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  Depth filters ?

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Author Topic:   Depth filters ?
poly
Senior Member

Posts: 26
From:Canada
Registered: Jan 2005

posted January 23, 2006 02:37 PM     Click Here to See the Profile for poly   Click Here to Email poly     Edit/Delete Message   Reply w/Quote
I read once that certain depth filters were effective to break and stop gels. Unfortunately, I can't find the information anymore on the net. Where can I find them?

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Tom C
Moderator

Posts: 683
From:Brodheadsville, PA USA
Registered: Jun 2001

posted January 26, 2006 07:58 AM     Click Here to See the Profile for Tom C   Click Here to Email Tom C     Edit/Delete Message   Reply w/Quote
They do not break true gels. They just trap them.

Depth can be obtained by stacking standard screens, like 5 X 325 mesh.

The other option is sintered metal fibers, which can be built with depth.

Tom C

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poly
Senior Member

Posts: 26
From:Canada
Registered: Jan 2005

posted January 27, 2006 02:33 PM     Click Here to See the Profile for poly   Click Here to Email poly     Edit/Delete Message   Reply w/Quote
Unfortunately, stacking standard screens doesn't work for us. We are stacking 15 screens (4x80 mesh, 10x250 mesh, 1x10 m) right now, and gels are still getting through. Diffenrential pressure goes up fast. The gels may be stopped for a while, forming a cake, but deform when delta P rises, and finally get through the media. We have to change our filter about every 12 hours, since our maximum operating pressure before shutdown is 6000 psi. With a new filter, back pressure starts at around 4200 psi.

I've read about sintered metal fibers but the information about it on the net seems really rare. This is the only site I could find talking about it: http://www.dynapore.com/Main.htm?http://www.dynapore.com/Products/Fiber.htm

Are those depth filters containing sintered metal fibers really effective? Are they widely used for filtering polymer? Do you have more information?

We haven't found officially what causes our gels. Me, I know what causes them but I'm only an operator with 20 years experience. I think we're heating our polymer way to much for what's needed, causing it to polymerize and crosslink in the few dead spots our extruder contains. For now, they only seem to agree that we need a better filter. This is only a patch, but what can you do!

You have offered me your services before, and I have talked to my employer about you but they want to find their own solution. Really stubborn bunch of individuals!

Thank you

Best regards

[This message has been edited by poly (edited January 27, 2006).]

[This message has been edited by poly (edited January 28, 2006).]

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Tom C
Moderator

Posts: 683
From:Brodheadsville, PA USA
Registered: Jun 2001

posted January 29, 2006 09:13 AM     Click Here to See the Profile for Tom C   Click Here to Email Tom C     Edit/Delete Message   Reply w/Quote
I have been involved in a few similar projects. The issues are:

Are you being supplied gels and how to reduce?
Are you making gels and how to prevent?
Can you prevent gels from being made with an additive?
What are the gels made of?
Can you break the gels in the extruder with proper screw design?
Are broken (smaller) gels acceptable in the product?
Can you trap and hold the gels in a filter?
How can the filter life be extended?

When all of these issues, questions, and attacked at once, usually a good combination solution can be found.

Tom C

[This message has been edited by Tom C (edited January 29, 2006).]

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poly
Senior Member

Posts: 26
From:Canada
Registered: Jan 2005

posted January 29, 2006 01:25 PM     Click Here to See the Profile for poly   Click Here to Email poly     Edit/Delete Message   Reply w/Quote
Yesterday, I have found an excellent article in one of your forums. In the single screw forum to be more precise. This gives a lot more to work on. By knowing what mechanism is involved with gel formation, I think I will be able to solve our problem or at least suggest a solution.

Heat and oxygen are two elements that are surely affecting our process, assuming that my technical staff are right by claiming the screws show no wear only by looking at them with the naked eye...!!! You can see with whom I'm dealing with here...!!!
http://www.pisa.org.za/Henk%20Lourens%20paper.doc

Thank you for your help. I'll keep you informed of our (slowwwww) progress.

Best regards

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