Tuesday, July 3, 2012

Advances in Technology for Deck Machinery

By Kathy Smith
July 2012

State-of-the-art deck machinery and cordage is found in more segments of the maritime industry, including tugs and research vessels. Whether connecting tugs and barges, launching and retrieving scientific research packages from the pitching deck of a research vessel or tethering an escort tug to a fully-laden tanker, deck machinery continues to make great technological leaps.

Coupling Tug and Barge
Missouri-based Intercon is supplying Crowley Maritime’s new Ocean Class tug building program with their DW275 European-style reverse waterfall winches. Allen Craft, Senior Vice President says, “The main idea behind a reverse waterfall is to lower the towing drum and center of gravity, which improves vessel stability.”

The hydraulically-powered 520-HP winches have 500,000 pounds of line pull. The towing drum holds 4,200 feet of 2 ¾-inch line, and the secondary drum holds 3,000 feet of 2 1/2-inch line. The auxiliary drum holds 300 foot of 1-inch line. Craft says the control is state-of-the-art. “They have touch screen control in the wheelhouse and a local station. In addition to controlling, they are also able to monitor static and dynamic line tension and line speeds, plus the amount of wire out.”

The Crowley tugs are 49.3 meters long, with a 14 meter beam, 10,880 HP and a offer a bollard pull of 150 metric tons. Intercon’s contract is to supply winches for four newbuilds.

Craft reports that Intercon’s tug/barge coupler system has been gaining more interest as the petroleum industry looks to more worksafe options. “It eliminates the need for conventional deck machinery because the tug is actually pushing a petroleum barge rather than towing it,” he says. “Our customers like the safety of the positive connection to the barge rather than it being at the end of a tow line.”

As Craft explains, there is a notch in the stern of the barge that the tug goes into bow first. The tug rams extend out and engage into the sides of the notch and are the only part touching the barge. The tug can pitch, but every other motion of the tug is echoed by the motion of the barge.

“Must less time is wasted waiting on weather, and fuel economy is improved when pushing,” he says. “The crews also prefer the stable ride that results from the tug following the motion of the barge. The benefits have resulted in many repeat customers.”

Because the tugs are dual-mode certified, they can be used as conventional tugs or in the pushing ATB capacity, and the couplers are installed below deck. Intercon provides two coupler rooms with all the machinery installed, which can be fit into new or existing tugs.

Precise Package Delivery
The US Navy’s Office of Naval Research has two new AGOR class research vessels under construction in Anacortes, Washington and Seattle-based Markey Machinery will be providing their new CAST6 deep-sea research winches for these vessels.

Markey’s research winch, the CAST6, will spool fragile fiber-optic cable up to 0.393 inches in diameter and 10,000 meters in length. As Markey’s Oceanographic Winch Sales specialist John C. Davis says, “An increasing number of the operators of these vessels are looking at ways they can reduce the stress and strain on their wires and cable. Our systems offer specialized motion compensation control to compensate for the motion of the ships and reduce the stress and strain that they are subjected to.”

He explains a sensor known as a “Motion Reference Unit” (MRU) measures the heave, pitch and roll of the vessel using accelerometers. The output from the MRU is plugged into a “Program Logic Controller” (PLC), which controls haul-in and payout in response to the MRU output, based on the motion of the vessel. The result is that the science package at the end of the cable is effectively decoupled from ship motion. The system can operate up to sea state 5 conditions.

One of the unique features of the CAST6 winch is that it can handle several different overboarding machines and easily accommodate a variety of different diameter wires or cables. “Our level wind system is controlled by programmable electronic touch screen,” Davis says. “It is driven by a 10hp vector-duty motor and simply by the push of a button, you can easily change from a wire size of .322 inch diameter cable (the standard for deep sea research) to a different size cable.

Engineer Peter Petrov adds: “The main design point of this machine is to keep it very simple and highly optimized for low inertia so we can quickly go in a reverse direction to accommodate for the motion compensation. Even though control of the machine is mechanical, it is very highly programmable, and with that, naturally comes the ability of changing wires, removing the whole drum, replacing a new drum in the place of the old one, and with just a push of the button, the spooling mechanism knows to change the wire and quickly adapts without changing the mechanical parts.”

