Metals pieces too small to be detected by metal detector

Hi all,

I have a situation with metal pieces(non ferrous/Stainless steal) in food. These pieces are clearly visible but can't be detected by Metal Detector. MD is working fine and responding to the all three test sticks. But its not detecting these pieces. The selected sensitivity of the Metal detector is standards e.g. 3.5mm for Stainless steal , 3.0mm for Non Ferrous and 2.5mm for Ferrous.
What shall i be doing in this case?
Please share your opinion.

Regards



Martin Blue

What is the size of the metals which are not getting detected???

Hi all,

I have a situation with metal pieces(non ferrous/Stainless steal) in food. These pieces are clearly visible but can't be detected by Metal Detector. MD is working fine and responding to the all three test sticks. But its not detecting these pieces. The selected sensitivity of the Metal detector is standards e.g. 3.5mm for Stainless steal , 3.0mm for Non Ferrous and 2.5mm for Ferrous.
What shall i be doing in this case?
Please share your opinion.

Regards



Martin Blue

Dear Martinblue,
Where do you get the standard of metal detector's sensitivity? Is it from the manufacturer?
There are standard about the sensitivity of metal detector based on the height or diameter product vs type of packaging. (from AIB and Tesco).
You can search on another thread.

Regards,
Hadi

What is the size of the metals which are not getting detected???

its 4-5 mm

Dear Martinblue,
Where do you get the standard of metal detector's sensitivity? Is it from the manufacturer?
There are standard about the sensitivity of metal detector based on the height or diameter product vs type of packaging. (from AIB and Tesco).
You can search on another thread.

Regards,
Hadi

these are our own standards based on risk assessment.These pieces were not detected even i took them out of the product and passed through MD on its own.

You should consult the metal detector supplier to come and calibrate the machine. The sensitivity does change over time so it is important to keep the metal detector checked and calibrated once per annum. You may need to change the standard metal pieces if the metal detector has lost its sensitivity.

Cheers

Ajay Shah
http://www.aasfood.com

I agree with Dr Ajay Syah.
IMO, the MD needs to calibrate.

Regards,
Hadi

Hi Martin

You ought to have your Metal Detectors on your PPM system and ideally you should be calibrating them at least annually, especially if your working towards TFMS or BRC.

The engineer who comes out will help advise you of the sensitivities.

If your metal detector isn't picking up 4-5mm of metal, when you say its set to 3.5 for stainless and 3.0 for non-ferrous then i think you ought to get them in sooner rather than later!

Caz x

I think you have to be a bit wary when selecting detector sensitivity. IME, pieces of metal which aren't uniformly spherical don't detect as easily as pieces which are (like the detection test pieces). So, the detector might be working perfectly well but if the pieces are flattened for example, it might affect the detection sensitivity.

Even if that is the case, it's worth getting the manufacturer in to ask their opinion.

Hi all,

Thanks for everyone's contribution. GMO's comments make more sense to me.
Keep up good work.
regards

Martinblue

Well we can close this thread now!!

Dear Martinblue,

A financially cheap suggestion -

Buy some stainless / ferrous ball bearings in the range 2 - 6 mm and arrange to pass them through the geometrical center of the detector.

Should be revealing !

Rgds / Charles.C

We had the same issue just recently. The metal was found by the customer sent back to us and tested on our metal detectors. The detectors failed every time. We do have our equipment calibrated twice per year, so I do not think that is the concern. The metal was a very fine shaving and may not have made up a 2.5mm sphere. Size and orientation of the material as it passes through the detector can change the results for sure.

One thing to remember when recalibrating (or verifying) MDs is to check for proper rejection timing. While some systems are obvious, others may require disassembly of a product line to set up a proper verification test.

Detection sensitivity can also be affected by the moisture levels of the products and also the salt levels in the food products too. The reason I know this is that I was informed about this by a Safeline metal detector engineer here in Australia who explained the principles of how the metal detector functions.

Cheers

Ajay Shah
http://www.aasfood.com

Hi, First one should analyse this hazard in your flowchart - locate the source - try to establish controls to eleminate this problem at the source. Second, please specify the characteristics of your food product - liquid or dry and homogenity etc. Depending on this, one can select proper filteration/decanting/magnets on line etc. steps. Thirdly.you can go for a more sensitive metal detector. Hope this is useful. Krishnan, India

Hi all,

I have a situation with metal pieces(non ferrous/Stainless steal) in food. These pieces are clearly visible but can't be detected by Metal Detector. MD is working fine and responding to the all three test sticks. But its not detecting these pieces. The selected sensitivity of the Metal detector is standards e.g. 3.5mm for Stainless steal , 3.0mm for Non Ferrous and 2.5mm for Ferrous.
What shall i be doing in this case?
Please share your opinion.

Regards



Martin Blue

I think you have to be a bit wary when selecting detector sensitivity. IME, pieces of metal which aren't uniformly spherical don't detect as easily as pieces which are (like the detection test pieces). So, the detector might be working perfectly well but if the pieces are flattened for example, it might affect the detection sensitivity.

