As an industrial machine, screw air compressors need to pay attention to many operating details when running to ensure smooth and effective operation of the equipment. We all know that machines will inevitably encounter problems of one kind or another. Let's briefly talk about the major factors that screw air compressors cannot start normally.
1. Unable to start
There are many possibilities for screw air compressors to fail to start, but experienced engineers generally follow the steps from simple to complex to consider the problem:
Electrical aspects:
First check whether the power supply wiring of the screw air compressor is correct, whether the power switch is closed correctly, whether the power fuse is blown, and whether the power supply voltage reaches 90% or more of the rated voltage. Check whether the components of the pressure relay of the air compressor are damaged and whether the given value of the pressure relay is appropriate. The start button has poor contact. This situation is not common, because the current screw compressors, unless they are really greedy for cheap and buy a very low-priced machine, generally will not have this problem, even if it occurs, it is also very simple to solve.
Operational failure:
At startup, the outlet switch is not turned on, the outlet pressure is set too high, the switch after the electrical circuit is not restored, and the voltage and current settings are unreasonable. Generally, screw air compressors have automatic protection devices, so when some parts of them fail, they cannot start normally. The start and stop control circuit has a relatively high failure rate due to the large number of electrical components and control points. Improper operation of the start button, stop button or switch may cause the host to fail to start or fail to shut down. For example, if the start button, stop button, emergency stop button, control panel, etc. are operated with excessive force, the button may be stuck on the edge of the button shell and cannot be reset.
Equipment failure:
Mainly includes air compressor motor failure, rotor locking, etc. If the air compressor works overloaded for a long time, the rotor tooth surface and bearing fatigue damage will be caused; the air compressor lubricating oil pipeline is blocked and lacks oil, causing the temperature of the yin and yang rotors and bearings to be too high and damaged and locked. If the bearings and yin and yang rotors are disassembled when repairing the air compressor, if the installation is not careful and the installation accuracy does not meet the requirements, the axes of the yin and yang rotors will not be parallel, making the yin and yang rotors unable to roll. In addition, the method of repairing the compressor is improper. When applying external force to the rotor, an incorrect method was adopted, which changed the axial and radial gaps between the yin and yang rotors and made it unable to rotate. In general, the manufacturer sets parameters such as lubricating oil level, oil pressure and filter pressure difference on the air compressor control system. If the above situation occurs, it will automatically shut down to protect the compressor. However, for convenience and money saving, some users often increase the set parameters or short-circuit certain alarm lines and pipelines, causing the equipment to be out of monitoring and causing failures.
The probability of motor failure in general air compressors is relatively low, but if it occurs, it will be more troublesome and professionals are required to eliminate and repair it.
2. Exhaust pressure is too low
Under normal circumstances, the exhaust pressure of the air compressor in service can be reduced due to the increase in altitude, but the increase in gas consumption cannot be ignored. If there is no large leak in the compressed air pipeline, it is a problem with the compressor unit itself. We can check whether there is a problem from the following aspects:
1. Whether the maintenance is timely
The exhaust volume of the air compressor decreases. First, check whether the air compressor has been maintained? Most of the time, the exhaust volume of the air compressor decreases, and there is no big problem, that is, the customer neglects maintenance. If the working environment is not ideal, the compressor air filter is easy to clog. In mild cases, compressed air can be used to remove dust; if the blockage is serious, a new air filter needs to be replaced.
2. Are all the intake valves open?
The air compressor exhaust volume has decreased. Check the unit. If it has just been maintained, eliminate the three filters and oil problems. At this time, check the compressor intake valve first. Remove the intake hose, turn on the compressor, and see if the opening of the intake valve is normal. The theoretical design service life of the general intake valve is 100,000 times. Because each manufacturer uses different brand batches and the quality is different, the failure of the intake valve may cause the exhaust volume of the unit to decrease.
If the intake valve cannot be opened when the air compressor is loaded, it can be determined that the exhaust volume decrease is due to the intake valve failure, which should be removed for inspection or replacement.
3. Motor failure
After eliminating the intake valve failure, if the exhaust volume of the unit still does not change, consider whether the motor is faulty. Due to a local short circuit in the motor coil, or bearing wear, motor shaft wear, the motor speed is lower than the rated speed, causing the compressor exhaust volume to drop. The motor coil, bearings, etc. should be inspected and repaired, and the compressor exhaust volume should be tested after repair. The belt-driven air compressor is close to this principle. The belt load and intact state should be considered. Sometimes the main engine speed is insufficient due to belt slippage or relaxation, resulting in low exhaust pressure.
4. The pressure switch sets the working pressure too low, and the upper limit of the pressure should be adjusted upward.
This situation is common in the case of changes in working conditions, or after the system has been adjusted, overhauled, etc., the system parameters have been moved. Otherwise, under normal circumstances, the working pressure will not be easily misoperated after it is set. It is not recommended that the compressor parameter setting be set arbitrarily by the user, but should be jointly set by the equipment supplier and the user, taking into account the working conditions and equipment operation characteristics, and setting a reasonable value.
