In its Ocean class, Crowley sets a new standard for offshore towing

Jul 7, 2012 02:38 PM
The 146-foot tug is the first of four Ocean class tugs built for Crowley.

The 146-foot tug is the first of four Ocean class tugs built for Crowley.

Responding to market expectations, Crowley Maritime, in conjunction with its subsidiary in Seattle, Jensen Maritime Consultants, has designed and engineered the Ocean class tugboat.

Bollinger Marine Fabricators, in Amelia, La., was awarded the contract to build four of the vessels. The first, Ocean Wave, was delivered in May. Ocean Wind, Ocean Sky and Ocean Sun will follow.

“Our 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,” said Ed Schlueter, recently retired as vice president of vessel management services for Crowley, which is based in Jacksonville, Fla. “So we picked 150 metric tons of bollard pull as the goal to shoot for.” In the end, the 146-foot, 10,880-hp tugs are expected to achieve 165 tons of pull.
 

Workers spooling 4,200 feet of 2.75-inch wire onto the Intercon double-drum waterfall winch.

The tugs are ideally suited to work with Crowley’s new 455 series of heavy lift barges that were built at Gunderson Marine in Portland, Ore., but Dan Babcock, manager of business development at Jensen, said they are outfitted for rig moves, oil field support, emergency response and firefighting.

The original deployment for the tugs is in the Gulf of Mexico, but the boats are classified A-1 Towing, FiFi-1, ABS, SOLAS and have an International Load Line Certificate. “They’re capable of worldwide operation,” said Eric Blumhagen, manager of naval architecture at Jensen.

The power behind Ocean Wave comes from two Caterpillar C280-12 Tier II light-fuel diesels with Reintjes LAF 5666 reduction gears and 153.5-inch, four-blade Cunial (an alloy of bronze, nickel and aluminum) CP propellers.

Enough room has been designed into the stacks of the Ocean class tugs so that the Caterpillar engines can be upgraded to Tier III and Tier IV as the technology and equipment become available to meet more stringent emissions regulations.

“The bollard pull/engine power is the starting point for just about every tug design,” said Blumhagen. “Then you build out from the engine, propeller and winch to meet your other requirements.”

Intercontinental Engineering (Intercon), of Kansas City, Mo., built a new winch system for the Ocean class tugs based on its 600-hp hydraulic DW275 double-drum waterfall winch. The new winch has the heavier towing drum on the bottom instead of its typical position as the upper drum, thereby lowering the vessel’s center of gravity and increasing the tug’s stability.

The winch, with a pulling power of 500,000 pounds, weighs 114 tons. It holds 4,200 feet of 2.75-inch wire on the towing drum, and 3,000 feet of 2.25-inch wire on the upper drum. The wire on the towing drum is under-wound as opposed to the typical over-wound wire on a standard unit. The change places the towing wire closer to the deck, resulting in a straighter vertical lineup with the shark jaws and towing pins. “So there is less load on the pins and less chance of the wire jumping out of the pins or the shark jaws,” said Blumhagen. “That really improves safety and it helps with the stability of the boat.”

A waterfall winch also has the wire running straighter off the drum than a side-by-side drum winch does, making for a better lineup with the shark jaws and towing pins that straddle the centerline of the aft deck.

With each vessel, Intercon is also supplying an ESW-125D windlass mooring winch and a 21-inch capstan for the bow. Another modification, primarily as a safety measure to keep crew off the deck and therefore away from the wire under tension, is the installation of wheelhouse winch controls that also have a touch-screen information panel.

One of the monitors that are part of the FiFi-1 firefighting system. Pumps and montiors are from FFS.



The system allows the operator to control the winch, shark jaws and towing pins from a safe vantage point. The emergency stop controls are close at hand. “We’ve done a lot of work on improving sightlines, making sure that the operators can see as much as they can so that they’re never operating blindly,” said Blumhagen.

A 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 local controls. For miscellaneous rigging tasks, a separate independently-driven shaft turns an auxiliary drum on the port side and a capstan on the starboard side.

“We did everything we could to minimize the amount of time the crew would have to be working on deck,” said Blumhagen. “We also put a covering on the winch so if the crew is working at the winch, they are in a sheltered location so they are not going to be hit by waves or put into danger.”

The Ocean class tugs are double-hulled and designed to prevent any overboard discharges of fuel or fluids. They also carry a Green Passport, which is a document developed by the International Maritime Organization that contains an inventory of all the materials used in the construction of a ship that are potentially hazardous to human health or the environment. At the end of the vessel’s working life, the scrap yard or recycling yard can then use the passport to determine the proper disposal or recycling of the materials.

In-Mar Systems of Gonzales, La., the company that supplied the Norwegian-manufactured Triplex shark jaws and towing pins, also supplied the FiFi-1 firefighting system, made by FFS, also in Norway.

The pumps are clutched in and driven off the crankshafts of the main engines.
 

One of two Cat C-280-12 Tier II 5,440-hp main engines with Rientjes gears.

The electrical requirements on Ocean Wave are provided by two 1,475-kVA shaft generators running off the mains. The tug also has a 340-kW Caterpillar C-18 Tier II harbor generator and a 125-kW Caterpillar C6.6 Tier II emergency generator.

There is a 5-ton crane on the aft deck and a 2-ton crane on the forward deck.

Ocean Wave and Ocean Wind are DP-1 tugs, while Ocean Sky and Ocean Sun will be DP-2, a level of station keeping that is currently expected in the Gulf of Mexico. “That was a response to customer demand for DP-2 qualified vessels in the offshore oil and gas business,” said Blumhagen.

The latter two boats will be 10 feet longer than the first two and will also have more electrical power from the shaft generators. In addition they will have two Berg electric VFD 500-hp bow thrusters and a Berg 500-hp stern thruster. (The DP-1 boats have one Berg electric VFD 850-hp bow thruster.) The extra length was needed to accommodate all of the extra gear to support a DP-2 boat. In the process, the upgraded boats were also able to increase their fuel and water capacities.

Robert Sauce, of Coastwide Electronics, works on the aft console.  Putting the winch controls in the wheelhouse protects the crew by keeping them away from the wire under tension.



Ocean Wave has accommodations for 13 people in quiet, two-person staterooms. The quiet is achieved by soft-mounting the engines to minimize vibrations through the hull. The engine room is also heavily insulated for noise with a floating floor immediately above the engines.

“We put a lot of effort into crew comfort, which ties into safety because you have a rested crew,” said Blumhagen. “The crew can sleep well because their quarters are quiet, and you end up with a safer boat.”

Following years of success with their Invader class tugs that ply the West Coast up to Alaska, Crowley expects the new vessels will establish the company as industry leaders for many years.

“We’re looking to the Ocean class to be our signature boat for the next 30 years,” said Schlueter.

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