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The specimen of ferrous metal stopped being detected


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#1 CFP

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Posted 28 August 2013 - 01:13 AM

Hello

The company where i work have a metal detector which detected a specimen of 1 mm of ferrous. Now, not detected and when i passed the specimen in the head detector the signal emitted is very low.

The specimen is unchanged.

Someone have a ideia what might have happened?

Thank you



#2 Setanta

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Posted 28 August 2013 - 12:09 PM

CFP,

 

Is 1 mm ferrous the standard you have your MD calibrated to? Or is this an item that was discoverd accidentally and not no longer gets a reading?

 

If 1 mm is what your test wand is and your MD is no longer detecting that, it sounds like your MD needs recalibration.  Perhaps I am misunderstanding the question.

 

Setanta


-Setanta         

 

 

 


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#3 CFP

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Posted 29 August 2013 - 01:53 PM

yes my MD was calibrated with 1mm ferrous.

Do you think that i have to recalibrat MD and use a new standart larger?

The technical DM can not see what is happening, and at this moment 1.5 Ferrous not being detected.



#4 Charles.C

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Posted 29 August 2013 - 05:40 PM

Dear CFP,

 

It sounds like you have some good questions to ask yr supplier of MD. After all, they presumably set it up for you?

 

It is rather unusual i think to use a 1mm test piece for ferrous. Not necessarily incorrect but most values quoted here are from memory  higher.

Perhaps you have a very top grade detector, or an unusually demanding customer. :smile:

 

Rgds / Charles.C


Kind Regards,

 

Charles.C


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#5 CFP

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Posted 01 September 2013 - 02:28 PM

The supplier set it up when introduced in company. Now is that the detector is giving problems.

In this moment not able to detected ferrous, but detected 5mm stainless steel.

Thank you.

Regards

CFP



#6 Charles.C

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Posted 02 September 2013 - 02:12 AM

The supplier set it up when introduced in company. Now is that the detector is giving problems.

In this moment not able to detected ferrous, but detected 5mm stainless steel.

Thank you.

Regards

CFP

 

Dear CFP,

 

The limits given in this post are probably fairly typical -

 

http://www.ifsqn.com...its/#entry59886

 

Hmmm. Looks like i was incorrect that 1mm is unusual, at least if yr product is dry and <50mm height. :smile:  However if so, a 5mm check for stainless (I assume 316)  looks a too-undemanding test for typical capability.

 

Rgds / Charles.C


Kind Regards,

 

Charles.C


#7 CFP

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Posted 02 September 2013 - 11:29 AM

Hello, Charles

The product is meat, so is  a wet product. Therefor 1mm is untypical. Now i am more relaxed. The 5 mm for SS are also not bad. 

Thank you

CFP



#8 cazyncymru

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Posted 02 September 2013 - 11:39 AM

If the metal detector had been previously detecting the 1mm test piece and now it doesn't, then there are a number of things that I think you should do.

  1. Check that the test piece is intact and undamaged. If it is, get a new one.
  2. Get your metal detector people in. You can't just change the piece size and say "hey it's OK at 5mm".  They are set up and calibrated specifically. How will you justify why you've gone from 1mm to 5mm without documentation from your metal detector service engineer? You should be setting your limits up with this engineer and carry out a robust validation.
  3. Is it a twin head detector? Has the wrong head been activated. We have metal detectors that we can pass either parchment or foil through, and these are calibrated (and validated) separately.
  4. And if you can't guarantee that it's working correctly, the it needs to be taken off line

Caz


Edited by cazyncymru, 02 September 2013 - 11:40 AM.


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#9 CFP

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Posted 12 September 2013 - 12:08 PM

Hello Caz

and thank you for the tips.

already verified the test piece. probably have to take the detector production line.

CFP



#10 Charles.C

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Posted 12 September 2013 - 01:08 PM

Dear CFP,

 

unless i misinterpreted yr posts 5 and 7, yr  1mm / 5mm comments were for different test materials, ie ferrous / stainless.

 

i don't think you ever reported what yr ferrous detection capability was after it failed to see 1mm ? if it saw ferrous 2mm ok then maybe less of a disaster. If the minimum ferrous capability actually was >=5mm then i agree with Caz you have an immediate problem. 

 

Regardless, such abrupt changes as you describe  certainly justify the steps listed by Caz and a visit from the service gurus.

 

Rgds / Charles.C


Kind Regards,

 

Charles.C


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#11 CFP

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Posted 16 September 2013 - 01:31 PM

yes, Charles you undsertand. Now is detect 2mm for ferrou and 5 for SS.

