0074im.jpg)
ETL 1110-9-10(FR)
5 Jan 91
But this diameter provides an anode length that is
still slightly less than that required for a 15-year
mode life.
Therefore, we will use a hoop diameter
that is 55 percent of the bowl diameter:
DE = 51.5 x 55% = 28.3 ft
4)
0.0625-in. diameter anode wire using equation 1-14:
8 DR
2 DR
0.0016 p
RA '
% 1n
(1n
)
DR
DA
H
Where:
p =
2000 ohm-cm (Water resistivity from
item 3 of paragraph 2-6a)
DR =
28.3 ft (Anode ring diameter from
step 2 of paragraph 2-6b)
DA =
0.00521 ft (0.0625 in)(Diameter of
anode determined in step 3 of
paragraph 2-6b)
H=
21 ft (Anode depth below water
surface.) (Anode depth determined
from the following calculations).
The anode depth below the high water line is
approximately 60 percent of the distance between the
high water line and the bottom of the tank. Water
depth = 35 ft, cf. design data section 2-6a.
Calculate RA:
[ln
8 x 28.3
+ ln
2 x 28.3
]
RA =
0.0016 (2000)
28.3
0.00521
21
RA = 0.113 [ln 43,455 + ln 2.70]
RA = 0.113 (10.68 + 0.99)
RA = 1.32 ohms
This is within the design limitation of 2.0 ohms.
72
Previous Page
