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ETL 1110-9-10(FR)
5 Jan 91
The number of anodes required for current
distribution equals the number needed for the
current requirement. To allow for a factor of
safety, use twenty anodes.
d)
Determine anode spacing.
Total riser length = 115 ft
Distance from bottom of riser to bottom of bottom
anode = 1.5 ft
Space consumed by anodes = 20 anodes x 4 ft each
= 80 ft
Total space consumed = 80 + 1.5 = 81.5 ft
Space remaining = 115 - 81.5 = 33.5 ft
For twenty anodes, there are nineteen spaces
Spacing =
33.5
= 1.76 ft or 1 ft 9 in.
19
Such an assembly is possible since anode rod
segments can be connected together with wire.
Since the anodes are spaced so close together, it
is better to use one long anode. Such an anode
has less flexibility than the disjointed cable
connected string, so there is less chance of its
vibrating or being damaged by water turbulence.
For one long anode made of 4-ft segments screwed
together, the number of anodes required is:
115 ft - 1.5 ft (distance from bottom) = 113.5 ft
113.5
= 28.4 anodes
4
Use 28 anode segments to keep the top segment
within the riser.
Total anode length = 28 anodes x 4 ft/anode = 112
ft.
Weight of the anode string will be:
2.4 oz/anode x 28 anodes = 67.2 oz = 4.2 lb
97
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