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Analysis and elimination of abnormal noise of Marine diesel engine.

Date:2017-06-06 Author: Click:

1 the abnormal noise fault is refers to the normal operation of diesel engine because of the moving parts in the process of abnormal damage (such as part, clearance is too large), the reason such as the abnormal state and abnormal noise (such as abnormal tapping, squawking noise).
Including the diesel engine cylinder, the cylinder, the supercharger surge, the valve mechanism knock, diesel engine attached mechanical fault made abnormal sound.
The emergence of abnormal noise indicates that the diesel engine has potential failure and the fault is deteriorating.
In the daily operation and management of Marine turbine, Marine engineer management personnel must keep watch, listen attentively, smell and touch frequently.
And one of the more practical and effective means is to listen attentively.

Because any machine in the process of work, send out the voice of the inherent and frequency, and when the sound length parts, quality, intensity, duration and other changes, its sound or frequency will change, the abnormal noise.

2 failure cases

Fault one: A tug the host in the car is running, when the speed reaches more than 3 0 0 r/min, run after A certain period of time, the oil temperature is more than 3 5 ℃ A, tapping machine appeared irregular, noisy.
At the same time, with the burning percussion sound, the rotation speed appeared 1 0 r/min, and the frequency was fast.
The temperature difference of exhaust temperature is larger than normal, but it is not beyond the specified range.
The noise main comes from the distribution mechanism, the frequency varies with the speed.
When cold or astern run, everything is normal.

Fault 2: a 6 l 3 5 wood oil machine in the case of non specific random fuel rack high-speed moving, diesel engine vibration and increase diesel engine running noise, noise, rotating speed in 0 ~ 2 0 r/l mi n fluctuations.

Cause analysis and exclusion of fault 1.

The main reasons for the abnormal noise in fault 1 are:

Improper valve clearance;

The valve spring is broken, the valve is bent and the rod sleeve is worn;

The CAM is loose or abnormal wear.
The valve mechanism was carefully examined.
First check the camshaft, whether the bearing clearance is too poor, eccentric grinding, inlet and exhaust CAM, whether the oil CAM is abnormal wear, except for the individual cylinder oil pipe is blocked, no abnormality is found.
Uncheck it and make sure it is smooth and smooth.
Timing of valve timing, inlet and exhaust gate of each cylinder are within the allowable error limits.
It is not found that the tooth ring and the teeth are loose, or the coordination between the gear and the shaft is loose.
Then the external components of the gas distribution system were checked and the gap between the tappet and the guide tube was not abnormal.
The gap between the valve and the valve guide rod is in the fan enclosure, and there are not many coals. The valve top lifting mechanism is not abnormal.
After the components are loaded, the test car is carried out. Although the noise is reduced, the fault still exists.

Then check the fuel system. The reason for the failure is:

Fuel injection timing is not allowed, the ignition sequence is different;

The high pressure oil pump plunger is too large, resulting in uneven oil supply.

The working condition of the oil injector is not good, which leads to the difference of combustion condition between each cylinder.
None of the above components appear to be defective.
The main performance of diesel engine abnormal noise in fuel system is cylinder.
But the fault phenomenon, obviously does not belong to the cylinder, and the combustion cylinder sign is also due to other causes of the subsidiary failure phenomenon.

Then the diesel engine governor is checked, and the abnormal performance of the governor is mainly caused by the change of diesel fuel supply, resulting in different combustion difference and abnormal noise of diesel engine.
The main original cause of the failure is not found in the component of the detuning speed governor, the precision and sensitivity of the calibration.

After the above inspection, fail to find out the root cause of the fault, the work in front of the checkpoint has what oversight, the deviation.

The following points are analyzed through repeated practical ship observation:

Noise from the distribution mechanism;

The noise is irregular, disorganized, the percussion of the valve is not regulated;

C. Only when the oil temperature rises, the speed exceeds the limit of 3 0 0 r/r ai n.

When reversing, the diesel engine is running normally, and the engine is in trouble, and it is increasing with the increase of the speed.

The following conclusions can be drawn:

The fault must be caused by the gas distribution mechanism;

The movement of the distribution mechanism loses its regularity under certain conditions.

