15th AUGUST 2009
Manufacturing specifications for Aircraft Warning Spheres
The aluminium sphere will last as long as the aluminium line
The aluminium is supplied by Hulett Aluminium (Pty) Ltd an ISO 9001company. The South African Burro of Standards numbers SABS 0157 and SABS 0157 are complied with. Hulett are an Eskom vendor.
In all areas other than those very close to the coast, Eskom typically utilise aluminium alloy
AA1350 incorporated with a steel core, for their overhead power lines,. For the coastal areas
they remove the steel cores (galvanic corrosion reasons) and make the total cable out of a slightly
higher strength alloy from the AA6063 family.
The Aircraft Warning Spheres are made from aluminium alloy AA1200, it has a similar corrosion resistance to the AA1350 and superior to AA6063. Therefore it is an ideal material for the application.
The powder coating will last at least 50 years
The powder coating conforms to the South African Burro of Standards Number SABS 1578. The spheres that we supplied to Eskom in 1969 have been on the lines for 40 years and the powder coating is still serviceable. The modern powder coatings are much better and last at least 50 years.
Hot dip galvanizing of steel bracket will last as long as the tower
The brackets are made from hot dip galvanized mild steel. The hot dip galvanizing is performed by Armco to the South African Burro of Standards SABS number 1461. Armco is an Eskom vendor. The hot dip galvanized bracket will last as long as the hot dip galvanized tower.
Helical formed wire
The helical formed wire component of the bracket meets the Eskom specification.
Design and Assembly
We are an approved Eskom vender and have been supplying aircraft warning spheres to Eskom since 1969. The spheres comply with Eskom document: SPECIFICATION FOR AIRCRAFT WARNING DEVICES USED ON OVERHEAD SUB-TRANSMISSION AND DISTRIBUTION LINES: SCSSCAAV7, dated November 2003. The design is covered by various patents. The welding, drilling and assembly is performed on jigs, every sphere is completed to the same high quality as the approved sample.
W E Jones