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)

Inte

nsity

(a.u

.)

Leak sound signal location

Time (ms)

Inte

nsity

(a.u

.)

Leak sound waveform

Detect leak position Detect leak hole size

DAS

Third party interference detection:

Position (m)

Inte

nsity

(a.u

.)

Sound signal location

Time (ms)

Inte

nsity

(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 rangeControl unit: +5 OC to +60 OC

Optical fibre cable: -30 OC to +70 OC

Control unit size 4U 19” rack enclosure

Operating Voltage90 – 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 ±0.1C

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 rangeControl unit: +5 OC to +60 OC

Optical fibre cable: -30 OC to +70 OC

Control unit size 4U 19” rack enclosure

Operating Voltage90 – 250 Vac

9-30 Vdc

Power consumption <180 VA

Distributed Strain Sensor (DSS)

7570 7572 7574 7576 7578 7580-200

20406080

100120

Distance (m)

Stra

in (

)• 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 rangeControl unit: +5 OC to +60 OC

Optical fibre cable: -30 OC to +70 OC

Control unit size 4U 19” rack enclosure

Operating Voltage90 – 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!