By: LARRY PEARSON Larry Pearson is a freelance writer based in Kenner, Louisiana, U.S.A.

Hornbeck Offshore Services Inc. (HOS), Covington, Louisiana, U.S.A., has taken a huge step forward in liquid cargo delivery with its introduction of a pair of 116.1 m by 21.9 m vessels with
4923 m3 capacity liquid mud and equally impressive amounts of other offshore liquids. Liquid mud capacity is realistically twice that of any other supply boat now serving the Gulf of Mexico
or any other vessels that are currently anticipated to join the service fleet.

Shown here are the series of Hornbeck Offshore Services (HOS) supply boats. Vessels are available in lengths of 61, 73, 81 and 116.1 m.

The HOS Strongline and the HOS Centerline began their lives as 121.9 m tankers. The M/V W.K. Williams was purchased in late 2002 from Freeport-McMoRan Sulphur, New Orleans, Louisiana, and the M/V Benno Schmidt in 2005 from an undisclosed seller. Both vessels were originally constructed to carry molten sulfur for McMoRan from an offshore well to land.

Both vessels are now called 370MPSV multi purpose support vessels and are 116.1 m long. They have undergone a complete transformation with only certain portions of their original hull and superstructures retained. The superstructures were basically gutted and expanded.  The pilothouse was lengthened by 2.45 m so that new wing stations could be added.

Main deck of the HOS Centerline. Regulatory requirements mandated the walkway installation.

The vessels each have an 8000+ deadweight tonne capacity and have a draft ranging from 2.3 to 5.84 m. Both vessels are ABS DPS-2 rated. “The hulls of these sister vessels, which were purpose built for the specific gravity of molten sulfur, make them uniquely suited to be converted to large liquid mud carriers,” said Todd Hornbeck, chairman, president and CEO of Hornbeck Offshore.

“In converting these two vessels, we were constrained by the existing hull and superstructure and the need to keep the vessel under 6000 GT to qualify as an OSV under the U.S. laws, to
maintain Jones Act qualifications and to comply with a maze of regulatory requirements,” said Carl G. Annessa, executive vice president and chief operating officer of Hornbeck Offshore.

Huge amounts of diesel power were added to the vessels. Older Caterpillar engines were removed and replaced by a propulsion power plant of four Caterpillar 3516C engines rated at a total output of 8400 kW. Using a diesel electric design, the engines were fitted to generators to run a pair of Rolls-Royce Marine steerable z-drives with fixed-pitch propellers. Each thruster is powered by a pair of 1119 kW electric motors, so each z-drive is rated at 2238 or 4476 kW for the entire propulsion system.

The four Caterpillar 3516C engines are dedicated to run only the z-drives and the vessel’s four other thrusters. Also added were three Caterpillar C-18 generators developing a total output
 of 1275 kW. To meet Safety of Life at Sea (SOLAS) and other requirements, a Caterpillar 3306 gen-set rated at 170 kW is located behind the pilothouse on the bridge deck. One of the major upgrades the vessel received was a new bow. The new bow was needed to hold a 1119 kW tunnel bow thruster and apair of azimuth drop-down thrusters each rated at 1119 kW.

The propulsion power plant of the HOS Centerline. Four Caterpillar 3516C diesels are connected to generators to supply 840 kW of electric power to the six thrusters.

The new bow units were built at Bath Iron Works, Bath, Maine, U.S.A. The Centerline first went to Bollinger Shipyards in Amelia, Louisiana, for initial evaluation, then onto Cianbro Corp.,
Pitsfield, Maine, and then to Offshore Inland in Mobile, Alabama, U.S.A., for finish work. In addition to the aft z-drives, there is an aft thruster also powered by a 1119 kW electric motor. “All of our propulsion motors are 1119 kW units in interest of commonality,” Annessa added.
Another major change in the rebuilding of these vessels is the below deck tanks, which were originally sized for molten sulfur. These original tanks were all removed and 18 tanks were added with three separate piping and pumping systems so three different cargos could be carried.

