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Location : Umbumbulu, South Africa
Study : Creosote retention and
penetration levels in Eskom
Distribution poles
Dates : 1996 – 2004
Eskom is South Africa’s largest
Electric Utility Company and was
established in 1923. It is the
largest producer of electricity in
Africa and is also one of the top
ten utilities in the world in terms
of power generation capacity and
revenues.
Eskom has a Service Area of over
470,000 square miles and had over 2
million Utility Poles in Service in
2000.
Field Liners have been in commercial
use since 1994 when
Eskom
in South Africa implemented
the very first generation mono-layer
Field Liner on 100 creosote treated
utility poles at Park Rennie in Kwa
Zulu Natal’s coastal area, South
Africa.
In 1996, following on from the
successful smaller scale trials at
Park Rennie, Eskom embarked on a
commercial level trial with 300
‘sub-standard’ poles to be installed
at Umbumbulu.
The South Africa Bureau of Standards
(SABS) Specification for gumpoles
treated with creosote requires (a)
creosote penetration of 15mm into
the pole and (b) creosote retention
of 130kg/m3 in the pole.
In 1996, gumpoles with standard
creosote penetration and retention
were placed into service at
Umbumbulu alongside 300 poles with
substandard penetration of 11mm and
substandard retention of 80kg/m3.
Photos
show the application of the field
Liner to sub-standard poles with 300
lined poles ready to be planted
Lined
pole showing clear signs of
biodiversity and an unlined pole
showing clear signs of creosote
leaching
Core
samples taken from lined
sub-standard poles show greater
creosote penetration than unlined
standard poles
The standard poles had no Field
Liners while the substandard poles
were protected by an early version
Field Liners. They were inspected
and analysed after 1, 2, 4 and 6
years’ service and it was found that
while the creosote retentions of
SABS standard poles dropped from 130
to 50kg/m3 within 4
years, those of the substandard
poles increased to values well over
the standard specification of
130kg/m3 in the same
period. Visually, the creosote
penetrations of the SABS standard
poles were seen to decrease within
two years and some of these poles
were rotting after six years whereas
the creosote penetrations of
substandard poles with Field Liners
had increased from 11mm to 22 –
24mm, which was well over the
Specification’s requirement of 15mm.
The only explanation possible of the
increase in creosote penetration
with lined poles is that the
creosote had seeped into the
untreated heartwood of the pole
instead of leaching out into the
soil environment. A further 320
poles were fitted with Field Liners
at Hluhluwe and 220 at Hodazhel in
1998.
In 1997, the first year of the Eskom
commercial trial results were
presented to the International
Research Group on Wood Preservation,
Whistler, Canada. The four year
results were presented to the 2000
International Conference on Utility
Line Structures in Colorado, USA and
in 2004, the 6 year results of the
Umbumbulu commercial level trial
were published in ‘Energise’, the
journal of South African Institute
of Electrical Engineers.
Year after year, test results from
the Eskom commercial trail at
Umbumbulu have proved the efficacy
of the Field Liner and have shown
that even sub-standard poles will
not only be protected but will
improve as a result of the
application of the Field Liner. By
1999, three years into the trial,
Eskom issued a National Stock Number
for the Field Liner,
adopting them as a standard for
installation on utility poles.
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