Leakage control in transmission
pipelines
Assessing Leakage in Transmission Mains
 Trunks Mains connect sources and distribution areas
 To assess leakage in Transmission Mains (TM) it is
necessary to measure flow in different cross sections
 District Metered area principle can be applied to TM
Trunk Mains Leakage Detection
•
Trunk mains (transmission mains) often have:
-
Large diameters
Low pressure
Non homogeneous pipe wall material (reinforced concrete)
Few access points
Long distance
•
All these make normal acoustic leakage detection difficult
and other techniques have been developed
•
These techniques are highly specialised and normally
done by contractors
Leak Detection With Acoustic Correlator
• Accelerometer / hydrophones
• Access pits (preferably tappings) required every 300m
• Cheap outright purchase; large civil works cost
• Only finds leaks when all variables in their favour
In-pipe Acoustic Technology
Sahara® system
A sensor head or probe is inserted into a pressurized transmission main through a
50mm diameter tapping point. The flow of water carries the probe through the
pipe and leaks are located by analyzing the acoustic signals that are generated by
leaks in the pipe wall or joints. Once a suspected leak has been located the probe
can be stopped at the position of the leak. It is possible to survey 2 km per
insertion.
Sahara system
Cable, acoustic sensor and
parachute
Sahara®
Cable Winch:
Sahara®
Real Time Tracking:
Sahara®
Not just leak detection – CCTV also:
• Internal Corrosion
• Liner loss or condition
• Pipe or valve defects
SmartBall® Water Main Leak
Detection
• Free swimming inline device
• Ideal for long runs of trunk mains
• Requires 100mm tappings for insertion
or extraction
• Tracked above ground every 1-2km
with receiving units
• All data is saved on the ball and
processed off site
®
SmartBall
Insertion:
®
SmartBall
Tracking:
®
SmartBall
Retrieval:
®
SmartBall
advantages
Following significant advantages can be seen relative to conventional correlator
technology:
1. Large Diameter Pipe: Unlike conventional correlation methods, SmartBall can be
used to detect leakage on large diameter pipe (>18” in diameter).
2. Pipe Material: SmartBall is not sensitive to pipeline material, as it is not dependant
on the pipeline to transmit the acoustic energy to surface mounted sensors.
3. Leak Sensitivity: Due to SmartBall rolling past the leak, it has optimum acoustic
sensitivity and can detect leaks smaller than two liters per minute (dependant of
line pressure and ambient noise floor).
4. The SmartBall system does not require the pipeline to be decommissioned and it
can survey long pipelines efficiently, accurately and cost effectively.
Application
SAHARA
• Shorter distances where laterals exist
• Existing tappings could be used
• Used to periodically monitor critical mains
• When accuracy is very important
SMARTBALL
• Long distances per insertion; up to 25km
• Doesn’t require tracking unless leaks are located
• Reservoir to reservoir
Disadvantages
SAHARA and SMARTBALL
• High Cost
• It’s necessary to commit the proprietary company for
implementation
Remote Field Transformer Coupling
system (PPIC)
Information on the location, distribution and number of wire
breaks anywhere along the length of PCP
(prestressed concrete pipe).
Knowing the broken wires it is possible to perform selected
rehabilitation of pipeline segments delaying pipe
replacement
RFTC Operation
 Remote Field Transformer Coupling technology functions
much in the same way as a radio transmitter and receiver. The
"transmitter" produces an electromagnetic field.
 The prestressing wires in the pipe amplify the signal.
 If there are broken pre-stressing wires, the signal does not
come through cleanly and the "receiver" picks up static, or
noise.
Internal equipment
External equipment
Advantage: no dewatering before inspection
Acoustic Emission Testing (AET)
 When a pipe is subjected to an external stimulus (change in
pressure, load, etc), localized sources trigger the release of
energy, in the form of stress waves, which propagate to the
surface and are recorded as acoustic emissions by sensors.
 The stress which can negatively affects the efficiency of the
water networks can be generated by different natural or
environmental reasons: earthquakes, overfloods, landslides or
rockbursts
AET applications
 Distressed pipes to know which pipes are continuing to
deteriorate and to give advance warning if failure is eminent;
 Critical pipes to detect if there are any deteriorating pipes in
locations where a failure would have catastrophic
consequences;
 Whole pipelines to determine if there are any pipes in the line
that are deteriorating and which sections require further
testing;
 Construction zones to learn if the pipeline has been
inadvertently damaged.