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Annual calibration of metal detectors - is it necessary?


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#1 dianep1

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Posted 21 July 2011 - 07:13 AM

Morning all,

Can any body tell me........is it necessary to have annual calibration certificate for a metal detector?? I have worked in previous companies that have insisted this is a standard requirement, but have recently spoken to Technical/Quality Managers who say it isnt a requirement , as the test piece itself is adequate proof that the detector is working.

Many thanks

Diane


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#2 Markcra

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Posted 25 July 2011 - 10:48 AM

Morning all,

Can any body tell me........is it necessary to have annual calibration certificate for a metal detector?? I have worked in previous companies that have insisted this is a standard requirement, but have recently spoken to Technical/Quality Managers who say it isnt a requirement , as the test piece itself is adequate proof that the detector is working.

Many thanks

Diane


Dear Diane

I'm not familiar with the BRC standard, but under ISO 22000 the requirement for calibration is to ensure that specified monitoring and measuring equipment is adequate to ensure the performance of the monitoring procedure. It goes on to state that where necessary to ensure valid results the instrument is to be calibrated....

I do not see the requirement to have the metal detector calibrated if the test piece represents the smallest amount of metal contamination that would be considered a food safety hazard from your process. Also bear in mind that the metal detector is not measuring a variable such as a temperature measurement.

Regards

Mark
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#3 Charles.C

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Posted 25 July 2011 - 12:12 PM

Dear dianep1,

If you hv a look at some of the other threads here relating to performance of metal detectors, the possible necessity for annual calibration is apparent. Of course, the value may well also depend on yr specific situation / the details of how the calibration is done. :smile:

Rgds / Charles.C


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#4 Madam A. D-tor

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Posted 25 July 2011 - 12:35 PM

Dear dianep1,

I myself, never understand, why it should be nessecary to calibrate the metal detector equipment, if you are already verifying the correct working, several times a day.
However, I see a lot of calibration reports for metal detectors. Mostly it is the same test as you do your self on a-few-times-a-day-frequency, done by the supplier. Mostly it is included in the annual maintenance inspection by the supplier.

Only the calibration report is no issue forme. I never include this in my audits. I think the preventive maintenance-inspection is compulsory to guarentee the equipment will be working perfect in the future.


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Kind Regards,

Madam A. D-tor

#5 Yuri

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Posted 09 August 2011 - 09:28 PM

Personally I think the most important is that the metal detector is working correctly. It would be interesting to know what exactly is done during the annual calibrations: if it is just confirming that the test pieces are ejected or not, there is no added value. If there is a full check of settings, study on the correct placement of the metal detector (not too many disturbing elements), etc ... this could be usefull.


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#6 Charles.C

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Posted 10 August 2011 - 06:25 AM

Dear Madam A.D-tor,

Only the calibration report is no issue forme. I never include this in my audits. I think the preventive maintenance-inspection is compulsory to guarentee the equipment will be working perfect in the future.


Precisely. :thumbup: But I don't quite understand why this makes it unnecessary to include in an audit? Do you mean that you consider that implementation of factory systems of preventive maintenance are not necessary to verify/audit ? Or (perhaps) that the metal detector would be a very low priority within yr normal check ? or ? :smile:

The annual objective is to know how close to perfection the unit is achieving, eg are the coils generating the magnetic field only 50% normal so that non-optimally shaped contamination will not be (correctly) detected.
Of course, it can also be argued that such ignorance equally implies a defect in the "daily" procedure for calibration of the detector which should be evaluated on both "good" and "bad" case scenarios. Rarely done IMEX.

I also suspect the not-so-unusual disinterest in annual checks is simply an extension of the engineer's No.1 favorite rule - "if it ain't (visibly) broke, don't fix it".

Rgds / Charles.C
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#7 GMO

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Posted 10 August 2011 - 06:28 AM

Dear Madam A.D-tor,



Precisely. :thumbup: But I don't quite understand why this makes it unnecessary to include in an audit? Do you mean that you consider that implementation of factory systems of preventive maintenance are not necessary to verify/audit ? Or (perhaps) that the metal detector would be a very low priority within yr normal check ? or ? :smile:

The annual objective is to know how close to perfection the unit is achieving, eg are the coils generating the magnetic field only 50% normal so that non-optimally shaped contamination will not be (correctly) detected.
Of course, it can also be argued that such ignorance equally implies a defect in the "daily" procedure for calibration of the detector which should be evaluated on both "good" and "bad" case scenarios. Rarely done IMEX.

I also suspect the not-so-unusual disinterest in annual checks is simply an extension of the engineer's No.1 favorite rule - "if it ain't (visibly) broke, don't fix it".

