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Reference projects - Offshore construction


DLT have been involved in a number of offshore construction projects, mainly in the skidding and lifting of heavy sub-assemblies within construction yards. We are able to design, supply & operate heavy lifting systems to carry out these operations together with full design of all temporary & strengthening works required. Recent examples of our offshore work include……….


Maari Field Wellhead Platform, Jacket erection, Malaysia
DLT were sub-contracted to design, supply and operate a skidding and jacking system to incrementally erect the 26m x 22m x 140m high 2800 tonne jacket structure. The jacket was erected in 8 sections, weighing up to 660 tonnes each. The bottom section was erected onto the onto the platform base by crane and used to support the skid system and jacking tower system for erection of the top 7 sections. Starting with the top jacket section, the remaining 7 sections were lifted onto a skid track one at a time and moved into position for lifting. The sections were lifted using our DL-TS3000 Mk1 jacking tower system, in 4 tower configuration and using 8 No DL-C450 climbing jacks. As each section was lifted the next section was skidded beneath and the jacket legs welded together. The combined sections were then lifted by the tower system. This process was repeated until the top 7 sections were supported on the tower system, weighing a total of 2400 tonnes. The tower system was then used to lower the top 7 sections onto the bottom section and align the leg joints for welding. Jacket erection took place from October to December 2007 and the finished jacked was surveyed as being plumb to within 10mm at the end of our jacking operations.

Sea Drill pontoon launch, Singapore
DLT were sub-contracted to side shift and launch 2 No 3600 tonne pontoon units at the Jurong Shipyard, Singapore, in May and June 2007 for the Sea Drill floating platform No 8. The fist pontoon was launched 125m down a 6 degree slope into the water in May. The second pontoon was side shifted 100m into position for launching and then launched down the same slope as the fist pontoon. The pontoons were supported on inflated air bags for all these operations and moved using 2 no DL-S185 strand jacks and 2 No DL-L30F/1/350/120/E power packs for a launching speed of 17 m/hour, controlled using the DL-P40 computer control system.

Corocoro FSO Mooring Line Tensioning, Venezuela
DLT were sub-contracted to assist in the installation of a FSO mooring line system 32Km offshore in the Corocoro Oil Field, Venezuela. DLT designed and supplied the strand jack tensioning system to pull pairs of mooring lines toward one another causing their anchors to plough into the sea bed and subsequently test load the mooring lines to a 700te tension. More>

Supply and operation of strand jack systems for replacement of thrusters
DLT have supplied and operated many strand jack systems for the replacement of thruster units on floating platforms. Strand jacks provide a compact and cost effective solution for handling heavy thruster units and we have developed a system of modular power packs and jacks that can be taken into confined spaces and through bulkhead doorways. We have supplied and operated systems for the following floating platforms:
- Stenna Tay (pictures below). 3 x DL-S60 strand jacks per thruster
- Sea Drill floating platform No 8 & 9, Singapore. 3 x DL-S15 strand jacks per thruster
- Global SantaFe drill ship, USA. 10 x DL-S15 strand jacks per thruster
- Daewoo Shipyard, Korea. 3 x DL-S15 strand jack system
- Frontier Drilling, Brazil. 3 x DL-S15 strand jack system

Load out of FPSO pontoon, Korea
DLT were responsible for the design, supply & operation of a strand jack system to load out a 14,500 tonne FPSO pontoon onto a delivery ship, for main contractor Hyundai. The deck was moved 125 metres using four 580 tonne capacity strand jacks.

FPSO mooring pendulum installation, Singapore
DLT were responsible for installation of 2 No 120 tonne mooring pendulums for SMOE in Singapore, using strand jacks to achieve a positional alignment of +/- 0.2mm for installation of 5 tonne pitch pins.

Dismantling of the Brent Spar oil storage platform
DLT were responsible for the design of a 2300 tonne lifting capacity lifting gantry for handling cut sections of the Brent Spar as it was decommissioned in a Norwegian fjord in 1999. The gantry used 4 No 580 tonne capacity strand jacks for lifting and a gripper jack system for longitudinal movement over the decommissioning barge. The legs and cross beams of the gantry structure were made from a proprietary tower system which were connected and braced using purpose designed steelwork.

Offshore load outs in Scotland
DLT (Zalcon) were responsible for the design, supply & operation of strand jacks systems for the load out of the following offshore structures in the 1990’s:
B.P. Bruce Jacket (above)
8,900 tonnes
320m load out
  
B.P. Bruce Deck
10,000 tonnes
180m load out
  
Shell Nelson Jacket
8,600 tonnes
330m load out
  
Marathon East Brae Jacket
9,800 tonnes
280m load out
  
Shell Dunbar Jacket
8,000 tonnes
250m load out