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AJL

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Posted 07 March 2022 - 09:59 PM

Hi,
Is there anyone that can tell me about pipeline metal detectors?
Interested in how it works with the test Pieces? How is it verified?
Thanks :D



GMO

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Posted 09 March 2022 - 04:43 PM

They have some significant disadvantages vs. in line conveyor detectors IMO.  I use them on bagging systems and the comments below are based on that.

Firstly they don't have a reject.  They stop and alarm.  What I'd advise as well though is that you link that to a double bag system.  So when it stops and alarms with a positive detection, a double length bag is produced.  It at least means it's less likely to go to consumer as it should be taken off by checkweighers (overlength) later on the line.

 

Secondly test mechanisms are not ideal.  The best option is dropping a ball in the flow but it takes careful management not to lose it or have it damage jaws.  What many sites do is have a food safe plastic "string" so they trigger the detector but remove the test piece.  For my mind it doesn't test the timing but auditors appear to accept it.

 

Thirdly, because the test stops the line you then either then have to restart it, or you do your second and third checks with no product.  Yeah.  Bad practices all round!  

 

So that's all the bad...

On the upside, if you can get around the above problems, throat metal detectors are cheap.  Your packaging can be metallic with no issue as you're detecting just before wrapping.  While x-rays or higher end metal detectors can cope with this, they cost more.  The sensitivity is often pretty good and they can cope with high throughputs.  Also while all of the above issues are a problem, having worked with them, I've also had fewer complaints come back later.  That might seem baffling but while it's hard to test the timing; it's also unlikely to be wrong on most packaging systems you're using these in.  You normally couple these below a multi head weigher and when the product falls will be when the test piece falls if you put it in flow as it's about when the cup opens.  What might scupper your jaws is if that test piece is more dense than your product of course but it's less prone to tinkering.  What you can't do is mess around with a reject arm or air jet.  Or mess around with reject timer settings on a belt system.  I bet you that 90% of the metal complaints I've had in my career have been at least in part due to someone messing with a reject system on a conveyor metal detector and that's really not very easy to do.  

So while I had and still do have my reservations, actually they're not bad.



Charles.C

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Posted 09 March 2022 - 05:01 PM

Also see parallel, semi-duplicate of OP -

 

https://www.ifsqn.co...es/#entry183694


Kind Regards,

 

Charles.C


AJL

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Posted 09 March 2022 - 05:07 PM

Thanks GMO- yeah my issue is that we make ice cream- and if we end up losing pressure then we will end up with a whole lot of cones with no ice cream in them.
We could potentially do the very first test with the balls (I also think the strips are a bit dodgy, you need to test reject, like you said).
Bit do you think we could get away with doing a check with balls and product at the start, followed by a check with no product at then end of run (run time is no longer than 6 hours).
Thoughts?We have one on site, but the production managers biggest reservation is the loss of pressure resulting in lost product. We basically CANYlT stop the line.
It has so many inputs- and ice cream melts if you stop the line. Basically a no go.



PieGuy191

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Posted 09 March 2022 - 05:24 PM

At a previous job, we used a pipeline system to pass raw chicken (fillets, trim, thighs, etc.) through and it worked very well.  It had a reject mechanism that would drop the test ball and surrounding product out through a ball valve and into a catch pan.  it did not open when the system lost power so nothing was lost accidentally. It was from Safeline.  Not sure how it would work with ice cream.  Also used one earlier in my career in a plant that produced fresh pork sausage.  It worked on the same principle as the one I described above.  However, I don't remember the manufacturer  of that system.



AJL

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Posted 09 March 2022 - 06:44 PM

Thanks Pie guy- what about loss of pressure/ the line stopping? Ever had any problems?
I am starting to suspect that the supplier who knocked it, just wants to sell us a metal detector. We have the pipeline anyway, so it's technically free, but this supplier of our metal detectors seems to have really put the production manager off. Thanks🙄



Scampi

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Posted 09 March 2022 - 06:50 PM

I agree with PieGuy   used pipeline MD for mechanically separated chicken, never lost pressure, a valve inside is triggered that forces the test piece (and the food item) to discharge out the side of the pipe ( you could/ should have this alarmed)

There was a port to put the test wand (flexible) into the pipe upstream of the MD, but after the processing steps

 

If it discharged without a test wand, ALL the material in the pipe (predetermined settings) was bypassed so that it did not end up in the final product--never had any issues

 

Never trust the salesman on anything!  Best to have this quoted out by 3 different companies (Loma, Rice Lake, Mettler Toledo etc)   The big companies should be providing you with efficacy prior to quoting.  They should also ask ALOT of questions to ensure you're getting the right machine for the right application


Please stop referring to me as Sir/sirs





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