Fuel management for tugs becoming an increasing challengeMay 2, 2008 12:00 AM
|The Sause Bros. tug Mikiona was designed for fuel efficiency with electronically controlled engines from MTU Detroit Diesel, Reintjes reduction gears, three-blade skewed propellers from Sound Propellers, NautiCan nozzles and NautiCan linked quad rudders. (Ron Karabaich)|
A typical tugboat design includes tankage for 10,000 to 30,000 gallons if intended for local ship-assist work, and up to 100,000 or more if intended for coastwise or offshore towing. On the upper end of the scale, a new 150-foot tug under construction at Eastern Shipbuilding in Florida for Harvey Gulf International will include tankage for up to 250,000 gallons of fuel, according to its designers, John W. Gilbert Associates, Inc. Needless to say, a visit to the fuel pump for any one of these boats can generate a huge invoice from the fuel supplier.
Although in many cases fuel costs are entirely or partly passed on to the clients, the pressure is still there to operate a tug’s engines as efficiently as possible, not only for the sake of fuel economy but also for increased health and longevity of engines and related machinery.
“We have weekly conference calls among all of our operating units, and fuel costs and how they relate to overall net profit is becoming a major topic,” said Marc Villa, president of Constellation Maritime in Boston, a unit of Marine Resources Group (MRG) of Seattle.
Villa, whose company was acquired by MRG in 2006, said he has seen the price of diesel fuel rise from 65 cents per gallon five years ago to $2.28 in mid-April of this year. “When you are buying fuel by the truckload — sometimes several truckloads — this topic becomes increasingly significant,” he added.
Every tugboat company faces this problem, regardless of location and regardless of the nature of its work. Modern tugs, with power ratings of 3,000 to 5,000 hp, burn large amounts of fuel when operating at full rpm — anywhere from 100 to 200 gallons per hour for a harbor tug pushing against a ship, or up to 3,000 to 5,000 gallons per day when towing a loaded barge in ocean conditions. The motivation to reduce fuel consumption does not appear to be a casual, transient interest. While diesel fuel prices may or may not have leveled off at $2 or more (depending on location) in early-summer 2007, few people actually expect them to diminish in coming years. Reduction in fuel use by tugboats, workboats and ships of all sizes is also linked to current efforts by major seaports to reduce port-related air pollution from stack emissions. For example, Foss Maritime estimates that its hybrid-style “Green” tugboat, expected to be built on the West Coast in the next year, will not only come with reduced stack emissions but may also turn in a reduction in fuel consumption by as much as 30 percent compared to identical tugs with more conventional power arrangements.
Typical strategies for fuel conservation include the following:
• Replacing older engines with newer, more efficient engines
• Shutting down main engines as often as possible between jobs
• Using shore power whenever possible between jobs
• Running at reduced speed in harbor situations
• Laying over at nearby piers and docks between ship-assist jobs
• Use of fuel-flow monitoring equipment for wheelhouse and shore-side management
• Education of captains and crews on savings through throttle optimization
• Adoption of streamlined hull design and towing gear, and outfitting a tug with more
fuel-efficient nozzles, propellers and rudders
• Attention to fuel price trends and spot buying opportunities
• Adoption of hybrid propulsion technology for tug fleets
• Use of alternative fuels such as “biofuel”
Chris Rowland, an officer at Wilmington Tug Co., Wilmington, Del., said engine replacement is the primary strategy for fuel savings at his company.
“We are in the ship-assist business and our first strategy has been to make sure that we have all of our engines as modern as possible, and that seems to be working for us,” he said. All but one of Wilmington’s tugs are set up with engines from Detroit DieselÂ (now MTU Detroit Diesel), with the oldest being from 2000 or 2001, he said. The company’s newest tugs are all built with MTU 4000 series electronically controlled engines that come with wheelhouse readouts of fuel burn rate and engine load.
“We try to encourage our captains to maintain an awareness of fuel consumption at all times,” he added. “That applies to how they move around the harbor to throttle settings when responding to requests for pilots when engaged in ship-assist work.
|Rice nozzles on the 3,000-hp tug Treasure Coast operated by Dann Marine Towing. Nozzles can substantially improve fuel efficiency. (Brandon Durar)|
Rowland said that the company’s newest tug, with both engines running full ahead, will burn about 100 to 110 gallons per hour per engine, and less than half of that at reduced speed.
