Pipeline leak detection system
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The document discusses pipeline leak detection technologies. It describes automated, semi-automated, and manual detection methods. Common current methods like satellite imaging, helicopter surveillance, and sonic sensors are outlined along with their limitations. An internally-based Real Time Transient Model (RTTM) method is proposed, which uses pressure, flow, temperature, and acoustic sensors along with modeling of the pipeline flow. RTTM can detect small leaks and estimate their location and rate. It is faster and less prone to false alarms than other methods but requires more complex modeling and instrumentation.
Pipeline leak detection system
- 1. Problems faced by Industries during PipelineTransportation Exposures LeaksEncroachmens Fire
- 2. Table 1: Causes of pollution expressed in the study area expressed in percentage (author-Newcastle University, UK, 2012) • Sources No of respondents Percentage well leakage 4 13 • Pipeline related sources 20 67 • Reservoir/tankers related 1 3 • Facility failures/ ageing 5 17
- 3. Classifying leak detection technologies We distinguish them in three categories: • automated detection - complete monitoring systems that, can report the detection of a gas leak without the need of a human operator, once they are installed (e.g. infrared sensors, fiber optic or cable sensors). • semi-automated detection - solutions that need a certain amount of input or help in performing some tasks (e.g. statistical or digital signal processing methods) • manual detection - systems and devices that can only be directly operated by a person (e.g. thermal imagers ).
- 5. Methods currently used and their problems • Low Orbit Satellite Imaging->Off line system : Once per month + image processing time ,Not effective if clouds present,Under ground pipeline : Hence nothing visible : Not sure whether we are looking at the images of land above our pipeline. • Helicopter Surveillance->In worse weather conditions, helicopter surveillance becomes impractical,Possibility of human error • Sonic vibration sensors->Risk of spurious alarms due to movement of vehicles etc. • Optical Fibre based monitoring • Meters are installed at at certain intervals and cumulative is checked that is net accumulation in a control volume should be zero->not a continuos method so will take time to detect where is the leakge
- 6. COMPARISON OF VARIOUS TECHNOLOGIES Technology Parameter/ Criteria Monitoring Additional equipment requirement Procesin g time Probabilty of false alarms Maintenan ce Cost Online Sonic sensors/ Threat scan Online Yes Continu ous High Required Very High Satellite Imaging Fixed No Fixed frequen cy No No High Optical Fibre based monitoring Online Yes Continu ous High Required Very High Helicopter monitoring Fixed frequency No Fixed Frequen cy NO No Low
- 7. The Motivation • The specific goals of pipeline leak detection include desired sensitivity, leak detection time, leak location capability, accuracy of leak volume estimates, and adaptability of a given technology to routine and non-routine activities. • The system presently used detects gas leakage but the industries want it on ppm and ppb level • For cost cutting linemen are used who use soap solution at joints to check which is not much reliable. • As important as detecting a leak is, the controller’s response is equally critical. There have been several cases where the leak detection system detected an actual leak and declared an alarm which was ignored by the controller so shifting to fully automated rather than manual and semiautomated • The pipeline leak detection system should be able to detect a leak as small as 0.5 percent (%) of the daily throughput.
- 8. Solutions that can be used • There are internally (observing hydraulic behavior) and externally (released fluid detection) based(Pipeline Leak Detection) PLD technologies. Computational pipeline monitoring (CPM) is an internally based PLD technology CPM uses pressure, flow, temperature, and/or acoustic instruments to measure single or multi- phase fluid parameters within a segment of pipeline. A Supervisory Control and Data Acquisition (SCADA) system monitors, processes,transmits, and displays the pipeline data to a controller in a control room. Using computer software programs to analyze the information and issue an alarm when a leak is detected • External methods include hydrocarbon vapor or liquid-sensing devices such as infrared sensors as well as aerial surveillance along pipeline corridors. chemical sensors, and electrical sensors.
