Big Motor Problems
By John G. Denham
I am impressed with the significant improvements that large diesel engine manufacturers are making in reducing offensive emissions, improving operational efficiency and cutting costs. When the “Firecracker Engineers” put their mind to it, it happens. Government is putting a lot of pressure on engine exhausts; the bigger the engine the more political pressure. Owners want more speed and efficiency and less cost. I have not observed any government involvement except to increase standards. The diesel engine manufacturing guys have addressed faster, more powerful, cleaner, efficient and less costly engines admirably, but there is another problem that effects operations: minimum speed.
The minimum speed limitation is an operational safety factor when maneuvering in confined, congested and special maneuvering areas. Rule 6 of the International and Inland Rules:
“Every vessel shall at all times proceed at a safe speed…” A gold mine for maritime lawyers.
The Pacific Maritime Magazine May 2008 issue’s feature article “Large Marine Diesel Engines” exemplified:
“APL recently ordered eight MAN B&W 14K98ME-C7 two stroke low-speed crosshead engines …will generate 115,000 bhp at 105 RPM …to be installed in eight new 10,000 teu container ships.”
As advertised the operating range of similar behemoths maybe as low 45 RPM and as high as 120 RPM. With direct drive and an efficient propeller the probable minimum speed may be 5.0 knots. Persons piloting such vessels may need to stop and start the engines any number of times due to circumstances; the engines are usually started with compressed air. Therefore knowing the quantity of consecutive start and stops is essential as an operating factor. There are two navigation considerations that must be resolved while en route: the safe speed of advance and the hydrodynamic effect of the vessel’s movement; the greater the speed the greater the effect. So far, ship handlers have developed procedures to reduce the speed of advance but as the engines become more powerful the solutions will be less effective.
While transiting a narrow channel there are three sub-factors involved that need to be considered to safely proceed: the bow wave, suction effect and the wake; all relate to speed and displacement. The details and an excellent explanation are provided in Caryle J. Plummer’s “SHIP HANDLING IN NARROW CHANNELS; Cornell Maritime Press.
Large direct drive diesel ships may have as many as 10 or 12 consecutive starts if the propeller is free rotating, but less if backing (need more air). Of greatest concern is an emergency full astern from full speed ahead; the air pressure may not be adequate to counter the propeller rotations.
Therefore, the ship owner must not only consider the environmental impact and economical advantage, but the cost of additional tugs and support services when entering congested and confined water. JGD.
John Denham is a retired USN Captain, Licensed unlimited Master and Pilot, maritime academy teacher,and author with extensive experience as a marine consultant. He writes for Pacific Maritime Magazine and is the author of The Assistant and DD 891.
Tags: · emissions, Engines, john denham
Photo by Seth White
The New York Times has the story on a California petition to limit ship emissions:
The California attorney general and a coalition of environmental groups have called for federal regulation to curb heat-trapping emissions from the worldwide fleet of about 90,000 oceangoing ships, including container ships, tankers and cruise ships.
The regulations, sought in separate petitions to the Environmental Protection Agency, would apply to United States territorial waters.
Only six countries generate more emissions of greenhouse gases than the world’s oceangoing vessels, said Michael Hirshfield, a senior scientist with Oceana, an ocean-protection organization.
The group’s petition, whose participants included the Center for Biological Diversity and Friends of the Earth, argues that “the sheer number of these ships, coupled with operating practices that use fuel inefficiently and poor government oversight, results in carbon dioxide emissions” equal to the emissions of 130 million to 195 million cars. Continue Reading….
Joe Angelo, the deputy managing director of Intertanko, a group representing independent tanker operators, said the best approach was “to reduce emissions worldwide — universally — not just unilateral action in the United States or the European Union.”
INTERTANKO’s solution? Here is a report from their June 2007 study on emissions:
The environmental footprint of ships, which carry 90% of world trade covering over 30,000 billion tonne-miles a year, is extremely light compared to other forms of transport. And yet despite the industry’s tonne-mile efficiency, it has been left behind by other sectors which are already regulated and compelled to use clean, environmentally friendly fuels. This means that the shipping industry has become an easy-to-pick fruit, recently targeted by politicians eager to show that they are still doing something on the environmental front.
A switch from residual fuel to marine diesel oil (MDO) means a comprehensive and practical strategy for an efficient and long-term reduction of air pollution from ships. Should one expect ships to reduce air pollution while still burning residual fuels? These fuels have a significant content of sulphur, nitrogen (that contributes to the NOx emissions and thereby ozone or a greenhouse gas), hazardous components including heavy metals and polycyclic aromatic hydrocarbons (PAH) that combine to create a cocktail of particulate emissions and generated sludge
The proposal that the shipping industry switches to distillate bunker fuel (MDO) according to a timescale that takes into account fuel availability, delivers immediate, real and global reductions in atmospheric pollution (SOx, NOx and PM). It deals with the cause of this pollution rather than the effect – i.e. rather than limiting the rulemaking development to cleaning up the pollution itself. These are among the reasons that this proposal has been gaining support from a number of IMO states – including Norway.
This seems to be in contrast with the California petition which calls for elimination of bunker fuel and a proposed reduction of vessel speed by 20%. Considering our industry lives by the motto “Time is Money” it’s not surprising that INTERTANKO is looking for alternative solutions or fighting any actions that would mandate speed reductions. I may be stating the obvious but wouldn’t speed reductions increase the demand for hulls? Wouldn’t this be in the interests of an organization of ship owners?
This debate is destined to expand in direct relation to the growth of our global warming problems. When the argument is settled, whether by the EPA or IMO, I doubt the solutions will be those suggested in the petition or by INTERTANKO but I’m hopeful the coverage will increase awareness and development of workable solutions… that is if the press can avoid misleading and counterproductive headlines like THIS.
CLICK HERE for Maritime News Discoverer stories on Vessel Emissions.
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Tags: · california_attorney_general, carbon_dioxide_emissions, emissions, Environment, environmental_protection_agency, friends_of_the_earth, global_warming, greenhouse_gases, intertanko, marine-pollution, Maritime, marpol, new_york_times, oceangoing_ships, petition, shipping-industry, Ships
