Calibration requirements for Metal Detectors

Hi, 

Refer to metal detector topic, I've a questions.

1. How frequent we need to calibrate the metal detector? I've a letter from manufacturer stated that our model of metal detector does not need calibration. However, auditor asking us to set calibration time.
2. How do we calibrate our metal detector?

 

Hi, 

 

Refer to metal detector topic, I've a questions.

 

1. How frequent we need to calibrate the metal detector? I've a letter from manufacturer stated that our model of metal detector does not need calibration. However, auditor asking us to set calibration time.
2. How do we calibrate our metal detector?

 

Hi req-sad,

"Calibration" has various interpretations, notably (1) detection capability validation, (2) routine machine overhaul/check-up

Please clarify what you/your auditor are referring to, eg Standard / clause ?

hello,

Metal Detector  must be calibrated at least annually by third party calibrator which is ISO 17025 certified.

In-house testing of sensitivity to test piece must be done on site's set frequency.

regards,

redfox

 

Hi, 

 

Refer to metal detector topic, I've a questions.

 

1. How frequent we need to calibrate the metal detector? I've a letter from manufacturer stated that our model of metal detector does not need calibration. However, auditor asking us to set calibration time.
2. How do we calibrate our metal detector?

 

hi,

You should prepare the annual calibration plan Both In-House and External Agency and it  must be calibrated by NABL accredited External agency [Third Party].

In-house testing of sensitivity to test piece must be calibrated on daily basis . There is no standard available for set the frequency . 

regards,

V.Sivachandran

Hi All

i deduce Posts 3,4 both referred to option (2) of Post 2. 

For BRC i identified "calibration" to (1), all done in-house, no further details ever requested by auditors. Any change in (2) would prompt (1).

(As per the Engineer's Law - If it ain't broke, don't fix it).

Over to the OP as to his specific interest

In all of my metal detection experience the term "calibration" is a bit of a misnomer in this specific context.  There is no actual calibration with any metal detector that you would need a technician for.  You are in fact calibrating it when setting it up to detect the metal test samples.  The samples are the control and the adjustment in sensitivity is your calibration to those samples.  

What your auditor is really looking for is a third party verification from a factory authorized technician that certifies that the metal detector system is capable of reliably detecting the required test samples and at what settings it was tested at. Also, that there are no underlying maintenance issues that could affect the overall performance of the system.  

The frequency of the certification services should be based on your own plan, or your customers requirements.  From the factory point of view it is usually recommended to be done on an annual or semi-annual basis. 

I hope this helps.

Eric 

Hi Eric,

Thks for yr input and Welcome to the Forum ! :welcome:.

May i enquire as to which Food Standards yr comments relate to ?

Hi Charles, 

Thanks for the welcome. 

My comments are more general and aren't specific to any individual standard.  But, I would think it relates to all of them.  

In my experience, I was the one issuing the certifications on the metal detectors so that my customers were able to satisfy their auditor requirements.  Although, there were a few instances where an auditor would look for something different, to my knowledge the certification was able to satisfy all standards.

Eric

Hello Charles,

Though in BRC (we are BRC certified site) no specific calibration frequency requirement for MD. But since our Metal Detecting step is a CCP the auditor required us for calibration once a year. Then our government agency which issue HACCP certification also requires us at least annually of calibration frequency on top of our every 30 minutes of specimen testing.

regards,

redfox

Hello Charles,

 

Though in BRC (we are BRC certified site) no specific calibration frequency requirement for MD. But since our Metal Detecting step is a CCP the auditor required us for calibration once a year. Then our government agency which issue HACCP certification also requires us at least annually of calibration frequency on top of our every 30 minutes of specimen testing.

 

regards,

redfox

Hi redfox,

Just to avoid confusion, can you explain what activity(s) is/are actually involved when you refer to "calibration" ?

I am guessing you mean a sequence of checking, for Ferrous/non-Ferrous/SS composition, the smallest diameter test strips which are detected by the MD ? In other words the exercise to determine the Critical Limit is equivalent to Calibration.

