Reasons and necessity for overhaul and maintenance of the main engine of oil-injected twin-screw air compressor: The structure of the head (also known as the main engine) of the oil-injected twin-screw air compressor is usually composed of a pair of intermeshing screws, the main engine housing, the high-pressure end and end cover, and the low-pressure end and end cover.
When the main engine of the twin-screw air compressor is operating normally, there is no contact between the screws, the screws and the main engine housing, and the high and low pressure end faces, which is mainly guaranteed by the following three conditions:
1. The processing of the screws, the main engine housing, and the high and low pressure ends is high-precision. This precision ensures that after the main engine is assembled, there is an appropriate gap between the screws and the screws and between the screws and the main engine housing. The size of the gap has fully taken into account the problem of deformation of the screw and the housing when the main engine is running at high temperature;
2. The size of the gap between the screw and the high and low pressure end faces is guaranteed according to technical requirements during screw assembly. When the main engine is running, the screw has no axial movement, and the radial displacement of the screw is guaranteed by high-precision bearings;
3. When the head is operating normally, the oil film formed by the lubricating oil prevents direct contact between the screws.
However, as the compressor runs longer, the bearings of the main engine will inevitably wear out, resulting in increased axial movement and radial displacement of the screw. This change will cause the gaps between the screws, the screws and the main engine housing, and the front and rear end faces to change. These gap changes are normal and allowed within the life of the bearings, and the resulting attenuation of the compressor's gas output and the increase in the main motor load are also normal and allowed.
As the unit's operating time approaches the main engine overhaul period, the life of the main engine bearings gradually approaches the maximum allowable time limit. At this time, the axial and radial movement of the screw gradually approaches the maximum design allowable value, which will cause a large change in the gaps between the screws, the screws and the main engine housing and the front and rear end faces. Although the main engine is still running at this time, it is time to consider planning an overhaul of the main engine.
Because once the unit's operating time exceeds the overhaul period, the bearing wear and the main engine clearance will reach the limit allowed by the main engine's technical conditions. At this time, the main engine is in a bad operating state, and the following serious consequences may occur at any time:
4. The head operating load increases, causing damage to the main motor and electrical system
The strong friction between the main engine screws, between the screws and the front and rear end surfaces, and between the screws and the main engine housing will cause the main engine's operating load to increase sharply. In addition, the operating load of severely worn bearings is also very large. In this way, the motor will be in an overloaded working state, which will seriously endanger the operation of the motor. In serious cases, if the electrical protection device of the air compressor unit is not sensitive or fails, it may also cause the motor to burn out.
5. The exhaust volume of the air compressor will be greatly attenuated.
The increase in the main engine clearance will cause a serious reduction in the efficiency of the main engine, that is, the exhaust volume of the air compressor will be greatly attenuated, which will have a certain impact on the normal production of the gas-using unit. Especially for those users whose air compressor exhaust volume is configured with a small surplus, due to the attenuation of the air compressor exhaust volume, when the gas consumption of the gas system is relatively stable, the compressed air pressure of the pipeline network will be reduced a lot, and the gas system equipment may not work normally or not work at all, thus affecting the normal production of the unit or causing temporary suspension of production, causing losses to the enterprise.
6. The more serious consequence is the sudden "locking" of the host.
Once such a situation occurs, if the electrical protection system does not respond in time or the protection fails, it may also cause serious damage to the main motor and electrical system.
For the treatment of the host "locking", on the one hand, the maintenance cost of the overhaul will be much more expensive than the normal overhaul, and on the other hand, because the host components will be damaged, the comprehensive performance of the host after repair will be worse than that of the host after normal overhaul. If the damage to the host is so serious that it is not worth repairing or cannot be repaired at all, it can only be scrapped and replaced with a new host, and the direct loss is very large. Because the cost of purchasing a new host is usually about one-third of the cost of purchasing the entire air compressor unit, which is much higher than the cost of overhauling the host under normal circumstances. Under normal circumstances, the comprehensive technical performance of a host that has passed the overhaul is very similar to that of a new host!