Reasons and necessity of overhaul of oil-injected twin-screw air compressor

The structure of the main engine (also known as the head) of an oil-injected twin-screw air compressor is usually composed of a pair of mutually meshing screws, main engine casing, high-pressure end and end cover, and low-pressure end and end cover.

When the screw air compressor is running normally, there is no contact between the screw and the screw, the screw and the main body shell and the high and low pressure end faces, which are mainly guaranteed by the following three aspects:

1. The processing of the screw, the main engine shell and the high and low pressure ends are all high-precision. This accuracy ensures that after the host is assembled, there is an appropriate gap between the screw and the screw, and between the screw and the host shell. The size of the gap has fully taken into account the deformation of the screw and the shell when the host runs at high temperatures;

2. The gap between the screw and the high and low pressure end faces is guaranteed during screw assembly according to technical requirements. The screw does not move axially when the main engine is running, and the allowable radial displacement of the screw is guaranteed by the high-precision bearings;

3. The oil film formed by the lubricating oil during normal operation of the main engine prevents direct contact between the screw and the screw. However, with the running time of the air compressor, the bearings of the main engine will inevitably wear out, which will cause the screw to produce axial movement and increase the radial displacement. This change will cause the screw and the screw, the screw and the main body housing And the gap between the front and rear ends changes. These gap changes are normal and allowable during the life of the bearing, and the resulting reduction in air compressor gas production and increase in the main motor load are also normal and allowable.

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 tends to the maximum design allowable value, and this change will cause a large change in the gap between the screw and the screw, the screw and the main body casing, and the front and rear ends. Although the host is still safe to run at this time, it is time to consider planning and overhauling the host.

Because once the operating time of the unit has passed the overhaul period, the bearing wear and the matching clearance of the main engine will reach the limit value allowed by the technical conditions of the main engine. At this time, the main engine is in an unsafe operating state, and the following serious consequences may occur at any time:

4. The increased operating load of the main engine will cause harm to the main motor and electrical system. The strong friction that may occur between the screw of the main engine, between the screw and the front and rear ends, and between the screw and the main engine shell will cause the main engine to increase its operating load sharply. The operating load of a heavily worn bearing is also very large. As a result, the motor will be in an overload working state, which will seriously endanger the safe operation of the motor. In severe cases, if the electrical protection device of the air compressor unit does not respond sensitively 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 matching clearance of the main engine will cause a serious decrease in the efficiency of the main engine, that is, the air compressor's exhaust volume will be attenuated by a large margin, which will have a certain impact on the normal production of the gas-consuming unit. Especially for those users with relatively small air compressor displacement configuration, due to the attenuation of the air compressor displacement, the compressed air pressure of the pipe network will drop a lot when the air consumption of the air system is relatively stable. It may happen that the gas system and equipment cannot work normally or cannot work at all, which may affect the normal production of the unit or cause a temporary shutdown of production, and bring losses to the enterprise.

6. The most 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 "locking" of the host, on the one hand, the maintenance cost of the overhaul will be much more expensive than the normal overhaul. On the other hand, because the components of the host will be damaged, the overall performance of the repaired host will be worse than that of the normal overhauled host. . And if the damage of the host is so serious that it has no repair value or cannot be repaired at all, it can only be scrapped and replaced with a new host, and the direct loss is the greatest. Because the cost of purchasing a new main engine is usually about one-third of the cost of purchasing the entire air compressor unit, which is much higher than the main engine overhaul cost under normal conditions, and the comprehensive technical performance of the main engine qualified for overhaul under normal conditions and the new main engine It is very similar!

7. Based on the above analysis, it can be seen that normal main engine overhaul work is not only the basic requirement for equipment maintenance, but also the basic requirement for enterprises to control normal equipment maintenance costs, avoid unnecessary capital losses and ensure normal production of enterprises!

Therefore, it is not only necessary, but also necessary to overhaul the main air compressor on time and according to standards!