TM 1-1500-204-23-1
Table 10-1. Part and Fabrics Affected by Moisture and Fungi
Part or fabric
Effects of moisture and fungi
Cotton, Linen, Paper, and Cellulose Derivatives:
Insulating and dielectric properties are lost or
Insulation, coverings, webbing, belting, laminations,
impaired by moisture, causing arcing, flash-overs
dielectrics, etc.
and cross talk. Fungi causes rot and complete
destruction.
Fiber: Terminal strips and insulators.
Moisture causes electrical leakage paths to form,
in turn, causing flash-overs, cross talk, and loss
of insulating properties Fiber terminal strips and
insulators are destroyed by fungi.
Fiber: Washers, supports, etc.
Moisture causes swelling which, in turn, causes
supports to misalign, resulting in binding of
supported parts Washers are destroyed by fungi.
Glass Lenses, windows, etc.
Fungi grow on organic dust, insect tracks, insect
feces, dead insects, etc. Dead mites and fungus
growth on glass obscures visibility and corrodes
nearby metal parts.
Laminated Plastics: Terminal strips and boards,
Moisture causes electrical leakage paths to form,
switchboard panels, etc, tube sockets and coil .
in turn, causing flash-overs, cross talk, and loss
forms, and connectors
of insulating properties Delamination occurs
and fungi grow on surfaces and around edges
Extreme temperature changes cause expansion
and contraction.
Leathers Straps, cases, gaskets, etc.
Fungus destroys tanning and protective
materials, causing rotting due to moisture
bacteria fungi.
Metals
High temperature and moisture vapor cause
rapid corrosion Fungus and bacterial growth
produce acids and other products which speed
corrosion, etching of surfaces, and oxidation
This interferes with the operation of moving
parts, screws, etc. and causes dust between
terminals, capacitor plates, air condensers, etc,
thus causing noise, loss in sensitivity, and arc-
overs.
Metals Two or more.
Different metals which have different potentials
when moisture is present cause electrolysis,
thus causing formation of salts and beep etching
of surfaces as one metal is plated onto the other
This happens at riveted and bolted joints,
bearings, slides, and screw threads.
10-11