- 9. What is a good leak Detection System
- 11. Real Time Transient Model Internally-Based System • RTTM means “Real-Time Transient Model”.RTTM LDS(leak Detection System) use mathematical models of the flow within a pipeline using basic physical laws such as conservation of mass, conservation of momentum, and conservation of energy. • RTTM methods can be seen as an enhancement of balancing methods as they additionally use the conservation principle of momentum and energy. An RTTM makes it possible to calculate mass flow, pressure, density and temperature at every point along the pipeline in real-time with the help of mathematical algorithms. • RTTM LDS can easily model steady-state and transient flow in a pipeline. Using RTTM technology, leaks can be detected during steady-state and transient conditions. • With proper functioning instrumentation, leak rates may be functionally estimated using available formulas
- 12. 12 Software Method - RTTM Advantages It takes into account the configuration of the pipe as well as the product characteristics. Very fast in detection and location Very less probability that it will produce False Alarms. Involves computer simulation of pipeline conditions using advanced fluid mechanics and hydraulic modeling. Can be used for anykind of Pipeline whether it is Underground or Overground or small or big. Measuring purely the flow won’t show up the true leak. RTTM measures the temperature and pressure at outlet and inlet. A robust set of algorithms calculates the flow.
- 13. 13 Software Method – Gradient Intersection Xleak
- 14. 14 Simulation Procedure - Leak in Pipe 8 Calculator Leak induced in Pipe 8 Optimizer
- 15. 15 Simulation Results- Leak in Pipe 8 Leak Simulated Pipe 8 Location(m) 450 Magnitude(kg/s) 2.611 Measured Flow 4.946 Measured Pressure (kPa) 2160.1 Pipe Functional Values 1 126.678 2 97.438 3 101.864 4 123.710 5 126.447 6 126.447 7 63.294 8 0.151 9 159.922 Estimated Magnitude(kg/s) 2.609 Estimated Location(m) 450
- 16. Analysis of Pipeline Leak Detection System
- 17. How calculations are done Balancing Systems Uses the principle of mass conservation Basic equations used in RTTM are: Continuity equation: Momentum Equation: Energy equation: dt dM tMtM L OI =− )()( .. 0= ∂ ∂ + x v dt d ρ ρ 0. 1 =+ ∂ ∂ + Df x p dt dv ρ 0. 1 =−− Ll dt dp dt dh ρ
- 18. Variables invoved in equation
- 20. 04-Nov-14 In this model Energy Conservation is not of that significance because it does not help in leak detection. It should be mentioned that this model is only for the pipeline flow in single phase gas or liquid . Modelling multiphase flow is much more complex and accuracy is not sufficient to be used in pipeline leak detection
- 21. Practical Test of the Model
- 24. DIAGNOSING AND LOCATING OF THE LEAKAGE
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- 29. • An RTTM module calculates estimates M_i,M_o for mass flow at inlet and outlet, respectively. This can be done using measurements for pressure and temperature at inlet (P_i, T_i) and outlet (P_o, T_o). These estimated mass flows are compared with the measured mass flows m_i,m_o yielding the residuals x=M_i - m_i and y=M_o - m_o. These residuals are close to zero if there is no leak; otherwise the residuals show a characteristic signature. In a next step, the residuals are subject of a leak signature analysis.
- 30. Assumptions • Isothermal pipeline flow • Newtonian fluid • Fully Developed Laminar Flow • Leakage treated as flow through orifice • Steady State
- 31. Solution
- 32. Discharge Coefficient • The discharge coefficient is the ratio of the actual discharge to the theoretical discharge, i.e., the ratio of the mass flow rate at the discharge end of the nozzle to that of an ideal nozzle which expands an identical working fluid from the same initial conditions to the same exit pressures.
- 34. 34 Software Method – Gradient Intersection Xleak
- 36. For a simple horizontal pipeline Pressure drops linearly if friction factor f and pipe diameter D are constant along the pipeline and in absence of a leak. If a leak occurs at leak location x_leak, upstream pressure drop will increased and downstream pressure drop will decreased .Practically the pressure drop can be determined by using double sensor s1 and s2 with known distance between them l_12 at upstream and another pair s3 ,s4with distance l34 at downstream
- 38. Disadvantages – It is a complex way of leak detection requires trained personnels and maintenance – The RTTM method costs much more than the other methods – Errors in instrument calibration could raise false alarms – The accuracy of RTTM is limited by multi-phase flow measurement accuracy
- 39. CONCLUSION