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Test pieces detection vs contaminant size


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#1 jayrency

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Posted 16 April 2017 - 02:32 PM

This is quite confusing for me, if I have a metal detector installed in the area, and I have set my test piece sensitivity to ferrous 1.2 mm (sphere), 2.5 mm Non ferrous (sphere), and 3.0 mm Stainless Steel  (sphere), will i be able to detect a 3.16 mm X 7 mm welding rod.?


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#2 MDG

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Posted 16 April 2017 - 03:31 PM

It should detect.


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#3 Charles.C

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Posted 16 April 2017 - 04:09 PM

This is quite confusing for me, if I have a metal detector installed in the area, and I have set my test piece sensitivity to ferrous 1.2 mm (sphere), 2.5 mm Non ferrous (sphere), and 3.0 mm Stainless Steel  (sphere), will i be able to detect a 3.16 mm X 7 mm welding rod.?

 

Insufficient data. eg -

 

Sensitivity determined how ?

magnetic field symmetical ?

welding rod made of ? circular x-section ?

3.16mm  is presumably the diameter ? uniformity +/- ?

xy orientation of rod = ?

 

PS - i anticipate the reason for the OP is that it wasn't detected ? :smile:


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Charles.C


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#4 redfox

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Posted 17 April 2017 - 01:43 AM

Hello jayrency,

 

Test piece size is the minimum size your metal detector can detect. 

 

 

regards,

redfox


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#5 Charles.C

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Posted 17 April 2017 - 04:35 AM

JFI, I noticed this (semi-promotional) caveat in another article -

 

Attached File  Detection Capability.png   34.4KB   5 downloads

 

 


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Charles.C


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#6 jayrency

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Posted 18 April 2017 - 04:32 PM

This is part of one from an audit. And I was not able to attend to. I know that there may be factor affecting the sensitivity nor the detection of contaminant.

1. Material property

2. Type of rod material

3. Orientation during the passes.

 

If a 3.16 mm X 7 mm welding rod passes through the MD with a 3.0 mm sphere SS setting minimum limit, it should be detected right?

Can you show me the computation based on  the mathematical dimension?


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#7 Charles.C

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Posted 19 April 2017 - 07:47 AM

This is part of one from an audit. And I was not able to attend to. I know that there may be factor affecting the sensitivity nor the detection of contaminant.

1. Material property

2. Type of rod material

3. Orientation during the passes.

 

If a 3.16 mm X 7 mm welding rod passes through the MD with a 3.0 mm sphere SS setting minimum limit, it should be detected right?

Can you show me the computation based on  the mathematical dimension?

 

Hi jayrency,

 

Perhaps you could answer some of the queries in Post 3

 

MD performances are discussed in the manufacturer's files attached in this post -

 

http://www.ifsqn.com...tor/#entry54841

 

You will see from various posts in this Forum that any MD is likely to occasionally exhibit false positives and false negatives. Sometimes for unknown reasons.


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Kind Regards,

 

Charles.C


#8 Charles.C

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Posted 20 April 2017 - 04:42 AM

This is quite confusing for me, if I have a metal detector installed in the area, and I have set my test piece sensitivity to ferrous 1.2 mm (sphere), 2.5 mm Non ferrous (sphere), and 3.0 mm Stainless Steel  (sphere), will i be able to detect a 3.16 mm X 7 mm welding rod.?

 

Hi jayrency,

 

I deduce yr rod is nominally 1/8 in diameter.

 

These are some reasons why yr OP is difficult to accurately answer  -

 

1st reason

Composition of ...
A welding electrode is made up of two parts: the actual metal, and the flux coating. The metal can vary from mild-steel, cast iron, stainless steel, high-tensile steel, copper, bronze, brass, or aluminum. The metal is then wrapped in a flux coating that is blends of cellulose, which is used by plants to give them flexibility, iron powder, and hydrogen. It is also blended with some Sodium, Titania and Potassium. The flux coating makes the electrical currents flow more evenly during the weld.

 

 
 
2nd reason relating to material of (a) yr SS reference and (b) welding rod sample
Attached File  MD Sensitivity - Material.png   161KB   4 downloads
 
3rd reason relating to  positioning of (a) reference sphere and (b) welding rod sample in magnetic field
Attached File  MD sensitivity - Transverse Coordinates.png   87.82KB   3 downloads
 
4th reason relating to orientation of sample in magnetic field
Attached File  MD Sensitivity - Axial Orientation.png   130.93KB   3 downloads
 
Analysis
 
I assume test spheres were placed on horizontal axis of a symmetrical magnetic field applied to a horizontal conveyor belt.
I assume SS test sphere was 316 type
 
Then IMO -
 
Best Case scenario for detection -
thin coating, iron rod, oriented axially
Should be easily detected
 
Worst case scenario for Detection
Thick coating, Stainless 316 rod, oriented axially
May not be detected
 
One Caveat - I have no idea how much effect a coating can have on the signal strength, I guess not so much.

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Kind Regards,

 

Charles.C





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