Because of different economic conditions, ship repairing countries have different policies for ship repairing. The capitalist countries with developed shipping industry have fierce competition, and their ships are updated very quickly. A new ship is often eliminated after 10 years of use and sent to the old ship market. Therefore, in addition to the necessary inspections and maintenance to maintain the ship's class, diesel engine repair implements the policy of minimizing repairs. In the 1950s, due to the weak foundation of the shipbuilding industry, China implemented the repair policy of extending the service life of ships as much as possible. Since the 1970s, with the development of the shipbuilding industry, this situation has changed a lot. Diesel engine repair

Types of maintenance Ship maintenance is usually divided into the following five types.

Sui Xiu is also called minor repair, once every 1 to 2 years. The repair interval for passenger ships and refrigerated ships should be shorter, and longer for general cargo ships and barges. Ship repairs should be carried out in the shipyard (see dry dock, floating dock) or on the row of ships. The annual repair is mainly maintenance, such as removing attached marine life and repainting the hull, inspecting the propeller and rudder, measuring the clearance of the tail shaft, grinding the bottom valve, and checking the main engine. Annual repairs are generally carried out in conjunction with annual inspections (see Ship Inspection). The surveyor will conduct general appearance inspections of more than 20 items such as hull and safety, lifesaving, fire fighting, lifting equipment, power plants, electrical and communication navigation equipment, etc. Repairs shall be carried out when defects are found, so that the ship can maintain the technical conditions of safe navigation before the next annual repair.

The overhaul is carried out once every 4-6 years, that is, one overhaul after 2 to 3 annual repairs. The repair scope is larger than the annual repair, which is preventive and is also carried out in the dock or row of the ship repair yard. Overhauls are generally combined with special inspections, and the surveyor will dismantle, inspect, measure and test more than 40 items of the hull and the main equipment of the whole ship. According to the inspection results, repair the items that may affect safe navigation until the next inspection and repair to ensure the service life of the ship.

Voyage repair is abbreviated as voyage repair. Before the annual repair or overhaul, the shipyard will send personnel to the ship docked at the dock, anchorage or sailing to assist the crew in troubleshooting temporary faults and keep the ship in continuous operation.