Ship repair bodies and equipment will be naturally worn out during operation, and certain defects will be exposed over time, and large or small damage will occur. In order to ensure continued safe use, repairs must be planned in a planned way. Planned maintenance repairs include voyage repairs, minor repairs and overhauls (or called medium repairs and overhauls).

Voyage repair: during the ship's operation period, it is the general repair works and general accident repairs that must be assisted by the shipyard or the voyage station that affect the navigation. The voyage repair should be carried out during the berthing time of the voyage, and the shipyard or the voyage station should be actively involved. Attach importance to voyage repair work, arrange repairs upon receipt of notice, and follow the ship for repairs when necessary, so as not to affect the ship’s transportation and production as much as possible.

Minor repair: It is a factory repair project that is carried out in a planned cycle and combined with regular inspections. The purpose of minor repairs is to eliminate excessive wear during operation and ensure the safe operation of the ship until the next scheduled repair period. Minor repairs are generally carried out at the same time as docking repairs. The minor repairs mainly focus on inspection and repair of the hull, rudder, shafting, sea valve, main and auxiliary engines, boilers, and special equipment for engineering ships. Generally, only the original equipment is adjusted, ground, replaced, and cleaned and maintained. , Except for navigation engineering ships, no paint decoration or reconstruction is allowed. The scope of the basic works for minor repairs is as follows.

(1) Derusting paint when the hull is corroded (when there is no rusted part and the paint is good, do not remove rust and paint casually), repair and replace a small amount of hull components, and make appropriate patching for the partially worn outer plates, decks or other plates Or digging up.

(2) The host is partially disassembled and assembled, the gap is adjusted, and the bearing is poured with lead. Unless there are special circumstances, the main engine of the ocean ship does not lift the crankshaft, the crankshaft of the main engine of the large river steamship does not leave the cabin, and the main diesel engine generally does not disassemble.

(3) General inspection and repair of auxiliary machinery and piping system, etc., parts can be repaired, but not painted or displaced.

(4) Cleaning the inside of the boiler, overhauling accessories, and repairing part of the furnace tube, small tie rods, welding cracks, but not peeling off the furnace coat or disintegrating. Not for special needs, do not do the hydraulic test casually.

(5) Inspection and repair of special engineering equipment can be used to repair and replace vulnerable parts such as dredging tools, mud pumps, pile hammers, and winches.

The interval between minor repairs is 12 to 18 months for motor ships, engineering ships, refrigerated barges, and food barges, for first-class oil barges, 18 to 24 months for barges and barges, and 24-36 for cargo barges and lower-class oil barges. For months, some barges had no minor repairs. The upper and lower limits of the interval shall be determined by the technical department of the ship-using unit according to the navigation area, operating conditions, and equipment conditions, but shall not exceed the upper limit.

Overhaul is a factory repair project carried out at regular intervals of 2-3 minor repairs combined with regular inspections. The purpose of overhaul is to conduct a comprehensive inspection of the hull, main and auxiliary engines and other equipment, focusing on repairing larger defects that cannot be resolved during minor repairs, and maintaining the strength of the ship and the safety and operating conditions of the main equipment. The problems found during the inspection during the overhaul should be repaired if they must be resolved. However, if the associated project can be safely used until the next minor repair, it can be recorded, continue to use, and be repaired in the future minor repairs. The scope of basic overhaul works:

① Regularly inspect the required disassembly and assembly works;

② Derusting paint when the hull is corroded;

③Repair and replace part of the hull, deck and frame;

④The main engine is allowed to be disassembled and repaired, and the main components can be replaced; the auxiliary engine can be repaired out of the cabin, or the whole unit can be replaced;

⑤The boiler is allowed to draw out the bladder, cut and replace the combustion chamber, and carry out the hydraulic test according to the inspection period;

⑥Painting renovation is generally not carried out during maintenance, but for the renovation project that has a small amount of engineering and has significant benefits in operation, it can be combined with the maintenance after verification and report to the superior for approval;

⑦The special equipment of the engineering ship should be fully dismantled and inspected, and the main components of the dredging, piling, lifting and other equipment and special electrical equipment should be replaced.

Overhaul is the type of planned repair. The determination of repair items must comply with the principles of safety, diligence and frugality. Generally, superstructures are not replaced, and main engines and boilers are not replaced on large ships.

Interval for maintenance: 4 to 6 years for motor boats, engineering ships, stranding boats, refrigerated barges, food barges, first-class oil barges, and sea steel barges; 6 to 9 years for river steel barges; cargo barges and There is no overhaul for the oil barge below level two.

The above repairs are arranged based on the interval time, and the scope of the project is only divided in principle. Due to the different types of ships, complex models and different technical conditions of the ships, if problems are found, they should be resolved based on the specific circumstances and seek truth from facts. Allows for projects within the scope of individual overhaul.