3.1.2
Aluminum
Aluminum [pipes] [tanks] shall not be protected to a potential more
negative than minus 1200 millivolts, measured between the [pipe] [tank] and
a saturated copper-copper sulphate reference electrode contacting the
earth, directly over the [pipe] [tank] [metallic component]. Resistance,
if required, shall be inserted in the anode circuit within the test station
to reduce the potential of the aluminum [pipe] [tank] to a value which will
not exceed a potential more negative than minus 1200 millivolts. Voltage
shift criterion shall be a minimum negative polarization shift of 100
millivolts measured between the [pipe] [tank] [metallic component] and a
saturated copper-copper sulphate reference electrode contacting the earth,
directly over the [pipe] [tank]. The polarization voltage shift shall be
determined as outlined for iron and steel.
3.1.3
Copper Piping
For copper piping the following criteria shall apply. A minimum of 100
millivolts of cathodic polarization between the structure surface and a
stable reference electrode contacting the electrolyte. The polarization
voltage shift shall be determined as outlined for iron and steel.
3.2
GROUND BED INSTALLATION
3.2.1
Shallow Ground Beds
Shallow ground beds shall contain size and quantity of anodes designed to
meet performance criteria of the cathodic protection system at an initial
operating current output density not exceeding [40] [50] [70] percent of
maximum recommended current output density.
3.2.1.1
Horizontally Buried Bare Anodes
Horizontally buried bare anodes shall be bedded on and covered with
metallurgical coke breeze in a trench excavated for the purpose at depths,
spacing and locations as shown. Anodes shall be completely surrounded by
the backfill at bottom, sides, and top for a distance of not less than 100
mm 4 inches. Backfill shall be compacted.
3.2.1.2
Vertically Buried Bare Anodes
Vertically buried bare anodes shall be installed in vertical holes in the
ground having a depth, spacing, and location shown. The holes in the
ground shall be sufficiently large to provide an annular space around the
anode not less than 100 mm 4 inches. The anodes shall be centered in the
hole and backfilled with calcined petroleum coke breeze or metallurgical
coke breeze. Backfill shall be compacted.
3.2.1.3
Horizontally Buried Canister-Contained Anodes
Horizontally buried canister-contained anodes shall be buried in a trench
excavated for the purpose at depths, spacing, and locations shown.
3.2.1.4
Vertically Buried Canister-Contained Anodes
Vertically buried canister-contained anodes shall be installed in vertical
holes in the ground having depth, spacing, and locations shown. The holes
in the ground shall be sufficiently larger in diameter than the canisters
to facilitate easy lowering into the hole and backfilling. The space
SECTION 13112A
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