[TowerTalk] Silica gel

Red Haines redhaines at acegroup.cc
Mon Sep 22 10:33:50 EDT 2008

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

More information about the TowerTalk mailing list