Analysis of compressor failure causes and countermeasures (2)

Overheating fault
     At the friction points between the crankshaft and the bearings, the crosshead and the slide plate, the packing and the piston rod, etc., the temperature exceeding the specified value is called overheating. The consequences of overheating: one is to accelerate the wear between the friction pairs, and the other is that the heat of the overheating continues to accumulate until the friction surface is burned and the lock is burned, causing major machine accidents. The main causes of bearing overheating are: uneven fit between the bearing and the journal or too small contact area; deflection of the bearing, bending and twisting of the crankshaft; too low viscosity of the lubricating oil, blockage of the oil circuit, failure of the oil pump, etc.; during installation There is no leveling, no clearance is found, the main shaft and motor shaft are not aligned, the two axes are tilted, etc.
compressor accident
     Breakage accident
     Crankshaft fracture: Most of the fractures occur at the transition of the fillet between the journal and the crank arm. The reasons are generally as follows: the transition fillet is too small (r is the crankshaft neck); during heat treatment, the fillet is not processed, causing the junction Stress concentration occurs everywhere; the fillet processing is irregular and there are local cross-sectional mutations; long-term overload operation, and some users increase the rotation speed casually in order to increase output, worsening the stress condition; the material itself has defects, such as blisters and shrinkage in castings. Song et al. In addition, it can also be seen that the oil hole on the crankshaft is cracked and caused to break.
     Breakage of the connecting rod: There are several situations: the connecting rod screw breaks. The reasons include: plastic deformation of the connecting rod screw due to long-term use; poor contact between the screw head or nut and the big head end surface, resulting in eccentric load, which can be so large that the bolt is It is as much as seven times the pure axial tension. Therefore, no slight skew is allowed, the contact should be evenly distributed, and the maximum distance between the contact points should not exceed 1/8 of the circumference, that is, 450; there is a problem with the processing quality of the bolt material.
     Piston rod fracture: The main fracture parts are the thread connecting the crosshead and the thread fastening the piston. These two places are the weak links of the piston rod. If it is due to negligence in design, sloppiness in manufacturing and operation reasons, , fracture occurs more frequently. If there are no problems in design, processing, and materials, the preload force must not be too large during installation, otherwise the piston rod will break when the maximum force reaches the yield limit. After long-term operation, due to excessive wear of the cylinder, the piston in the horizontal row will sink, causing additional load on the connecting thread. If the operation continues, the piston rod may break. This should be paid special attention to during maintenance. In addition, if the piston rod is subject to a strong impact due to damage to other parts, the piston rod may break.
     Cylinder and cylinder head rupture: Main reason: For water-cooled machines, if you forget to drain the cooling water in the cylinder and cylinder head after running and stopping in winter, the cooling water will freeze and burst the cylinder and cylinder head, especially in In the northern region of our country, the cooling water must be drained after parking; because the water was interrupted during operation and was not discovered in time, the temperature of the cylinder increased, and cooling water was suddenly added, causing the cylinder to burst; because the dead center gap was too small, the piston Loose nuts, metal objects falling into the cylinder, and the plugs on the piston coming out will cause the piston to hit the cylinder head and cause it to break.
     Fire and explosion accidents
     Carbon deposits often occur in oil-lubricated compressors, which we do not want, because carbon deposits will not only cause the piston rings to get stuck in the grooves, cause the air valves to work abnormally, reduce the airflow channel area and increase resistance, but also Under certain conditions, carbon deposits will burn, causing the compressor to explode. Therefore, the lubricating oil in the cylinder cannot be supplied too much, and gas that is not well filtered and contains a large amount of dust cannot be sucked into the cylinder. Otherwise, carbon deposits will form and contact with gas containing a large amount of volatile matter will cause an explosion. In order to prevent combustion and explosion, maintenance must be planned and the grease in the gas storage tank and pipelines should be cleaned regularly.
     In addition, there are also the following operational reasons for compressor combustion and explosion accidents: before the compressor is tested with hydrogen, oxygen, and nitrogen, the air is not purged with low-pressure nitrogen, causing an explosion. Due to lack of operating knowledge, the valve from the compressor to the gas tank was not opened after driving, causing the exhaust pressure to rise sharply and cause an explosion. Therefore, to prevent this type of accident from happening, you must be familiar with the operating procedures before driving, and pay close attention to the pressure gauge value after driving. In general small and medium-sized compressors, it is best to cancel the gate valve on the pipeline from the compressor to the gas storage tank, leaving only the check valve. In addition, compressor operators should receive pre-job training.
     Because the high-pressure stage air valve of the compressor is not tight, the high-pressure and high-temperature gas returns to the cylinder and generates high temperature near the exhaust valve. When there is carbon deposit, it will cause an explosion. In order to avoid accidents, the exhaust valve must be inspected, the leakage parts must be checked, and the fault must be eliminated at this time.