Block pre‑outfitting is one of the core technologies of modern shipbuilding. Installing piping, cable trays, equipment foundations and other outfitting items at the block stage can significantly reduce work at height and cross‑operations in the dock. However, pre‑outfitting imposes extremely high demands on precision: if the positional deviations of outfitting items on blocks accumulate, serious problems such as flanges failing to align and foundation misalignment will occur during berth assembly. Jiangsu Haizhongzhou Shipping Industry Co., Ltd. has established an “outfitting precision control network” to keep the positioning error of pre‑outfitting within millimetres.
The core of outfitting precision control is datum transfer. For each block during its fabrication stage, Haizhongzhou first establishes the block’s own reference system on the cradle – including a longitudinal datum line, transverse datum line and height datum points. These datum points are projected from the block’s 3D model onto the actual workpiece using optical instruments. After the block structure is welded, a total station is used to re‑measure the actual coordinates of the datum points and calculate the deviation from theoretical values. The installation and positioning of all outfitting items are based on these verified datums, rather than directly measuring the relative positions between outfitting items, thereby avoiding error accumulation.
For the positioning of pipe flanges and penetrations, Haizhongzhou uses a “simulated pipe” technique. Before actual pipe installation, adjustable‑length simulated pipes (with flanges at both ends) are pre‑routed on the block. The simulated pipe can quickly adjust its length and angle according to the reference system, determining the optimal pipe routing and flange interface positions. Once confirmed, the length and flange angle data of the simulated pipe are entered into the system as the basis for formal pipe fabrication. This method avoids the waste of repeatedly cutting and welding pipes on the block, while ensuring that pipe interfaces can be precisely aligned after block assembly.
The positioning of equipment foundations is even more demanding. Taking the main engine foundation as an example, the flatness and levelness deviation must be controlled within 0.1 mm per metre. Haizhongzhou performs the finishing of the main engine foundation at the block stage, using a laser tracker to measure the actual coordinates of the foundation surface and generating a deviation colour map via computer. For out‑of‑tolerance areas, manual scraping or mechanical milling is used to correct the surface until the contact spot density reaches no less than eight spots per 25 mm by 25 mm area.
After pre‑outfitting is completed, Haizhongzhou performs an “outfitting completeness check” on each block. The check includes the coordinates of pipe interfaces, the perpendicularity of flange faces, the position of cable trays, the levelness of equipment foundations, and so on. All inspection data form a block outfitting report, which is shared with the owner and classification society before the block leaves the workshop. It is this pursuit of precision from millimetres to micrometres that has enabled Haizhongzhou’s pre‑outfitting rate to exceed eighty‑five percent, while the outfitting rework rate in the dock is controlled below five percent.