The analysis suggests that only the transmission mechanism can cause the six cylinders to lose their regularity.
Thoroughly remove the CAM shaft transmission mechanism, when the disassembly and the backward car installation, the fault source is exposed: the camshaft transmission gear and the shaft's overrunning coordination have a slight loosening.
It is found that the camshaft and transmission gears are slightly loosened, the flat key is worn, and the shaft of the reverse gear and the transmission gear key have not expired.
Ahead, under the condition of cold, speed under 3 0 0 r/mi n between the drive gear and camshaft cooperate to be able to meet the requirements, and when the hot, speed more than 3 0 0 r/mi n, by fitting clearance on the relationship between the heat bilges cold shrink, and higher transmission torque, disable cooperate, led to the change of valve clearance, oil changed, lost the rule, makes the diesel engine running disorder, produce abnormal noise of failure.
Due to the change of load on diesel engine during the voyage, the performance of the fault is different.
Finally, according to the actual conditions of the site, the new matching of the flat key, the coordination surface of the shaft and transmission gear is cleaned, and the epoxy resin bond solidifies.
After the repair, we will try the car.

The reason of failure 2 analysis is that this diesel engine string is followed by a generator and a water supply pump.

The failure occurred after the replacement of the high pressure oil pump base.
Fixed bolt and the oil pump after the main reason is the base to replace seat disc hole 2 mm, small for over a long period of time, as a generator to the original machine, without fail, when used as a feed pump prime mover, due to the load increases, the load fluctuation is very big, lead to high pressure oil pump convex shaft and the shaft is different, make the diesel engine rotating speed high and low, the stronger the governor effect, speed fluctuation of smaller, and oil incisors will come back to high-speed moving, produce abnormal noise.

5. Causes and troubleshooting of other abnormal noises.

In this paper, the fault analysis and elimination methods of other abnormal noises are briefly described.

5.1 piston collision valve.

The reasons are as follows:

The valve clearance is not correct, such as the fault of the camshaft transmission device when repairing;

The valve clearance is too small;

The valve head is loose, so that the punch is automatically turned in the direction of rotation;
Valve stem bending deformation, stem guide hole too dirty, make valve movement blocked;

The valve springs are broken so that the valve cannot be seated in time.

5.2 gearbox abnormal noise failure.

The reason is that the gear is worn too much, the gap between the gears is too large, and there is a knock on the sudden reduction of speed.
The removal method is to correct the gear clearance and replace the new gear when the wear is serious.

5.3 cylinder cylinder sound is in the early stage of the cylinder, the piston will be overheated, and the dry friction of the piston and the cylinder wall can be heard;
When the cylinder takes place, the cylinder crank will have a knock over the stop position, and the speed of the diesel engine will drop rapidly or stop by itself.
Cylinder emergency treatment method is to increase the amount of oil cylinder oil first, such as overheating phenomenon has not changed, can use single cylinder cut-out, reduce speed, strengthen the measures, such as piston cooling until eliminate overheat.
When the cylinder is found, it is necessary to slow down and then stop, and continue to increase the piston coolant.
At this time, do not strengthen the cylinder cooling, or it will aggravate the cylinder, make the accident worse.
If the piston is killed, the car can be cooled for a period of time after the piston has been cooled.
When the piston is killed, it can inject kerosene into the cylinder and then move the flywheel or cart after the piston is cold.
If the piston still does not move, can remove the crank pin bearing cover, lift the piston out, side hanging side to knock piston top, side note kerosene, do not die hard hanging.
When the cylinder is inspected, the cylinder marks on the piston and cylinder sleeve are carefully polished with the oil stone, and the damaged piston ring must be renewed.
If the damage of piston and cylinder liner is serious, it is best to replace it.
When the lifting cylinder is filled, it is necessary to carefully check whether the oil supply on the cylinder sleeve is normal.
If the replacement of new piston and cylinder liner requires a period of grinding, the load must gradually increase, otherwise the new parts will be damaged.
If the cylinder accident cannot be repaired or allowed to be repaired, the sealing method can be used to continue the voyage.

5.4 the flywheel and coupling screw loose will produce abnormal noise when starting and stopping, and stop and tighten the screw.

