a hole in an end cap designed to be tight fitting with the cable and
protected from sharp edges with a plastic or rubber grommet. The anodes
shall be centered in the canisters and the annular space filled with coke
breeze compacted in place.
2.1.4
Anode Connecting Cables
Anodes shall have connecting cables installed at the factory. For deep
ground beds, each anode located in the borehole shall be accompanied by a
reel of continuous cable having the length indicated. No spliced
connections will be permitted in deep well cables.
2.1.5
Mixed Metal Oxide Anodes
Mixed metal oxide anodes shall be of the size indicated and shall conform
to the following requirements.
2.1.5.1
Conductive Material
The electrically conductive coating shall contain a mixture consisting
primarily of iridium, tantalum, and titanium oxides. The average
composition is generally a 50/50 atomic percent mixture of iridium and
titanium oxides, with a small amount of tantalum. The resistivity, as
tested by the manufacturer, shall be no more than 0.002 ohm-centimeter, and
the bond strength shall be greater than 50 MPa 7.25 ksi to guarantee the
current capacity life and the quality of the conductive ceramic coating.
The adhesion or bond strength shall be determined by epoxy bonding a 2.54
mm 0.1 inch diameter stud to the ceramic coating and measuring the load to
failure (about 70 MPa 10.15 ksi) of either the epoxy or the interface
between the coating and the substrate. The anode must be inert and the
electrically conductive ceramic coating dimensionally stable. The ceramic
coated anode shall be capable of sustaining a current density of 100 ampere
per square meter 10.764 square feet in an oxygen generating electrolyte at
66 degrees C 150 degrees F for 20 years, to ensure the current capacity
life. An accelerated current capacity life test shall be performed by the
manufacturer on every lot of anode wire used to construct the anode as
described. The mixed metal oxide coating shall be applied to the wire
anode by a firm that is regularly engaged in and has a minimum 5 years
experience in manufacturing and applying mixed metal oxide coatings to
titanium anode substrates. The mixed metal oxide must be sintered to the
titanium surface as to remain tightly bound to the surface when bent 180
degrees onto itself.
2.1.5.2
Anode Life Test
The anode wire material shall sustain current densities of 100 ampere per
square meter 10.764 square feet in an oxygen generating electrolyte for 20
years. The manufacturer shall certify that a representative sample taken
from the same lot used to construct the anode, has been tested and meets
the following criteria. The test cell sustains a current density of 10,000
ampere per square meter 10.764 square feet in a 15 weight percent sulfuric
acid electrolyte at 66 degrees C 150 degrees F without an increase in anode
to cathode potential of more than 1 volt. The cell containing the anode
shall be powered with a constant current power supply for the 30 day test
period. The representative sample shall be 125 mm 5 inch in length taken
from the lot of wire that is to be used for the anode.
SECTION 13112A
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