7 replies to this topic

[Dr Vu]

i have some processing lines which use Xrays... 7 of them and only 4 have Xrays.... and others because of need ( nature of products etc) they do not need xray.... and within those 4 lines with Xrays there is some targeted products that MUST pass thru an xray.. Best practice with Xray is to use stone from country of origin of the product.
Due to nature of the processing (high humidity and heat), the stone and glass do not pick up all the time and we tend to focus on the targeted products and put those on hold and the rest depending on COO and past experience, we let go without re-adjusting.We have tried to correct humidity and heat but we have failed.......To balance my Operational and HACCP needs i have some options which i hope the team will help me with. Due to the nature of the Foreign Object. removal by xray can it be designated as a CP even though you do not have enough for each line? how would you do it when there is constant failure to pick up some challenge test pieces.

Here are my options...
option 1 officially challenge X-ray with metal samples only ( and do stone and glass separately on a different form ) option 2 officially select few products that NEED to be X-rayed and have 2 forms - the official form and the "for reference use only" form which will be for all other products. Procedure will be for any other products we turn off Xray and follow that during the audit - but in real life keep challenging the X -ray
option 3 use market available stone (alumina) during audits, and our stones during any other time..
option 4 use a bigger stone/glass sample- validate your process and with the heat and humidity you can shift your standard as long as you can back it up with data

Edited by vulindlela, 18 June 2012 - 11:04 AM.

[MM1]

Hi vulindlela,

We also use X-rays as a final inspection of foreign objects in product. we use S/S 1.5mm and glass 4.0mm along with std Fe,NonFe as test pieces. These are for our verification checks for the detector. As a validation we have passed various sizes of stones, metals and bone fragments to ensure that they are picked up. As a validation report we have printed the screen images of the objects detected. And the auditors are happy with this. You can go for option 4 as you have suggested, you need to validate the system by using smaller size pcs, this indicates what is the smallest piece your instrument can detect. The test pieces can be slightly bigger since the test pieces are used to ensure that instrument is working satisfactorily.

MM

[Dr Vu]

Hi vulindlela,

We also use X-rays as a final inspection of foreign objects in product. we use S/S 1.5mm and glass 4.0mm along with std Fe,NonFe as test pieces. These are for our verification checks for the detector. As a validation we have passed various sizes of stones, metals and bone fragments to ensure that they are picked up. As a validation report we have printed the screen images of the objects detected. And the auditors are happy with this. You can go for option 4 as you have suggested, you need to validate the system by using smaller size pcs, this indicates what is the smallest piece your instrument can detect. The test pieces can be slightly bigger since the test pieces are used to ensure that instrument is working satisfactorily.

MM

do you use stone to challenge your Xray at any time or just during the validation? and if that's the case doesn' t the auditor challenge you on that?.. for me stones are the most common contaminant.... all this material will pass thru a metal detector when we package it later on in the process.. ..Can i just skip metal checks and just check for stone and glass?

[Brian Meek]

Hi Vulindlela
Your tests should be representative of your production and the limits set require the test to work without fault all of the time. So setting the limits of the test sample pieces is critical in making your test both representative and most importantly repeatable. Limits are set by either yourself or by your customer in theirs or your specification and so if you are in control of the specification for testing then you can legitimately alter the limits to make your test representative and repeatable.

X Ray and the images produced are a product of density and should not be effected by heat and humidity unless the product is, which in your case is the stone contaminant so the density will remain constant if the stone is constant.

X Ray works in simple terms by shining a bright light through an object and taking a picture of the reverse of the object. The more you block the light the less light is transferred to the picture. The pictures are only taken in a grey scale not colour so the darker the object the more dense it is. Colour is added by software which interprets the grey scale and apply's a colour to it.

So in your case what you are actually seeing is a difference in the density of the stone your are trying to detect which is causing your failure rather than humidity or heat.

The first question I would ask is: Has the system ever picked up these stone contaminants correctly, I am assuming the answer to be probably not.

The only option you can take is option 4: Increase the test sample sizes until you are able to reject them accurately each time you test them.

Kind regards

Brian

[Alan Johnson]

Hi Vulindlela,

Just to add to the discussion, it is not clear if the high humidity and heat is related to the product or the environment, if it is the product then as already stated it should have no affect on the detectability of the stone/glass samples. However, there may be issues with wide variations in environmental temperature on the performance of the X-ray equipment, especially with older machines or machines that do not have temperature compensation built into the electronic sensors.

Stone from the country of origin is not so important, unless the country has only one type of stone. It is the density and size of the stone which is the determining factor in detection. For example, high density stone like granite (2.7) will be more readily detectable than the same size stone made from sand (1.6). If you are using spherical 'stone' test samples from an X-ray supplier it is likely to be a form of ceramic bearing, which will have a density in the range 2.3 to 3.0, glass will be around 2.3.

If stone foreign bodies are a big issue for you and they cannot be readily detected in the finished product then it may beneficial to look at other points in the production process such as the incoming raw material(s), detection levels (especially to non-metallics) will be improved if the product height being scanned is minimised and made more uniform, such as bulk flow.

Option 4 appears the best route for repeatable validation, this is generally adopted industry wide.

Best Regards
Alan

[Dr Vu]

Hi Vulindlela,

Just to add to the discussion, it is not clear if the high humidity and heat is related to the product or the environment, if it is the product then as already stated it should have no affect on the detectability of the stone/glass samples. However, there may be issues with wide variations in environmental temperature on the performance of the X-ray equipment, especially with older machines or machines that do not have temperature compensation built into the electronic sensors.

Stone from the country of origin is not so important, unless the country has only one type of stone. It is the density and size of the stone which is the determining factor in detection. For example, high density stone like granite (2.7) will be more readily detectable than the same size stone made from sand (1.6). If you are using spherical 'stone' test samples from an X-ray supplier it is likely to be a form of ceramic bearing, which will have a density in the range 2.3 to 3.0, glass will be around 2.3.

If stone foreign bodies are a big issue for you and they cannot be readily detected in the finished product then it may beneficial to look at other points in the production process such as the incoming raw material(s), detection levels (especially to non-metallics) will be improved if the product height being scanned is minimised and made more uniform, such as bulk flow.

Option 4 appears the best route for repeatable validation, this is generally adopted industry wide.

Best Regards
Alan

our machine is the older type.. and during a time of the day when temp/ humidity goes up, so does the Xray mis -fire..

[Alan Johnson]

our machine is the older type.. and during a time of the day when temp/ humidity goes up, so does the Xray mis -fire..

This sounds to me like 'array' drift, the sensor that collects the X-ray signal having passed through the product/contaminant is varying depending on the environmental temperature. These arrays age with time and this is accelerated by them being constantly hit with ionising radiation (X-rays) as do any electronic devices, the higher the X-ray energy generally the shorter the useful lifetime. Replacing the array may help if for example the machine at one time was able to detect the non-metallic samples in the product you are running, but over time it has lost this capability. It may also be possible to upgrade the X-ray system with an air-con unit, which may stabilise the internal temperature and so minimise the drift. These options may not be available if the unit is no longer supported by the manufacturer. I hope this helps.


Best regards


Alan

[Doug Pedersen]

Hi Vulindlela
I work with Alan but I am based in Toronto. I'd be pleased to help you. my email is xxxxxxx
Regards
Doug Pedersen

Edited by Charles.C, 27 June 2012 - 05:53 AM.
email address removed