Operations depending on the type of vessel

Lifting and cargo handling operations in offshore activities are continuous, intense and essential for both the construction, maintenance and operation of oil and gas exploration and production infrastructure.

With the prospect of accelerating oil exploration and production in the Brazilian pre-salt, there is a firm expectation of high demand for offshore lifting services in the coming years, in addition to a new frontier for Brazilian lifting engineering, which is the construction of wind farms offshore off the coast of Brazil.

Accompanying this growth, there are more and more specialized vessels, with technology in growing evolution, that carry out offshore lifts. From the point of view of vessels and their cranes, two examples are provided.

FPSO

They are floating platforms in the shape of a ship, which produce, store and transfer the oil produced. Brazil has the largest quantity in operation in the world, around 50 FPSOs, a number that will increase in the coming years with several orders already placed by the operators.

They have between two and five cranes for routine lifting, which involves removing and placing loads on board the platform and support vessels (PSV). These loads include containers, baskets, tanks, buckets, hoses for transferring water and fuel, among others, with essential items for the operation of the platform, including food.

The cranes have a capacity of 25 to 70 t, being of the “on pedestal” type, with lattice or articulated boom. The lattice boom can be up to 60 meters long.

These cranes are also used for onboard maintenance, construction and modification activities, lifting pipes, structures and equipment.

PLSV

They are pipeline launchers that transport fluids from the wells to the platform and vice versa. The PLSV also perform various ancillary operations in the construction and maintenance of subsea infrastructure.

They have various lifting and handling equipment, with cranes between 50 and 400 tons, which may have an active sink compensator (AHC), which stabilizes the position of the cargo during submarine lifting, regardless of the ship’s movement.

They also have a central opening for access to the sea, called a “moon pool”, which is less affected by waves, through which loads can be lifted with less dynamic efforts, preventing them from being lifted by the side of the vessel.

A large number of auxiliary lifts are carried out on board to support the launch of the lines, using special accessories such as ultra high strength steel connectors, HMPE fiber slings, shackles with remote disconnection, in addition to conventional ones, such as winches, snatch blocks , high-capacity shackles, chain slings and textile straps. The quantity of these items can reach two thousand in a single ship.

Due to the complexity and number of lifts on these vessels, the design of the lift, training of all involved and continuous inspection of accessories and equipment are essential, preserving lives, the environment and property.

AHTS

Anchor Handling Tug Supply, or anchor handling tug, is one of the most versatile vessels in the offshore environment, as in addition to handling anchors, it can perform complex operations such as launching subsea equipment, installing torpedo piles, ocean towing and positioning platforms, changing the heading of FPSO platforms, support for salvage, among others.

It can also perform in conventional offshore supply activities, such as transporting containers, pipes, fluids, fuel, in addition to firefighting and rescue.

With lengths between 70 and 95 meters and a width between 16 and 25 meters, they have a wide deck, with an admissible load of up to 12 t/m² to support the various equipment and accessories that will be moved, launched or recovered from the sea.

They are equipped with winches, with a capacity of up to 700 tons, the most common being in the range of 450 to 500 tons, with a storage capacity of thousands of meters of steel cables or fiber cables.

An important feature of the AHTS is the traction capacity it can impose on the towing or handling cable, which is called bollard pull, whose value varies depending on the size of the vessel, and can be between 100 and 400 tons.

In handling, moving and towing operations, steel cables, synthetic fiber cables, chains, large lifting accessories such as shackles, swivels, hooks, triangular plates (triplates), among others, are used. to the winch, offer various means of moving and lifting large capacity.

They generally have cranes that assist in handling cargo on deck, which operate by moving longitudinally on rails on both sides of the ship, with a capacity of up to 5 tons.

They may also have an auxiliary crane in the winch area and an A-Frame type crane at the stern, with capacity for up to 350 tons.

Gables

Cranes are floating cranes made up of an “A”-shaped boom (A-frame) placed at the bow of the vessel when in operation, whose main characteristic is that it does not have a slewing system. In English they are known as sheerleg, a term that brings the idea of “simply legs”, when in their origin, they consisted of a raft and two or three beams from which a pulley came out for lifting loads.

In Brazil, the term “cabrea” is also popularly used for floating cranes whose boom is not A-frames and has a slewing system. In this article, it is only about the sheerleg type.

The lifting capacity ranges from a few tons to 10,000 tons, being the largest in Brazil with a capacity of 3,600 tons, in operation at Estaleiro Jurong Aracruz.

The larger cranes are generally self-propelled and some have a deck with an area to transport the load to be lifted.

As advantages, there is the variety of uses, low draft in relation to the capacity, sailing with the load hoisted, little loss of operating radius due to the positioning of the boom in the bow, several lifting configurations using jib and independent blocks, among others.

Disadvantages include slow navigation speed, need for partial demobilization of components for long-distance navigation, not executing the boom turn, requiring the turn of the entire vessel.