 

Thanks all!!



#12 QLD

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Posted 17 September 2013 - 12:03 AM

a few things to consider.

 

1) have the settings been changed. It is common with meat to adjust the phase angle / sensitivity setting of the metal detector to offset changes in moisture content and/or temperature.

 

2) it could be related to where the sample is positioned in relation to the aperture of the metal detector. Close to the edge means better sensitivity to smaller samples. Dead centre is worse case performance and should be used imo for test piece challanging.

 

3) the head could be unstable or require recalibration



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#13 Charles.C

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Posted 17 September 2013 - 04:48 AM

Dear QLD,

 

(apologies to CFP for stealing yr thread :smile: )

 

Thks for comments.

 

Out of interest, would you regard 2mm as an (Australian acceptable) (minimum) capability for ferrous sensitivity ?. :smile:

 

i hv never seen any Australian opinion as to what metallic dimension constitutes a significant safety hazard ?

 

After all the previous discussion here, it appears to me that the US requirements, although textually impeccable to the, semi-worst case, "general public" from a safety / preventive POV, have created an illogical MD operational requirement in view of the inevitable MD sensitivity limitation. The current Canadian CFIA website includes a caveat of similar meaning in their rather cool (IMO) model haccp format. Plus their safety operational interpretation of minimum  "hazardous" metal size appears to conveniently match equipment capabilities (well, ferrous anyway). :smile:  Similar comment perhaps for European POV although there I hv seen some medical backing data.

(I have avoided the topic of  whether a CCP or not, well-done elsewhere).

 

So far,I rather get the impression that the US (numerical) position is a singular one. :sofa1:

 

Rgds / Charles.C


Kind Regards,

 

Charles.C


#14 QLD

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Posted 19 September 2013 - 06:13 AM

Hi Charles,

 

I do not expect anybody to achieve any particular level of detection as a hard and fast rule. I do expect people to understand their process, the associated risks, have suitable control measures, to be able to justify why their standards are what they are and to understand the limitations of their system.

 

I would not ignore any metal less than 1mm but thinking out loud would likely consider it a lower risk. I tend to consider more what is it, what is it made, what shape is it, how much could there be of it and how likely we might be of finding it or not. … and of course what risk is it to the consumer.

 

I think generally most companies here would be happy with 1.5mm – 2.0 mm Fe as their standard for spherical test pieces. I don’t think generally this is based around any particular risk but more that it is easy to achieve the “tick in the box” without much thought to process design or motivation for continuous improvement beyond this.

 

I have recently heard talk of people referring back to the Tesco standard (their reach is far!) for both suppliers of metal detectors and ingredients as a rough guide but not experienced this personally.

 

But really a metal detector is nothing more than a tool to alert us of a process failure within its capability.



#15 scppvjune

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Posted 19 September 2013 - 07:18 AM

Hello,

Agree with points of Caz and QLD.

CFP, I think you need to call your MD supplier and request them to check the MD for you. You indicated that the MD had been calibrated with 1 mm and was able to detect without problem in the past, but now it is able to detect Fe 2 mm instead of 1 mm. You need your MD supplier to recheck what wrong with its sensivity. As discussion above, there should be no safety issue about the change of the size of Fe from 1 mm to 2 mm. However, you need a robust evidence to proof for machine sensitivity validation. If you cannot find the root cause for this weird case, it might have a chance that the MD might not be able to detect 2 mm Fe as well in the future and you might need to increase the size of the test piece again. After validation, you need to update your HACCP and ensure that your buyers aware of the sensitivity change as well.

By the way, I am curious why the range of your test pieces are too wide: 1 mm Fe and 5 mm SUS. In my opinion, 1 mm Fe is very small, so the MD should be able to detect SUS < 5 mm. Are you validate the MD before final decision to use these test pieces to calibrate your MD according to the pre-determined frequency? How about Non-Fe?



#16 Charles.C

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Posted 19 September 2013 - 01:51 PM

Dear QLD,

 

Thks for the reply. Nice to see the Australian laid-back philosophy extends to metal detectors. :smile:

 

I deduce there has been no official Australian viewpoints expressed on this matter, ie no particular criticisms of typical sensitivities as CLs. Lucky you.

 

But really a metal detector is nothing more than a tool to alert us of a process failure within its capability.

 

 

 

I just heard the Codex Tree come tumbling down.

 

Rgds / Charles.C


Kind Regards,

 

Charles.C





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