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Subsea Pin Pile Installation Frame
Houlder has delivered a pin pile installation frame to Saipem as part of the Shah Deniz gas field development in the Caspian Sea.
The development, 100km from Baku, Azerbaijan, requires the installation of eight steel jacket foundations for two new platforms. These are to use pin pile foundations temporarily prior to the installation of skirt foundations.
Saipem deployed the innovative pin pile installation frame on the deck of the heavy lift ship Derrick Barge Azerbaijan (DBA) tasked with the jacket installation. It horizontally restrained and adjusted the inclination of 140m, 525t steel foundation monopiles – keeping them vertical as they are driven in 95m of water (pictured above.) This requires the frame to deliver operational horizontal force resistance of 75t in any direction within a 4m diameter operating envelope.
Houlder delivered the contract under a typical turnkey arrangement – being accountable for the design from initial concept through to fabrication. The 80t frame was supplied ex-works and packed ready for transport. Houlder sent a team of engineers to manage the installation in Baku.
Dario Frisinghelli, Saipem T&I and Subsea Project Manager commented “The restraining frame was used for offshore installation of all 8 foundation Pin Piles. The system, acting by hydraulic jacks on two degrees of freedom in the horizontal plane, proved greatly effective during operation. This allowed Saipem to maintain the verticality of the Pile during the transient phase of self-weight penetration to depth of 24m into the seabed. This control was particularly important during the first meters where a layer of hard soil resulted in an extremely reduced penetration speed affecting the overall instability of the pile.”
The pin pile installation frame comprises the following;
A cantilever base structure – this deck frame is a steel, bolted sub-assembly welded to the side of the DBA vessel
Base horizontal restraining frame – this can adjust the pile position through +/- 2m of port`/starboard transverse movement driven by large transverse cylinders.
Top horizontal restraining frame – this can adjust the pile position through +/- 2m of for/aft longitudinal movement driven by two cylinders attached to the cantilever base structure.
Restraining arms – these grip the 2.5m diameter monopiles directly with non-friction pads maintaining a 50mm air gap. Hydraulically driven, their closed position is at maximum cylinder extension to prevent crushing.
Access gangways – bolted to the top frame structure, main gangways provide easy access for human intervention at the pile and restraining arms as required. Secondary gangways provide access to pins and cylinder valves.
Key to successful operation are primary and secondary control systems that allow cylinders to maintain smooth, equal displacement at all times. For example, under normal operation the transverse cylinders work under closed loop position control. This ensures they remain aligned with an expected accuracy of 20-30mm.
James Russell, Houlder Director of Marine Equipment commented, “We were able to bring our combined understanding of vessel operations, heavy lifting and pile handling to support Saipem with a challenging installation. Our approach of fully integrating our pile installation equipment design and build teams also supported delivery against tight timescales and to budget. “