They are very versatile cranes, able to perform in various types of lifting in rivers, sheltered waters (inshore), open sea (offshore) performing, for example:

• Port support: cargo handling between quays and vessels;
• Naval construction: assembly of large modules on the hull;
• Construction in general: assembly of bridges, ports and offshore structures;
• Salvage: rescue of sunken vessels;
• Decommissioning: removal of offshore structures and subsea equipment
• Offshore wind farms: execution of foundations, assembly of jackets, towers and wind turbines.

With the growth of port concessions and the increase in maritime works in Brazil, the tendency is for the use of gables to grow, being another great option for the lifting engineer to specify in his projects and works.

OCV – Offshore Construction Vessels

Construction in the open sea, or offshore, has been advancing more and more, not only due to the increase in oil and gas production, but also due to the new frontier of renewable energy, mainly offshore wind energy.

In increasingly deeper waters and increasingly complex constructions, increasingly versatile ships are required, with technology that increases the performance and safety of lifting.

Modern OCVs can present very different characteristics from each other and many are of the multipurpose type, being able to perform several types of operations. Some of these features:

• Length between 90 and 200 meters, width from 18 to 35 meters;
• Free main deck, with large areas for handling loads to be lifted. Some do not have a false edge on this deck;
• Cranes with active sink compensation (AHC – active heave compensation) for air lifts and subsea lifts, capable of reaching depths of 3,500 meters;
• Winches with high traction capacity, able to work with high modulus fiber cables and with AHC;
• Moonpool for subsea lifts;
• Active balance stabilizers (roll), whose function is to reduce the lateral balance of the ship during lifting operations;
• The most modern ones have ROV or interface ready for their installation.

Because they are versatile, they are used in various offshore operations, including:

• Lifting in air from 100 to 1,000 tons, of the most diverse equipment and structures;
• Subsea lifting for installation or removal of equipment and pipelines;
• Decommissioning of subsea equipment and pipelines;
• Construction of foundations, assembly of towers and wind turbines for offshore wind farms;
• Intervention in oil and gas wells;
• Diving support;
• Installation and handling of lines, anchors and stakes.

With the growth trend of offshore construction in Brazil and the advent of offshore wind farms, more and more of these fantastic ships will be used in our waters.

CV – Crane Vessels

In 1920, the US Navy converted a warship built in 1898 into a crane ship with a lifting capacity of 250 t. In 1985, the Dutch company Heerema launches its semi-submersible crane ship Thialf, with a total lifting capacity of 14,000 tons. In 2019, the same company launches another crane vessel, also semi-submersible, with a capacity for 20,000 tons.

How much weight can you lift in the open sea to assemble or disassemble structures? What are the limits of offshore construction – or deconstruction? Is there room for larger crane ships?

Crane ships are highly specialized vessels, equipped with one or more large cranes, generally with boom turning capacity, used for lifting heavy loads, which can reach up to 20,000t.

Generally, the largest crane ships have a semi-submersible hull and the medium-sized ones have a catamaran or monohull type. The first type has the advantage of offering greater stability, but with a greater draft.

The current record for offshore lifting with a rotating boom crane is held by SSCV Sleipnir, which lifted, in one go, the topside of Noble Energy’s Leviathan platform, weighing 15,300 tons.

This crane ship, the largest of its kind in the world, has a maximum lifting capacity of 20,000 tons, divided into 2 rotating booms with a capacity of 10,000 tons each. An unprecedented feature in it is to operate with LNG.

Despite not being noticed, in Brazil, these crane ships occasionally operate, assembling offshore platforms. The most recent was the already mentioned Sleipnir, which set up a jacket and topside of a platform in the Campos Basin, in early January 2020.

The perspective is for an increase in the use of crane ships in Brazil, mainly due to the new frontier of decommissioning platforms in shallow waters and offshore wind farms.

Crane Ships for Offshore Wind

Without a doubt, the new frontier of renewable energy in Brazil is offshore wind, where wind turbines are built at sea, away from the coast.

Despite Brazil lagging behind other countries, there are concrete prospects for intense investment in the sector, with several projects already in the environmental licensing phase.

The construction of offshore wind farms requires speed, handling large loads, many of them fragile, heavy loads, complex lifting, all in an environment with waves, currents and strong winds.

For these challenges, the shipbuilding industry is offering crane ships that are increasingly specialized in offshore wind construction, with the following main features:

• Large deck for storage of all wind turbine components, including the foundation, with areas that can reach 10,000 square meters;
• Large cranes, with large capacities, ranging from 1,300 to 5,000 tons, and lifting heights of over 180 meters.
• Legs fixed to the seabed that allow you to raise the hull and move it away from the waves, greatly reducing the movement of the vessel (jack-up)
• They operate in water depths from 20 to 100 meters;
• Use of fuels that reduce CO2 emissions.

There are also super specialized ships, specific for loading, transporting, lifting and installing foundations and jackets, base structures for wind turbines, which have cranes of up to 5,000 tons and a deck area that can reach 10,000 square meters. Among them, there are also ships specialized in transporting wind turbine components in long-haul navigation, which was previously done on conventional ships.

Brazilian lifting engineering must prepare itself to act in these new projects, which will involve complex lifting from the manufacture of components, shipment in ports, maritime transport, offshore installation, maintenance and decommissioning.

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