measurements taken, the current and voltage of the rectifier shall be
adjusted as required to produce a minimum of minus 850 millivolts "Instant
Off" potential between the structure being tested and the reference cell.
This potential shall be obtained over 95 percent of the metallic area
without the "Instant Off" potential exceeding 1200 millivolts.
1.3.2
Isolators
Isolators are required to isolate the indicated pipes from any other
structure. Isolators shall be provided with lightning protection and a
test station as shown.
1.3.3
Anodes and Bond Wires
Anodes shall be installed in sufficient number and of the required type,
size and spacing to obtain a uniform current distribution of 2.5
milliamperes per 0.09 square meters square foot minimum to underground
metal surfaces. For each cathodic protection system, the metallic
components and structures to be protected shall be made electrically
continuous. This shall be accomplished by installing bond wires between
the various structures. Bonding of existing buried structures may also be
required to preclude detrimental stray current effects and safety hazards.
Provisions shall be included to return stray current to its source without
damaging structures intercepting the stray current. The electrical
isolation of underground facilities in accordance with acceptable industry
practice shall be included under this section.
1.3.4
Surge Protection
Approved zinc grounding cells or sealed weatherproof lightning arrestor
devices shall be installed across insulated flanges or fittings installed
in underground piping as indicated on the drawings. The arrestor shall be
gapless, self-healing, solid state type. Zinc anode composition shall
conform to ASTM B 418, Type II. Lead wires shall be number 6 AWG copper
with high molecular weight polyethylene (HMWPE) insulation. The zinc
grounding cells shall not be prepackaged in backfill but shall be installed
as detailed on the drawings. Lightning arrestors or zinc grounding cells
are not required for insulated flanges on metallic components used on
nonmetallic piping systems.
1.3.5
Sacrificial Anodes
Sacrificial high potential magnesium anodes shall be located as required to
provide localized cathodic protection or supplemental cathodic protection
for the impressed current system. Each sacrificial magnesium anode shall
be routed through a test station. The magnesium anode shall not be
connected to the pipe.
1.3.6
Nonmetallic Pipe Systems
When nonmetallic pipe is approved, direct buried or submerged metallic
components of the pipe system shall have cathodic protection. Metallic
components are connectors, tees, fire hydrants, valves, short pipes,
elbows, tie rods, or other metallic equipment. As a minimum, each metallic
component shall be protected with a 4.1 kg 9 lb magnesium anode connected
through a test station. The use of nonmetallic pipe does not change other
requirements of the specifications such as submittals, testing, or design
calculations for each metallic component. Deviations due to the use of
nonmetallic pipe shall be approved by the Contracting Officer.
SECTION 13112A
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