Hyflo pulls its weight offshore

Hydraulic systems & components

3rd Quarter 2010 Hydraulic systems & components

Installing subsea pipelines in the offshore marine environment is a complex and difficult task.

It requires specialised marine vessels and pipe laying barges from which the pipe sections are assembled and laid onto the ocean floor. This method is effective offshore, but closer to the shoreline the tide conditions and lack of water depth become a problem. To overcome this a powerful mechanical device is needed to pull the pipeline ashore from the barge in order to connect to a base point on land. These pipelines can convey anything from water to crude oil.

Pipeline contract

A well known construction company was awarded a contract for the installation and commissioning of a 48 inch (1219 mm) diameter submarine pipeline for an oil refinery in India. The pipeline would transport crude oil from oil tankers to the land-based refinery.

The lay barge was positioned 3 km offshore, where the pipe was assembled and prepared to be pulled along the seabed. The balance of the 15 km pipeline was laid with the barge.

Linear winch by Hyflo

Hyflo was approached to design, manufacture, supply and commission the hydraulic system for the linear winch. A maximum pulling capacity of 3000 kN was required for the submarine shore pull.

Linear winch and hydraulic power unit setup during pulling operation. The winch is anchored with a hold back arrangement in excess of 3000 kN. At the rear end of the winch, the specialised shackles with load cells can be seen

3000 kN pulling force

The linear winch had a steel framework consisting of hydraulic rams for the linear motion, one stationary wire gripper and one dynamic gripper. Four hydraulic cylinders were used, each with a 250 mm diameter bore and 3,2 m stroke. Each of the four cylinders had a pulling capacity of 760 kN linear pulling force. The cylinder shafts were treated with a special corrosion protection product in order to withstand the harsh marine environment. With a 3,2 m cylinder stroke, the winch had the ability to work through a spelter socket connection on the pulling cable without disconnecting the load from the winch.

The rod ends of the cylinders were connected to a wedge type wire gripper. A pull head was welded to the end of pipe with a steel wire rope connected between the pull head and gripper on the linear winch.

Hydraulics housed in container

A standard 6 m container was modified in order to house the hydraulic power unit and auxiliary hydraulic equipment, which included the control station. The power unit consisted of a 176 kW diesel engine driving a load sense, horse power controlled, hydraulic pump set. The pump supplied pressurised hydraulic fluid to the cylinders for the pulling operation. The horse power controlled pump allowed the linear rope puller to operate at maximum speed with loads up to 1500 kN. With loads exceeding 1500 kN, the winch speed was controlled based on the system pressure. With this arrangement it was possible to optimise the winch cycle time based on the load. During the operation the pulling load was recorded using load cells. This information was valuable for the pulling operation as well as for future reference.

24/7 operation

A 24-hour pulling operation was required to prevent the pipe from settling into the sand and getting stuck. During the pulling operation, Hyflo trained the client in the operation and maintenance of the winch.

For more information contact Lee Penderis, Hyflo, +27 (0)21 514 3037, [email protected], www.hyflo.co.za

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Hydraulic systems & components

Hyflo pulls its weight offshore

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