Above: The Crowley tug Warrior is shown
underway amid sheet ice in Alaskan waters. In recent years Crowley
has been one of the primary marine towing companies involved in
regularly scheduled long distance open water towing with fixed equipment
like container barges, operating on established routes.
This category of tugs includes primarily vessels of convention
tug hull design with sheer but without raised forecastles, that
are equipped with fenders to make them usable in docking operations
if needed, but whose primary function is ocean towing along established
routes. Crowley Maritime is one of the primary operators of tugs
of this type, using them in service from the US East Coast to ports
in the Caribbean, and from the US West Coast to destinations in
Alaska and elsewhere in the Pacific.
These tugs are generally slightly smaller than traditional seagoing
tugs, but have similar range capabilities. They usually are of greater
displacement and have much larger fuel capacities than tugs that
are used in coastal barge towing between destinations within the
United States. In some instances they may operate with notch barges,
but in most operations they are used for astern towing. For this
use they are equipped with large multiple drum towing winches and
are provided with long towing cables.
The typical size range of these tugs is around 140 feet, and the
typical machinery installation is 6000 to 8000 horsepower. They
are almost invariably twin screw vessels for safety and propulsion
system redundancy in long distance open ocean operations. The Crowley
Invader class is typical of this type of tug, having 7000 installed
horsepower and being used in operations on the East and West coasts.
Above: The tug Intrepid is shown underway
towing a pair of large barges astern in San Francisco Bay. This
tug is nearly as long as a World War Two Army LT type, and is capable
of extended ocean towing operations.