moisture, temperature, air, and the
absence of direct sunlight are most fa-
vorable to the growth of fungi. Unfortu-
nately, this is a portion of the pole usually
hidden from view and it is close to the
natural breaking point of a pole under
strain. Thus, it is the most critical part of
the pole and warrants special inspection
and maintenance.
absence of direct sunlight are most fa-
vorable to the growth of fungi. Unfortu-
nately, this is a portion of the pole usually
hidden from view and it is close to the
natural breaking point of a pole under
strain. Thus, it is the most critical part of
the pole and warrants special inspection
and maintenance.
3.2. DETECTION OF DECAY. Two methods are
generally used to determine the presence and
the degree of decay in poles. Sounding a pole
with a hammer, mechanical sounding tool, or
electronic sonic pole tester will usually detect the
presence of decay. Boring the suspect pole with
a brace and bit or an increment borer will
confirm the presence and determine the degree
of the decay.
generally used to determine the presence and
the degree of decay in poles. Sounding a pole
with a hammer, mechanical sounding tool, or
electronic sonic pole tester will usually detect the
presence of decay. Boring the suspect pole with
a brace and bit or an increment borer will
confirm the presence and determine the degree
of the decay.
3.2.1. Sounding.-Experienced personnel
can detect internal decay pockets by using
a 1- or 2-pound hammer to make sound
tests above ground or at groundline after
excavation. A mechanical device, such as
the "M-pact-O Pole Sounder' (marketed by
the Engineers Tools Corp., Lake City,
Iowa), can be used for grounding sounding
without excavation.
can detect internal decay pockets by using
a 1- or 2-pound hammer to make sound
tests above ground or at groundline after
excavation. A mechanical device, such as
the "M-pact-O Pole Sounder' (marketed by
the Engineers Tools Corp., Lake City,
Iowa), can be used for grounding sounding
without excavation.
The sonic pole tester (such as the "Pol-
Tek,"
Tek,"
distributed by the Chapman Chemical
Co., Memphis, Tenn.) is a device that is
used on poles and crossarms scheduled for
periodic testing. Basically, this instrument is
a sonic generator which injects a sound
impulse into a pole and then records the
time required for this impulse to pass
through the pole and impinge on a
receiving unit
used on poles and crossarms scheduled for
periodic testing. Basically, this instrument is
a sonic generator which injects a sound
impulse into a pole and then records the
time required for this impulse to pass
through the pole and impinge on a
receiving unit
homogeneity of the wood in addition to its
thickness will determine the time for
propagation of the impulse through the
poles.
thickness will determine the time for
propagation of the impulse through the
poles.
Tests indicate that while the sonic pole tes-
ter will not always indicate the degree of
decay and its extent, with a high degree of
accuracy it will pick out poles which are
decaying or have internal voids, cracks, or
fractures which may or may not decrease
the strength of the pole significantly. 'the
instrument does not register any pole as
good when it actually contains any signifi-
ter will not always indicate the degree of
decay and its extent, with a high degree of
accuracy it will pick out poles which are
decaying or have internal voids, cracks, or
fractures which may or may not decrease
the strength of the pole significantly. 'the
instrument does not register any pole as
good when it actually contains any signifi-
Figure 1. Typical internal decay in a 20-year-old
western red cedar pole. Areas of advanced decay
are surrounded by narrow zones of wood in early
states of decay.
Figure 2. Internal decay in a Douglas fir pole that
was in service about 11 years. Areas of advanced
decay ere surrounded by wide zones of wood in
earlier stages of decay.
3 (FIST 4- 6)