With a minimum of 150 metric tons of bollard pull and an Intercon towing winch with 500,000 pounds of pulling power, Crowley Maritimeâ€™s new Ocean-class tugs are designed for the future.
The company, based in Jacksonville, Fla., expects the new vessels to establish Crowley as industry leaders for many years.
â€œOver the lifetime of the boats, they will be towing anything and everything that anyone wants to move to wherever,â€ said Ed Schlueter, vice president of vessel management services for Crowley.
The first two of the 146-foot, 10,880-hp tugs, Ocean Wave and Ocean Wind, are scheduled to be delivered from Bollinger Marine Fabricators in Amelia, La., in late 2011 and early 2012. Two additional vessels, Ocean Sky and Ocean Sun, have been added to the contract.
|The Crowley Ocean-class tugs (facing page) will each have an Intercon double-drum, reverse-waterfall winch, which will provide a lower center of gravity and increased stability. (Photo courtesy Crowley Maritime Corp.)|
â€œOur customers are looking for a minimum of 120 tons of bollard pull for their drilling rigs and barges and whatever else that they would want to tow,â€ said Schlueter. â€œSo we picked 150 metric tons of bollard pull as the goal to shoot for.â€
Regulation has become a growth industry, it seems, so predicting and designing propulsion, safety and environmental systems that will be compliant over the years is difficult. The Caterpillar-powered vessels will be Tier 2, as required now, but they are configured to allow for upgrading to higher tiers as regulations are stiffened in the future.
â€œWhen you look back at the environmental concerns we had 25 years ago,â€ said Schlueter, â€œand you fast forward to today and think of what it might be 25 years from now, itâ€™s just going to be staggering.â€
The vessels will also be double-hulled and designed to prevent any overboard discharges of fuel or fluids. They will be DP1 and FiFi-1, as is becoming expected in the oil field service market.
â€œCrowley really stresses safety,â€ said Steve Rheams, Gulf Coast marketing and sales manager for Intercon. â€œAnd they are really striving for cleanliness. They really want these boats to be green.â€
Crowley chose Intercontinental Engineering-Manufacturing Corp. (Intercon) for the winches. The company is based in Kansas City, Mo. â€œWe have a very good history with Intercon and we feel very comfortable with them,â€ said Schlueter.
â€œWe are one of the last surviving manufacturers of deck machinery that is still designing and building in America,â€ said Rheams.
Interconâ€™s president, Brian Everist, has made a conscious decision to continue to operate from the heartland of America, according to Rheams.
Each Intercon ship-set will consist of a model DW275H double-drum, reverse-waterfall-style towing winch for the stern and an ESW-125D windlass, mooring winch and 21-inch capstan for the bow. In-Mar Systems is supplying Norwegian-built Triplex shark jaws and towing pins. The Gonzales, La., based company is also supplying the FiFi-1 firefighting systems, also manufactured in Norway by FFS.
Crowley chose a waterfall winch instead of a side-by-side winch because the wire runs off the drum at a straighter line through the shark jaws and towing pins straddling the centerline of the aft deck.
â€œWe wanted to reduce that angle considerably and the waterfall winch does exactly that,â€ said Schlueter.
The choice to go with a reverse-waterfall winch instead of the standard double-drum waterfall winch was to lower the vesselsâ€™ center of gravity (VCG). The winch, with wire on both drums, weighs 114 tons. The towing drum, with 4,200 feet of 2.75-inch wire, weighs 29 tons, while the 3,000 feet of 2.5-inch wire on the second drum weighs 17.5 tons.
On a typical waterfall winch, the towing drum is above the lighter drum. The reverse waterfall winch flips that weight distribution, thereby contributing to a lower VCG. The reverse waterfall is also under-wound as opposed to over-wound on the standard unit. The result is that the wire runs off the drum closer to the deck, effecting a straighter vertical lineup with the shark jaws and towing pins.
â€œThe reverse winch in the towing mode adds considerably to the stability of the boat,â€ concluded Schlueter.
â€œWe designed the winch specifically for these vessels,â€ said Rheams. Although the design is based on Interconâ€™s 600-hp hydraulic DW275H double-drum waterfall winch, they performed some heavy modifications, not the least of which was reversing it.
Another modification is the installation of wheelhouse winch controls with a touch-screen information panel. The system allows the captain or operator to control the winch, shark jaws and towing pins from a safe vantage point and eliminates the need to have crewmen in harmâ€™s way on the aft deck, especially in heavy seas and inclement weather. The emergency-stop controls are close at hand.
â€œWe really feel that the captain has got to have complete control over the vessel and the wire,â€ said Schlueter.
The touch-screen panel indicates such data as static and dynamic wire load, the speed and amount of payout and rewind load, the wire slippage and hydraulic pressure amounts and an alarm for both. There is also a set of controls on deck, local to the winch.
For miscellaneous rigging tasks, a separate independently driven shaft turns an auxiliary drum on the port side and a capstan on the starboard side.
The bow unit is a combination of windlass, mooring winch and 21-inch capstan. The wildcat is sized for 1.25-inch chain, and the mooring winch drum takes up to 600 feet of 1.25-inch soft line. It is electrically powered. However, a variable frequency drive (VFD) unit, installed in a cabinet below deck, affords the vast range of control similar to a hydraulic system.
There are two sets of controls for the unit, one local to the winch and the other mounted in the wheelhouse. An emergency backup switch can be employed to bypass the VFD panel and operate at reduced power.
Seattle-based Jensen Maritime Consultants, a subsidiary of Crowley Maritime, worked with Schlueter to design the Ocean-class tugs. Schlueter said that the tugs are ideally suited to work with Crowleyâ€™s new 455 series of heavy lift deck barges being built at Gunderson Marine in Portland, Ore., but they are designed as overall general-purpose vessels, outfitted for rig moves, oil field support, emergency response and firefighting.
The original deployment for the tugs is expected to be in the Gulf of Mexico. â€œBut over the lifetime of the vessels, they could be anywhere in the world. There are no restrictions on the boats at all,â€ said Schlueter.