When Aries Marine Corp. crews assembled around the beginning of this year for sea trials on two platform supply vessels, they expected a unique experience. As the trials concluded, they were convinced they were aboard the best boats they'd ever sailed.
The stars of the show: two diesel-electric, integrated z-drive PSVs, Betty Pfankuch and Dwight S. Ramsay. The 292-footers from Eastern Shipbuilding Group Inc. in Panama City, Fla., were in service this spring from the Aries yard in Morgan City, La. Ramsay has since gone into service in Mexico.
Dubbed the Tiger Shark class, Pfankuch and Ramsay are currently the largest-capacity purpose-built PSVs in the Americas. They also may be the industry's most environmentally sound vessels and the ones best able to fight platform fires.
On top of all that, they're a pleasure to operate, said Capt. David Loew, Ramsay's initial master. During the delivery, Loew and his crew experienced the interplay of the four Cummins 16-cylinder turbocharged Tier II diesel engines, Hyundai gensets, Schottel z-drive main thruster systems with Converteam variable-speed electric motors and bow thrusters.
The 190-by 54-foot cargo deck.
"It was an eye-opening experience for all of us," Loew said. "For a vessel this size, this boat handles great with the azimuthing drives. To be as massive as it is, everyone was amazed at its turning and maneuverability and its ability to stop."
Witnessing the propulsion system in action does not involve descending a ladder into the engine compartment. Instead, the diesel-electric generators are installed forward on the main deck level. While maneuverability and station-keeping are critical roles for the PSV, the offshore industry increasingly is looking for greater cargo capacity too.
"Bigger is better nowadays in the world of supply vessels," said Chuck Lindsay, project manager at Eastern Shipbuilding. "It has actually aided us to have a larger vessel with all the sophistication on it. By moving the power generating plant above the deck, you get the maximum capacity of cargo."
Pfankuch and Ramsay were designed by Aker Yards Marine (U.S.) Inc. in Houston, now known as STX U.S. Marine. Pfankuch entered service fulfilling spot contracts out of Port Fourchon, La.; Ramsay was fitted out for service with the Mexican state-owned oil giant Petróleos Mexicanos, or Pemex, under a four-year contract. Both are U.S.-flagged.
The pumps for the firefighting system, supplied by FFS, like the monitors.
Dwight S. Ramsay is Aries Marine's founder. Betty Pfankuch is his late wife.
The original design contract called for a vessel length of 282 feet. Aries upped the size later to increase the below-deck cargo capacity.
Chuck Levert, director of sales and marketing at Aries Marine, is enthusiastic about the two boats' capabilities.
"Our customers don't even realize it yet, what these vessels can do as far as station-keeping, safety, firefighting capabilities and cargo-transfer rates — and the money they'll save in the long run on tank-cleaning and dry-dock expenses," Levert said.
Aries calls Ramsay and Pfankuch its "Green Design" PSV class. That's a nod to the Tier II engines as well as the ships' cargo configuration. No liquid cargo that may be harmful to the environment is carried in any hold that touches the inside of the ships' hull shells. Instead, drilling fluids are contained in a tank farm below the main deck.
"It's basically a double-hull tanker design. We wanted a green vessel and we wanted to be ahead of the curve," said Bill Purvis, marine superintendent with the Aries supply boat division.
The arrangement exceeds International Maritime Organization standards for vessels that transport fuel or drilling fluids.
The potable water capacity is 16,491 gallons. Seven internal tanks can transport a total maximum capacity of 14,351 cubic feet of bulk mud, and there are eight dedicated tanks for liquid mud holding a total of 19,406 barrels. Two tanks are devoted to methanol, as much as 1,715 barrels. Two other tanks can hold 2,000 gallons of lube oil. Additional pressurized tanks are reserved for dry, powdery substances.
"This is the first purpose-built PSV with this capacity," Purvis said. "It can legitimately carry 15,000 barrels of 18-pound mud."
As much as 1,000 gallons of liquid mud can be discharged per minute through 4-inch hoses (fuel is discharged via 3-inch hoses). Each liquid mud tank has its own Butterworth-designed heated cleaning system.
Each vessel is equipped with a Converteam/ADP Duplex Series C dual redundant DP-2 dynamic positioning system. There are four joystick steering stations — one each forward and aft in the pilothouse and one each on the port and starboard bridge wings.
The four Cummins engines total about 9,800 hp. "The dramatic improvement is we have more horsepower available to the bow thrusters and more horsepower available to the props,â€ Lindsay said. "The available power to maintain station is an improvement."
Loew was impressed by the propulsion redundancies.