Even if that is the case, it's worth getting the manufacturer in to ask their opinion.

Agree 100%. It is very common that metal foreign bodies that are "wire"-like cannot be easily detected from the MDs... if that is the case you need to investigate your raw materials for presence of metal contamination. Had a similar issue with organic sugar, that was contaminating my end products. The supplier of the sugar ended up paying ~50K because of the contamination

What can be done to avoid metal contamination then? As metal detector is failing even it is calibrated as per schedule and hourly against test sticks. Sizes of metals that are not being detected are 5-8mm but MD does detect 2.5 mm sticks. May be metals in sticks are spherical and that is failing are (5-8 mm) strips shaved from bigger pieces.



We can’t get rid of the machine where the metals are coming from due to some operational reasons…Any suggestions……………..



Looking forward for your thoughts...

regards




Martinblue

Dear Martinblue,

As previously implied by AS, most people would, I think, hv already pulled the agent/technical backup for the metal detector into this situation ? And ??

I find it difficult to believe that a MD which readily rejects a 2 - 2.5mm certified test piece will not see a 8mm contamination object of (I presume) a matching metallic material / surrounding matrix placed in a similar axial location, regardless of the geometrical shape of the contamination. Or is it something weird like an optical fiber [are they metallic? ] ?.

Something looks to be wrong "somewhere", eg the contamination is outside the geometrical detection capabilities of the instrument due to XYZ. This may well be specialised knowledge (ie conveniently not mentioned in the standard manual).

Rgds / Charles.C

I think you have to be a bit wary when selecting detector sensitivity. IME, pieces of metal which aren't uniformly spherical don't detect as easily as pieces which are (like the detection test pieces). So, the detector might be working perfectly well but if the pieces are flattened for example, it might affect the detection sensitivity.

Even if that is the case, it's worth getting the manufacturer in to ask their opinion.

Hi GMO,
Can you please give any suggestion how to detect these smaller metal pieces which are not within the specs of metal detector settings, apart from increasing the sensitivity of Metal detector.
And possibly what kind of explanation i can give to our customer regarding this, saying it is with in our Metal specs might not be good idea.

Regards

Martinblue

Tricky.

First thing; I think you said it was stainless? Not all stainless steels were created equal and I suspect they vary in detectability which might explain the differences.

Next thing; look at your procedure, is it really 'right'? If your testing procedure isn't correct, perhaps you're fooling yourself on your sensitivity. Generally the least sensitive part of a detector is in the centre of the aperture but have you tested in lots of different positions and checked rejections?

I take it you have checked these pieces made up into test packs? Just to make sure it's not that these pieces are being detected and they're just being missed because of poor practice on your shop floor. (I've had people empty a metal detector test bin and put it all back on the line...)

Next as we've all suggested, bring in your metal detector manufacturer. Get them in to calibrate and advise. They will know far more than I do!

Last thing, it's really against the principles of HACCP to have a machine you know to be contaminating a product and to allow it to continue to do so. Perhaps if you post about the source of the issue we might be able to help think of ideas to prevent it?

Dear Martinblue,

Not new information but (obviously depending on yr details) some possible caveats/checking-to-do/justification here –

Alternatively, metal fragments may be detected in the finished food by an electronic metal detector. The use of electronic metal detectors is complex, especially with regard to stainless steel, which is dificult to detect. The orientation of the metal object in the food affects the ability of the equipment to detect it. For example, if a detector is not properly calibrated and is set to detect a sphere 0.08 inch (2 mm) in diameter, it may fail to detect a stainless steel wire that is smaller in diameter but up to 0.9 inch (24 mm) long, depending on the orientation of the wire as it travels through the detector. Processing factors, such as ambient humidity or product acidity, may affect the conductivity of the product and create an interference signal that may mask metal inclusion unless the detector is properly calibrated. You should consider these factors when calibrating and using this equipment.

( http://www.ifsqn.com...dpost__p__46636 )

GMO’s last comment is surely crucial– what/where/how is the root cause ?

Rgds / Charles.C

What can be done to avoid metal contamination then?

We can’t get rid of the machine where the metals are coming from due to some operational reasons…Any suggestions……………..

Looking forward for your thoughts...

regards
Martinblue

As GMO has indicated your primary focus should be on removing the root cause rather than worrying about the detector sensitivity - it is never going to remove all the metal pieces but fixing the problem might!

All of this thread is prime support for the whole "MDs are not CCPs", as in fact in this case it's acting as a prime piece of verification that your maintenance programme isn't working.

That all said, my MDs are still staying as CCPs. I just don't want the audit hassle.

All of this thread is prime support for the whole "MDs are not CCPs", as in fact in this case it's acting as a prime piece of verification that your maintenance programme isn't working.

Are you saying they are OPRP's then?