Marine diesel engines are the source of power on ships and are the main components of ships. Because the composition and structure of marine diesel engines are abnormal and messy, some problems will inevitably sometimes appear in the working process. This is detrimental to the normal operation of marine diesel engines and ships. Diesel engine repair, in order to ensure the normal operation of marine diesel engines, early detection and removal of these faults is very important. Next, the editor of Guangdong Ship Maintenance will analyze the common problems of marine diesel engines from several aspects, so as to help us understand marine diesel engines very well and make ships work safe and useful.

Marine diesel engines can be classified from different aspects according to the fault status. For example, according to the severity of the fault and the damage formed, it can be divided into four categories: nominal fault, severe fault, general fault and mild fault; it can also be classified according to the time of the fault and the onset of the fault. The parts of the product can be divided into sudden, gradual, machine failure and component failure; according to its factors and scenes, it can also be divided into three categories: abrasion failure, misuse failure and fragile failure. Each type of fault corresponds to a different part. Next, let's introduce and analyze the fault scene and factors in detail.

1. Malfunctions and occurrence factors of marine diesel engines

Malfunctioning scene of marine diesel engine

When a marine diesel engine malfunctions, it will generally be accompanied by the following scenes:

⑴ Abnormal sound

A normal working marine diesel engine has certain rules for its noise. When something goes wrong, the sound becomes abnormal. For example, when the piston touches the valve, there is a metal knocking sound; when the fuel supply angle is too large, there is a burning knocking sound; when the cylinder leaks, there is a bragging sound; when rotating parts collide, there is a conflict sound.

⑵ Abnormal appearance

Such as blue smoke due to burning engine oil; black smoke due to poor incineration; oil leakage and air leakage due to failure of the sealing surface.

⑶ Abnormal temperature

For example, when the oil supply angle is too late or the load is too high, the exhaust temperature is too high; the bearing is overheated when the bearing is burned; the water temperature and the oil temperature are too high when the cooling system fails.

⑷ Abnormal action

For example, when the balance fails or the foundation is not strong, the oscillation is too large; when the speed control fails, the speeding or traveling car appears; the starting system is faulty, and the marine diesel engine cannot start.

⑸ Abnormal pressure

For example, when the valve and piston ring seal fails, the cylinder pressure is too low; the crankcase pressure is too high; the oil pressure is too low when the slippery system is faulty; the air pressure is too low and too high when the pressure boost system is faulty.

⑹ Abnormal smell

For example, when the electrical system is faulty, it shows a burnt smell; when the oil is burned, it shows the smell of smoke.

2

Causes of malfunction of marine diesel engine

There are many factors that cause the failure of marine diesel engines. It is caused by improper design, structure and material selection, poor quality of processing, equipment, and debugging, as well as improper operation and poor protection and maintenance. Here is a brief introduction to the factors that cause problems in the aspects of operation, protection, maintenance and processing.

2.1 Operational factors

Faults caused by illegal operations account for a large proportion of the faults of marine diesel engines. There are ideological negligence, technical unfamiliarity, and faulty customary practices. The most common illegal operations have the following aspects:

⑴ The starting time is too long.

⑵The cold car starts to increase the load quickly without warming up the car.

⑶ Insufficient running-in, high load work.

⑷ Emergency parking with load.

⑸ Lack of driving on the oil surface.

⑹ Lack of driving on the water.

⑺ Overload or overspeed work.

⑻ The water temperature and the oil temperature are abnormal and continue to work.

⑼Quick parking during high-speed and high-load work

2.2 Factors in protection and conservation

Failure to follow the rules for protection and maintenance can also simply cause problems. The most common fault factors include the following aspects:

⑴ Adding or replacing new engine oil is not timely.

⑵ The oil filter is not cleaned in time.

⑶ The diesel filter is not cleaned in time.

⑷ The air filter is not cleaned in time.

⑸ Check and adjust the valve clearance in time.

⑹ Checking and adjusting the fuel supply early angle is not timely.

⑺ Check and adjust the fuel injector in time.

⑻ Check and make up for the electrolyte to the battery if it is not timely.

⑼ In winter, the ship's diesel engine is not discharged in time after parking.

2.3 Factors in disassembly and assembly during repair

Disassembly and assembly errors are also one of the main factors leading to the failure of marine diesel engines. Among them are the following aspects:

⑴ The injector gasket device is incorrect.

⑵ The cylinder liner device is incorrect.

⑶ Gear meshing is incorrect.

⑷The nut device is incorrect.

⑸ Over-value related to the fit gap.

⑹ The orientation of the piston ring device is incorrect.

2.4 Factors in processing

Most of the factors in this regard are the wrong use of the data, the content of the data has quality problems and certain parts of the machining are ignored, which makes it not meet the requirements. The shortcomings in this aspect are difficult to find in the device, and it is exposed after a period of use, and then the parts are damaged. The main table is now the following aspects:

⑴ The quality does not meet the requirements.

⑵The raw materials do not meet the requirements.

⑶ The heat treatment does not meet the requirements.

⑷Machining does not meet the requirements.

⑸ Eliminate stress that does not meet the requirements.