Pipeline leak detectioneLearning – Part 1 of 2
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Title here again in Arial 24 max. one lineAgendaPipeline leak detection
Historical developmentLeak detection system requirementsCauses of leaksLeak detection optionsNon-continuous leak detectionContinuous external leak detectionContinuous internal leak detection
Title here again in Arial 24 max. one lineAgendaPipeline leak detection
Leak localizationHuman Machine InterfaceAdditional functions in leak detectionTypical applications of leak detection systems
IntroductionHistorical development
3 | Pipeline leak detection
3000 BC 500 BC 400 BC
Copper pipes for water transport
First transport ofhydrocarbons
Supplying Peking with natural gas
Factors influencing the construction of pipelines:
Discovery of crude oil
Development of refineries
Dependency of oil transport
Invention of the automobile
IntroductionHistorical development
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19th century
IntroductionCurrent situation
| Pipeline leak detection5
Oil, crude oil, refined products, natural gases, condensate, process gases, water and salt water
Title Contents of requirement
Leak detection system requirementsOfficial requirements
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TRFL Technical Rules for Pipelines
API 1130 Computational Pipeline Monitoring for Liquids
API 1149 Pipeline variable uncertainties and their effects on leak detection
API 1155 (replaced by API 1130) Performance criteria for leak detection systems
CSA Z662 Oil and gas pipelines
49 CFR 195 Transport of hazardous liquids via pipeline
Leak detection system requirementsPerformance criteria
8PipePatrol E-RTTM8 | Pipeline leak detection
Label Description
Reliability• Avoid false alarms
• Reliably detect leaks
Accuracy • Accurate localisation of leaks
Robustness• Detect failing sensors
• Fall-back strategies in the event of sensor failure
Sensitivity• Minimum detectable leak rate
• Detection time
F
Causes of leaks
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In Out
Fatigue cracks
Stress corrosion
Hydrogen indexing
Material manufacturing errors
External influence
Leak detection options
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Non-continuous Continuous
External systems
• Fibre optic cable
• Acoustic systems
• Sensor hoses
• Video monitoring
Internal systems
• Pressure point analysis
• Mass balance method
• Statistical systems
• RTTM-based systems
• E-RTTM
• Inspection by helicopter
• Smart pigging
• Tracking dogs
Leak detection systems
Non-continuous leak detectionInspection by helicopter
Leak detection methods:
Laser
Infrared camera
Leak sniffer
Usage conditions:
Detecting small gas leaks
Accuracy depends on weather conditions
Poor weather conditions make helicopter flight difficult
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Non-continuous leak detectionSmart pigging
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Types of pigging:• Cleaning pigs• Batching pigs
Smart pigs• Magnetic flux leakage method• Testing using the principle of ultrasonic
Non-continuous leak detectionSmart pigging
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Usage conditions:Detecting existing and potential leaksZero or baseline piggingPipeline must be piggableAccuracy of measurement depends on the pig velocity
1 - 5 m/s
Non-continuous leak detectionTracking dogs
Trained to smell certain odorant
Usage conditions:
Short pipelines, segments
Containment of leak sites
Certification difficult
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External leak detectionFiber optic cable
Usage conditions:
Accurate localisation of leaks
Limited length possible
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Laser
0 s
°C
Many reflections required
Cable position must be selected according to the medium
Gas
Liquids
L
Usage conditions:
Acoustic sensors directly on the pipeline or with steel rods for underground pipelines
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sL
A AA A A A
• Large number of sensors for longer pipelines
Difficult to detect small leaks
0
dB
A
External leak detectionAcoustic systems
External leak detectionVideo monitoring
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Usage conditions:
Short distances
Continuous leak detection may be possible
Pump
External leak detectionSensor hoses
Usage conditions:Monitoring short pipelinesSmall leaks detectableCable position must be selected according to the medium
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Gas detector
Pump time
Gasconcentration
∆
Internal leak detection
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PLTLP0 T0
Internal leak detectionOverview of the systems
Extended-RTTM
Volume comparisonmethod
Statistical systems RTTM-based
P T P T
Pressure point analysis
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t0
dp/dt
Internal leak detectionPressure point analysis
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In
P
Out
Upper threshold
Lower threshold
Internal leak detectionMass balance method
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30
25
20
15
10
5
0
30
25
20
15
10
5
0
Difference
Uncompensated mass balance
In/Out
InOut
Out In
Internal leak detectionStatistical systems
23 | Pipeline leak detection
In Out
LeakNo leak
Alarm
