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ETL 1110-9-10(FR)
5 Jan 91
2-7.
Elevated Water Tank (No Icing Will Occur).
This impressed current design is for a tank (figure 2-15) that has
not been built; thus, it is not possible to measure current
requirements and other factors. Calculated estimates are used.
a.
Design data.
1)
Tank will be ellipsoidal on both top and bottom.
2)
Tank dimensions will be:
Capacity = 500,000 gal
Diameter = 56 ft
Tank height (from ground to bottom of bowl) = 115 ft
Overall tank depth = 39 ft
Vertical shell height = 11 ft
High water level = 35 ft
Riser pipe diameter = 5 ft
3)
Water resistivity is 4000 ohm-cm.
4)
Design for a 20-year life.
5)
The tank water will not be subjected to freezing.
6)
Segmented rod anodes will be used; 4-ft long by 0.138-
in. diameter. Note: Segmented rods have an advantage
in that they can be field assembled using factory-made
connections.
On the other hand, continuous wire
(.0625-in. diameter) is also available in long lengths
(typically 500 ft).
These can be fabricated with
factory-made wire connections but their overall length
must be specified. Continuous wire will almost always
be less expensive.
7)
All wetted inner surfaces will be uncoated.
Area
above water will be coated.
8)
Electric power available will be 120/240 V AC, single
phase.
9)
Design for a current requirement of 2.5 A per sq ft
for the bowl and 8.0 A per sq ft for the riser. Due
to the velocity of the water in the riser, the riser's
current requirement is typically much higher than the
bowl.
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