Introduction: A Typical Lift Bag Operation
By James Carter
The most important factor to consider when refloating a sunken boat is stability. As the boat is raised from the bottom to the surface it must be maintained in a level and upright position. If the boat is upside down or lying on its side on the bottom it is necessary to bring it to an upright position before beginning the lift. This can be accomplished by initially attaching the bags to the boat so that they are well above its center of gravity and then slowly adding air to them until the boat is brought to an upright position.

If the boat is securely stuck in the mud or buried in sand, it is necessary to break it loose from the bottom before attempting the lift. To do this, the contractor must first attach some bags to the boat that have less lift than is needed to raise the boat. The bags are then filled completely with air. A strong line is then attached to one end of the boat, ideally to a very strong bow or stern cleat. If no such attachment is available, the contractor should run a sling around the hull about one quarter of the way from the bow or the stern.

A small lift bag is then used to bring the end of the line to the surface. The team attaches one or more large lift bags just a few feet below the surface. These bags are filled with air while the team waits for the boat to be pulled loose from the suction of the mud. Sometimes it will take considerably more lift to break the boat loose from the mud than to actually lift it.

Once it breaks loose, the large bags will come to the surface and the boat will be suspended just off the bottom. At this point, more bags are attached to the boat to finish the lift. It is important to fill all the bags completely with air at the bottom. If the boat begins its assent to the surface with a number of partially filled lift bags, it could rise to the surface much too rapidly as the air within the bags expands and increases their lift.

Once the boat is on the surface the next challenge is to get it high enough in the water so it can be pumped out and refloated. It usually requires considerably more lift to get a boat high enough in the water to pump it out than to merely bring it to the surface.

Finally, more lift bags are added to the boat to level it out and get it above the gunnels so it can be pumped out. Ideally, this work should be done in calm shallow water. If possible, the boat should be towed to shore and grounded. This makes repositioning the lift bags much easier. In some situations the boat can be grounded at high tide and then dewatered at low tide. The lift bags can then be used to keep the boat level as the tide comes in.

The following companies offer some of the best equipment in the industry to accomplish this and other marine lifting tasks. First we'll focus on some deck-based lifting equipment, followed by several underwater lift bag offerings.

InterOcean Systems Supplies the US Navy
InterOcean Systems recently completed factory acceptance testing of the US Navy's prototype Joint Modular Lightering System (JMLS) Winch at the company's manufacturing facility in San Diego, California. JMLS Winches will be mated to lightering tugs in support of the Navy Construction Battalion's (SeaBees) mission of Strategic Sealift Logistics Over the Shore.

Operations using specialty equipment involve moving cargo from ship to shore for staging and distribution. Mission planning for moving cargo through the surf zone considers a high rate of casualties. Considering this factor, the Navy requires specialized equipment that is both robust and reliable for heavy operations and salvage in difficult environments.

To meet operational needs in this environment, the Navy decided to double the working capacity of their existing winch designs, while concurrently cutting weight to improve the JMLS Tug's stability. To accomplish the tasks of anchoring, mooring, ferrying, and salvage, both of the winch's drums are required to load hundreds of feet of one-inch minimum diameter wire rope, and heave in or pay out at high speed and loads for extended periods of operation.

The specification for design listed the additional needs for a line-handling capstan and controls to deliver hydraulic fluid power to the JMLS tug's bow-mounted A-frame. The most stringent requirement was the specification of noise limits to be below a level that would demand the winch operator use personal hearing protection.

The result of InterOcean's "clean sheet of paper" design exceeded expectations. In addition to meeting the load/speed performance and dimensional and weight specifications, the noise specification was met using a commercial off-the-shelf diesel engine as the prime mover for the hydraulic power system. With the winch running, communication with the operator is like speaking with someone on a traffic-congested street corner or in a crowded restaurant. This reduced noise level enables safe communication even while the winch is heaving full throttle.

Furthermore, the use of a standard commercial diesel engine enhances maintenance and supportability of the winch during extended deployments without immediate spare stockpiles.

The engineering, development, and fabrication achievements of InterOcean's staff produced a system that satisfied the needs of the U.S. Department of Defense. This same process applies to the commercial industry's need for reliable and robust self-contained cable handling systems.

InterOcean's five decades of marine design and construction experience includes the development of many application specific cable handling systems, ranging from motion-compensating traction winches for deploying camera equipment to fully-integrated oceanographic data gathering systems, which are portable or integral as "ship sets" on research vessels.

InterOcean Systems provides global support to an extensive line of both standard and custom cable handling systems for a full spectrum of marine applications. Complementing their winches, InterOcean can exclusively supply standard or custom equipment, accessories, and engineering assistance for all types of applications and requirements on deck, as well as underwater. The company's products are used worldwide to reliably complete tasks like overboarding lines, spotting a load underwater, remotely inflating lift bags, and closing an underwater electrical contact.

Dynacon's Active Heave Compensation System
Dynacon has developed an Active Heave Compensation System which addresses the problems of excessive power requirements associated with current active compensation strategies. The system recently delivered 10Hp/ton of compensated load, which greatly reduces the cost of the prime movers.