Probability
Statistical variable
Internal leak detectionRTTM
Conservation of Mass
Real-Time Transient Model
Conservation of Momentum
Conservation of Energy
In Out
L
PL
Internal leak detectionRTTM
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TLP0 T0
F0 FL
∆
Change in pipe contents
Change in pipe contents
RTTM-compensated mass balance
t
= compensated leak rate
Internal leak detectionE-RTTM
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PLTLP0 T0
F0
∆
Residual x ≡ F0 – F0 Residual y ≡ FL – FL
∆
FL
F0 FL
Internal leak detectionE-RTTM
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PLTLT0P0
F0 FL
F0 FL
∆
s
Residual x ≡ F0 – F0 Residual y ≡ FL – FL
Residuals x and y are used by the system as decision values
Leak signature
x
∆
Internal leak detectionCapabilities of internal systems
Method Typical min. detectable leak rate
Time to detect leak (liquids)
Time to detect leak (gases)
Detectable types of leak
False alarm frequency
Accuracy of leak localisation
Pressure point analysis
> 5% Short Long Spontaneous leaks
High High with additional pressure sensors, dependent on sampling rateMass balance
method> 1% Long Very long Spontaneous
and creeping leaks
High Average with additional pressure sensors
Statistical methods
> 0.5% Long Very long Spontaneous and creeping leaks
Slight Average with additional pressure sensors
RTTM > 1% Short Short Spontaneous and creeping leaks
Average High
E-RTTM > 0.5% Very short Short Spontaneous and creeping leaks
Slight High
Leak localizationOverview
Possibility of combining methods
Improving accuracy
Reducing problems in localizing
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Gradient IntersectionMethod
s
p
Wave PropagationMethod
t
sExtended Wave Propagation
Method
t
s
Leak localisationGradient Intersection Method
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p
sL0 sLeak
In
P
Out
P
p0
pL
Advantages• Localising: spontaneous, creeping leaks • Good accuracy with stationary operation Disadvantages• Accuracy depends on length of pipeline• Pipeline geometry must be taken into consideratio
Leak localisationWave Propagation Method
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t
sL
sLeak
p0
pL
tLeak
Δt
0
In
P
Out
P
Advantages• Good accuracy
Disadvantages• No localizing of creeping or small leaks • Fast sampling required
• Can be used during operation and pauses
Leak localisationExtended Wave Propagation Method
6 | Pipeline leak detection
t
sL
sLeak
p0
pL
tLeak
0
In
P
Out
P
• Good accuracy
P P
p2
p3
HMI (Human Machine Interface)
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HMI (Human Machine Interface)
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Added functions in leak detectionEfficiency analysis
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87% efficiency
100% efficiency
Inventory calculation
Operator training
Theft detection
Hydraulic profiles
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Added functions in leak detection
Added functions in leak detectionBatch tracking
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Batch trackingTracking products and mixing zones
Batch schedulingScheduling arrival times and capacities
Scheduling of delivery
Reducing waste
Typical applications
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Typical applicationsFPSO to refinery
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• Long pipelines with large diameters• Substation measurements impossible
Typical applicationsOil field to refinery
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• Long pipelines with large diameters• Changes in viscosity and density• Elevation and temperature differences
Typical applicationsOffshore drilling rig to refinery
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• Changes in viscosity and density• Substation measurements impossible• Large diameter
Typical applicationsRefinery to tank farms
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Several products with various densities
Typical applicationsGas field to refinery
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• Long pipelines with large diameters
• Elevation and temperature differences
Typical applicationsChemical plant to chemical plant
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Heavily transient operation of pipelines
Typical applicationsSea to city
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Long pipelines with large diameters
Choosing the right leak detection system
No leak detection system isthe perfect choice for every application
Selection of the system depends on:
Desired results
Costs
Installation conditions
Individual adaptation leads to optimal performance
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What requirements are placed on the application?
Title here again in Arial 24 max. one lineSummaryPipeline leak detection
1. Historical development2. Leak detection system requirements3. Causes of leaks4. Leak detection options5. Non-continuous leak detection6. Continuous external leak detection7. Continuous internal leak detection
Title here again in Arial 24 max. one lineSummaryPipeline leak detection
8. Leak localization9. Human Machine Interface10. Additional functions in leak detection11. Typical applications of leak detection systems
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