The overall general protection was very good for systems 55, 57, and 60 

 through 65 of the 12 systems. 



PRACTICES RECOMMENDED BY CEL FOR PROTECTING ANTENNA TOWERS* 



Antenna towers and supporting communication equipment are widely 

 scattered throughout the world. Many are at remote locations that have 

 very corrosive environments (Figures 2 and 3) and very limited mainte- 

 nance services available. Thus, the greatest care must be taken in 

 siting, designing for corrosion control, and planning maintenance if 

 vital communication systems are to be kept operable. 



Types of Antennas 



Most antenna towers and supporting equipment are constructed of 

 (1) steel, which corrodes readily (Figure 4); (2) galvanized steel 

 (Figure 5), which can provide several years of protection before requir- 

 ing a coating; (3) or aluminum, which can provide many years of service 

 uncoated but is usually coated in a severe environment. Circularly 

 disposed (Wullenweber) antenna arrays are unique in that wood is used in 

 much of their structural supports (Figure 6). Treated wood is generally 

 used to prevent termite attack. All towers should be coated to provide 

 visibility to aircraft unless acceptable warning lights are used. 



Design for Corrosion Control 



Faulty design is often a major factor leading to the corrosion of 

 structures and equipment exposed to exterior weathering (Ref 4) . Loca- 

 tion, structural features, and joining require special consideration in 

 towers and communication equipment construction. 



Facilities should be located as far as possible from the sea and 

 from winds carrying salt spray. It has been noted that towers located 

 several miles from an ocean have their greatest degree of corrosion at 

 150- to 200-foot elevations where concentrations of sea salt carried by 

 winds are greatest. Sand borne by winds may cause erosion of coatings 

 or metal on towers. Similarly, towers should not be located downwind 

 from sources of corrosive industrial pollution. 



Box, rectangular, and tubular beams are much less susceptible to 

 corrosion than tees, channels, and I-beams because the latter permit 

 greater accumulations of salt, moisture, and other contaminants that 

 accelerate corrosion or are more difficult to clean and coat. It is 

 good practice to smooth all welds, edges, and other rough surfaces 

 before coating to permit easier, more uniform coating application. 

 Stairs, railings, ladders, and support trailers present irregular or 

 inaccessible surfaces difficult to coat (Figures 7 and 8). 



"Based on a paper presented at USAF High Work Safety Conference at 

 Norton Air Force Base, December 5-7, 1978. 



