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 7.1.2.2 Physical Tests. In addition to visual inspections, several physical tests are
available to aid pole inspectors in determining the presence of biological damage. Some of these
methods are very basic while others involve sophisticated electronic equipment. Nondestructive
testing equipment is currently being developed to provide estimates of residual strength in poles. In
all cases, considerable experience is required to interpret the results, especially with the newest non-
destructive testing devices for wood poles.
Sounding. Sounding is probably the most common method of inspecting
poles for internal voids. The pole is firmly hit with about a one-pound hammer from ground level
to as high as one can reach. A crisp sound usually indicates the pole is solid. A dull thud indicates
wet and possible rotten wood and a "drum" sound indicates a void. The sound produced varies con-
siderably, but experience will eventually lead to distinguishing between sound wood and the various
defects. Sounding usually detects only the worst poles. Naturally, to develop experience, it helps to
sound a pole and then bore or cut it apart to determine which defects are actually present.
Boring. Where decay or insect attack is suspected, the pole is generally bored
for confirmation (Figure 7-4). Increment bores are most commonly used. The core can be closely
examined at the site and also saved for later culturing or microscopic examination. An effective,
but simple way to save increment cores is to insert them into soda "straws", seal the ends and label
for identification. Protected in this manner, increment cores can be shipped to a laboratory for
biological studies.
Poles that sound suspicious should be bored near deep checks which occur, at or one foot below the
ground line. If rot is detected, the poles should be bored at three or four points around the circum-
ference. The shell thickness, depth of preservative treatment, and pole circumference are deter-
mined. Minimum circumference tables can be used to determine if the pole should be replaced,
reinforced, field treated or scheduled for reinspection.
When boring holes above ground, the tool should be oriented slightly upward. This prevents water
from accumulating in the hole. At ground line, a 45 degree angle downward is generally used. All
openings made during inspection should be treated with the appropriate preservative as registered
by the EPA. The holes should be plugged with preservative treated dowels. These dowels can
loosen and work out of the holes so treatment of the hole itself is important. Protective goggles and
other safety equipment as appropriate should be worn as preservative can squirt out of the hole as
the dowel is being driven or as the hammer strikes the treated wood.
In lieu of taking increment cores, poles are sometimes drilled, preferably with a bell-hanger's bit
which produces a quantity of shavings. Decay is "detected" by the operator on the basis of change
in resistance of the wood to the bit, and by odor of the decayed wood. No other confirmation of
decay is attempted.
7-6
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