Nace CP 1, Course Manual

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Field Measurements 5:32
CP 1 – Cathodic Protection Tester Course Manual
©
NACE International, 2000
02/01/05
antimony metal in the bottom of a nonmetallic tube. The slug is connected
to a terminal on the top of the tube.
It is important to keep the antimony shiny and bright. Use fine non-metal
bearing sand paper or emery cloth for cleaning. Do not use steel wool or
other metallic abrasive since particles of metal may become embedded in
the antimony and affect the reading.
The two cells are placed close together on the soil and connected to a
voltmeter. It doesn’t matter which cell is connected to which terminal of the
meter since it is the potential between the two electrodes that is of interest.
Take care not to get any copper sulfate on the antimony slug. There is a
scale on the side of the antimony electrode that is calibrated in millivolts
and pH. Once the potential is obtained, the pH can be determined from the
scale.
Use of Pipe Locating Devices
During corrosion testing, it is often necessary to accurately determine the
location of such buried items as a pipeline, conduit, or storage tank. Also, it
is important to determine points of electrical continuity and discontinuity.
A pipe and cable locator can be a great time saver for making such
determinations.
Most locators include a transmitter and receiver. The transmitter is a source
of radio frequency AC that is used to impress a signal on the structure. The
receiver picks up the signal on the structure and provides it to the user as an
amplifier sound. The sound of the signal, such as the frequency and rate of
the pulse, can be controlled by the transmitter. The receiver controls the
volume of the signal. The sound of the signal can be received through
earphones or a speaker. In a noisy area earphones may be necessary. If your
job requires constant use of a pipe locator, you may prefer the speaker type.
There are two types of pipe locators. Some locators contain both types in
one unit:
•
Conductive
•
Inductive.