Photos courtesy Eastern Shipbuilding Group
The Deepwater Horizon disaster underscored the need for firefighting equipment aboard PSVs. Ramsay’s two bridge-mounted fire monitors can spray 1,200 gpm.
"In a damage-control situation, this compartmental situation is excellent," Loew said. "Every system is backed up. We can have a complete loss of our engine space and still be able to operate everything."
Full operating speed is 13 knots. The PSV can sail at 9 to 10 knots on 70 percent power or "economy run," Loew said.
"The power draw is so small that to maneuver around the dock here, I just need to operate on one generator, with one on standby," Loew said. "If you're running full ahead, you don't have to throttle down to change the direction of the thrust."
The excess available power enables the PSV to run supplementary operations such as remotely operated vehicles, accommodation modules or pipeline treatment systems. The diesel electric system results in favorable fuel-efficiency — 185 gallons per hour at 9 to 10 knots and 296 gallons per hour at 13 knots. Crews reported that it's also less noisy.
"The noise level is just minuscule, with the electric drives and everything so insulated," Loew said.
"They are the smoothest and quietest vessels that I have ever known," Lindsay added. "I would attribute that to the constant speed of the diesel generators that supply the power. When you are on the bridge, you are not able to tell how many generators are running. … With the z-drive propulsion in DP mode, it just swings wherever it needs to go. When the electric motor ramps up, it's a smooth ramp. There's no bang-bang of the clutches."
Another feature — with clear safety benefits — is a forecastle that is not open to the elements.
"The fully enclosed forecastle protects the anchor-handling windlass and bollards, and the people handling it are protected," Loew said. "The captain can operate the windlass from the bridge deck."
After Deepwater Horizon, investigators and consultants identified several firefighting issues that may have complicated the ability of responders to rescue survivors from the rig, and the offshore industry now prefers its PSVs to have the most robust firefighting systems available. Pfankuch and Ramsay have two fire monitors perched atop the bridge, spraying 1,200 gallons per minute.
A "whole-ship deluge system" can form a curtain of water that protects the entire vessel, allowing it to maneuver right up against a burning rig, run hoses out and fight the blaze. That system adds an additional 7,436 gallons per minute.
The Tiger Shark vessels can save the operator money because they may be out of service less often, said Tim Casey, Ramsay's first chief engineer for Aries. Both ships have underwater inspection markings known as UWILD, or underwater inspection in lieu of drydocking.
"You can send a diver down and they can survey the entire bottom of the boat," Casey said. "That's going to standardize future inspections and save us from having to do (some) dry-docks."
A hatch also enables inspectors to drop sonar units and other equipment down through the hull to facilitate bottom surveys for rig operators, said Loew.
Brian Gauvin photos
Top, Chief Engineer Tim Casey at the engine room console. Bottom, Capt. David Loew on the bridge.
Inside the PSV's hull, a dry-bilge cleaning system uses vacuum to cycle water through and process it on the spot instead of accumulating and storing it.
"On most workboats you have a wet bilge and it's a big slop bucket," Casey said. "We have a dry bilge."
Lindsay pointed out that the arrangement of the propulsion system forward allows for a wide-open area on the main deck. The deck cargo area is 190 feet by 54 feet — over 10,000 square feet.
"You have a massive amount of free-cargo area for your deck cargo," Lindsay said.
Crew quarters on each vessel total 32 berths in 13 staterooms. Each stateroom has its own TV and DVD player. There are 12 heads and 12 showers. The galley is served by a 600-cubic-foot walk-in cooler and 400-cubic-foot walk-in freezer.
The designers attempted to make the vessels as self-sustaining as possible. At a capacity of 264,548 gallons of fuel oil, their endurance rating is 35 days at 10 knots. Casey said Ramsay's reverse-osmosis watermaker, which transforms salt water into fresh potable water, can process 2,000 gallons per day.
"They can make their own water, and they can treat their own sewage," Lindsay said.
It's probably inevitable that offshore exploration and drilling operators will covet PSVs with larger capacities that can save the companies time and money, all while achieving the greatest-possible safety capabilities.
After constructing the two Aries vessels, Eastern Shipbuilding received an order for five similar Tiger Shark-class boats for the Brazilian market, backed by a $241 million loan guarantee from the U.S. Maritime Administration. Those vessels, for Boldini SA of Rio de Janeiro, will be slightly modified to meet the Petrobras PSV 4500 design requirements. Each will be 280 feet, 6 inches long.
Aries believes Dwight S. Ramsay raises the bar for the industry in the Gulf.
"It's a different animal," Levert said. "It's totally different than any vessel operating in the Gulf today, and it'll probably be the standard from now on."