Therefore, the air compressor failure should be discovered in time, and the correct judgment and treatment should be carried out.

1 failure phenomenon

The faults caused by air compressors are caused by many factors, and different faults show different phenomena. The air compressor abnormalities commonly encountered are mainly as follows.

(1) Abnormal operation: If the air compressor cannot be started, the pressure cannot be established after starting or stopped before the working pressure is reached.

(2) Abnormal sound: If there is abnormal knocking sound, friction sound or safety valve discharge air.

(3) Abnormal temperature: If the oil temperature is too high or too low, the surface temperature of the parts and the temperature of the compressed gas are too high.

(4) Abnormal appearance: If the air compressor leaks oil, leaks, and vibrates seriously.

(5) Abnormal smell: such as "burnt smell" of rubber and insulating materials; "oily smell" of oil evaporation.

The above anomalies are often related to each other. A fault may manifest as several anomalies, and an anomaly may be caused by several faults. After we find the abnormal phenomenon in the working of the air compressor, we must carefully analyze the cause of the fault, in order to correctly find the fault location, thereby eliminating the fault and making the air compressor work normally.

2 failure cause analysis

2.1 improper use of maintenance

In use, it is not strictly operated according to the operating procedures, or even illegal operation; improper maintenance or lack of maintenance; poor storage and damage to parts, causing compressor failure. The following are common.

(1) The engine oil is not used as specified. Since the air compressor oil of the diesel locomotive does not have a preheating device, if the winter compressor oil is not used as specified in the winter before using the air compressor, the viscosity of the oil will increase. When the viscosity of the oil is increased, the fluidity is deteriorated, so that the oil pumping amount of the oil pump is lowered, resulting in poor oil supply, and the friction surface is likely to form semi-dry friction or dry friction, thereby increasing the frictional resistance of the machine member, and the wear is intensified, and the temperature is increased. Raise, and even cause parts to burn out.

(2) Failure to add or periodically change the oil in time, resulting in insufficient oil quantity or deterioration of oil pollution and loss of required lubrication performance, which deteriorates lubrication conditions and causes wear of parts. In serious cases, accidents such as “cylinder” and piston stuck may occur. Therefore, in the application, the quantity and quality of the oil must be checked in time. When it is insufficient, it should be added and replaced when it deteriorates. The oil level should be between the highest and lowest line of the oil mark. The air compressor should not be started and operated when the inorganic oil or oil level is below the minimum oil level.

(3) The air filter is not cleaned in time, the air circulation resistance is increased, the intake air amount is reduced, the filtration effect is reduced, causing serious wear of the cylinder, the piston and the like, and the efficiency of the air compressor is lowered, and the power consumption is increased. The quality of the compressed gas deteriorates, even at all, and it can also cause oil contamination.

(4) The valves are not inspected and maintained in time, causing the valve gap to be too large or too small, and the valve springs are broken, which deteriorates its performance and cannot work normally, thus Reducing the reliability and economy of the air compressor. The failure rate increases.

Only by fully understanding the requirements of the air compressor in use and the changing laws of the technical conditions of each machine, to achieve correct use and timely maintenance, can effectively prevent the resulting faults.

2.2 Air compressor assembly and adjustment errors

All parts of the air compressor have strict technical standards and requirements during the repair, from decomposition, cleaning, inspection, maintenance to assembly. Failure to pay attention to the quality of the repair will cause malfunctions in the operation of the air compressor. The following are common.

(1) The clearance between the piston and the cylinder does not meet the requirements. The installation position and direction of the piston ring are wrong, causing the piston to leak and simmer. The piston and the cylinder wall are strained and the piston is stuck.

(2) The conicality and ellipticity of the crankshaft main shaft, the connecting rod bearing bush and the journal exceed the allowable value, and the tightening torque of the matching clearance or fastening bolt does not meet the specified requirements, resulting in accelerated wear, burning or abnormality of the machine. Knocking.

(3) The direction and position of the inlet and exhaust valves are incorrectly installed, resulting in the air compressor not working properly; the sealing of the valve plate and the valve seat is poor, so that the compressed gas flows backward.

(4) The oil pressure constant pressure valve is improperly adjusted, causing the oil pressure to be too high or too low, so that the fuel consumption is increased, and even the pipeline bursts, or the wear of the machine is accelerated, and the machine parts are burnt when it is severe.

(5) After the air compressor is assembled, the cylinder clearance is not checked and adjusted according to the regulations, causing the clearance to be too large or too small, causing the piston to collide with the cylinder head to be damaged or the gas pressure is reduced, and the gas pressure efficiency is lowered.

Strict repair of specifications, improvement of maintenance equipment and implements, improvement of repair skills, and enhanced inspection and acceptance of maintenance are effective ways to improve the quality of maintenance and an effective measure to prevent and reduce compressor failures.

2.3 Impact of environmental conditions

China has a vast territory, and the geographical and climatic environments in the south and north are quite different. These have brought some new problems to the use of air compressors. Therefore, it is necessary to understand the impact of environmental conditions on the use of air compressors in order to take measures to ensure proper use and maintenance.

(1) The effect of winter on the use of compressors.

The winter temperature in the northern region is generally low, and the cold period is long, the wind and snow are high, and the altitude is high. The viscosity of the oil increases with the decrease of temperature. According to the experiment, when the temperature drops from 0 °C to -20 °C, it is commonly used. The viscosity of No. 16 oil has increased nearly 15 times.

Therefore, when using the compressor in winter, the oil should be used strictly in accordance with the regulations, and the cold insulation measures for the cooling compartment of the diesel locomotive should be completed. The doors and windows and Shutters should be closed, and the cold shelter should be closed. When the locomotive is parked for a long time, it should be placed in the garage.

(2) The impact of summer on the use of compressors.

Summer temperatures in the southern regions are generally high and the humidity of the air is high. Due to the high temperature, the viscosity of the oil will decrease, the lubrication condition will be worse, the wear of the machine will be intensified, and the oil consumption will increase. The amount of expansion of the gas after heating will increase the actual intake air volume of the cylinder, and the air compressor efficiency will decrease. The consumption is increased; at the same time, due to the high humidity of the air, the quality of the compressed air is lowered, and the parts are easily rusted and moldy, affecting the use and even causing damage.

Therefore, in the operation of the locomotive, the working condition and tightness of the air compressor fan and the pulley should be checked frequently to maintain the fan's specified speed and sufficient hurricane volume; timely open the louver and other ventilation devices.

3 suggestions

Diesel locomotives should consider screw air compressors with high replacement efficiency, low vibration, low noise, stable operation, good reliability, less wearing parts and low cost. In the northern region, the air compressor is equipped with an oil preheating device to ensure that the oil has a suitable temperature when the air compressor is started in winter. An air drying device is installed in front of the air compressor inlet in a region with high air humidity in the south.

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