LIFTING, HANDLING & PILING MECHANICAL DETAIL
PILING INTO THE EQUIPMENT MARKET
“When it comes to pile foundations, offshore contractors continually look to improve installation
accuracy and safety” says James Russell, Houlder’s Marine Equipment Director.
The equipment typically uses self-contained hydraulic power to drive large motion- control actuating cylinders controlled by single cRIO controllers and bespoke software. These are located within a central cabinet housing standalone safety systems and other hardware.
CONTRACT DETAIL
Operators have chest pack controllers comprising an HMI screen and joystick. The packs interface with the HPU, hydraulic manifold plates, hydraulic cylinders and locking pins to provide position data and warning alarms.
ACCOUNTABILITY
Houlder takes accountability from initial design work through fabrication to testing, installation and setting to work. Fully integrated project teams are formed at the start of each project. Design work benefits from the company’s practical knowledge of ships and operational expertise in construction.
Ease and speed of installation are key to the equipment’s success and the company’s joined up approach provides efficiency savings and mitigates technical and operational risk.
The company is an independent provider of offshore engineering working from offices across the UK and the USA. The company’s engineers have responded to the above offshore construction challenge with a range of deck equipment that lifts, upends, manoeuvres and restrains piles against environmental forces. Clients using the company equipment also benefit from the company’s aligned naval architecture, offshore construction and vessel integration expertise.
TURNKEY APPROACH “Our turnkey approach provides savings and mitigates risk” James continues.
Piles vary from 500t jacket pin-piles to 900t, 8m diameter monopiles installed in water depths that reach 60m. One size rarely fits all and Houlder has focused on flexibility with its range of pile restraint arms and frames. They keep piles in position and vertical against forces up to 240 tonnes equating to 4.6m maximum wave height and currents of 2.5 knots.
SAFE OPERATION
Houlder ensures safe operation through thorough accidental load calculations and Failure Mode and Effect Analysis (FMEA) on all its equipment. A safety gap is maintained around piles to prevent accidental damage and minimise the risk of clashing.
Control loop systems keep components aligned within very small tolerances (+/- 5mm). Overall risks associated with human intervention are minimised by the provision of remote control for normal operations.
CASE STUDY
As an example, Saipem recently installed an innovative pile restraining cantilever frame on the heavy lift ship Derrick Barge Azerbaijan (DBA) to support jacket installation. It horizontally restrains and adjusts the inclination of 140m, 525t steel foundation monopiles - keeping them vertical as they are driven in 95m of water. 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 turnkey arrangement and the complete 80t frame was supplied ex-works and packed ready for transport. The company then deployed a team to Baku to supervise installation.
Dario Frisinghelli of Saipem commented “The restraining frame was used for offshore installation of all eight foundation pin-piles. The system, actuated by hydraulic jacks on the 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 a depth of 24m into the seabed. This control was particularly important during the first metres where a layer of hard soil resulted in extremely reduced penetration speed affecting the overall stability of the pile.”
FRAME DETAIL The 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 fore/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
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