Offshore pipeline laying, what can marine cranes do?

As a key facility for transporting important resources such as oil and natural gas, offshore pipelines’ safety and stability are of vital importance. In this field, marine cranes play a role that cannot be ignored. Today, let us learn about the importance of marine cranes in the offshore pipeline laying process.

Pipe laying method

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The S-lay method is the preferred method for laying pipelines in shallow to moderately deep waters and takes its name from the unique S-shaped structure formed during the laying process. Individual pipes are systematically welded together on board and undergo rigorous quality assessment. Afterwards, the string of pipes slowly left the stern of the ship and fell into the water under the guidance of the stinging needle. As each pipe section is added and extended into the sea, together they form the iconic “S” shape, the most cost-effective solution.
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The J-lay method is a newer deepwater installation technology. Its name comes from the unique “J” shape the pipe forms during laying, extending from the surface of the ship to the seafloor. The J-lay method is suitable for pipes from 10 inches to 50 inches in diameter in deep and ultra-deep water. Multiple pipes are pre-assembled into “strings” and then placed vertically in specially designed J-lay towers on the laying vessel. The J-type laying method has greater resistance to water flow and higher pipe installation accuracy.
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Unlike the S-Lay and J-Lay methods, the Reel-lay method involves fabricating the pipe onshore prior to deployment. After the pipe is manufactured, it is wound onto a vertical roller (also called a carousel) on the ship. During installation, the drum lay method can be used in an S-lay or J-lay configuration, depending on the capabilities of the pipelay vessel. This method is more efficient in short pipe laying operations.
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The pulling method is often used when installing multiple pipes that are bundled together. This method is achieved using tugs, buoyancy modules and weighted chains. Specifically, there are four methods:
▶Bottom drag method
Bottom-drag pipelay is an attractive method that guides pipe laying along the seabed without the use of buoyancy modules.
▶Off-bottom dragging method
The distinguishing feature of the off-bottom towing method is the careful installation of buoyancy modules on the pipeline, which are cleverly connected together by chains to maintain contact with the seabed, allowing it to hover approximately 1 to 2 meters above the seabed.
▶Medium and deep drag method
During complex pipe installations, mid-deep dragging is a sophisticated technique that applies controlled tension to hold the pipe in place.
▶Water surface towing method
The surface towing method involves towing the pipe on the water. In this method, a tugboat is used to tow the pipeline, and the buoyancy module plays an important role in keeping the pipeline afloat. This method uses two tugs, one responsible for towing and the other responsible for towing, to ensure the controllability of pipeline transportation.

The role of marine cranes in pipeline laying

During the laying process of offshore pipelines, marine cranes are mainly responsible for lifting and positioning tasks. Marine cranes can lift prefabricated pipe sections into predetermined locations. Then, with precise manipulations, the pipe sections are placed into their correct positions. In this process, the stability and accuracy of the marine crane are crucial.

The submarine environment is harsh, and pipelines may be affected by various external forces during laying and operation, such as ocean currents, wind waves, submarine landslides, etc. At this time, Oucha’s marine cranes can also respond to various emergencies in a timely manner and protect the safety of pipelines through their powerful lifting capabilities.

Conclusion

The laying of offshore pipelines is a complex and time-consuming process. The existence of marine cranes can greatly improve construction efficiency and shorten the project cycle, thus improving the economy of submarine pipeline transportation.

Our technologies are widely used in various fields, including offshore oil production platforms, platform supply vessels, offshore floating production, storage and offloading vessels (FPSO), offshore construction vessels, liquefied natural gas (LNG) vessels, etc. It has always maintained excellent safety and stability as well as strong lifting capabilities, winning the trust of customers around the world.