ETL 1110-9-10(FR)

5 Jan 91

RC

=

0.0 ohm (Resistance of the tank-to-

water

and

negative

wire

is

negligible)

b)

Calculate the total resistance of the main anode

rods circuit (RT):

RT = 1.33 +0.13 + 0.0

RT = 1.46 ohms for main anodes.

c)

Calculate the total resistance of the stub anode

rods circuit (RT):

Where:

RN = 21.03 ohms (from step 12)

RW = 0.13 ohm (same as main anode header)

RC = 0.0 ohm (negligible)

RT = 21.03 + 0.13 + 0.0

RT = 21.16 ohms for stub anodes.

14) Design riser anode.

a)

Current requirement = 14.5 amp (from step 4)

b)

Number of anode rods required from step 6 = 15

rod segments (4-ft long each)

c)

Select riser anode system.

For proper current distribution in the riser

pipe, the anode units should not be placed too

far apart. It is generally considered that each

anode unit protects a length along the riser pipe

equal to 1 times the spacing of the anode from

the riser pipe wall plus the length of the anode.

The length of riser protected by one 4-ft long

anode located 2.5 ft from the riser wall is

therefore:

(2.5 x 1.5) + 4 = 7.75 ft

Number of anode required for a 115-ft riser:

N=

115

= 14.8 or 15 anodes

7.75

96

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