The main diesel engine is the heart of a vessel, and its installation quality directly determines the vessel’s vibration, noise and propulsion efficiency. An engine weighing several hundred tonnes must be precisely lowered onto the engine room foundation and aligned with the shafting to within microns, imposing extremely high demands on the installation process. Jiangsu Haizhongzhou Shipping Industry Co., Ltd. uses the combined technology of “epoxy chocks plus laser alignment” for main engine installation, ensuring long‑term stable operation of the engine.
The first step of main engine installation is foundation preparation. The main engine foundation consists of two or three longitudinal girders and multiple transverse bulkheads, and its top machined surface requires extremely high flatness and levelness. Haizhongzhou pre‑machines the foundation at the block stage, and after assembly performs a final precision milling. During milling, a laser tracker measures the elevation of the machined surface in real time, with machining accuracy controlled within 0.1 mm per metre. A contact spot check on the foundation plane requires no fewer than six spots per 25 mm by 25 mm area.
The lowering of the main engine uses a computer‑controlled synchronous jacking system. Hydraulic jacks are installed at four or six lifting points on the engine, and the computer synchronously controls the lifting speed and stroke of each jack, keeping the engine level during lowering to avoid stud jamming or chock cracking due to tilting. After lowering, the gap and offset between the engine crankshaft output flange and the intermediate shaft flange are measured. Haizhongzhou uses a laser alignment instrument, requiring a gap deviation not exceeding 0.05 mm per metre and an offset not exceeding 0.1 mm.
The gap between the engine and the foundation is filled with epoxy resin chocks. Epoxy chocks have high compressive strength, low shrinkage and good vibration resistance. Before pouring the epoxy, Haizhongzhou blasts the foundation surface and applies a primer, then installs moulds. The epoxy resin and hardener are mixed in proportion and poured through the injection port. After full curing, the moulds are removed, and the chock thickness and contact area are measured, requiring a contact area of not less than eighty‑five percent. Compared with traditional steel chocks, epoxy chocks better adapt to uneven foundation surfaces and do not cause corrosion.
The foundation bolts are tightened using the hydraulic tensioning method. Haizhongzhou calculates the required preload based on the bolt diameter and material, and loads in three stages – fifty percent, eighty percent, one hundred percent – holding for five minutes after each stage before proceeding to the next. After tightening, a dial gauge is used to measure the displacement of the engine feet to confirm that the engine has not been distorted by bolt tension. Finally, cold alignment and hot alignment verification are performed. Cold alignment is carried out at ambient temperature, while hot alignment simulates the thermal expansion of the engine during operation, adjusting shim thickness by calculation to ensure that shaft alignment remains acceptable under hot conditions. It is this fine operating procedure that has kept the vibration levels of Haizhongzhou‑installed main engines well below the code limits during sea trials.
