Leak Detection and Leak Prevention

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Simulation Software Limited has significant experience in the field of pipeline leak detection and this has been fully exploited within VariSim to create some of the best software based leak detection approaches for oil and gas systems. The VariSim Leak Detection technology provides high accuracy, high capability leak detection on all single phase pipelines and conforms to the requirements of API 1130. Our systems have been installed on liquids pipelines and gas pipelines including offshore pipelines where instrumentation possibilities are limited to offshore platforms.  

LEAK DETECTION PRINCIPALS

Our systems expand the capabilities of the two principal software-based methodologies that analyse the physical reaction to a leak in the pipeline.

Explosion from leak

  • Pressure transients will emanate from the location of the leak when bursts occur
  • What goes into a pipeline must come out 

Balancing techniques can detect seeping leaks over extended timeframes and pressure monitoring techniques can detect large leaks very quickly. It therefore makes sense to combine these effects to ensure the full range of leak detection capability. Although the physical reaction to a leak will never change, the way that the physical reaction is interrogated can always be improved upon.

If the instrumentation permits and if the system is not a simple one, SSL will recommend that a compensated balance system is used. These systems use the VariSim simulator to compensate for changes in the pipeline inventory thereby maximising accuracy levels and reducing the false alarm rate.

VariSim significantly improves capability on pipelines with transient conditions, variable product properties and changing flow regimes (including slack line conditions) which are commonly found on many pipelines worldwide. If the pipeline is transporting gas, a simulator will always be used to accommodate for the highly compressible nature of the gas.

Balance and Pressure wave methods provide a response (a value derived from the method used) that can be analysed to detect the presence of a leak. The compensated balance methods produce imbalance responses in addition to important divergences between measured and calculated values of pressure and flow at key locations on the pipeline or network (UF flow responses and UP pressure responses). The pressure wave method monitors the change in pressure at key locations on the pipeline and verifies the presence of a true leak by verifying the times at which the pressure changes occur.

GENERATING TRUE ALARMS

SSL are continually investing time and resource into the development of its leak alarming processes as it recognises fully that any alarm system that continually raises false alarms will be rendered un-usable. The alarm process which uses the responses generated from the balance and pressure wave methods uses any combination of the techniques to minimise false leaks.

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1. Advanced incoming measurement analysis to verify optimum instrumentation performance.

2. Employment of dual filtering and statistical methods including WALDs probability tests.

3. Weighted assessment of the responses.

4. Pattern evaluation of response timings

 

Output from the leak detection process includes the leak size, volume lost and the location of the leak that are calculated using advanced methods appropriate to the pipeline or network geometry. The leak detection process resides as a plug-in in VariSim and uses all the familiar and powerful viewing capabilities of the VariSim environment. Data from the leak detection process can also be exported to VariView for SCADA style graphical display or to the SCADA system itself.

Leak Detection Interface

 

 

 

VariSim
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VariView

 

 

 

LEAK PREVENTION

Leaks in pipelines often develop when high surge pressures are generated in the pipeline, particularly when such surge pressures are repeatedly experienced in the same location. VariSim can monitor the pipeline pressures against the MAOP of the pipeline and generate alarms for the operator each and every time over-pressurisation occurs. Operators can then assess the frequency of the alarms and the location in which over-pressurisation occurs and steps can be taken to prevent the surge pressures if required.