Electricity and Control August 2021

PLANT MAINTENANCE, TEST + MEASUREMENT

Advances in pipeline leak detection

The high rate of false alarms in standard pipeline leak detection systems can force system operators to waste labour and other resources chasing down problems that don’t exist. In some cases, false alarms are so prevalent that operators in the field view the detection system as unreliable and simply turn it off. KROHNE advises that newer technology provides an advantageous alternative.

I f a pipeline leak detection system is draining resources unproductively, or is completely shut down, there is little point in having one. Fortunately, newer technology provides an alternative. The most significant development in this field in recent years is Extended Real Time Transient Model, or E-RTTM, leak detection. Basic RTTM systems have been around for decades, but were only as good as the mathematics used to develop the model. E-RTTM is enhanced with a pattern recognition element to better filter out false alarms, provide faster leak detection and enable operators to locate the source of a leak more accurately. The basics of E-RTTM Traditional pipeline leak detection approaches simply compare the outlet flow with inlet flow. By comparison, E-RTTM uses software to create a hydraulic model of the pipeline and then analyses a feed of real-time information – including, for example, flow, pressure, and temperature measurements – to create a model of expected results. The software then compares expected results with actual performance so any mismatches can be identified. The addition of pattern recognition provides a second stage of evaluation to filter out false alarms by validating the model to determine if it fits a certain pattern for a seeping leak or a major leak. Essentially, it provides a confidence check. E-RTTM systems can be configured for various applications across the oil, gas, water and chemical industries. Applications include, for example: oil field to refinery pipelines, multiproduct pipelines from refineries to tank farms, pipelines carrying desalinated water to cities,

and non-continuously operated pipelines for transport products, such as jet fuel.

The business case Until relatively recently, a system like E-RTTM would have required specialised computer equipment. Today, with the available memory and processing speeds of most commer­ cial computers, that functionality is much more accessible. This supports a better business case for investing in the technology. E-RTTM systems can be adapted to devices already in­ stalled on a pipeline, as opposed to other systems which require a physical installation. They can also be applied only to critical areas, such as river crossings or in densely populated areas, instead of an entire pipeline. Additionally, as well as leak detection, robust E-RTTM systems will support enhanced theft detection and batch tracking, plus monitoring of tightness and lifetime stress. Batch tracking is an operational benefit which typically relies on time-based estimates. The enhanced system pro­ vides real-time tracking, which makes for better scheduling and use of resources at delivery points or terminals. This is an important benefit for businesses or utilities running tight operations. Small or gradual leaks are often not covered by standard pipeline leak detection systems, as pressure and temper­ ature changes along the pipeline can mask small losses, so basic tightness monitoring requires traditional pressure testing where the pipeline is taken out of service and filled with water. E-RTTM systems offer an alternative to gradual leak detection by using standard pressure and temperature instrumentation. Pipelines are also subject to stress from external influ­ ences, such as temperature extremes, mechanical shock and vibrations, which can have a major effect on their lifespan. Regulations often require operators to document and evaluate these effects. E-RTTM systems include stress monitoring of the pipeline, without the need for human in­ teraction, to provide base data for an assessment of the pipeline’s remaining service life. These results provide for predictive maintenance planning, to ensure the next integ­ rity check happens when necessary and before a critical condition arises. □

Extended Real Time Transient Model, or E-RTTM, leak detection provides for reliable leak detection and more accurate leak location.

For more information visit: www.krohne.com

24 Electricity + Control AUGUST 2021