MIL-HDBK-1004/10
potential on one side of the flange and measuring the change in potential on
the other side of the flange. If little or no potential change is noted, the
isolating flange is effective. Test stations with provisions for future
bonding should be installed at each buried insulating flange.
Bonds. Bonds between structure sections and to foreign structures
10.5.4
should be made with No. 4 AWG, 7-strand insulated cable unless larger cable is
required. Each bond should be brought into a test station to determine bond
effectiveness and to install resistive bonds if required.
Electrical Connections. Electrical connections to the structure
10.6
are commonly made using thermo-weld techniques. The connections should be
inspected visually before and after insulation is applied. If safety or other
conditions preclude the use of the thermo-weld process on site, the leads
should be attached to metal tabs by thermo-welding and the tabs either
soldered or mechanically attached to the structure. All electrical
connections should be insulated. Other electrical connections should be
thermo-welded where practical as this method of connection is extremely
reliable. Mechanical connections should be of the proper type for the
intended use and should be properly assembled. All connections should be
inspected before and after insulation.
Test Stations. As described in paras. 6.7.3 and 7.10.4, test
10.7
stations are required for initial test and adjustment of the cathodic
protection systems, and for future inspection and maintenance. Attachment of
"spare" test leads to buried structures is recommended as excavation to
reconnect test leads is expensive. All test station leads should be either
color coded or labeled with a metal or plastic tag. The connections to the
structure should be inspected prior to burial of the structure. Whenever the
structure will be located under a paved area, or whenever paving is installed
over a protected structure, soil contact test stations as shown in Figure 56
should be installed.
Sacrificial Anode Installation. Sacrificial anodes should always
10.8
be installed at least 3 feet below grade whenever possible. The top of the
anode should be at least as deep as the structure to be protected. Horizontal
sacrificial anode installations should be used only if obstructions such as
rock outcrops preclude vertical installations. Anodes suspended in water
should be installed according to the system design and a cable connection
between the structure and the suspension link is normally required. Anode
lead wires should never be used to suspend, carry, or install the anode.
Vertical. As shown in Figure 117, sacrificial anodes are commonly
10.8.1
installed vertically in augered holes. If caving or unstable soil conditions
are encountered, a thin metal (stovepipe) casing may be used. Anodes should
be located on alternating sides of the pipe when possible to reduce
interference and allow for more even current distribution. Any impermeable
wrapping should be removed from packaged anodes prior to placing them in the
holes. The cloth bag used with packaged anodes should be carefully handled as
loss of backfill will result in reduced anode output. The anodes should be
lowered into the holes either by hand, or by the use of a line attached to
either the anode, if bare, or the top of the bag of backfill. The anode lead
cable should not be used to lower the anode into the hole as the anode-to-
cable connection is easily damaged. Sufficient slack should be left in the
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