Crane Barge: Specialized Floating Lifting Device for Maritime Operations

Crane Barge: The two terms that make up the term Crane barge are Crane and Barge. It follows that crane barges are specialized boats used for lifting, loading, and unloading operations that include a crane or cranage system mounted to their deck.

While many cargo ships are equipped with deck cranes, a crane barge is a ship that is utilized only for heavy-lift cranage operations. They can travel over the vast oceans and are mostly self-propelled.

Therefore, in all practicality, a crane barge can be thought of as a floating lifting device for maritime activities similar to those utilized for ground-based building projects. Since lifting operations for construction in the water have existed for many years, the idea of a crane barge is not new; it dates back to the 14th century.

Crane barges are useful for a variety of tasks, such as:

  • All kinds of activities involved in offshore construction, installation, and repair work.
  • Operations in rivers and canals. Piling is one of the common works that take place in river banks and canals. This involves driving filling materials known as piles for bank retention and reinforcement. Other operations involve installing bank protection materials like nicospan and also constructing embankments.
  • Carrying out dredging operations in waterways.
  • Installing pipework, cabling and other underground or underwater installations.
  • Dismantling of civil structures in coasts, rivers, or in shallow water close to the shore.
  • Salvaging operations of vessels grounded, damaged, or sunk.

Crane Barge Construction and Types

 Practically speaking, a crane barge consists of an open deck platform with a simple hull form that holds the crane or cranes.

The crane barges have the following kinds and configurations from a design perspective:

Simple cranes

These are barges with a flat hull that have one or more basic lifting cranes mounted on them. Larger versions have the capacity to raise loads up to 2000 tonnes, and occasionally even higher. These cranes have two options: rotation and fixation.

Derrick Barges

They can hoist a very large range of weights thanks to their completely rotating crane system. These are mostly employed in offshore maintenance and construction projects.

Larger derrick barges are capable of lifting over 1000–1500 tons, while smaller ones are limited to 50–500 tons.

Today, derrick barges have grown in capacity, and some cranes can lift more than 10,000 tons together.

Most of the barge’s length lies ahead of the stern, where the derrick or derricks are located. Barges should be designed to distribute structural loads uniformly across their entire width when the crane operates.

The derrick barge’s propensity to list is one of its frequent issues. For the same reason, a counterweight is therefore frequently included to maintain the barge’s balance when there is no load or only a partial load.

Swing engines can be used to further counteract the list during operations. Two or three swing engines may be fitted, depending on the derrick’s size and lifting capability.

In addition to their natural capacity to carry large loads, derrick barges have the benefit of being flexible and having a 360-degree range of motion.

Sheerlegs

Sheerleg cranes are able to hoist large loads because of their A-frame, which is composed of structural components that resemble tubing or trusses. But they cannot, in fact, rotate. The capacity of sheer leg cranes ranges widely, from 50 tons to 10,000 tons.

The larger sheerleg crane barges can move themselves, but the smaller ones are frequently stupid and require towing from one location to another. Sheerlegs often use an outboard engine’s propellers or the deck as their propulsion system.

In order to hoist the weight, the sheerleg barge places itself in a favorable lifting position. Once the load is lifted, the sheerlegs alter their locations to keep the balance. The sheerleg crane barges’ deck engines must be able to withstand a variety of sea states that could cause motions in all six degrees of freedom.

hefty lift Crane Barges

Mostly employed for offshore installations and construction, these crane barges are capable of lifting extremely heavy cargoes. The hoisting device or crane is positioned symmetrically on both hulls in most twin-hull systems. Thus, the weight is raised from the middle.

The massive crane is fixed and can extend to a suitable height to accommodate lifting larger-sized loads. It forms an interlocking arch-like structure between the two supporting hulls. Several tugs or powerful self-propulsion systems frequently pull these crane barges.

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The Design Concept of a Crane Barge

The Design Concept of a Crane Barge
(Credit: Science Direct)

Even though we’ve only covered the uses and different kinds of crane barges thus far, an engineer or designer’s design philosophy for each of them is based on a few universal principles:

Strength and Integrity of Crane Barge

Ensuring the structural soundness and strength of a crane barge is one of the most crucial design elements. A crane barge’s only function is to raise various weights according to specifications.

