Posted 28 February 2002
The first edition of Australian Stainless featured the flagpole which towers over the new Federal Parliament building in Canberra. Ten years on and fifteen years since it was erected, the flagpole is well on the way towards its planned 200 year life. A condition survey was recently carried out by an ASSDA member for the Joint Houses of Parliament Committee.
The statistics: the 81m high structure is constructed mainly from 16mm thick hot rolled 304L plate: the base plates are 321 and the clusters supporting the flagpole proper are unpolished, cast 304 equivalent (CF-8). The four triangular legs rise diagonally for 28m from the top of walls to the east and west, before curving to vertical 4m below the lower cluster. The legs continue for a further 15.5m to the upper cluster and terminate 5.1m above the upper cluster. The circular tapered flagpole extends 25.7m above the upper cluster.
The corner and face welds of the leg plate joins were ground using grits down to #120 to match the bold plate surfaces.
As the flagpole was assembled 18 months before Parliament House was completed, it was exposed to the dust and pollution of a construction site; since Parliament opened it has experienced air quality of a rural environment.
Although quite safe, the inspection required a good head for heights while using a "lie back and enjoy it" lift up one leg or the less steady 7m scissor lift to reach the lower plates of the legs. A 40 power theodolite lent by the ACT Survey Office completed the inspection of inaccessible areas.
The overall appearance of the flagpole is outstanding. The rib marks, plate to plate welds and polishing patterns along the legs all add to the visual impact. The multiple heated weld joins are as bright as the rest of the surfaces. Slight deposits at drip points aren't obvious to the casual observer and were easily removed with a damp cloth. The location of these deposits was determined by the prevailing weather.
Encouragingly, neither design crevices nor minor fabrication anomalies have caused obvious corrosion in 15 years' exposure.
Occasional small round rust spots, probably caused by pollution during construction, were visible at a distance of about 30cm. There were fewer spots near the masthead probably due to better rain washing and less pollution. The spots were readily removed with water and a plastic scourer and when examined at X30 did not show pitting. Consistent with surface profile expectations, the unpolished top of the legs showed no signs of spots. Surface profile measurements around the base of the legs showed surface roughness between 1 and 1.5 micrometres with a vertical polish direction.
And the future? 304 is ideal for this environment and with the decision to clean off drip line deposits and monitor selected areas for changes in appearance, it is expected that the flagpole will still be brightly glistening in the sun in 2200.
This article featured in Australian Stainless magazine - Issue 20, February 2002.