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position. Repeat the search in other directions where there may be a pipeline crossing.
By means of induction search, you can detect the missed pipeline of the passive search and other
pipelines that do not sense the 50Hz signal.
Technique:
Keep the distance between the receiver and the transmitter. In the inductive connection mode, the
transmitter emits signals to the target pipeline and also sends signals into the air, which may cause
interference in the detection work near the transmitter. The inspector needs to check that the
receiver is detecting the signal in the pipeline instead of the signal
directly from the transmitter. Move the transmitter a meter or two.
If the signal from the pipeline also moves along with it, this indicates that the receiver is too close
to the transmitter. Another way to check whether a receiver receives a transmitter signal is to
point the receiver tothe transmitter. If the signal strength does not change or increase, it means
that the receiver received the signal directly from the transmitter. In this case, reduce the
transmitter output power and the receiver sensitivity. The receiver may also have to leave the
transmitter 25 to 30 meters away. Do not place the transmitter on the manhole cover as this will
prevent the signal from being applied to the target pipeline
.
4. Pipeline Tracking, Positioning and Depth Measurement
Apply the transmitter signal to an accessible location on a buried pipe or cable such as containers,
valves, street lamps, etc., track the area outside of the pipeline and make a mark.
For those Pipelines that need to be detected, they can be traced till they reach covers, street lights
and fire hydrants, etc. on the ground. Then apply the transmitter signals on them and trace it from
this position back.
Position and Measure the depth of key points and feature points of various pipelines in the area,
mark at each detection point, record relevant pipeline data and detection results, and then sort
the data recorded and draw the pipeline map.
VIII Common Pipe Detection Techniques
1. T- Shape Detection
Once the tracking of the pipeline has been completed and markings have been made, the
receiver can be used to track the pipeline once more. However this time it is traced about one
meter away from one side of the pipeline that has been detected and parallel the receiver with the
line. At this time no signal from the main line (or signal is small) can be detected, but the response
to the branch can be significant.
The most reliable way to locate the branch pipe is to apply the transmitter signal to the end
of the branch pipe. This signal will flow from the branch to the main line and then to both sides of
the main line. The receiver surface is at right angles to the main line and the signal is tracked along
the main line. The receiver will have a zero response above the T-branch joint. The zero position is
the exact location of the T-branch joint.
2. Parallel Pipeline Detection
Parallel pipelines are a common phenomenon in pipeline detection. In pipelines intensive
