetic soils. Ciea and Schiebel has also made advances and I believe that Ebinger is a real contender, but Guartel have long since ceased production.

Metal-detection - and getting the best from a particular model in the field - are large subjects requiring a good knowledge of demining needs, and some knowledge of how detectors work. These subjects are covered in the Metal- Detector Handbook.For a more detailed introduction to their use, see Chapter 6 of the Generic SOPs or Metal-detector setup

For detailed metal-detection procedures actually used in the field, see Metal-detector setup.