The system utilizes sensors that are currently used in passively heave compensated systems. The system accepts low sample rate subsea signals (if available) to enhance overall system performance. If a control system fault occurs, the system reverts to passive heave compensation.

Dynacon has operated out of Bryan, Texas, since 1986, and specializes in custom manufacturing of cable handling equipment including winches, hydraulic power systems, A-frames, and other ocean-related equipment. Their product line also features ROV launch and recovery systems.

Schoellhorn-Albrecht Deck Equipment
Schoellhorn-Albrecht has been serving the marine industry with a complete line of high quality marine deck equipment for well over a century. They began by providing steamboat engines and deck equipment for river boats built in Alaska and used on the Yukon River during the gold rush days of 1898-1900.

Today, Schoellhorn-Albrecht continues to design and manufacture mooring equipment such as capstans/winches, deck fittings, accommodation ladders, and anchors.

Their Model SA1014 family of capstans offers tremendous power in a small package. Applications include barge handling, material handling, and messenger line handling. These capstans are used by the Panama Canal Commission, the St. Lawrence Seaway, the US Army Corps of Engineers, and many commercial shipyards, with hundreds of units in service throughout the world.

These deck-mounted capstans range from 3Hp to 15Hp in a variety of line pulls and speeds. The proprietary gearbox design is a helical worm gear train contained inside a rugged cast iron housing. An oversized output shaft and bearings provide shock resistance and a 35,000-pound bollard rating. Running pulls up to 10,000 pounds are normally provided by a Design "D" Crane & Hoist Duty motor, but the company also offers pneumatic, hydraulic, and explosion-proof capstans. Optional brakes and custom control packages are available on all units.

In contrast, Schoellhorn-Albrecht's through-deck Model 22300 family of capstans is designed for shipboard applications, including barge moving, buoy handling, and general line handling. They are used by the US Coast Guard, the US Army Corps of Engineers, and commercial shipyards. Mounted through the deck, these capstans range from 5Hp to 25Hp in a variety of line pulls and speeds.

The main gear reduction is a high-efficiency planetary reduction. A secondary reduction inside the capstan barrel minimizes shock loads to the main power train. With running pulls up to 25,000 pounds and a bollard rating of 100,000 pounds, these capstans are built to take punishment in stride. Available barrel sizes range from 12 to 24 inches, both smooth and whelped. Electric units feature a Design "D" Crane & Hoist Duty brake motor for smooth engagement of heavy loads. Pneumatic, hydraulic, and explosion-proof versions are also available, with custom control packages available on all units.

Harbor Branch Winches and Handling Systems
Harbor Branch - Ocean Engineering and Production offers a variety of marine winch designs, A-frames, and handling systems. The 1K Series Winch Model is part of the standard product line that will include full ocean depth capabilities. Typical applications are in support of ROV umbilical and tethers, tow bodies and survey cabling, oceanographic sensors, and custom systems.

The Articulating Docking Head (ADH) is a positive locking mechanical interface that is fitted to commercial off-the-shelf articulating cranes. The system was developed to satisfy current industry and military requirements for a compact and effective means of launching and recovering both tethered and autonomous vehicles. The ADH's capabilities make it versatile and cost-effective. Its features include positive locking mechanism, articulating capability in both azimuth and altitude, compatibility with a range of sizes and cranes.

As part of their standard product line, Ocean Engineering and Production also offers the Model 1K winch. Its features include 20Hp, full drum line pull 2,500 pounds, bare drum line pull 5,000 pounds, line speed range from 75 feet per minute (bare drum) to 150 feet per minute (full drum), heavy duty sealed bearings, and fail safe brake.

JW Automarine Lift Bags
With over 30 years of experience, JW Automarine is a leader in underwater lifting bag design and manufacture. The UK company supplies many of the world's industry sectors, including salvage, civil engineering, offshore petroleum, and defense. They have provided a variety of buoyancy solutions over the years, including reducing the draft of a quarter-million-ton oil rig platform in 1976 by providing and installing 22,500 tons of buoyancy, and more recently opening the Kursk sub's hatch with a 500kg lift bag.

Salvage lifting bags are needed urgently when a disaster has happened and salvage must take place. Most salvage operations using lifting bags are straightforward projects, but sometimes they present a challenge.

Such was the case of the Ehime Maru, the Japanese fishing vessel sunk by the US Navy sub Greeneville last year off Hawaii. The salvage company appointed to raise the vessel from 2,000 feet (600m) came up with a novel solution to the problem of using underwater lifting bags conventionally at that depth.

The solution was to modify standard totally enclosed units, which have a five-ton displacement, by filling them with syntactic foam. This was achieved by making an opening in the end of the lifting bag and filling it with the slabs of foam and then securing the opening.

The effect of this modification reduced the potential lift of each unit from five tons to approximately 3.5 tons. 15 units were manufactured and supplied. This scheme reduced the weight of the fishing vessel by 50 tons at depth, allowing it to rise to the surface in a controlled manner.

