UFC 3-570-06
JANUARY 31 2003
second system's rectifier. If the potential of the structure with the rectifier
still on remains approximately the same or changes in a negative direction
when the potential of the structure with the rectifier off changes in a
positive direction (less negative), they are not shorted. If both potential
measurements change more positive approximately the same magnitude
(less negative) when one system's current is interrupted, the two
structures are shorted together.
If both systems have impressed current systems and a clear indication of
the shorted condition has still not been identified, turn off both rectifiers
and follow procedures in paragraph 7-9.3.
7-9.3
Testing for a Short Between Two Structures Without Cathodic
Protection on Either Structure. Take a potential measurement of both structures, by
changing only the structure connection, without moving the copper/copper sulfate
reference electrode.
Figure 7-23. Testing for a Short Between Two Structures without Cathodic
Protection on Either Structure
V oltm et er
T est St at io n or
T est St at io n or
M eta llic C on ta ct
M eta llic C on ta ct
+ -
2
1
R eference
E lect rod e
S tru c tu re W ith o u t C P
S tru c tu re W ith o u t C P
7-9.3.1
If the two potential measurements are significantly different (over 25 mV), the
two structures are not metallically shorted together. Under normal conditions, steel
structures should have a potential between approximately -0.35 volts DC and -0.65 volts
7-36
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