3M CablePipe Locating Techniques Manual

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4.2 The Dyna-Coupler can identify one of several
CATV cables which fan out from a common
point, as in a header pedestal. Even though signal
is coupled onto each cable, the cable with the
Dyna-Coupler is clearly identifiable because it
has the strongest signal. If the header is not
grounded in the pedestal, do so using the ground
rod and the ground extension cable. This helps
shorten the ground return path and increases
signal. 4. Applying Signal to CATV Cables: Dyna-Coupler Method
4.1 The Dyna-Coupler...

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5. Locating Cable Slack Loops
5.1 To identify the presence of a slack loop in the cable path, first locate and mark the cable path.
Retrace the path in the following manner:
Find the strongest response over the marked cable path and press the gain adjust key.
Hold the Receiver so the handle is perpendicular to (across) the cable path, and retrace
the cable path. When the Receiver passes over a slack loop, the tone increases and the bar
graph closes. Mark each response.
6. Locating Cables from...

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Section 5  Pipe Locating Techniques
1. Introduction
1.1 Read Section One of this manual to learn more general information about each of the following
signal application methods. The following paragraphs provide specific instruction on applying
signals for pipe locating.
2. Applying Signal to Pipe: Induction Method
2.1 The Induction method broadcasts signal into an area.  No access to the cable is necessary.  Use
this only when there are no other buried conductors present, or when locating all...

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3.2 A far-end access point may not be available to apply a far-end ground. If this is the case, you can
still use the direct-connect method. The red lead connected to the pipe sends signal current in both
directions from the application point. The signal continuously Ôleaks offÕ the pipe and returns to
the Transmitter ground rod connected to the black lead. The rate at which the current leaks away
from the pipe determines how far down the pipe the signal can be detected. Two factors that
control this...

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A. Direct-Connect Method on Tracer Wires
3.3 To locate tracer wires buried with nonmetallic pipe, connect the TransmitterÕs red lead to the
tracer wire at an access point. The black lead is connected to the ground rod.  For best results,
ground the tracer wire at the far-end. If you cannot access or locate the far-end, use a high
Transmitter frequency. Otherwise, use a low Transmitter frequency.  If you use a high frequency,
be aware that in some installations a tracer wire for a service line may not...

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4.2 You can control the direction of the signal on
the pipe by using the ground rod and ground
extension cable to apply ground to that part of
the pipe where signal is not needed, as shown.
The external ground keeps the signal off the
pipe on that side of the Dyna-Coupler. Since
the signal is being sent to only one part of the
pipe, the signal magnitude is greater on that
part.
4.3 When you use the Dyna-Coupler to
apply signal to a metallic service line
at a gas meter, always ground the
valve. This...

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6. Locating Pipe with Impressed Cathodic Protection
6.1An impressed current cathodic protection system uses an AC powered rectifier as a source of DC
current. The current flows from buried anodes to the pipeline to protect it from corrosion.
6.2To trace the path of the pipe, use the second harmonic of the 50 or 60 Hz passive power frequency
(100 or 120 Hz) in Peak mode. This frequency is especially sensitive to rectified AC signals.
6.3You can also locate the anodes and find a broken anode lead using...

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Section 6  Locating Faults
1. Introduction
1.1 Sheathed cables with a metallic shield (CATV and some telephone cables) can experience damage
to the sheath which exposes the shield to contact with the earth. These damaged spots on cables
are called sheath faults because the damaged sheath allows water to enter the cable creating a fault
which may degrade service. Buried power distribution cables have no shield but damage to the
insulation can expose the conductor to earth creating a fault condition....

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2. Locating Sheath Faults
2.1 To locate a sheath earth return fault, the Transmitter sends a current down the shield to the
damaged sheath (the fault) and back to the ground rod through the earth.  The operator uses the
earth contact frame to find the point where the current stops traveling through the shield and starts
traveling through the earth.  At the same time, tracing tone may be applied to the faulted section to
help find the buried cable. This is especially useful if the cable passes under...