There are six SSCV's in the world. These self-propelled vessels are constructed on floaters that can be submersed some twenty meters below the sea level during offshore operation. This results in a highly stable positioned upper deck, even under very rough wind and sea conditions. Huge cranes are mounted on the main deck. The vessels are used for the construction of oil/gas production platforms offshore.
The first crane ships for offshore construction were ship-shaped, usually modified oil tankers with a single crane mounted on the hull. However, the relatively high sensitivity to wind and sea conditions limits the number of construction days a year (especially in the North Sea). An SSCV can work nearly all year around. The higher hoisting performance of the cranes also allows platform upper decks to be installed in one, or only a small number of pieces, reducing expensive offshore hook-up activities.
Balder and Hermod are two of the first SSCV's and were build in 1978 and 1979. Both vessels have two
cranes on the stern. Balder and Hermod are originally sister ships, but the Hermod has undergone a
major upgrade in the mid-eighties, and Balder was converted into a DCV
(Deep water Construction Vessel) in 2001.
After completing its work near Sable Island in Canada, Hermod was docked in July 2004 at shipyard
Keppel Verolme in Rotterdam, the Netherlands.
Machine Support was asked to do the alignment of the stern tube and nozzle with a dismounted propulsion shaft but with a mounted intermediate shaft. Machine Support mounted their laser alignment equipment on the intermediate shaft and afterwards the measured values were corrected with the sagging of the shaft due to its own weight. In this way the alignment was known between the stern tube and the propulsion line and was found good. Although the alignment of the A-frame bearing was out of tolerance and had to be machined to the correct line. This was done within 0.05 mm accuracy over a length of more than 12 meter. Then we did a shaft load reaction force test on both the star board and port side shaft line. For this measurement we have developed a fast and accurate system, which makes it possible to get a direct overview and report from the results. It is directly available in a digital chart and can be printed out at the same time. When the other work on Hermod is finished, the crane vessel capable of lifting 9000 t. will leave for a new job.