From this point forward, the structural engineering work must be completed for a given barge with a specific maximum crane lifting capacity in a way that ensures the system will not be damaged when lifted within the specified load limitations. Speaking of the system, it can now be further divided into two heads from a structural perspective:

The cranage, or lifting system

The lifting mechanism or cranage’s suitability or capability is the focus of this section. This crane’s design is identical to that of any other land-based crane whose primary function is to safely lift loads within designated maximum limits, sometimes known as safe working limits, or SWLs in technical parlance.

Everybody knows that cranes, whether they are used for shipping, industry, or construction, have a specific SWL capacity, and that running above it puts the system’s structural integrity at risk of failure.

Similar to this, the maximum allowable limit that can be reached before loads can be hoisted also applies to cranes that are mounted on barges. The crane is built to meet certain requirements, meaning that every structural component—such as the boom, legs, or foundation—must be able to support the specified load and still function properly.

The Barge Structure

The barge’s hull structure is constructed by the specifications of the cranage and the anticipated loads it will lift. The hull is constructed of appropriate steel components, much like any other vessel, and is further strengthened by reinforcing members. The deck plate is the most crucial component in this case.

The explanation is clear since the deck bears the brunt of all the loads originating from the crane and the weight that is raised. Thus, the deck plate is reinforced not only by increasing its thickness to the proper level but also by making it more rigid.

The most important part of the plating is the area that supports the cranage foundation; it is extensively reinforced and further fortified with additional materials to ensure load transmissibility. Twin-hull configurations, such as those used in big lift crane barges previously discussed, are highly favored from a structural perspective for contemporary designs involving heavy loads due to their highly effective load transmissibility and uniformity.

Flotation and Stability

Following loads, this is the next crucial area to be concerned with. Lifting underwater carries far more risks than lifting on land. Furthermore, stability is a major concern anytime there is any external load lifting involved.

One crucial thing to keep in mind is that, when lifting operations are taking place on a crane barge, the hull must be in a stable equilibrium state in both the transverse and longitudinal axes.

Thus, at this point, two crucial factors must be considered:

Positioning the Lifting System or Equipment

Since the Crannage cannot be mounted at any random location, its arrangement is crucial for stability.

The system must be positioned at a thoughtfully chosen point such that, when lifting operations are performed for specified maximum loads, the moment created does not materially change the vessel’s overall stability. No cranage should be positioned at the side shell or at the extremes of a particular deck area; instead, it should be put somewhat inward and toward the midships.

The cranage’s arm or boom is another crucial component that must be taken into account at this particular time, so its length is carefully chosen without sacrificing its lifting capacity and reach. For extremely heavy load lifting, the most stable configuration is twin-hull crane barges, where the cranage system is equally distributed and supported between two hulls.

Hull Stability

Crane Barge
(Credit: Marine Insight)

The hull is designed to ensure both longitudinal and transverse stability, taking into account the cranage and the loads to be lifted.

From the perspective of the hull, stability is now designed in the same manner as other boats. The hull’s dimensions are chosen so that, under both full load and no load circumstances, the overall setup maintains balance.

The barge’s dimensions should, first and foremost, be such that, under full load conditions, the displacement is sufficient to provide the appropriate buoyancy without sinking.

The breadth and depth of the hull for transverse stability should be such that the vessel still holds together at the highest moment produced by the maximum load lifted in conjunction with the maximum outstretch of the arm.

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Crane barges hence typically have a large width to depth ratio. The freight lift will also be stowed in the expanded deck area.

Depth and draft are kept high so that even at maximum moments and at a certain list level, the countering moment is adequate.

Yet too deep waters are avoided as they may add to the hull’s weight, which is undesirable for loading.

By providing the stability parameters, a restoring moment will be generated if the vessel lists during lifting operations.

Modern designs often include swing engines or anti-roll mechanisms to maintain stability under all circumstances.

Power and Propulsion: A crane barge is designed to lift and move large, heavy loads.

The number of tugs and their ability to draw bollards when hauling barges depend on the weight of the barge.

Because the propulsion system of self-propelled heavy load barges must bear both its own weight and the weight of the cargo hoisted, it must be calibrated to an extremely high degree. Nonetheless, these barges have relatively low speed requirements.

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