Rgds / Charles.C


The problem I've found in most companies is that the preventative maintenance check is 'are there any bits hanging off?' and 'is the belt undamaged?' because the engineers on site have not felt confident enough to do anything more involved with a metal detector as they generally don't have experience in them, so if you are going to rely on preventative maintenance, it's worth checking what they're actually doing.
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#8 Dr Ajay Shah

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Posted 10 August 2011 - 11:28 AM

I would like to inform you all that the phase changes on the metal detector with moisture and salt levels and so iit is important to ensure that the metal detector can detect the test pieces at various moisture levels. It therefore imporatnt to verify that your particular metal detector is functioning properly. I learnt all this from a metal detector engineer who is a specialist at maintaining metal detectors


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Dr Ajay Shah.,
BSc (Hons), MSc, PhD, PGCE(FE)
Managing Director & Principal Consultant
AAS Food Technology Pty Ltd
www.aasfood.com


#9 shea quay

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Posted 17 February 2012 - 05:47 PM

We used to calibrate our metal detector once a year. A guy came out, passed our test sticks through the detector, the belt stopped, we gave him 100 euro, he gave us a meaningless certificate. In order to try to end this madness, we've purchased a second set of certified test wands the same detection level as our current ones. Every week as part of our Maintenance programme, we pass our "floor" wands in product through the detector and note the reading. Then we pass our "office" wands in the same product through and compare the results. If the difference is over 1,000, we call out the engineer. It's far from an exact science, I accept (the figure of 1,000 was picked out of the air), but it is starting to build up a bank of historical evidence that I hope will convince our BRC auditor and in time allow us to be a bit more precise with our target limits. The other advantages are that it tests the metal detector across a range of products (such as, as Dr. Shah states, different moisture levels) as well as validating that our "floor" test pieces are working. No idea if this is/isn't going to be acceptable or not, but will be arguing the case strongly in the audit.


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#10 Charles.C

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Posted 18 February 2012 - 07:24 AM

Dear shea quay,

Thanks for the ingenious and interesting post. I hv a few queries.

1000 what ? I presume not a multiple !? do you mean that floor wand gives say 980,000 units and office must give 979,000 - 981,000 units? It's surely more a question of percentages. :smile: And i presume it will depend on the "natural" variation of the response to different products as you mention.

My first (simple) auditorial question as to yr procedure would be to request evidence that the principle of yr procedure has been validated “somewhere else” since it appears, to put it politely, “ad hoc”. Can you ?

One obvious query is that yr office wand which is de facto acting as the “primary master” must “normally” be regularly certified. The frequency is debatable but I predict most auditors will not be too happy with more than 1 year (after all the 100euro is not their money :smile: ) as a starter. A similar problem arises with weight masters, eg brass or stainless reference weights, how often must they be checked, etc etc. Some people gather evidence that no significant (for their application) change occurs in, say, 5 years, this might then be acceptable as evidence to extend the frequency.

I wish you the best of luck however I strongly suggest that yr QA team also acquire a certified piece of the Blarney Stone in advance, just in case. :biggrin:

Interested to hear how you get on.

Rgds / Charles.C


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#11 shea quay

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Posted 21 February 2012 - 08:36 PM

Sorry Charles, yes, it's +/-1000 units, but yes, using a percentage (I'm going to say 5) does sounds much better. The breads we produce are broadly similar.

As for "ad hoc" - completely. Who knows, there could be either a non-conformance or a Nobel Peace prize in it for me!

Good point on the validation of the "primary master". When we started this we got the old set calibrated. They were four years old and still within tolerance levels. We are using the defence of if these sticks were being used consistantly on a factory floor and were within tolerances after four years, then the primary master which is only removed from the office once weekly should last 646 years (floor sticks are used once an hour; 24 times a day, average 350 production days a year, for four years). Therefore, calibrating the test sticks every five years henceforth even sounds over cautious!


Surely, even you would agree, that is fairly flawless logic! Stockholm here I come!



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#12 Charles.C

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Posted 21 February 2012 - 11:47 PM

Dear shea quay,

I agree yr shelf-life conclusion is possible / probable. In truth i was being a bit bookish, in reality and MEX, I predict one can get along quite well without re-calibration of test pieces if they are demonstrably resistant-to-change, eg perhaps something like this –

http://www.teststandard.com/

Should be accompanied by suitable certification, eg certified traceable to someone prestigious like NIST. Most auditors probably know far less about metal detectors than you do.

I appreciate the preventive maintenance aspect of monitoring meter readings but the minimal validation requirement seems to me to be only that the machine should ring/kick appropriately. Nonetheless, if the auditor has a checklist which includes "independent calibration minimum annually" a dialog is probably unavoidable. :smile:

Rgds / Charles.C


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