Pipelines used as bulk carriers of crude oil and natural gas
Used in water distribution systems
Results of Leakages include: Loss of product, Environmental hazards, Loss of life
Methods of leak detection:
Hardware Method: This method is used to detect leaks with instrumentation outside the pipeline.
Software Method: This method uses different instruments to monitor internal parameters (such as pressure, flow, temperature) that infer product release. It is also known as computational pipeline monitoring (CPM).
- Acoustic Emissions
- Fiber Optic Sensing
- Vapor Monitoring
- Multi-hop Sensor Wireless Network*
- Good sensitivity to leak
- Very accurate in leak locating
- System costs are usually high
- High complexity of installation
Software Methods-Balancing System :
- Balancing Systems: Uses the principle of mass conservation
Types of Balancing systems:
- Volume Balance
- Compensated Mass Balance
- Model Compensated Mass Balance
- It is simple to implement
- Cost effective
- Can be affected by instrument error
- High rate of false alarms
Software Method – Pressure Analysis:
Gradient Intersection method
- This method uses SCADA (Supervisory Control and Data Acquisition) values to calculate the theoretical hydraulic profile or baseline of the pipe
- The presence of a leak can be determined from a specific deviation or combinations of several deviations from the baseline
Advantages: Estimation of leak location can be determined
- Dependent on instrument sensitivity.
- Smaller leaks typically take longer time to detect.
- Does not give magnitude of leak
Software Method – RTTM:
Real Time Transient Modeling (RTTM) involves computer simulation of pipeline conditions using advanced fluid mechanics and hydraulic modeling.
Basic equations used in RTTM are:
- It takes into account the configuration of the pipe as well as the product characteristics.
- Very fast in detection and location
- It is a complex way of leak detection
- The RTTM method costs much more than the other methods
- Requires many instruments, controller training and maintenance.
- Errors in instrument calibration could raise false alarms
Generalized Likelihood Ratio:
- This is a statistical method modeled after the flow conditions in the pipeline
- A mathematical model that describes effects of leaks and biases on the flow process is used.
- Can detect leaks in pipeline branch, location in the branch and magnitude of the leak.
- Can identify various types of gross errors