A well known construction company was awarded the contract for the installation and commissioning of a 1219mm diameter, 15km submarine pipe line for an oil refinery in India. The pipe is of steel construction with a cement coating. The pipe line would transport crude oil from oil tankers to the land based refinery.
For the pipe installation the lay barge was positioned 3km offshore, where the pipe was assembled and prepared to be pulled along the seabed. The balance of the 15km pipeline was laid with the barge.
Hyflo, Cape Town Branch was approached to design, manufacture, supply and commission the hydraulic system for the linear winch with a maximum pulling capacity of 3000kN for the submarine shore pull.
The linear winch is a steel constructed framework that consists of hydraulic rams, for the linear motion, one stationary wire gripper and one dynamic gripper. For this linear winch four hydraulic cylinders are used, each with a 250mm diameter bore and 3.2m stroke. Each of the four cylinders has a pulling capacity of 760kN linear pulling force. The cylinder shafts are treated with a special corrosion protection application in order to withstand the harsh marine environment. With a 3.2m cylinder stroke the linear winch has 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 are connected to a wedge type wire gripper. A pull head is welded to the end of pipe with a steel wire rope connected between the pull head and gripper on the linear winch.
A standard 6m container was modified in order to house the hydraulic power unit and auxiliary hydraulic equipment including the control station. The power unit consisted of a 176kW 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. With the horse power controlled pump the linear rope puller can operate at maximum speed with loads of up to 1500kN. With loads exceeding 1500kN the winch speed is controlled based on the system pressure. With this arrangement the winch cycle time was optimised based on the load. During the operation the pulling load was recorded using load cells. This was valuable information to have during the pulling operation and to use for future reference.
A 24 hour pulling operation was required to prevent the pipe from settling into the sand and becoming stuck. During the pulling operation Hyflo trained the client in the operation and maintenance of the winch.