Leaders in Pipelin
e Survey Systems
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SYSTEM MANUAL Version 6.03i
80
16.2.1. Connecting to the Pipeline
When making a connection to the pipeline it is important to establish a low resistance
connection and to ensure that the connection point is electrically connected to the pipeline.
Many common mistakes are easily rectified:
Connection to rusted
component
−
Use a file or sand paper (abrasive) to prepare a
clean area for a good electrical connection
Connection to isolated part, e.g.
isolated valve, isolated valve
wheel, test post not connected
to pipeline being surveyed
−
Try alternative connection
Damaged Generator Cables
−
Connect the
Ground
and
Pipe
cables together
to short circuit the Generator. Select
AUTO
and the current should reach 600mA with a low
circuit impedance, unless cables are faulty.
Connecting to a pipeline above
the ground – often there is an
insulating joint underground
−
Make alternative connection on the correct side
of the IJ, or use IJ to increase survey distance
(see 8.6)
16.2.2. Establishing a good earth
Similarly, a low resistance connection is required when establishing a good earth, whether
connecting to a physical part of the pipeline or using the Earth Spikes provided.
Use all three
Earth
Spikes
at 90° to the pipeline, positioned as far away as possible.
Drive
Earth Spikes
deep into the ground.
Ensure the spikes are not moved from side to side (both during and after installation)
so that ground contact is maintained along the length of the spike.
If the ground is dry, remove the
Earth Spikes
and fill the holes with water before
replacing them. Ensure ground contact along the length of the spike.
Brush away an area of topsoil and lay the
Earth Spikes
horizontally before replacing
the topsoil.
As above but with soil wetted with water.
As for above but with a layer of tin foil (cooking foil) underneath the spikes.
16.2.3. Use alternative earth connection
1) Fences with metal posts can be used as an earth connection. It must be
remembered however, that where a fence crosses the pipeline, readings cannot be
taken in this area.
2) Use the ground bed of a TR (Transistor-Rectifier) station.
Make sure the TR
station has been turned off and disconnected to avoid damage to the Signal
Generator.
3) Isolation Joints (IJ) can be used. Connect the Signal Generator
Pipe
connector to
one side of the IJ and
Ground
connection to the other – it doesn’t matter which.
You can now complete two surveys starting at the IJ, one in each direction going
away from the IJ.
When using a metal structure as an earth connection point, care must be taken during
lighting (electrical) storms. Any lighting strike receive by the metal structure will be passed
to the Signal Generator which could result in damage being caused. The surveyor must
be aware that although the potential for a lighting strike could be some distance away, the
type of metal structure being used could carry this high voltage signal for many miles, for
example a long metallic fence.
