Damen Shiprepair Amsterdam installs crane boom extension on jack-up vessel ‘Sea Installer’

Damen Shiprepair Amsterdam

  • Date: June 2016
  • Ship name: ‘Sea Installer’
  • Ship type: Offshore Construction Vessel / Jack-Up

Type of tasks performed for this project:

  • Conversion
  • Modifications

Damen Shiprepair Amsterdam (DSAm), part of the Damen Shiprepair & Conversion group, carried out major modification works on the jack-up vessel ‘Sea Installer’.

The principle scope of work involved the extension of the main crane boom giving ‘Sea Installer’ the increased reaching capacity required to handle bigger offshore wind installation projects.

With the increasing size of offshore wind turbine components, this major modification work brings ‘Sea Installer’ into line with growing demands of offshore wind industry.

Other work comprised structural modifications necessary as a consequence of fitting the larger crane.

Damen Shiprepair Amsterdam is equipped with excellent facilities capable of meeting the highest expectations in both speed and quality.

Damen Shiprepair Amsterdam

Stable foundation

To create a stable lifting foundation – allowing for a maximum of 0.3 degrees of tilt – the quayside at DSAm was levelled prior to the vessel’s arrival at the yard. This required laying around 800 cubic metres of sand, topped off with 750 dragline crane mats.

Once ‘Sea Installer’ arrived, work began with the removal from the vessel of all crane-related components including the boom, boom rest, A-frame, winch and hook block pockets. The crane boom was then lengthened by inserting a new extension supplied by the client, A2SEA, together with the new A-frame.



With all the elements composed of high tensile S690 steel there were strict timing issues that had to be followed.

“This material requires distinct and carefully planned procedures. Before welding, it needs to be heated up to 200°C to remove any traces of water,” explained DSAm Junior Project Manager Remco van Dam. “Then, after slight cooling, the welding itself needs to take place at the correct temperature in a protected environment. For this, we constructed air-tight welding tents.”

Once welding was complete, cooling could then take place prior to checks and testing.

“We performed our own initial checks after 24-hours in case any additional welds were needed. The main point with S690 is that you cannot rush things. If you go too fast, it can set you back three days,” Mr van Dam added.

Further non-destructive testing took place after 48-hours including inclining and load testing up to 770 tonnes.

On completion of the final tests, two mobile Mammoet cranes were used to lift the extended crane boom back onto the vessel.


Installing the larger crane on the ‘Sea Installer’ had numerous implications on existing on board structures.

The boom rest needed replacing, which in turn necessitated additional modifications to the accommodation area. In order to house the main hook and auxiliary hook in both long and short mode, the existing auxiliary hook block pocket was replaced with a new construction comprising a main and two auxiliary hook block pockets.

Niron Staal, also part of Damen Shiprepair & Conversion, supplied the new boom rest, hook block pockets, trolley rail and support stools.

The winch was replaced with a larger, 900-tonne capacity, winch, work that included all the necessary adjustments to the electrical, hydraulic and cooling systems. The vessel’s main mast also needed structural modifications.

While the ‘Sea Installer’ was at the yard, DSAm also carried out standard maintenance jobs such as painting the main deck, pipe renewal, renewal of forward mooring line rollers and thruster inspection.

In addition, divers replaced the Spudcan anodes and the liferaft davit was moved, a job that entailed underdeck stiffening at the new location, releasing the old foundations and welding these at the new location.

Safe and cooperative

As is standard working practice at DSAm, safety issues were top of the agenda for yard personnel and the vessel’s crew who remained on board throughout the works.

The smooth running of the entire project was facilitated by the joint efforts of the DSAm and A2SEA personnel. 


‘Sea Installer’

‘Sea Installer’ is 132 meters long with a beam of 39 meters and is A2SEA’s second-generation wind turbine installation vessel. The vessel is able to transport and install up to eight 3.6MW turbines has been designed to operate in the more challenging conditions that are encountered further offshore and in deeper water. The extended crane can slew 360 degrees, extend 100 metres and lift 900 tonnes.


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