Bob,
In MHO, I have always assumed the desiccant was 'virgin' dry when it was
vacuum sealed into a bag by a SUPPLIER - therefore, IT should not outgas
moisture - but, if the CONTENTS of the bag did outgas, the desiccant was
there to pick it up.
On the other hand, if the desiccant was old/previously used, I would think
that moisture would be drawn from it - potentially contaminating the
contents - to some degree. Along the lines of you may be thinking. Read
as, "Make sure one, or both are dry before re-bagging.
How about this concept - If you are not sure that the desiccant is fresh,
virgin material, don't vacuum seal it in the bag.
I don't figure a quickie nitrogen blow-through does an adequate job of
removing the moisture from the components just before sealing the bag, but
it may do a fair job of excluding the potentially humid atmospheric air - so
a FRESH desiccant could be of benefit.
I don't know what the actual vacuum level is, but it does appear to reduce
the internal pressure to a sub-atmospheric level - otherwise why would
blister packs, etc. (which are bagged up) be partially collapsed.
Anyway, I am certainly no expert, but have found the discussion to be
interesting.
Steve Creswick - Gentex Corporation
-----Original Message-----
From: bbarr [mailto:[log in to unmask]]
Sent: Wednesday, May 01, 2002 11:06 AM
To: [log in to unmask]
Subject: [TN] Vacuum Sealing
In the responses to Steve's question on vacuum sealing, there were two
responses that have me wondering. Both posters said not to use desiccant in
combination with vacuum (though for different reasons.) Most every bag we
get here direct from the device manufacturer or from distributors has the
bag sucked down tight, and with desiccant. Are the vendors doing something
truly wrong? Are there any device manufacturers out there that can clarify
this?
Thanks.
Regards,
Bob
=======================
Robert Barr
Manufacturing Engineering
Formation, Inc.
Voice: 856-234-5020 x3035
Fax: 856-234-6679
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