“It’s that last couple of hundred rpm where we see the fuel burn rate maybe double, but we find that we can usually stay away from those levels in most situations,” said Rowland.
Villa, of Constellation, said his crews find it much easier to control fuel burn with a Caterpillar-powered tractor tug than with an older conventional tug, typically with EMD power.
“The electronically controlled Cats are easier as they give the captain measurements in the wheelhouse to see if we are getting an efficient fuel burn,” he said. The 5,000-hp z-drive tug Leo, built in 2006, is the most fuel-efficient in the Constellation fleet, he said.
Villa added that he keeps all of his tugs on shore power whenever they are at the dock, a practice that is easy to accomplish in a small harbor like Boston. “And, whenever the skippers go off to a more distant tug job, we ask them to think in terms of getting out there or getting back at speeds that will give us the best fuel economy.”
Like many other companies, Constellation Maritime passes along a portion of its fuel costs to its customers in the form of a fuel surcharge based on a percentage of the amount billed for a tug job.
Vane Bros. of Baltimore also chose Cat power for its new fleet of wire towing boats and those 3516-B electronically controlled diesels provide helpful monitoring equipment for use by both engineers and captains, according to Jim Demske, port captain.
“It’s a simple system that works,” he said. “We have monitoring control panels in the engine room and in both pilothouses. We also have Kobelt electronic clutch controls that allow our captains to accurately synchronize the engines, while fuel consumption and maximum speed are displayed right in front of them.”
TradeWinds Towing, which operates a single 80-foot tug on offshore assignments on the Gulf Coast and East Coast, reports that it has already achieved roughly 15 percent savings in fuel consumption after a switch this year to a pair of Mitsubishi S12R-MPTK diesels with Reintjes reduction gears. “We heard from a number of people that these were really fuel-stingy engines and so far that is proving to be true,” said Rachel Smith, operating partner with the 2-year-old company. “We are now rated at 2,800 hp with slightly higher speed and the engine room is about 20Â° cooler, which must have a beneficial effect on everything,” she added. “Our older engines were at the end of their lifespan so we had to repower, but choice of engines can make a huge difference in operating economy.”
Smith said that her company’s tug, Miss Liss, typically refuels at supply docks specified by clients that are paying the fuel bill. She added that with the tug engaged in a variety of daily work assignments — everything from standing by and maneuvering barges inshore to offshore towing — it is hard to get a good handle on fuel usage. Without electronic readouts on fuel burn her crews calculate fuel consumption by day tank observation, she added.
While some electronically controlled diesels provide fuel-burn readout, some tug companies are taking advantage of more elaborate fuel management systems provided by companies like FuelTrax, FloScan, Micad Marine or Stellar Marine, among others. These systems provide an array of fuel-related data of use both by the captain with his hands on the throttles and by shore-based vessel and fleet managers hundreds or thousands of miles away. With engine and fuel data transmitted by satellite to data centers and then to easily accessible Web sites, shore managers can tell exactly how much fuel was burned on a particular ship-assist or towing job or which captains or mates tend to operate with what, in an automobile, might be called a lead foot.
“It’s all about throttle optimization,” said Roger DeLaughter of Houston-based Nautical Control Solutions, which markets the FuelTrax system. “In most cases, fuel savings is the primary advantage to our system. “The system analyzes the forces working against a vessel and helps the captain find the point of throttle optimization to achieve the best speed mode or best economy. It usually involves pulling back the throttles just to the point where the vessel can go as fast as possible using the least amount of fuel.”
The 3516B Caterpillar engines on the Vane Bros. tug Choptank, rated at 2,100 hp each, are electronically controlled and can provide fuel-burn data to help the crew optimize fuel usage. (Gregory M. Walsh)
Some fuel management systems take on a more active role, actually taking over throttle management from the captain to achieve maximum economy while still maintaining a desired speed range.
Mark Babcock, naval architect and engineer for Sause Bros. Ocean Towing Co., Coos Bay, Ore., said his company is considering various fuel management systems for its fleet of oceangoing tugboats. “We’ve tested one of these systems and we had good success whenever we had captains who were willing to participate with the system,” he said. “Right now we are working to evaluate different systems, but we know that the key will be in educating our captains and mates to get involved with these systems as they are introduced.”