5.5 abnormal noise of supercharger.

One of the faults is that the supercharger vibrates too much.
It is necessary to stop and check whether the blade is broken, whether the bearing is damaged or whether the bearing shock absorber is properly assembled, whether the air seal is friction, and whether the turbocharger impeller has friction with the fixed parts.
According to the actual inspection, the processing is conducted separately.
Therefore, there is an iveco 4 0 T1 0 passenger car. The idling of diesel engine is unstable, the exhaust pipe has a "sudden" sound, and the car is unable to drive.
The fuel injection pump after the professional maintenance station should not be a problem.
Check the injection pressure and normal;
It is normal to check the pressure of cylinder cylinders. However, when the oil inspection is done on the fourth cylinder, the speed of diesel engine has not changed significantly, indicating that the cylinder does not work.
At the same time, there is a special phenomenon that the diesel engine is in balance in the moment when the rotary oil injector is returned to the tubing joint.
However, the diesel engine is not in balance after the tightening of the return tubing joint about l O s.
Finally, it was found that the return pipe was blocked.
When the return oil pipe is blocked, the return oil that can't be discharged in time is stuck behind the needle valve and when it accumulates to a certain extent, the back pressure of the needle valve increases, which eventually makes the injector unable to work, which causes the above phenomenon.

The problem that should be paid attention to in the use of 6 return oil installations.

Prevent blockages.
Some diesel engines have a one-way oil return valve on the diesel filter, which cannot be screwed to death.
Does not back to the oil valve of the return pipe to keep the clear when the diesel engine fault, poor acceleration and automatically shut down in the cause of the problem has not been found before, will not hastily return pipe blocked (but allowed temporary blocking) as a means of checking, otherwise the oil return device will lose the function of adjusting oil pressure, serious when the engine will not work.

Prevent leakage.
Check whether the return valve and its seat are worn or corroded regularly, and whether the oil return valve is covered by debris to prevent internal leakage and backflow of the oil return valve.
If the amount of oil is too large, it will cause the injection pump to suck in air, the diesel engine to work feebly or automatic flameout.
On the other hand, it is necessary to maintain the seal of the return line to prevent external leakage.
The oil spill in the back pipe is not only polluting the environment - it is also easy to suck in air and waste fuel.
According to the determination, the oil output of each fuel injector is 0 when the diesel engine works.
5 k g.
Therefore, it is necessary to check whether there is any damage to the tubing, whether the joint washers are pulling and changing, and if necessary, place them on the plate to grind the washers or replace them with fine sand cloth.

Prevent misloading.
When maintenance and assembly fuel system, oil return valve can not be installed in the inlet end of the fuel injection pump, the oil return valve cannot short-ship zero or the wrong location, also cannot use ordinary tubing joint bolt instead of oil return valve.

The diesel engine's return pipe should not be attached to the intake pipe, because this part of the return oil is not pressurized and atomized, if the direct inhalation of the internal combustion of the cylinder will have undesirable consequences.

First, it causes incomplete combustion of fuel, increases the fuel consumption, and forms a large amount of carbon deposits to shorten the service life of diesel engines.

Second, the diesel engine in the cold starting and low-speed operation of the exhaust pipe to emit white smoke, resulting in the diesel engine running weak;

The third is that the return oil that enters the cylinder is not controlled by the governor, and when the oil return is too large, it is easy to cause the "flying car".
Therefore, if the back pipe of the original machine is connected to the inlet pipe, it should be modified according to the specific conditions of the aircraft, and it is better to receive the fuel tank.
If it is to be connected to the fuel filter, the terminal should have a one-way valve and be in good condition, otherwise the oil in the filter will reverse the flow injector.

If you find too much oil, you should find out the reason in time.
The amount of oil returned is too large, and the flow of the jet through the injector must be reduced, so that the injection pressure is reduced, the fuel injection time is delayed, and even the diesel engine is extinguished.
Cause the cause of the large amount of oil, in addition to the injector needle valve and needle valve body wear, also note to check on end and needle body face under the injector body is not smooth or there is damage, when it is necessary to grinding, or change the injector matching parts.



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