This is not quite the same, i think, as the activity described in 1st paragraph, Post 6, since in above procedure no changes are made/envisaged to the MD instrument settings. (in some MD manuals such changes can, I think, also be user-made to optimise sensitivity for different food martices. This could also be described as "Calibration" but would presumably also be included as a part of a, maybe annual, "maintenance" check performed typically by a local MD representative)

I have a suspicion that we are all talking at cross-purposes. :smile:

PS - I guess yr 30min. reference is regarding the interval (not actually a frequency) during a process for checking that the MD test piece(s) defined in the critical limit can be adequately detected. i call this Validation of the critical limit/MD but I daresay opinions vary.

Hello Charles,

 

Though in BRC (we are BRC certified site) no specific calibration frequency requirement for MD. But since our Metal Detecting step is a CCP the auditor required us for calibration once a year. Then our government agency which issue HACCP certification also requires us at least annually of calibration frequency on top of our every 30 minutes of specimen testing.

 

regards,

redfox

Just thinking outside the box here, but would an annual service of the MD by either the manufacturer or equivalent tick the box? Even though they (more than likely) won't be making any changes to the machine, they will be verifying that it is performing to standard. Plus, that way you're covering both the calibration and routine maintenance requirements  :gleam:

Hi All,

Calibration of metal detectors is a really popular topic !.

Just as an example (the OP left it open) – here are the relevant BRC requirements –

6.4.1

The site shall identify and control measuring equipment used to monitor critical control points, product

safety and legality. This shall include as a minimum:

•  a documented list of equipment and its location

•  an identification code and calibration due date

•  prevention from adjustment by unauthorised staff

•  protection from damage, deterioration or misuse.

 

 

Here is BRC’s (Generic) definition of Calibration –

Calibration

A set of operations that establish, under specified conditions, the relationship between values of

quantities indicated by a measuring instrument or measuring system, or values represented by a

material measure or reference material, and the corresponding values realised by standards.

 

 

So how should one define “Calibration” in the context of a Metal Detector and its Specific User ?

Searching yielded  4 interpretations of MD “Calibration”  –

(1) Services Companies offering a Package approach with specific "Calibration" Procedure undefined, eg  –

Company 1 MD Calibration.pdf   159.11KB   476 downloads

Company 2 MD Calibration.pdf   21.92KB   323 downloads

(2) Multiple Calibrations

One User using 2 Calibrations + Regular Maintenance (!!) ( Detailed Daily  own test sample / 6-month manufacturer Package (Procedure unstated)/Annual maintenance)

Dual MD Calibrations.pdf   468.33KB   285 downloads

(3) Daily Calibration with test samples

MD Daily Calibration.pdf   290.93KB   289 downloads

You-tube -

https://www.youtube....h?v=nuPaKXgxeco

https://www.youtube....h?v=Y0ZAOg4PCnI

(may now be blocked, 200919)

[Both still working 11th May,2023, Charles.C]

(4) No Calibration

tesco - Metal Detector Calibration.pdf   29.58KB   322 downloads

And from previous forum threads (among many) –

http://www.ifsqn.com...s-it-necessary/

2012

http://www.ifsqn.com...ctors-accepted/

2013

http://www.ifsqn.com...etal-detectors/

2014

Perhaps you can take your pick as far as “Calibration” is concerned although route (3) is presumably the financial winner as long as no auditor rumblings (I reserve  Preventive Maintenance as a separate topic in its own right).

addendum

Unfortunately not sure where the quote originally occurs but this may explain the entry in category 4 -

According  to  the  BRC,  metal  detectors  cannot  be  calibrated  technically  but  the  sensitivity  is  optimized.  The sensitivity can then be verified using standard sized rods or balls of different types of metals to ensure the metal detector  detects  these.  Further  validation  of  the  metal  detector  by  controlled  spiking  of  the  product  is  also
essential.