Other challenges for lifting bags will take place later this year when 40 giant, totally enclosed, 35-ton lifting bags will be fitted to the hull of a 45,000-ton vessel being built in a dry dock. The vessel, at that stage of build, will not clear the sill during the float out, so by fitting 1,360 tons of buoyancy to the stern section of the 900-foot long vessel, a clearance of six inches will be achieved.

As with most products, ongoing research and development is essential for a company's future prosperity. JW Automarine has listened to customer experience and suggestions over the years, the culmination of this being the launch of a new revised range of underwater lifting bags. These bags include various innovations, such as the introduction of CE markings, making these the first underwater lifting bags in the world to receive this accreditation. A comprehensive logbook will accompany each unit, along with an integral detailed label identification system. The design revision has enabled increased strength and durability and has also improved diver usability.

Future initiatives will be the launch of a range of totally enclosed cylindrical lifting bags with a capacity range of 50kg to 35,000kg. This range is being designed for surface support, pipe flotation, and vessel draft reduction, as opposed to the standard commercial range that combines deep lift with surface support. Visit www.jwautomarine.co.uk.

Variety from Carter Lift Bag
Washington-based Carter Lift Bag manufactures and stocks over 30 different sizes and styles of air bags for underwater lifting and other specialized applications.

The company's open bottom, or parachute bags as they are often called, come in lift capacities from 25 pounds to 10 tons. These are general use lift bags for everything from raising sunken logs to lifting bulldozers that fall through the ice. The smaller bags are made from a lightweight but very strong urethane coated nylon material that rolls up into a neat compact roll. The larger bags are constructed from very heavy vinyl-coated nylon fabric that has a high tear strength and is very abrasion-resistant. These bags are all fitted with manually operated dump valves.

Carter's totally enclosed pillow bags are available in lift capacities from 250 pounds to 6,000 pounds. All their pillow bags are equipped with large-capacity overpressure valves capable of adequately venting the expanding air on a rapid free ascent from any depth. These bags have a rectangular pillow shape that allows them to lay flat against the hull of a boat so that they will not roll back and forth on long ocean tows like round lift bags do. Heavy nylon straps go completely around the bags and come together to a heavy galvanized steel lift ring. These pillow bags are excellent for refloating sunken boats because, unlike open bottom lift bags, they can be attached under the bottom of a boat's hull and still be inflated to full lift capacity while lying on their side.

The Boulder Bags line is designed to get the maximum amount of lift in the minimum amount of water. For example, the 2,000-pound Boulder Bag gets its total lift in less than three feet (1m) of water. This bag has one stainless steel attachment ring located at its center. Boulder Bags were originally developed for lifting boulders out of the way of gold dredgers in the shallow rivers of California's mother-lode country, but they are equally well-suited for deep ocean salvage jobs. Because their low profile offers a minimum amount of drag, they are also excellent for long, open-water towing jobs.

Carter's Ocean Salvage Tubes are long, cylindrical, totally enclosed lift bags with lift capacities of 1,000 pounds to 4,000 pounds. They are great for pipe-laying and other construction projects, but where Ocean Salvage Tubes really shine is when they are used in raising sunken boats. They can be used vertically to bring the boat out of deep water. When the boat is suspended near the surface, the bags can be slung under the boat with one end on each side to get the boat high enough out of the water to pump out. In shallow water, two bags can be slung together, one on each side of the boat, like pontoons.

Subsalve Lift Bags
Subsalve USA has been designing and manufacturing underwater flotation since 1977, and is celebrating its 25th anniversary this year. Subsalve products have been used in all facets of the diving and underwater industries worldwide in applications including offshore construction, oilfield maintenance, salvage, pipeline and cable installation, coastal infrastructure construction and repair, power plant and utility work, scientific applications, ROV work, public safety, and military applications. Any object that needs to be either placed or removed in any body of water is a potential candidate for the use of underwater flotation.

Underwater flotation is used when conventional surface lifting gear is either unavailable, inconvenient or not cost-effective. Sometimes contractors encounter a job in a remote, difficult to access location, an object may be under another structure and not accessible by lifting equipment, or an object may be too long (pipeline or cable) and only underwater flotation will work. The company's open-bottom parachutes are available in 13 sizes, from 25 pounds to 70,000 pounds of buoyancy. Their enclosed pillow shaped bags are available in six sizes, from 200 to 6,000 pounds of buoyancy. And their pontoon-shaped bags come in eight sizes, from 1,000 to 70,000 pounds of buoyancy.

Subsalve has also developed a patented VRS 2000 vehicle recovery system and its Mark V underwater ordnance disposal system, used by navies throughout the world.

The company designs and manufactures custom products and systems, as well. Examples include rocket booster flotation systems for NASA, helicopter recovery systems for the US Coast Guard, a transducer flotation system for US Navy attack subs, propeller changing lift bags, inflatable plugs, turiodal lift bags for nuclear power plants, flotation systems for ice vehicles, retrieval systems for Tomahawk missiles, underwater decompression habitats, underwater welding tents, and even flotation systems for tourist submarines.