UFC 3-570-06
JANUARY 31 2003
structures (valves, tanks), and the anodes are evenly distributed along the structure to
be protected, each anode protecting a small portion of the whole structure. Distributed
impressed current systems are commonly used to protect the interiors of water storage
tanks, both ground level and elevated structures. The remote type of groundbed can be
installed near the surface, either horizontally or vertically, or they can be installed deep.
Distributed systems are installed like the previously discussed sacrificial anodes, with
the addition of a continuous header cable which connects the anodes to the rectifier (or
other power source) and a structure lead from the power source to the protected
structure.
2-7.3.1
Vertical Remote Impressed Current CP Systems. These systems are
commonly used for pipelines in remote areas. This is usually the most economical
choice when there are not other utilities in the area and there is sufficient room to locate
the anodes remote from the structure. Vertical placement of the anodes in the earth
tends to lower the total resistance to earth of the system (versus horizontal). The
distance to remote earth varies according to the resistivity of the earth, usually 91 to 213
meters (300 to 700 feet).
Soil resistivity testing should be done in the area of a proposed anode bed to
locate an area of low resistance to place the anodes. Care must be taken to ensure
that that low resistance area is not continuous to the protected structure. Poor current
distribution may occur if this condition occurs. In some cases, the best location for an
anode bed may be in higher resistivity earth. The resistance of the anode bed can be
lowered by adding additional anodes, using longer anodes, or by increasing the spacing
of the anodes.
Figure 2-26. Vertical Remote Impressed Current Cathodic Protection System
Vertical or
Special Backfill
Horizontal
Anode
Anodes
Lead
Structure
Typically Over 400 Feet
Lead
PIPELINE (CATHODE)
2-7.3.2
Horizontal Remote Impressed Current CP Systems. These systems are
commonly used for pipelines in remote areas where a rock stratum is located near the
surface or where other soil conditions would require horizontal installation to ensure the
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