Integrating energy savings and engine protection

Sep 02 2014


Though fuel-saving practices such as slow steaming are widespread, energy efficiency continues to be a pressing concern. Vessel fuel bills remain high – and will likely become even higher for those sailing in ECAs after January, 2015.

Catastrophic engine damage due to cat fines is also on the rise, along with safety worries related to multi-fuel operation. Yet in the face of these complex and interrelated issues, the Alfa Laval adaptive fuel line offers new levels of savings and protection, the company claimed.

Fuel costs, emission legislation and cat fine difficulties are all deeply intertwined. With HFO already at a premium, everything possible is being done to enable slower steaming and reduce fuel consumption.

Meanwhile, emission legislation is forcing the use of even more expensive distillates, as well as the use of low-sulphur HFO. The fact that the latter has a higher average cat fine content can be tied to a growing number of cat fine attacks, which have increased despite the revision of ISO fuel specification 8217 to a 60 mg/kg Al+Si limit.

“Part of what we’re seeing is a consequence of the effort to curb emissions, which is making traditional fuel cleaning even more demanding,” said Niclas Dahl, Alfa Laval market unit manager, marine energy. He referred to a recent study by Man Diesel & Turbo’s PrimeServ, in which cat fines had a proven role in 84% of 226 investigated cases of poor engine cylinder condition. “These cat fine attacks are an energy issue, as well as a safety concern, because the wear deteriorates engine efficiency even if it doesn’t lead to catastrophic failure.”

“When it comes to the fuel line, energy efficiency and protection are often two sides of the same coin,” said Dahl. “Our R&D has therefore focused on using the synergies that exist. Through a combination of new thinking and new technology, we’ve created a truly adaptive fuel line that saves energy as well as the engine.”

There is much that can be done to optimise individual fuel line components, such as choosing separators with Alcap functionality.

Much can also be done with the fuel line construction to prevent cat fine attacks, such as ensuring that tank floors are slanted and that return pipes extend from the tank bottom rather than the top. According to Dahl, however, “Finding large-scale energy benefits and really maximising protection requires looking further than traditional component roles.”

Alfa Laval’s recently launched FCM One booster, Dahl said, is an excellent example of such thinking. “The FCM One goes beyond traditional booster capabilities, including those of our original fuel conditioning module,” he explained. “It works with multiple fuels, reacts to multiple parameters and handles multiple levels of information, which gives it a much broader influence on the fuel line as a whole.” The Alfa Laval adaptive fuel line saves energy and improves protection by four distinct means- feed optimisation, system supervision, multi-fuel management and waste fuel recovery.

Since the adoption of slow steaming, most vessels spend little time at full engine load.

Nonetheless, fuel lines are constructed and operated as if full load were the norm. “This is an opportunity missed and not only because feed pumps and separators that run on full consume unnecessary energy,” said Dahl.

“Decreasing the flow rate through the separator increases the time the fuel spends within it, which improves the removal ofparticles.”

This is the principle utilised by FlowMate, a new Alfa Laval system that adjusts the flow of fuel to match the engine load. “By using automatic control and variable frequency drives to reduce the flow at partial load, we make use of the available synergy,” Dahl said.

“The principle is obvious. Why use more energy for fuel cleaning when using less energy will mean even better cat fine removal?”

In addition to FlowMate, the Alfa Laval adaptive fuel line has dedicated heater control that keeps the fuel’s temperature at the recommended 98 deg } 2 deg C. “This parameter is surprisingly overlooked on board,” said Dahl. “Without proper control, the fuel temperature can easily drop to 85 deg C, which necessitates a 40% flow reduction to maintain separation efficiency.”

Even when the flow is optimised and separation efficiency is high, spikes in cat fine levels are impossible to rule out. In rare cases they may be caused by off-spec fuels, though they are more likely to occur when latent cat fines in the tanks are stirred up by rough seas.

Preventing such attacks from damaging engine cylinders is essential, because damaged surfaces reduce combustion efficiency and may eventually result in engine failure.

To keep cat fines from entering the engine, another new system is incorporated into the Alfa Laval adaptive fuel line - Catguard. This measures cat fine levels at several pre-engine sampling points, warning of any elevation.

Such real-time measurement enables crews to take immediate countermeasures, as well as to trace the root causes of the problem.

A similar function is provided by the FCM One, whose engine-specific monitoring of fuel consumption takes into account the pulsations of the fuel injection system. “While not a measurement of engine efficiency per se, the monitoring of fuel consumption quickly indicates when efficiency losses occur,” said Dahl. “Like Catguard, it allows immediate action to be taken and root causes to be traced.”

The FCM One has yet another important role in the adaptive fuel line, especially for vessels that will sail in ECAs. When multiple fuels are used on board, it safeguards fuel changeover and enables automatic blending for an economical match of a given sulphur target.

“Multi-fuel operation creates difficulty for operators, since residual and distillate fuels have very different characteristics,” said Dahl.

“The changeover between fuels must be well controlled, especially when it comes to viscosity, or there will be alarms and delays that result in more burning of expensive distillate.”

One System

Sophisticated automation and temperature control are central to an energy-efficient changeover. The FCM One uses one controller, a single algorithm and integrated cooling to keep viscosity within a tight range – even when changing between different fuel blends.

“The FCM One puts everything into one system, including the option of an electronic fuel record book to prove ECA compliance,” said Dahl. “ That means uninterrupted transitions where less distillate is consumed, even when there are changes in engine load.”

Feed optimisation, system supervision and multi-fuel management – combined with individually optimised components – create a fuel line that truly adapts to changing conditions. This in itself saves a great deal of energy, even as it provides better protection for the engine.

What remains is to recoup the small losses that occur at various points in the system, which account for 0.5 to 2% of a vessel’s total fuel consumption. In this respect, PureDry is the crown jewel of the Alfa Laval adaptive fuel line, as it allows virtually all of this oil to be recovered with ISO 8217 quality. At present, PureDry is claimed to be the only equipment capable of recovering the HFO fraction of waste fuel oil in accordance with MEPC.1/Circ.642.

“PureDry is a unique and long-awaited opportunity for shipowners and operators, since it lets them get the maximum amount of energy from the fuel they bunker,” said Dahl. “All that remains is bilge-quality water and a tiny fraction of super-dry solids, because everything else is returned as reusable fuel.”



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