UFC 3-570-06
JANUARY 31 2003
structure to be protected.
WARNING: Do not use any metallic structure for a temporary anode that is shorted to
the structure being tested. This will result in very large current surges that can cause
injury to personnel and damage to equipment. For Navy projects, when conducting
work on or near circuits energized lines or parts of equipment operating at or above
50V, utilize work practices identified in OPNAV P-45-117-6-98.
7-10.2
Existing Metallic Structures. Existing metallic structures, such as metal
fences, culverts, abandoned pipelines, or abandoned wells can be used as temporary
anodes or to supplement installed temporary anodes. If any existing structure is to be
used, it should first be tested to see if that structure is shorted to the structure to be
tested (see appropriate paragraph in 7-9) The area of the temporary installation should
be well scouted to determine if any possible temporary anodes exist or if any foreign
structure is in the area. Do not use pipelines or tanks for temporary anodes that would
be adversely affected if leaks occurred.
7-10.3
Temporary Anodes. The number of temporary anodes required depends
on the available voltage source, the amount of current desired, and the resistivity of the
soil. If the number of anodes is doubled, the amount of current is approximately
doubled. If the soil resistivity is doubled, the current is cut in half. In very low resistivity
soil, two or three anodes may be sufficient, and in very high resistivity soil, a high
number of temporary anodes may be required. The amount of current desired depends
basically on the quality of the coating on the structure being tested. Very well-coated
structures will exhibit a noticeable potential change with a small amount of current (1 or
2 amps), while poorly-coated structures will not exhibit a noticeable potential change
except with a large amount of current (10 to 20 amps). If the voltage is doubled, the
current is doubled. Consequently, if the voltage source is low, more temporary anodes
will be required, if the voltage source is very high, only a few temporary anodes will be
required.
7-10.4
Installation of Temporary Anode System. The installation of a temporary
anode system is often required to perform current requirement testing. Normally copper
ground rods are used. Any metallic ground rod can be used as well as any metallic pipe
or conduit. Streams, ponds, rivers, lakes, bays, oceans, or other standing water in the
area of the temporary anode location make an ideal location for obtaining a low-
resistance-to-earth anode bed. In these wet locations, the ground rods can be simply
laid in the water. Normally ground rods are cut in half to make 4- to 5-foot sections.
These ground rods (or metallic pipe or conduit), are sharpened and driven into the
ground until approximately 0.3 meters (one foot) are above the ground level. These
rods should be installed approximately 4.5 to 6 meters (15 to 20 feet) apart to lower the
resistance to earth. In high resistivity areas, when higher test current is required, water
sprinklers can be used over a period of time to lower the resistance. In extreme cases,
an excavation can be made, then small diameter steel pipe can be pushed into the
7-39
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