In addition to liquid mud, the vessel can carry 4923 m3 of brine, 3903 m3 of cargo oil, 247 m3 of potable water, 5225 m3 of rig fuel and 5686 m3 of rig water. The tanks feature a self contained liquid mud mixing and cleaning system with large paddles that reduce the time to
clean the tanks, saving the customer this cost. A flume tank was also added to dampen the roll of the vessel.

The HOS Centerline has received certifications by the Coast Guard allowing operations as a supply vessel, construction vessel and as a petroleum/chemical tanker. It received certifications “L,” “I,” “D” and “O” in October 2009. With certifications “D” and “O,” the HOS Centerline can carry crude oil as well as other flammable liquids in significant amounts, thereby making the vessel an ideal platform for various well test, flow back and dewatering
projects in deepwater. Its ability to carry crude oil also makes this vessel valuable for use in emergency response situations involving crude oil production disruptions before or after major weather events such as hurricanes.

In addition to the certifications and classifications mentioned above, the two vessels are certified Oceans-SOLAS, SIP and classifications +A1, +AMS, +DPS-2, ACC, American Bureau of
Shipping, Loadline, Oil Tanker/Chem Tanker/Offshore Support and OSV. “Our insistence on these multiple classifications and certifications makes these two vessels absolutely unique in the industry and can replace what normally would take two or three ordinary vessels,”
Annessa said.

Operating as chemical tankers, both the HOS Centerline and the HOS Strongline can carry hundreds of chemicals including alcohols, acids, esters, ketones and other noxious fluids, as
well as more common products such as water and apple juice. The three pumping systems can
deliver products up to 227.3 m3/hr.

The four hose reels on the ship. The hose is 76.2 m long and 10.2 cm in diameter.

The vessels are uniquely configured with hose reels located forward to allow the ships larger standoff distances in heavy weather discharges. The ships are fitted with positive displacement
pumping systems, allowing a constant discharge of liquid cargos even at installations with large air gaps. The cargo deck is 61 m by 18 m, with a deck loading of 5 tonnes/m2. There is also 8.5 m by 18 m of covered deck area. The vessels feature multifunctional ISO sockets integrated into
the fore deck to accept standard-sized containers.

The vessels have accommodations for 78 people — the crew size is 13, leaving 65 accommodations for construction and company executive personnel. “The entire  accommodations area, galley and lounge were completely rebuilt as was almost everything
else on these two ships,” Annessa added.

The vessels also have water makers onboard with 18 927 L/day capacity. There are three Hydra Pro stores cranes on each vessel that will mostly be used to move material and equipment around the deck and perishable stores into and out of a 24 m3 freezer. Both vessels have been designed for the addition of equipment for construction projects. “We have deck
space to install a large crane and to take onboard two ROV control centers and the A-frames necessary to launch them,” Annessa reported. “We can easily install a moon pool and a deep-sea winch, and will do so if projects require this equipment,” he said.

Shown here is an aerial view of the 116.1 m HOS Centerline. Its distinctive layout places the superstructure aft and the main deck forward, the reverse of other supply boats in service. The vessel resembles a tanker, which is the original service of the ship, hauling molten sulfur.

“Every team needs a leader. The construction manager for the conversion of these two vessels was Randy Tredinich. Randy did a fantastic job having to deal with several shipyards plus the myriad of difficult regulatory certification challenges that developed on these very complex conversion projects,” Annessa said. In addition to diverse capabilities, the HOS Strongline and HOS Centerline look totally different than any other supply vessel. The superstructure is aft,
resembling a large tanker. “This layout has several advantages, not the least of which is the workers and crew report a considerably smoother ride with their accommodations aft, not above the bow,” Annessa explained.

The HOS Centerline was delivered in February 2009 and received its final certifications in November 2009. The HOS Strongline will be delivered in the first quarter 2010.


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