bottom of the pipe, with the approval of the Contracting Officer.
3.3.2
Underground Metal Pipe Line
Anodes shall be installed 610 mm 2 feet below the line to be protected
unless otherwise noted on the drawings. To facilitate periodic electrical
measurements during the life of the sacrificial anode system and to reduce
the output current of the anodes if required, anode lead wires in a single
group of anodes shall be buried a minimum of 610 mm 2 feet and each anode
lead wire shall be connected to an individual terminal in a test station.
The anode lead cable shall make contact with the structure only through a
test station. Resistance wire shall be installed between the anode lead
cable and the pipe cable in the test station to reduce the current output,
if required.
3.3.3
Lead and Resistance Wire Splices
Lead wire splicing, when necessary, shall be made with copper split bolt
connectors of proper size. The joint shall be carefully wrapped with at
least 3 layers of electrical tape. Resistance wire connections shall be
done with silver solder and the solder joints wrapped with a minimum of 3
layers of pressure-sensitive tape.
3.3.4
Magnesium Anodes for Metallic Components
As a minimum, each metallic component shall be protected with [2] [_____]
[4.1] [7.7] [_____] kg [9] [17] [_____] lb magnesium anodes located on each
side of the metallic component and routed through a test station. Fire
hydrant pipe component shall have a minimum of [2] [3] [_____] [4.1] [7.7]
[_____] kg [9] [17] [_____] lb magnesium anodes routed through a test
station for each hydrant. Pipe under concrete slab shall have a minimum of
[5] [_____] [7.7] [_____] kg [17] [_____] lb anodes for each location where
metal pipe enters the building under the slab. A permanent reference cell
shall be provided adjacent to the pipe entrance to the slab. Conductors
shall be routed to a test station. Each valve shall have a minimum of [2]
[_____] [4.1] [_____] kg [9] [_____] lb magnesium anodes routed through a
test station. Sections of metallic pipe 6.1 m 20 foot long, when used
where force mains are within 3 m 10 feet of the water pipe, shall have a
minimum of [4] [_____] 7.7 kg 17 lb anodes.
3.4
MISCELLANEOUS INSTALLATION
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NOTE: The cathodic protection system will fail
unless full engineering considerations are applied
to selection, location and installation of
electrically conductive joints and electrically
isolating joints including the use of underground
type dielectric coatings (not paint).
Adequate electrical conductivity of a pipe joint
made by means other than welding should be
determined by the "corrosion expert." Allowable
electrical resistance depends on the cross sectional
area of the pipe metal, the resistivity of the pipe
metal, and the effectiveness of the coating on the
pipe. Effectively coated pipe underground requires
only a fraction of the electrical conductivity at
joints needed for bare pipe. Shop painted pipe is
SECTION 13112A
Page 31
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