 

metal detection, 2010.pdf   126.35KB   356 downloads

Hello Charles,

Actually we still waiting the "calibrator" to come to our site this coming November. It is the first that the calibrator would calibrate our MD since BRC auditor required us and the local HACCP certification. As Eric says, it might be a certification from a competent authority that auditors want to see. As our experience when the machine failed to detect the test piece we adjust the sensitivity to that specific kind of metal and size. I think that already a calibration. Like other measuring device, weight and temperature, though we have in-house calibration, still the auditors are still looking for the 3rd party calibration certificate. We have to follow what auditors are looking to avoid NC.

regards, 

redfox

Hi redfox,

May I suggest the appropriate challenge is "Show me the word "external" !"

PS - is this the same auditor who demanded you show him/her a original hard version of the BRC Standard ?

Really thanks for your reply. I think what my auditor need is certification from a competent authority (external calibrator). Even we do routinely checking everyday on our MD. 

Ya like what redfox said "We have to follow what auditors are looking to avoid NC" :gleam: .

Really thanks for your reply. I think what my auditor need is certification from a competent authority (external calibrator). Even we do routinely checking everyday on our MD. 

 

Ya like what redfox said "We have to follow what auditors are looking to avoid NC" :gleam: .

Hi req-sad,

I appreciate that people generally prefer to avoid confrontations. It is also worth remembering that BRC audits/CBs are themselves audited for "consistency" by their Accreditation Board.

It would be interesting to know what the BRC Interpretation Guidelines recommend  "to demonstrate that measuring equipment is sufficiently accurate and reliable to provide confidence in measurement results".

Hello,

Does anyone knows if the annual calibration must be carried out with product (and metal pieces) or the product is not necessary and using only metal pieces is enough?

Please, take into consideration that I refer to the annual calibration.

Hello,

Does anyone knows if the annual calibration must be carried out with product (and metal pieces) or the product is not necessary and using only metal pieces is enough?

Please, take into consideration that I refer to the annual calibration.

4-year old thread.

I suggest to refer to Post 12

With respect to "sensitivity" it will usually vary with the food matrix.

afaik, unless stated otherwise, MD literature data typically assumes the test piece is directly passed through the MD.

For example -

metal_detection_guide.pdf   1.51MB   161 downloads

(Pg 13/32)

I find the general discussion to be interesting, but I haven't seen a single discussion about the specifications for the sizes of the various test artifacts/specimens. I do see a fair amount of information related to densities of various materials,

but this would appear to be worthless without knowing what the actual size limits are for each of nominal test artifacts/specimens. And, once you have a nominal size and specification, where does the measurement uncertainty come into consideration? Yes, you can have a record of your routine verification/validation/calibration, but it would seem to be relatively meaningless without some reference to the metrological traceability that ius the foundation of the entire process.

*Zombie thread"

So I think there are a few nuances in this area Calibration Assessor's first post has caused me to dredge up from my memory banks....

I haven't seen a single discussion about the specifications for the sizes of the various test artifacts/specimens. 

I've done some work on this in the past.  Firstly I had an auditor challenge me on the grade of stainless steel I chose for my test pieces.  So that's a valid question.  I wrote a risk assessment (I'd chosen 316 and most of our equipment was 316 which was a good start.  Some was 304 but I think I found a reference saying that was easier or at least no harder to detect).

Secondly, why the size?  This is where this reference comes in: 

CPG Sec 555.425 Foods, Adulteration Involving hard or Sharp Foreign Objects | FDA

It's the only reference to an authoritative source I've ever found which considers "what size could cause harm".

Next there are considerations that not all contaminants are spheres.  I'm not sure if it's still in this manual but the old version had a brilliant section in it about detectability of different shapes.  Worth a read anyway:

Guide to Metal Detection Technology

But from that you should be approaching the test piece size as trying to get the smallest possible, under 7mm but smaller still considering the lower detectability of wires etc.  That's where your supplier should help in validating what size can be consistently detected in your products without excessive false rejects.  

That was always the basis of my validation of test piece choice and size (along with the, let's face, it, more an annual service visit than a calibration one).  

I've just downloaded that metal detection guide again (I'm so old I used to have it in hard copy), yes the section is still there in "orientation effects" and how wires particularly or long thin strips can be harder to detect in certain orientations.