Fabrication process and delivery
Not only were there several design and engineering challenges that needed to be addressed, but also the entire fabrication process and delivery to the client needed to be safeguarded. As always our engineering team was up for the challenge and after an initial orientation phase the design and engineering works started in earnest.
The objective of the block baskets is to support the lower blocks of the crane in stowed position and also provide access to the lower blocks for inspection and maintenance purpose. In close cooperation with Allseas the design was agreed upon. The design needed to take several major design restrictions into consideration; such as actual positioning and clearance issues with other equipment on the vessel and access for inspections and maintenance. Once the design was in place the actual engineering process could commence. Considering the relatively large weight of the main and auxiliary blocks, 200 tons and 50 tons respectively, and the significant environmental survival conditions (significant survival wave height Hs =14m) resulted in rather complex FEM models being generated of both block baskets. Once the FEM models were completed the actual process of generating all the fabrication drawings was started.
As with everything on Pioneering Spirit – the biggest construction vessel in the world – the block baskets are gigantic. The main and auxiliary block basket have outer dimensions (L, B, H) of approximately 8.0m x 10.0m x 9.0m and 4.0m x 5.0m x 5.0m respectively. The total weights of the baskets are approximately 45 tons and 12 tons respectively.
Both baskets have been fully outfitted with ladders, stairs and railings. All walkways have been fitted with composite offshore grating. These gratings require less maintenance and are lighter, more slip and corrosion resistant than regular steel gratings. The main hoist block basket has almost 80m2 of walkways while the auxiliary block baskets walkway area is limited to 12.5m2.