The 200M vibratory hammer was adapted for this submarine application (-/- 275m) . Precautions were taken and handling tools such as a hydraulic hose reel were included in the scope.
Because of the slope and the importance of drilling down vertically, a support casing was vibrated into the seabed with an PVE 200M vibratory hammer to guide the LLD Drill. Operating at 275m depth is a challenge for a vibratory hammer. First, the high atmospheric pressure must be compensated for, secondly the handling of 275m length of hydraulic hoses needs to be meticulously planned. At 200m depth water pressure is 21 bar, the 200M gearbox was connected to an onboard air compressor to supply air pressure. The regulation system’s 1-inch air hose was part of the hydraulic hose package. The 200M’s gear box fitted with special seals and pressure compensation ensured no sea water entered the machine.
The 2.3m diameter support casing had a length of 26 meters. The support casing helped the drill traverse a 20m mud layer to reach the hard soil layers. With the casing securely clamped by the vibro it was guided down to the piling position by ROV (remotely operated underwater vehicle). A Jean Lutz inclination sensor gave feed-back to the team about the verticality of the pile, ensuring it met the specified inclination. The 280m hoses were handled by a hydraulic hose reel.
So, why bring a 200M vibro all the way from The Netherlands? With the enormous cost associated with a remote project like this, every tool used is chosen to be of highly dependable quality. LDD and Dieseko are a trusted combination. The ability to offer onsite support by a team of specialized Dieseko engineers was also a major factor in awarding the contract.