Offshore Construction Archives - DUC Marine Group

Installation of a boatlanding

ducmarinegroup — Thu, 04 Mar 2021 11:35:03 +0000

INSTALLATION BOATLANDING

30 km North of Helgoland, Germany.

Because the distance of the fenders of several CTVs to the existing current sports of the boatlanding was not sufficient, the Client asked DUC Marine Group to install two extension pieces. For this job DUC mobilised a big Multicat, a CTV, a RIB and a Rope Access Team. The ladders were loaded in the port of Delfzijl (Holland) and were prepared on deck for installation.

Because of the lifting height and the movement of the vessel on the swell, DUC was careful not to damage the steel structures and decided to hoist the pipes with an electric hoist and a Rope Access Team. Due to the existing inter array and export cables anchoring was prohibited. Mooring with ropes to the jacket was also prohibited.

To overcome this problem the extension pieces were gently lowered into the water with the Multicats Deckcrane and connected to a 5 ton lifting bag underwater. The lifting bag was then towed to the boat landing and hoisted into position. All bolts were tightened to the correct torque. In total 4 pieces were installed.

Categories: Boat landing, Maintenance and Repairs, Offshore, Offshore Construction and Installation, Oil and Gas, Renewables, Wind Park, Rope Access

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Grout lines removed

ducmarinegroup — Tue, 22 Dec 2015 08:49:56 +0000

GROUT LINES 28.4 KM REMOVED

Contract
In the middle of August 2013 DUC Marinegroup received a contract from RWE Innogy, for works on the offshore windfarm Nordsee Ost, located some 30 km North-East of the Island of Heligoland in the German Bight. The contract comprised the removal of temporary grout and hydraulic lines, which were utilized during the installation of 49 offshore foundation jackets during the winter season in the North Sea.

The jackets were installed for the later mounting of the 6 megawatt turbines. The hoses run from a service station at the top of the jacket (25 m above MSL), on the outside of the structure over the bracings to the foundation sleeves at the bottom (25 m below MSL). A typical jacket was fitted with 4 hydraulic lines and 8 grout lines.

Partnership
For the industrial climbing works DUC Marinegroup teamed up with the Rope Access Group from the Netherlands. It proved to be a very fruitful partnership between DUC and the Rope Access Group teams, to be continued again.

Personnel and equipment
Directly after signing the contract a project team was set up and work preparations commenced. Instead of a DP-2 vessel DUC chose to deploy a big multicat to be converted into a dive support vessel. In less than three weeks DUC mobilized the following:
–   A full Rope Access Team;
–   A crew transport vessel;
–   A full dive team;
–   A dive support vessel with a three point mooring, a LARS-system, a combined dive control/deco container, a nitrox container, 3 extra TLQ’s with 8 persons capacity and an office;
–   A 10 m RIB with a SRS-system.

Home port for the operations was the island of Heligoland. In the south-harbour a temporary stockpile was set up to store the removed hoses. Whenever possible, the dive support vessel stayed offshore and divers worked in 24-7 shifts, whereas the Rope Access team worked 12 hr shifts and sailed every day by CTV to and from Heligoland.

The grout lines were left partly filled with grout. The hydraulic lines still contained hydraulic oil. Before cutting the hydraulic lines all underwater valves had to be opened by the divers. The RAT-team flushed the lines with fresh water and detergent. All out coming fluids were collected and disposed. The service stations were then removed.
In total DUC had to remove some 28.4 km of hoses. The divers and the RAT-team used special hydraulic tools to cut the lines in easy manageable lengths, which were then stored in skips onboard the dive support vessel.

Satisfied by the accomplished work DUC Marine Group was assigned – during the job by RWE Innogy to carry out extra diving activities in the wind farm:
– The installation of several sonar- and motion transponders;
– The removal of debris in the proposed cable array;
– Inspection of several J-tube bellmouths;
– Inspection – and repairs of gratings, railings etc. after recent storm damage.
During the project the DUC fleet increased. During the busiest period DUC was in Heligoland with two dive support vessels, two dive teams, three CTV’s, an anchor handling tug and two RAT-teams.
Logistically, DUC Marine Group faced a lot of downtime due to inclement weather conditions during the winter working season.
However the project was successfully completed in good time and much quicker than anticipated, without any injuries and to the full satisfaction of our client RWE Innogy.

Categories: Offshore, Maitenance and Repairs, Offshore Construction and Installation, Renewables, Rope Access, Survey and Inspection, Wind Park

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Installation of a single-point buoy

ducmarinegroup — Tue, 22 Dec 2015 08:22:51 +0000

INSTALLATION OF A SINGLE-POINT MOORING (SPM) BUOY IN ROMANIA

Early June 2008, the workship RAM departed to the Black Sea in Romania for a major job for Van Oord Offshore. The RAM travelled via the Rhine, the Main Danube canal and then the Danube to arrive in the port of Midia, where the Rompetrol oil company has a large refinery. An SPM buoy had to be installed 8 km off the coast to make it possible to receive large cargoes.

The job was a follow-up to the work done with Van Oord in 2007, where assistance was given during the installation of, and subsequent coating repairs to, the Workum – Medemblik gas pipeline (using a habitat).

Before the six anchors to which the buoy is moored could be installed, 8 km of approximately 800-mm diameter pipe was to be installed using a large pipe layer.
The DUC divers performed regular inspections of the ‘touch down’ locations, the pipe trench and the position of the new pipeline.
In the meantime, the RAM was used in the port as a crane ship for the assembly of the SPM buoy and the Pipe Line End Manifold (PLEM) that forms the connection between the pipeline on the seabed and the subsea hoses that are attached to the buoy.

The connection of the PLEM to the pipeline and the connection of the hoses to the buoy were made at a depth of 27 metres. For this reason, we chose to use our own Nitrox systems.

After the connections were made, all of the attachment bolts were tightened using a “Hydratight” system.
The diving activities were completed in November, after which the RAM remained at the site to perform various tests. The activities for DUC Marinegroup were completed in January 2009, including all of the tests. The main activities that DUC was involved in for this project were the use of our workship the RAM, the execution of all of the diving activities, including the dimensioning and installation of the spool piece, hydratightening, inspections, the connection of the hoses between the PLEM and the buoy, etc.

Categories: Offshore, Offshore Construction and Installation, Oil and Gas

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