Hawk Measurement Systems
Smart Sensor Technology
for Gas Pipeline Monitoring

Fibre Optic Distributed Sensor
(FOS)
 The optical fibre cable is the sensor:
• The multiple core Fibre To The Home
(FTTH) cable can be used as a
distributed acoustic and strain sensor.
• The standard loose tube
telecommunication fibre cable could be
used as a temperature sensor.

 The optical fibre cable is the sensor:
FOS
• Ideal design integrates loose tube fibre (for temperature sensing),
tight buffered fibre (for strain and acoustic sensing) and adhesive tape
together in one cable, so it could stick to flat surface.
Sheath
Loose tube
Optical fibre
Adhesive tape

Distributed Acoustic Sensor
(DAS)
Position (m)
Intensity(a.u.)
Leak sound signal location
Time (ms)
Intensity(a.u.)
Leak sound waveform
Detect leak position Detect leak hole size

DAS
 Third party interference detection:
Position (m)
Intensity(a.u.)
Sound signal location
Time (ms)
Intensity(a.u.)
Sound waveform

Performance Specifications for
DAS
Maximum fibre length 50 km
Spatial Resolution 0.5 m
Location accuracy Within 5 m or better
Identify activities
Gas leak, Gas pressure and leak hole size, digging, normal vehicle, human
and animal passing etc.
Acoustic wave bandwidth 0 – 20 kHz distance pending
Real time detection Yes
Two channel detection to minimize signal fading Yes
Tolerance to single cable fault* Yes
Fault Detection / Reporting Programmable fault alarms and reports
Sensor Life Time >30 years
Operating temperature range
Control unit: +5 OC to +60 OC
Optical fibre cable: -30 OC to +70 OC
Control unit size 4U 19” rack enclosure
Operating Voltage
90 – 250 Vac
9-30 Vdc
Power consumption <180 VA
* Both fibre ends need to be accessible (DAS2)

Temperature Detection
(Joule-Thomson effect)
• Leakage from a compressed gas line is identified by the development of a cold spot
due to the pressure release known as the Joule-Thomson effect. Typical Joule-
Thomson effect figures for natural gas are -0.5°C/ bar x delta p which indicates that
small pressure changes result in significant temperature variations.
• The pipeline outer surface being rapidly cooled by the Joule-Thomson effect, a
temperature gradient develops in the soil around the pipeline surface. The speed of
the temperature gradient development depends on the type of soil and may vary from
a few seconds to a few minutes.
• The cooling effect is independent of the soil temperature and that the magnitude of the
cooling effect remains the same regardless of soil temperature.

 Fibre optic sensor detection of temperature change over a
12m region:
Distributed Temperature Sensor
(DTS)

Performance Specifications for
DTS
Maximum fibre length 50 km
Spatial Resolution 0.5 m
Location accuracy Within 5 m or better
Temperature Resolution 0.1 C
Temperature Accuracy ±0.1C
Signal Averaging 1 to 16,000,000
Data collection time
1 to 30 seconds, dependent on distance, accuracy and
interrogation method.
Fault Detection / Reporting Programmable fault alarms and reports
Sensor Life Time >30 years
Operating temperature range
Control unit: +5 OC to +60 OC
Optical fibre cable: -30 OC to +70 OC
Control unit size 4U 19” rack enclosure
Operating Voltage
90 – 250 Vac
9-30 Vdc
Power consumption <180 VA

Distributed Strain Sensor
(DSS)
-20
30
80
130
7570 7575 7580
Distance (m)
Strain()
• The strain change at a pipe surface and deformation of a pipe could be
detected by optical fibre cable. Multiple cables can provide strain detail
along more than one axis.

Performance Specifications for
DSS
Maximum fibre length 50 km
Spatial Resolution 0.5 m
Location accuracy Within 5 m or better
Strain Resolution 2με
Strain Accuracy ± 2 με
Signal Averaging 1 to 16,000,000
Data collection time 1 to 30 seconds, dependent on distance, accuracy and interrogation method.
Fault Detection / Reporting Programmable fault alarms and reports
Sensor Life Time >30 years
Operating temperature range
Control unit: +5 OC to +60 OC
Optical fibre cable: -30 OC to +70 OC
Control unit size 4U 19” rack enclosure
Operating Voltage
90 – 250 Vac
9-30 Vdc
Power consumption <180 VA

Multiple Parameter FOS
• Combination of sound, temperature and strain detection minimizes the
chance of false alarm
DAS-Sound
DTS-Temperature
DSS-Strain
• Fiber optic sensing can detect and localise leaks continuously and
accurately along the entire length of the pipeline.
• It detects the signature of leak: Leak sound, cool spot due to leak and
strain change.

• Distributed sensor can
continuously monitor vibration,
strain and temperature on pipe line
for the entire length of optical fibre.
• Fibre optic cable is easy to install.
• Fibre optic cable is passive –
No electrical power required.
• Little or no maintenance required.
Fibre Optic Sensing
• Fibre optic sensing has low cost.
• Fiber optic sensor is weather independent without being compromised
by rain, fog etc, and not disturbed by moisture, dust or smog.

Scope of Monitoring
• Vibration and sound of leak and third party intrusion
• Temperature
• Stress, strain along tensile members and cables attached to pipeline
• Emergence of pipe deformation
• Loss of ground support due to soil erosion

HAWK Fibre Optic Sensor
(HAWK FOS)
• HAWK fibre optic sensing data collection
system compares outputs from multiple
technologies to improve sensing reliability
and discriminate against false positives.
• Advanced cable design improves
sensitivity of both temperature and strain
measurement.
• Enhanced acoustic sensing technology
virtually eliminates signal fading.
• Simple filtering and performance
enhancement software.

Thank You!