7 replies to this topic

[matthewcc]

Hello everyone, 

 

I didn't see the answer to this anywhere in my searches of the forum: When we are doing metal detection, do we need to use a 'blank' or known uncontaminated test piece along with the ferrous, non-ferrous, and stainless-steel test pieces? Coworkers are saying it is not necessary, and I am wondering how, if a blank is unused, we know that uncontaminated product will pass through successfully.

 

I've found some information online saying that the use of a blank is critical for establishing a baseline, ensuring that the detector is not overly sensitive, and ensuring calibration, but I was uncertain if this will be convincing.

 

We are manufacturing dietary supplements in the United States and have an SQF food safety certification and NSF GMP certification.

 

Thank you,

Matthew

[liberator]

I don't think you'd need a blank piece, that's what your daily production already is, is it not, it's blank and free of metal contamination?

 

The metal detector should already be calibrated for the product and "nothing"

 

Hence the need to check your detector on a regular basis with your test pieces to confirm it's working.

[GMO]

Some retailer codes of practice require you to do a memory test where you pass through the test pieces with known uncontaminated pieces. 

 

I.e.:

 

Test piece - normal pack - test piece - normal pack - test piece

Where all of the test pieces are put into or on the packs and made into test packs as you normally would where those packs have already passed through a metal detector and those "normal" packs are just packs you've already passed through your metal detector.

 

The point of it, I think, is to prove that your detection and rejection system isn't overly sensitive so only the metal containing packs are rejected. I suppose the thought process is that if you have loads of false rejects you could end up with poor behaviours or risk in reprocessing of those with temptation to put them back on the line. We did this as part of a start and end of shift check as well as the normal consecutive testing we'd do then and at periods throughout the shift.

 

Is it worth it? Ah I'm not sure. Honestly we only did it because the UK retailers started to introduce it as a requirement. 

[MDDF]

We don't use a blank.   Every bag that goes through is a blank, like liberator said.   I agree, never been called on it...

[jfrey123]

Never used a blank myself.  I wasn't even aware companies sell blank md test standards.  I don't see a benefit at all in such a concept.

[GMO]

The way it's used in the UK in memory tests you don't have a "blank" test stick, you just have a pack without a test stick as part of the memory test.

[G M]

Because of the physics behind metal detectors you want product present during testing, the product without a test piece in it is your control.

 

Only during the first set up of new equipment would I even consider running a dummy of some kind.

[Baohan88]

Hello

 

In my opinion, a blank test is generally not required for routine metal detector checks if you are already using ferrous, non-ferrous, and stainless-steel test pieces. These test pieces are sufficient to verify that the detector is functioning properly and can detect contaminants at the required sensitivity.

 

However, using a blank product can be a good additional practice during testing for setup the machine or troubleshooting to confirm that these non-contaminated products can passes without false rejects. You can test once/shift with the in the following order: Fe sample -- blank sample -- Non-Fe sample -- blank sample -- SS sample, if the machine only reject the test pieces and approved the blank sample, this mean you can confidently say that the machine still work normally.