Quantity
Detecting bubbles New technology applied to the bunker industry can overcome issues caused by entrained air, says Michael Murphy, managing director, Pacific Rim, for CiDRA Corporate Services
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nsuring that the correct quantity of bunker fuel has been loaded has become a critical operational management concern for ship owners, and this has primarily been driven by the unpredictable cost of oil and the need for ship operators and owners to be competitive. Ensuring the accuracy of bunker supply has seen new techniques being developed by the industry, which has traditionally relied on tank dipping/ ullage measurement, as well as more sophisticated inline mass and volumetric solutions. Certainly, inline measurement has its advantages, but even that may be subject to error, particularly through the presence of entrained air (or gas), which can distort the volume received and measured. As an example, air can enter the fuel through a range of pumping processes, but its presence can be measured and offset (if present) through real-time monitoring and alarm. The SONARtrac flow platform is such an inline measurement system. It has the ability to detect the presence of entrained (usually unseen) air from as low as 0.01% through to gross bubbling at 10%-20% air/oil content. This is detected and measured by the SONARtrac system in real time. SONARtrac systems offer the unique
World Bunkering Spring 2014
ability to provide an ‘air alarm’ during a bunker loading process, so empowering the receiving crew to act and request preventative action from their suppliers. They also have an accurate totalising function – to confirm the actual volume of air (or gas) delivered to the ship’s bunker tanks as part of the fuel load. SONARtrac’s air measurement capability principally exploits the speed of sound (SOS) dependence with air (or gas) in fluids. Within the SONARtrac sensor is a passive acoustic array, which detects separate sound signatures and tracks these in the space and time domain as they propagate through the bunker fuel during loading. This SOS measurement technique is similar to that used in SONAR towed array systems in submarine warfare, so the physics is well proven and understood. Principally there is a logarithmic dependence of SOS with entrained air (or gas) content, which the SONARtrac system correlates, measures and displays in real time – simply put, the less air the faster the SOS and the more air the slower the SOS. This logarithmic dependence means extremely high sensitivity and accuracy over large dynamic percentage ranges of entrained air. SONARtrac is a well proven solution in other harsh operating environments
and industries, which includes mining and the offshore oil and gas industries, and has a high reliability, since it is clamped externally onto the pipeline and has no moving parts. Weighing less than 10kg, the installation of the SONARtrac system typically takes less than one hour, and the unit can be powered by a range of AC/DC supplies readily available onboard ship. For more sophisticated management systems, the SONARtrac system can be integrated into a shipboard control room distributed control system (DCS) via a range of supported electrical interfaces and protocols. The shipping industry spends many billions of dollars each year on bunker fuel, and the port of Singapore alone is reporting a spend in excess of $40 billion per year. Indeed, single shipping companies can easily expend upwards of several billion dollars per year on bunkers, so even the detection and correction of entrained air content of just a few per cent could lead to significant operational savings. SONARtrac technology is here to help the industry, as well as port authorities, to protect fuel investments and bring improved operational performance through the detection and measurement of entrained air in bunkers.
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