STQ saves 45 to 50 litres per hour on each of its vessels

Testimony from Pierre-Paul Desgagnés, Director of Maritime Services at the Société des Traversiers du Québec, cited in Maritime Magazine No. 22.

The first systems we tried were ultrasonic flow meters, back in 1985. That system offered only very poor accuracy. In 1989, a French company replaced our ultrasonic system with its own device, made up of two mechanical volumetric counters (with oval gears) very similar to those found on fuel dispensing pumps. The device had no way of compensating for fuel expansion caused by temperature variations.

Much better results were obtained with this system and, even though we were often led to doubt its accuracy, we kept it for ten years. Many chief engineers, however, were not satisfied with the results. In 1997, STQ decided to install another system aboard the Félix-Antoine Savard, a ferry powered by two Caterpillar 3608 engines. This system uses a wide-tolerance volumetric flow meter, measuring flow at both inlet and outlet. Prototype testing showed the measurement principle was sound, although accuracy did not fully meet expectations.

The engineers then drew up the product specifications: the ability to compensate for fuel expansion caused by temperature variations; the ability to compensate for changes in viscosity; enough clearance that the engine’s fuel supply would not be cut off should a foreign object cause a blockage; solid, robust construction able to withstand the extreme hydraulic pulsations of the engine; simple design and installation; sustained accuracy and reliability. The real difficulty lay in neutralising the effects of temperature variation, and the only way to achieve this was through intelligent microprocessor-based sensors. Field testing began in 1994, in partnership with the Northwest Territories Power Corporation (SETNO). The flow meters, sensors and calibration techniques all had to be modified to improve the system’s accuracy and reliability.

During the Félix-Antoine Savard’s early voyages, the device made it possible to determine the load delivering the best energy efficiency. Results were compared at 85% and 95% of maximum continuous power (MCP). At 85% MCP, surface speed was 15.5 knots, against 16.5 knots at 95%. The differences in fuel consumption were dramatic: that 10% gap allowed savings of roughly 100 litres per hour per engine. In other words, one extra knot of speed costs 200 litres an hour! Without this new technology, measuring that increase precisely would have been impossible.

Following the initial success of the Félix-Antoine Savard, STQ purchased devices for four more vessels. Efforts then focused on working with the officers: each would log total consumption for their watch in the ship’s logbook. Officers compared their respective results over set periods and, using the system’s data, collectively developed strategies to optimise consumption without compromising safety or reliability. They embraced the approach without reservation and set themselves realistic short- and long-term consumption targets.

Since then, STQ has averaged savings of 45 to 50 litres per hour on each vessel thanks to the system. STQ’s vessels run 5,000 service hours a year… on a conservative 45-litre reduction, that means 225,000 litres saved per vessel, or $48,375 a year.

STQ’s officers are now thoroughly comfortable with the system and confident in its performance and accuracy. The next step is to introduce preventive maintenance based not on service hours but on fuel consumption — the best indicator of an engine’s work.

Last winter, an incident aboard the Jos Deschênes helped diagnose a problem. The chief engineer had replaced an injection rack sleeve on one of the engines. The captain, unaware of this, noticed that the engine’s consumption — normally 295 litres per hour at the standard throttle setting — had dropped to 276 litres per hour, while the other engine remained at 295. Closer investigation revealed low exhaust temperature and low boost pressure. The chief engineer re-examined the sleeve he had fitted and found the rack needed adjusting. He used the fuel consumption monitoring system to make the adjustment, and exhaust temperature and boost pressure returned to normal. This anecdote confirms how useful the system is.