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test point to ensure that there is adequate cathodic protection current available to the system to meet protection
criteria.
SHORT IDENTIFICATION TEST
To determine if there is a short on the system, some knowledge of the CP area is required. Is the structure bare or
coated? How large is it? Has the protection level changed dramatically in a short time? When the CS-10 is
connected to the structure, as in the current requirement test, and current is applied in the continuous mode, does
it take more current than would be anticipated to increase the protective level? If so, there is a high probability that
there is a short (additional load connected) to the protected system.
SHORT LOCATION TEST
To locate the short(s) on a protected system, the CS-10 can be connected to the structure to increase polarization,
as in the current requirement test above, but operated in the interrupted mode. At various points on the protected
structure take both “off” and “on” Pipe to Soil readings. Subtract the “off” reading from the “on” reading and record
that difference (delta V) with the location. As you approach the short location, the delta V will decrease toward 0
and as you pass and leave the short location, the delta V will increase again. The lowest resistance short will
usually be identified first so another test for shorts should be performed to ensure that all shorts have been located
and cleared.
INSULATOR LOCATION TEST
To determine the location of buried insulator, hook the CS-10 to the structure and a temporary ground to increase
the structure polarization and switch to the interrupted mode as in the short location test above. Then take half cell
readings until there is dramatically reduced on/off switching. This will indicate that the location is beyond an
insulator. Pinpoint location can be completed with an Audio Frequency Locator such as Tinker & Rasor’s Models
PD or Mark V Ranger .
CASING TEST
Connect the CS-10 so that it will depolarize the casing to a temporary ground. Take initial half cell readings of the
pipe and the casing, apply a small amount of current (approx. 30 mA) and take another set of half cell readings. If
the pipe and casing are both less negative, there is probably a somewhat low resistance path between them.
However, if the pipe is slightly more negative and the casing less negative, there maybe no short. Apply a larger
amount of current (approx. 100 mA) and take another set of half cell readings. If the pipe and casing are still less
negative, a low resistant path is still indicated. If the pipe and casing keep the same reading as each other, the
path has low resistance. If the pipe is still a little more negative and the casing less negative, any short is of very
high resistance. Additional current steps will help determine if there is a high resistance (electrolyte) connection
between the pipe and the casing rather than a short.
TESTING INSULATION JOINTS WITH A COMPASS
A magnetic compass used as a “lay-on” ammeter is a valuable means of checking insulating joints such as insulating
unions and flanges. It will work on parallel flanges as in a manifold. The CS-10 makes this test simple.
The compass must not be liquid filled and its needle must not drag on the dial when the compass is laid on a steel
pipe. A machete or wrench is a handy steel surface to check it on. Because the compass reacts to a magnetic
field created when DC current flows, it will indicate whether or not a current is flowing through the insulator to be
tested.
CORROSION MITIGATION INSTRUMENTATION
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