The document discusses underground utility detection and locating buried pipes and cables. It covers several key topics:
- The importance of safety when digging and how locating utilities helps avoid damage
- Common utility detection techniques like electromagnetic induction, ground penetrating radar, and cable locators
- How cable locators work to detect active and passive signals around buried lines
- Processes for sweeping an area and tracing individual utilities using cable locators
- Standards and guidelines for underground utility mapping in Malaysia
3. Safety on site is a necessary ingredient of all civil works.
Information provided by locating before digging is an essential
contribution to safe digging.
Spiking a buried power cable or fracturing a pipeline is a cause of
serious and dramatic danger that can mutilate or even kill.
Knowing their presence and position helps avoid the possibility of
damage.
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5. What’s all this about locating?
It’s about ;
• reducing unnecessary cost
• efficient working
• site safety
• maintaining essential services to the community
Information is the end product of locating buried utility pipes and
cables.
Positive, accurate and precise information is the only kind of
information worth having or worth paying for.
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6. Faulty or incomplete information can misled, it can be the cause of
unnecessary cost and it can expose people to danger.
Underground Utility Mapping is a process to determine the utilities
beneath the ground surface.
Such as : telephone line, power distribution cable, natural gas
pipeline, fiber optic line, street light cable, water
pipes,sewerage etc.
Faulty 01 Faulty 02
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7. Electromagnetic induction was discovered
by Michael Faraday in 1831
The earliest record of using electromagnetic
technology to locate buried cables dates
from around 1910
Michael Faraday
1791-1867 7
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8. The photograph shows a cable locator from a coil wound round a
wooden truss; the coil is just visible at the front of the truss
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9. Survey and Mapping Department are responsible
to manage utility mapping for Malaysia (24th
August 1994)
To handle disruption of existing utility services
due to excavation works
Follow the ‘
Standard Guideline for Underground Utility Mapping
’
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10. Underground utility installations involved the use of different
materials and sizes and can be placed at different depths.
In addition, the environment in which it is buried can vary from
one place to another and can be packed with a variety of utility
placement.
This makes possible the need for using more than one
technique to detect its position.
The selection of appropriate techniques is essential to ensure
effective detection.
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11. In general, the detection techniques that can be used can be
classified as follows:
• Electromagnetic
Pipe and Cable Locator (PCL)
Terrain Conductivity
Resistivity Measurements
Metal Detectors
Ground Penetrating Radar (GPR)
Optical Methods
X-ray Methods (Penetrating Radiation)
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12. In general, the detection techniques that can be used can be
classified as follows:
• Magnetic
Magnetometer
Total Field Measurements
Gradiometric Measurements
• Elastic Wave
Seismic Reflection
Seismic Refraction However, utility detection activity typically
Acoustic Emission involve two types of equipment
* Pipe and Cable Locators (PCL)
* Ground penetration radar (GPR).
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14. A PCL does not locate buried pipes or cables
It detects a magnetic field around the line created by an alternating
current-ac-flowing along the line.
This magnetic field forms a cylindrical shape around the line and is
known as the ‘SIGNAL’
PCL should be able to provide
accuracy of ± 5% from the
true value of location and
depth.
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17. Signal;
• Active Signal
Is produce by a signal transmitter and applied to a line so that it can be
located and traced with a receiver.
The signal transmitter can also flood an area with signal so that all the
lines in the area can be located
• Passive Signal
Occur ‘naturally’ on lines as an effect of 50/60Hz electric power energy or
VLF radio energy
** Despite the existence of passive signals the best signal to
locate and trace a line is an active signal which has been
deliberately applied for the purpose of locating and tracing
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18. Active Signal;
• An active signal is applied to a line from a transmitter so that the
line can be traced and located with a receiver.
• To ensure more accurate result, these mode should be used;
Direct Connection
Induction
Clamping
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19. Direct Connection
• The output ac voltage from the signal transmitter is connected directly
to the pipe or cable at an access point such as a valve, meter or end of
the conductor, and the circuit is completed by a connection to a stake
or the ground connection point
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21. Induction
• The aerial in a signal transmitter fed with an ac voltage sets up a
magnetic field through the coil returning through the earth below it.
• In the first drawing the transmitter aerial lies parallel to line AB and its
field links around the line which therefore has a signal induced on it.
• There is no linkage and no signal induced on line CD at right angles to
the aerial.
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22. Clamping
• Uses the induction principle to give similar result to direct
connection, but without electrical contact to the line.
• The output from the signal transmitter is applied to a target line
by clamping round it with a split toroidal magnetic core, which
carries a primary winding magnetizing the core with the ac signal
• The line becomes the secondary of a transformer, and will carry a
strong signal, provided that it is adequately grounded on each
side.
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24. Passive Signal;
• Are ‘naturally’ present on many buried pipes and cables.
Eg. Power cables which carry currents as part of their normal duty.
• Current flowing in a cable produces a magnetic field or passive
signal.
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25. Passive Signal;
• Very low frequency long wave radio energy from distant
transmitters is present in the atmosphere world-wide.
• The ground provides return paths for this energy, and burried
metallic lines form preferred paths.
• They then act as aerials re-radiating these signals.
• The signals are strong enough to be located in most part of the
country.
• This can be check by trial and error before relying on them for
location work.
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27. Sweeping
• To locate any conductor underground
• Walk in grid pattern as shown on illustration
• Sweeping in two perpendicular directions
• ‘STOP’ when you get a response
• Move the transmitter to that point and trace the conductor
you’ve found out of the area of interest, marking as you go.
• Return to your starting point and resume sweeping, looking for
more conductors to trace.
• When finished sweeping using the inductive method, sweep
again using passive power mode.
• This technique will reveal all grounded metal pipes and cables,
and non-conducting lines with properly installed tracer wires.
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29. TRACING
• To trace an individual pipe or cable, it’s best to apply signal to
the targeted line with the conductive method or the inductive
clamp method.
• If this isn’t possible, you can still use the inductive method but
other conductors are more likely to pick up a signal.
• Move slowly while tracing the cable, moving the receiver side
toside over the trace path. Pay attention to handle alignment.
• Mark the path as you go, and, if in manual gain mode,
remember to adjust gain periodically as you move away from
the transmitter and signal strength declines.
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32. Ground-penetrating radar (GPR) is a geophysical method that uses
radar pulses to image the subsurface.
This nondestructive method uses electromagnetic radiation in the
microwave band (UHF/VHF frequencies) of the radio spectrum, and
detects the reflected signals from subsurface structures.
GPR can be used in a variety of media, including rock, soil, ice, fresh
water, pavements and structures. It can detect objects, changes in
material, and voids and cracks.
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33. Depending on the depth and soil conditions, a range of frequencies
should be used:
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36. The American Public Works Association (APWA) Uniform Color Codes for
temporary marking of underground utilities are listed below:
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37. Marking on site
Normally Marked:
Power Line - P
Water - W
Sewer - S
Telephone Line - T
Gas Pipe - G
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38. ABC & XYZ of Locating Buried Pipes and Cables (for the beginner
and the specialist)
• Radiodetection Limited
Locating 101- A quick guide to underground locating
• Schonstedt
Pekeliling KPUP bil. 1/2006 – Garis Panduan Pemetaan Utiliti
Bawah Tanah
• Jupem
Pekeliling KPUP bil. 1/2007 – Garis Panduan Ukuran Pepasangan
Utiliti
• Jupem
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