Hi-Force, UK manufacturer of high pressure hydraulic tools, recently undertook its largest lift project ever as part of a supply contract to the State Oil Company of Azerbaijan Republic (SOCAR).
The SOCAR contract involved the supply of 20 pieces of custom manufactured 1012 ton lifting capacity cylinders, 4 units of 700 bar maximum working pressure, split flow pump units, a PLC control system and over 1,2 km of high pressure, hydraulic hose, all combined to create a precise jacking system capable of lifting 16 192 tons to a maximum height of 900 mm. The demand for this system was brought about by SOCAR’s requirement to lift a deepwater jacket measuring 151 metres in length and 80 metres in width in order to carry out vital maintenance to the skidding system on which the jacket was positioned prior to it being mobilised offshore in the Caspian Sea.
It was decided that the lift would be carried out using 16 cylinders, each of 1012 tons lift capacity, strategically placed in 16 lifting positions spread across the footprint of the jacket as it lay on its side. These cylinders would be operated in banks of four from four split-flow hydraulic pump units which would subsequently be controlled by a centralised PLC control system. The control system would ensure that the cylinders would lift simultaneously, regardless of the loading on each cylinder, in a synchronised fashion and would remain within a maximum of 1 mm of stroke variation to each other throughout the duration of the 605 mm total height of lift.
The race then began to complete the manufacture of the 20 monster cylinders, as well as the pump units, PLC and accessory items. With safety as the number one priority, the decision was taken to manufacture and supply Hi-Force failsafe hydraulic cylinders to carry out this lift. Failsafe cylinders, while lifting the load via hydraulic power, also incorporate a mechanical load holding facility that enables the load to be secured mechanically both during the lift (in case of hydraulic failure) and after the lift has been completed. This would then allow the maintenance of the skidway under the jacket to be carried out without the need to place any additional mechanical load holding blocks underneath the jacket.
Considering the huge load to be lifted and the relatively high piston extension required (605 mm), it was decided that the lift would be carried out in 10 mm intervals, with the cylinder piston mechanical load holding rings being secured at each 100 mm interval. This would minimise the risk and consequences in the very unlikely event of any hydraulic failure.
After initially raising each cylinder piston to a point where all 16 were in contact with their respective lift point on the jacket, the system was operated and the jacket lifted to a height of threshold of 1 mm across all 16 units. Once this initial 100 mm lift had been achieved, each cylinder was inspected and the piston mechanical load holding rings were wound down to secure the load mechanically prior to the lift height being increased by a further 100 mm to 200 mm. This procedure was repeated at each 100 mm interval of the lift until the required lift height of 605 mm was achieved and each cylinder piston load holding lock ring was secured mechanically.
Throughout the lift the hydraulic pressure present in each cylinder was continually monitored to ensure that there was no danger of any cylinder being overloaded beyond its individual capacity of 1012 tonnes at 700 bar maximum working pressure, with readings taken from the display unit of the PLC control at each 100 mm interval.
Upon completion of the lift at the 605 mm required height, final readings were taken from all 16 cylinders and the total weight of the jacket was calculated to be a colossal 10 455 tons.
For more information contact Roy Pursey, Hi-Force Hydraulics, +27 (0)11 314 0555, [email protected], www.hi-force.com
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