With Sause’s newest tugs, Babcock said the company has a goal of achieving maximum fuel efficiency while towing a loaded oil barge at a speed of about 9 knots and burning an average of roughly 3,400 gallons per day in open-ocean conditions.
Foss Maritime, based in Seattle, reported recently on tests it made with FloScan Instrument fuel computers in 2002 involving its 4,300-hp coastwise tug Justine Foss. The tug, powered by twin EMD 12-645 diesels, was towing a barge back and forth between Alaska and Washington, burning about 80,000 gallons of fuel for each 2,000-mile round trip. As a result of documented fuel savings from these tests, Foss has outfitted other oceangoing tugs in its fleet with the FloScan equipment, according to company reports. The beauty of these systems is that the tug operator can reach maximum fuel efficiency simply by adjusting throttle settings and noting the effect on a computer readout.
On the other side of the country, Moran Towing Corp. is outfitting half a dozen of its newest tugs with FuelTrax equipment to study the advantages of that system. The latest Moran tug to receive a fuel-monitoring package is the 5,600-hp ocean towing tug Pati R. Moran, expected to be delivered from a Maine shipyard this summer.
This offshore boat, equipped with an articulated coupler system, will have automatic throttle control as part of the FuelTrax system, according to Jim Coyne, vice president of new construction. “The system will automatically keep adjusting the throttles to optimum settings as conditions affecting the vessel, like wind and sea conditions, are regularly changing,” said Coyne. “In many situations our customers are actually paying for the fuel, so we want to do everything we can to ensure maximum fuel efficiency. It’s in everyone’s interest to optimize fuel consumption.”
It may be beyond the means of most tug operators now, but hybrid power is beginning to make its way into the engine room with likely reductions in fuel consumption for successful applications. From a tugboat perspective, hybrid power so far amounts to forms of diesel-electric power with batteries used to store some of the engine power for use when needed.
As of this spring both Foss Maritime and Seabulk Towing said they were working with engineers and naval architects to come up with a hybrid system that could reduce stack emissions and lower fuel consumption. The idea is for an engine room set up with modestly sized main engines, plus a couple of auxiliary power generators, a massive battery bank and a motor-generator on each shaft that can turn the shaft by battery power or allow the main engines to do all or most of the propulsion work.
It looks as though the use of biofuel could soon play a role in many aspects of the transportation world, possibly including tugboats. The use of biofuel mixes is known to have beneficial environmental effects as well as advantages for the reciprocating engines that use it, but whether or not its use results in fuel cost savings has yet to be seen.
Nevertheless, the use of biofuel is seen as part of the formula for the diesel fuel of tomorrow.
A handful of American tugboat companies have experimented with the use of biofuel, even though sources of the fuel are not plentiful.
Pacific Tugboat Services of San Diego, Calif., has experimented with biofuel and is now looking for a way in which it can become a source of the fuel, not only for itself but also for other maritime users in southern California. “It’s rather hard to obtain here now, but we are looking at the idea of having our company somehow becoming a distributor of this sort of fuel to help it get out to the market,” said Steve Frailey, a vice president with Pacific Tugboat Services.
While his company is primarily focused on renewing its fleet engines to attain fuel efficiency, Frailey said they did run some biodiesel through some of their tugs with no ill effects.
“We would continue this if it is affordable and if we can get it delivered. But we can’t spend more just to be green. That would be nice but things are just too competitive around here to be able to do that. It has to be close in price or actually less for it to make sense for us.”
Frailey said his company has been paying roughly $2.40 per gallon for straight diesel fuel over the past year. With prices like those, fuel burn efficiency is certainly everyone’s problem.
When it comes time for total refurbishment of a tug, some companies have elected to add nozzles, high-performance propellers and rudders in an effort to boost bollard pull, speed and fuel efficiency. Companies like Rice Propulsion, Custom Nozzle Fabricators (CNF) and NautiCan Research claim that addition of nozzles and high-performance props can provide multiple benefits, including reduction of fuel consumption by 10 to 20 percent or more.
Penn Maritime recently added NautiCan nozzles and a triple-rudder system to its 126-foot, 4,300-hp tugs Tarpon and Dolphin with a resulting increase in towing speed by about 2 knots with the same oil barge, while simultaneously achieving a noticeable decrease in fuel consumption, according to Penn officials. (Tarpon was refitted with nozzles in 2006, while Dolphin was undergoing these upgrades in a shipyard this past spring.)Edit Module