Don't depend upon silica gel packs for long term moisture control in
less than hermetically sealed containers. Silica gel has a finite
capacity for absorbing water and, in any container that can "breathe,"
becomes saturated in a matter of days to months.
A box assembled with screws will "breathe" quite effectively. It is
better to assure that moisture, either vapor or condensation, can escape
through drains and ventilation.
This is especially important in applications that experience temperature
changes. Moisture will condense on the coldest parts. It condenses on
the outside walls when temperature drops, then evaporates from there and
condenses on the colder interior parts as temperature rises. A small
dissipation of energy in those interior parts goes a long way toward
preventing condensation on them.
The electronic modules in undersea cables were designed with large sumps
in their bottoms. The electronics were mounted in the upper volume.
These modules experience almost no temperature change while in service.
They were sealed as well as technology permitted and the 'sump' volume
was large enough to provide desired service life before the level of
water reached the electronics.
73 de WOØW
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