Unit Fabrication

In most instances the 2-dimensional sub-assemblies will be built into 3-dimensional block assemblies. The size of the block assembly will have been decided at an early stage of the planning process ideally at the structural design stage. Constraints such as lifting capacities and dimensions that can be handed are taken into consideration also the provision of breaks at natural features ensuring the block are self supporting and easily accessed etc. Panel assemblies used in the block may well have dimensions restricted by the plate length that can be handled at the machining stage and this can subsequently influence block length. In the machinery area the block size and arrangements can be decided by zone outfit considerations.

Each block should be designed for maximum downhand welding but may have to be turned for this purpose. Also block are turned to effect outfit installation particularly those containing machinery flats in the aft engine room areas where pipework etc. can be fitted on the underside of the flat with the block in the inverted position and then it is turned to install equipment above the flat . A block’s centre of gravity is calculated and lifting lugs so provided that these operations can be undertaken, and finally the block can be suspended for erection at the building dock or berth and drop into place in the correct plane.