Generator Set Failure Analysis and Maintenance

Fault checking

Principles and methods

The cause of diesel generator set failure is usually caused by many factors, different faults show different phenomena, to eliminate the fault, you must first find out the cause of the fault, in practice through seeing, listening, touching, smelling and other feelings, to find the abnormal performance of the diesel engine, so as to find problems, solve problems, eliminate faults.

The general principles for judging diesel engine failure are: combined with the structure, the principle of connection, to clarify the phenomenon, combined with the reality, from simple to complex, from the table and the inside, by the system segmentation, to find the cause.

In the long-term production practice, people have groped and summarized a set of inspection methods of “one look, two listening, three touches, and four sniffs”, and observed and judged the operation of the diesel engine through instrument monitoring and the feeling of human organs.

Abnormal operation

After the diesel engine runs for a long time, it fails and usually encounters the following phenomena.

(1) Abnormal sound during operation When the diesel engine runs, it emits abnormal tapping sounds, cannon sounds, bragging sounds, exhaust sounds, periodic friction sounds, etc.

(2) Abnormal operation of diesel engine is not easy to start, severe vibration occurs during work, the load cannot be dragged, and the speed is unstable.

(3) Abnormal appearance of diesel exhaust pipes emit white smoke, black smoke, blue smoke, oil leakage, water leakage, air leakage and so on in each system.

(4) Abnormal temperature oil temperature or cooling water temperature is too high, bearing overheating, etc.

(5) When the diesel engine is running with abnormal odor, it emits odors such as odor, burnt smell, and smoke smell.

After the diesel generator set runs in, after finding the above abnormal phenomena, it is necessary to conduct a careful investigation, analyze and judge the fault according to the fault phenomenon to find out the location and cause of the failure. Sometimes a fault may have several abnormal phenomena, such as high-pressure oil pump wear, can show both difficulty in starting, can also show insufficient output power, but also can show low speed instability and other phenomena. Sometimes an anomaly can be caused by several failures. Therefore, when the diesel engine is running abnormally, it is necessary to carefully investigate the causes of abnormal phenomena, which requires us to be good at making analytical reasoning judgments, grasp the essence through the phenomenon, find out the causes and parts of the failure, and troubleshoot.

Check the method

(1) According to the abnormal sound to determine the fault of the part with a pychic cone or with a half-meter long end of the sharpened thin iron bar, for “listening needle judgment”, one end of the ear, the other end touches the surface of each inspection part, you can more clearly monitor the abnormal sound of the part, the size and nature of the sound. The sound emitted by different parts is often different. For example, the impact sound of the main bearing clearance is too large, the sound of the valve and the piston hitting is crisp, and if the flywheel keyway is loose, it will issue a “Oh! Phew! “The impact sound and so on, so according to the different sounds, to determine the part of the fault.”

(2) After the local stop method is used to judge that after fault analysis, if the fault is suspected to be caused by a certain cylinder, the cylinder can be stopped, and whether the fault phenomenon disappears is observed, so as to determine the cause and part of the fault. For example, if the diesel engine emits black smoke, the analysis is that the nozzle of a cylinder is blocked, and the oil supply can be stopped for the cylinder, and if the black smoke disappears, the judgment is correct.

(3) Use the comparative method to judge whether the failure may be caused by a certain part or component according to the analysis of the obstacle, and then replace the part (or component) with a new part, and then start the operation to compare whether there is a change in the working conditions before and after the diesel engine, so as to find out the cause of the failure.

(4) Using the heuristic method to judge according to the analysis of the cause of the failure is difficult to judge, it can be used to change the technical state within the local range, observe whether the working performance of the diesel engine has an impact, and determine the cause of the failure. For example, the diesel engine can not produce the specified power, suspect that the compression stroke pressure of a cylinder is insufficient, is caused by the large gap between the cylinder and the piston tight seal, at this time the cylinder head is opened to inject a small amount of oil into the cylinder to improve the sealing condition, and then reinstall the cylinder head, if the pressure increases, the output power increases, indicating that the analysis is correct.

Diesel generator sets after a long time of use, its failure phenomenon is many, due to the different types of diesel engines, domestic and imported its structure and use environment is different, the cause of failure is also different, therefore, in the processing of problems, the specific problems should be made according to different situations to make specific divisions. Correct analysis and judgment of the cause of diesel engine failure, is a meticulous work, should not be in the cause of the failure before the random dismantling, so that not only can not eliminate the fault, but also may be reinstalled disassembled parts, components, to meet the technical requirements to cause new failures.