The output sheave of the level line is mounted inside of a flagging block that allows the operator to reeve the cable to different overboarding points without any intermediate turning sheaves or fairleading blocks of any kind. This has a dramatic time-saving advantage when a research vessel is preparing to depart port on a new research mission. “There is also a lower turning sheave that is instrumented for scope counts and tension that provides output to the wire rope monitoring system that feeds into a shipboard-wide instrumentation system.”

Davis reports that unique operator controls provide a link between the onboard research cranes and the Markey winches, allowing the safe launch and recovery of packages over the side of the vessel.

Allied Systems is manufacturing a set of cranes with docking heads that will eliminate the need for crew to use tag lines to steady the equipment as it elevates off the deck and is deployed under water.

“This deep-sea line borrows proven Render/Recover® controls from Markey’s hawser line of winches to reliably secure instruments to a specialty docking head using cable tension alone. Secured by the CAST6, a crane launches or recovers the instrument without the need for tag lines, allowing operations to proceed in deteriorating sea states,” Davis explains. “By removing those ‘hands’ from the deck, you improve the safety of operations. It’s a specialized integration, the winch and crane create an effective handling system. That’s another advancement that the CAST6 winch provides in relation to previous versions of Markey’s legacy deep-sea research equipment.”

The trend toward electrically driven winches is very apparent onboard ships in the United States academic research fleet. “They are more highly efficient, there is less maintenance involved, and interfacing them to the electronic digitally programmable controls makes the entire system seamless from operator to package,” says Davis. “You consume less energy and that means there are fewer emissions and pollutants. As well, you don’t have to dispose of hydraulic oils so you are handling less waste.”

Strong but Soft
Keeping mooring and tug lines working safely and securely is what Washington-based Samson Rope has been doing for more than a century, and they continue to develop new products for today’s market needs.

“We’ve spent a lot of time going to the market and finding out what the needs of our customers are and then spending time trying to develop something different,” says Terry Crump, Director of Sales for the Americas. “We’ve been handling high-modulus polyethylene fiber (HMPE) for longer than most companies and we’ve developed some methods of manufacturing it that enable safe operations.”

In fact, company technicians spend a lot of their time in the field on vessels or in shipyards showing crews how to handle and splice ropes, and generally how to deal with them on a daily basis to get a good safe service life out of them. “That hands-on experience has really paid off,” adds Crump. “And over time, we will go back to the vessel and inspect the lines to see how they are doing and perform residual strength testing. We’ve gotten a lot of positive industry feedback from companies like British Petroleum, Alaska Tanker and Shell.”

Samson has provided several of Shell’s LNG carriers with Amsteel®-Blue made with Dyneema® (HMPE) and is readying to supply mooring lines to Chevron as their current newbuild LNG program continues.

One of Samson’s newest tug line products is called Saturn-12, a line made with Dyneema® which can increase residual strength up to 15-20 percent. “It has a coating that we put on it that really enhances the yarn-on-yarn internal abrasion, and tug companies like Crowley and some of the companies down in the Gulf, G&H Towing and Moran are starting to use it,” Crump reports. “They are seeing a much longer service life, and the higher residual strength gives them a greater degree of safety when they are handling big tankers.”

Dyneema® fiber is also used in Samson’s Dynalene product that also helps with abrasion challenges. Dynalene is permanently spliced over the rope, acting as a cover and is easily installed anywhere on the rope. “It gives tug operators some real good protection because when they go to do an assist on a big tanker, they don’t have any control over what the surface conditions are like on these ships,” says Crump. “By putting this chafe protection on it, operators don’t have to worry that their lines are going to get cut.”

Tug and mooring customers are also using a lightweight, high-strength flowing rope, Quantum-12, that can grip a capstan or H-bitt. An overlay of EMAD yarn of polyester is spun around some of the fibers of the Dynema® to increase the coefficient friction because Dynema® is very slippery and doesn’t tie off very well. Crump says the British Navy has converted over to it and the US Coast Guard is also starting to use it.