MIL-HDBK-1004/10
As connecting wires in sacrificial anode cathodic protection
systems are themselves cathodically protected, insulation is not as critical
as in portions of impressed current cathodic protection systems. Type TW,
Type RHW-USE, or polyethylene insulation may be used. Anode lead wires should
never be used to suspend, carry, or install the anode. Anode cables are
commonly No. 12 AWG with Type TW insulation. Unless otherwise necessary, other
connecting wires should be No. 12 AWG solid copper for single anodes.
When currents larger than 1 A flow in any portion of a sacrificial
anode circuit, the most economic wire size should be determined using the
methods outlined in para. 6.7.1.4. Instead of the cost of power used in the
determination of economic wire size for impressed current cathodic protection
systems, the cost of additional anodes to overcome the resistive losses should
equal the annual fixed costs for the cable size being analyzed.
Connections and Splices. Wire splices and connections (refer to
7.9.2
para. 6.7.2) should be kept to an absolute minimum and the type of connection
used should have both low resistance, high reliability, and good resistance to
corrosion. Connections should be made using either exothermic or mechanical
connections (refer to para. 10.6). Insulation of underground connections
should be made by using encapsulation in epoxy or insulation with hot coal-tar
enamel followed by wrapping with pipeline felt. Above grade connections, such
as in test stations, are usually mechanical connections and should be
carefully taped in order to prevent corrosion due to the entry of moisture.
a)
The following connections are required for sacrificial anode
systems:
(1)
Connection between anode(s) and structure.
(2) Connection between cable and anode (usually factory made
or connection is attached to cast-in-core)
(3)
Necessary bonds and test wires
The need for additional connections and splices should be carefully evaluated.
As in the case for impressed current systems, the location of all necessary
splices and connections should be specifically shown on the design drawings.
The need for additional splices and connections should be determined by the
designer of the system and not left to the discretion of the installer.
Bonds and Insulating Joints. Bonds and insulating joints are
7.9.3
required for some sacrificial anode cathodic protection systems. Guidelines
presented in paras. 6.7.4. and 6.7.5 should be used for all bonds and
insulating joints.
Test Station Location and Function. The most common type of test
7.9.4
station used in sacrificial anode cathodic protection systems is the current-
potential test station shown in Figure 75. In this test station, the anode
lead wire is connected to the structure lead using a 0.01-ohm resistor (shunt)
which is used to measure the current output by measuring the voltage drop
across the shunt. The second structure lead is used to measure the structure
potential using a noncurrent carrying connection thus eliminating any
potential drop along the conductor. The second structure connection can also
134
Previous Page
