Pipeline leak detection
Transportation of fluids in pipelines is increasing all over the world, and with good reason: pipelines are among the safest and most economical transportation systems over long routes. Here, leaks pose a potential safety risk: they occur for a wide variety of reasons, from earthquakes, corrosion and material failure to drilling by product thieves. Special leak detection systems are often used to limit these risks.
Selecting a suitable system
Selecting a suitable leak detection system is not an easy task: the system must meet the needs of the particular application and comply with regulations, for example API 1130, API 1175, TRFL or CSA Z662 Annex E.
From RTTM to E-RTTM
The RTTM ("Real-Time Transient Model") is currently the leading technology for internal leak detection systems. RTTM is a mathematical model that compares measurements taken during the actual operation of a pipeline with those of "virtual pipeline", or a computer simulation of the pipeline, in real time.
KROHNE has extended RTTM technology to E-RTTM for continuous internal monitoring of pipelines: E-RTTM stands for Extended RTTM, which combines RTTM principle with leak signature analysis using leak pattern detection.
An E-RTTM leak detection system creates a virtual image of a pipeline based on real measured data. Measurement values from flow, temperature and pressure sensors installed at the inlet and outlet of the pipeline and along the pipeline in places such as pump and valve stations are crucial. The flow, pressure, temperature and density at each point along the virtual pipeline are calculated from the measured pressure and temperature values.
The model compares the calculated flow values with the actual values from the flow meters. If the model detects a flow discrepancy, the leak signature analysis module then determines whether it was caused by an instrument error, a gradual leak or a sudden leak.
Handling changing or transient pipeline operating conditions
E-RTTM provides a high degree of sensitivity and quick leak detection with real-time comparison of existing measuring results against leak signatures, which are stored in a database. Comparison of measurement values with the leak signatures is also critical to reliability because it provides a high degree of protection from false alarms.
E-RTTM-based leak detection systems are able to handle changing or transient operating conditions that are not recognized by less sophisticated internal leak detection systems. An E-RTTM-based leak detection system works with dynamic values, which also affects robustness: the system can adapt automatically and very quickly to changes in the operating conditions such as sensor failure, communications failure, a valve closing or a product change in the pipeline.
E-RTTM is the basis of the KROHNE PipePatrol leak detection system. It is suitable for monitoring liquid and gas pipelines (including liquefied gas and supercritical products) and meets all the requirements of API RP 1130, API 1175, TRFL and CSA Z662 Annex E.