5 replies to this topic

[MartLgn]

Hi all.

I work for a manufacturer of composite cans of the type drinking choc and powdered milk are packed into, we are developing a pack for a customer who currently packs their product into metal cans which are hermetic.

A few points to ponder.....

The customer requires 100% testing of cans for hermeticity.

Our containers are made from paperboard with foil/poly liner and metal ends.


The problems I have are

1.that the tests we currently carry out for hermeticity involve having both ends on the can which is fine in the lab but leaves the can unable to be filled.

2. If a can fails proves to not be hermetic, how do I establish which part of the can allowed the air to enter?


Does anyone have any experience of hermeticity testing ? all guidance would be appreciated.

[yorkshire]

Firstly you need to get your customer to define / quantify what their view of "Hermeticity" is. I only put this because alot of materials have some permeability to gases and seals will burst under excess pressures.

We used to test packets / drums were correctly sealed by placing them in a water bath and pulling a vacuum in the headspace above the bath. If there were any leaks we could see the air bubbles and pinpoint the exact location of leak. This may help for locating the source of a leak but you would certainly not be able 100% test.

The only way I've seen to test the seals of such tubes (one end capped ) was by "pressure decay". A head went down onto the tube where pressure was applied and a sensor inside measured any pressure loss.

Sorry I don't know any more than that but will be interested to find out more.

Edited by yorkshire, 29 March 2005 - 03:40 PM.

[Simon]

Hello Martin,

The problem you are going to find is that hermeticity testing (as far as I know) is usually destructive so it can only be through sampling and not 100% as your customer requires. Similar to Yorky the type I have seen is where lidding material is heat sealed to the open end of the cardboard tube which is then placed in a dry vacuum chamber. If the lid blows the seal is (was) hermetic.

Just searching on the internet there does seem to be more advanced methods of testing for a hermetic seal (see link below). Whether this is viable for 100% testing in a production environment is another thing.

http://www.semiconfa...om/hermtest.htm

I do know someone who is expert in this area and if I can get hold of him I will ask for his views.

By the way for posting this case study you have won a free book.
Choose one from the list at the link below and email me with your choice and your postal address. Please note the books highlighted in red have now gone.

http://www.saferpak....p?showtopic=950

Regards,
Simon

[okido]

Hello Martin,

In the meat and cheese packaging industry hermeticity of seals is also tested. We call this testing for pinholes in the seal rather than hermeticity of the seal. (Interesting to now what permeability is required.)
The packed product either in bags or trays is tested by inflating it with compressed air and keeping it under water. The advantage of this method is that it quick, accurate (100%) and easy to perform with very little equipment.
We also use a He sniffer. The product is filled with He and the He level around the product is measured. High levels of He indicate a leak. This is expensive equipment and it is not as accurate as the method above.
If you pack the product under modified atmosphere you can also measure the specific gases that are used.

Regards, Okido

[MartLgn]

Thanks, Yorkshire, Simon and Okido for sharing your experiences. It seems apparant as Simon states that testing for hermeticity is by its very nature destructive or at least makes the container unfillable as it must be sealed.

This is a new situation for my company, we produce hermetic composite containers in the US, Europe and Asia and carry out many batch destructive tests but no plant has apparantly ever been asked to test 100% of cans for ''leakers''.

[Mrs. DG]

Hello. I found this thread in regards to hermetic container. Very helpful information. I am questioning the fact that a cardboard can be considered a hermetically sealed container; the package has its limitations by nature. I can understand this term for canned items.

 

Can someone share their leak testing protocols, number of leakers allowed in a given sample size, what the sample sizes are, and what kind of action must be taken if whatever threshold you have established is exceeded?

 

I need to establish all this for a new business line using a cardboard container.

 

Your expertise is very much appreciated.

DG.