3. Exhaust oil content is too high
For those companies that pay attention to air quality, whether the air contains too much oil is very critical. There are many reasons for this problem, mainly the following reasons: 1. The oil level is too high; 2. The filter or throttle hole of the oil return pipe is blocked; the third is that the oil-gas separation core is damaged; the fourth is that the gas production pressure of the compressor is too low; the pressure valve fails; and there is also a problem with the lubricating oil itself. If the lubricating oil used has too much foam, it will also cause the oil content of the gas to increase.
1. Too much cooling oil added to the compressor
Too much lubricating oil is added, more than the allowable range. During the operation of the compressor, although the separation system separates the oil and gas, the gas will also draw the cooling oil into the gas during the gas discharge, resulting in too high oil content in the exhaust gas.
2. Failure of the oil return pipeline
During the operation of the screw air compressor, the oil return pipeline shoulders an important responsibility. A pressure difference will be formed between the oil separation inside and the compressor inlet. Under the action of this pressure difference, the oil return pipeline is responsible for transporting the oil gathered at the bottom of the oil separator back to the compressor for continued use in the next compression cycle. If the oil return line is blocked, broken, or installed incorrectly, the oil accumulated at the bottom of the oil separator cannot be transported back to the compressor, resulting in too much oil accumulated at the bottom. Then, the oil that has not been transported back to the compressor will be discharged with the gas, and oil will appear during the exhaust process.
3. Damage to the oil separation core
During the operation of the screw air compressor, if the oil separation core is damaged, such as broken or perforated, it loses its oil-gas separation function. In other words, the mixed gas and the exhaust pipe of the compressor are directly connected, and a large amount of cooling oil is not separated. It is discharged from the body with the gas, resulting in oil-carrying failure during the exhaust process.
4. System pressure control is too low
If the system pressure control is too low, the centrifugal force in the separator will be less than the centrifugal force required for work, and the role of the separator will not be fully reflected, resulting in the oil content of the gas in the next link separator being too high, exceeding its separation range, which also leads to the separation of oil and gas, and oil-carrying failure during the compressor exhaust process.
5. Failure of pressure valve
During the operation of the screw air compressor, the function of the pressure valve is to ensure that the system pressure is controlled above the pressure during operation. If the pressure valve fails, the system pressure will not be guaranteed. Due to the large gas consumption of the air compressor, the system pressure will be too low and the return oil pipeline will not be able to return oil. The oil accumulated at the bottom of the oil separator will not be able to be returned to the compressor, and will be discharged from the compressor with the compressed gas, causing oil-carrying failure during the exhaust process.
6. Unqualified cooling oil quality
If the air compressor is added with lubricating oil with poor defoaming properties, or the ambient air humidity is high, or the bottom of the lubricating oil station leaks, etc., the lubricating oil will foam, causing the oil content in the exhaust to increase.
4. Exhaust temperature is too high
It is not uncommon for the exhaust temperature of the air compressor to be too high. Therefore, there are many articles on this type of analysis. We will not talk about them all. We will summarize them from the two aspects of mechanical failure and lubricating oil:
Mechanical failures include: a. Oil stop valve failure; b. Air compressor oil filter failure; c. Thermal control valve (temperature control valve) failure; d. Air compressor oil quantity regulator abnormality; e. Air compressor oil cooler abnormality (this failure is common in water-cooled compressors); f. Air compressor head failure, including poor lubrication and unreasonable design of the head itself, poor installation, etc.; g. Air filter failure; h. Oil-gas separator failure; i. Temperature sensor and computer failure, abnormal reading.
The impact of air compressor oil includes: a. Insufficient air compressor oil; b. Air compressor oil deterioration, oil fluidity deterioration, and reduced heat exchange capacity; c. Improper selection of air compressor oil viscosity; d. Poor quality of air compressor oil: poor thermal oxidation performance, poor viscosity-temperature performance, poor air separation capacity, etc.
5. The air compressor cannot be unloaded
Loading and unloading are the basic functions of the compressor. If it cannot be loaded or unloaded, the air compressor is useless. Because if it cannot be loaded, the air compressor will not output compressed air; if it cannot be unloaded, after there is no compressed air demand downstream, it can be imagined as: "The consequence of constantly inflating a balloon". If the air compressor continues to load and run when it exceeds the rated pressure during operation, it will reach the set pressure value, causing the screw compressor to trip and stop, or the safety valve to operate.
If there is no situation where the actual air consumption of production is greater than the gas output of the compressor unit and there is a large amount of leakage in the pipeline, then the compressor cannot be unloaded. There may be the following main reasons:
a. The pressure switch is improperly set or it floats after setting, reporting false numbers; b. The intake valve is poorly operated, stuck, etc.; c. The discharge solenoid valve fails when the system stops using gas, and the performance state is that the pressure rises slowly, not all at once like loading; d. The control circuit fails; e. The loading solenoid valve fails, such as loading while unloading, and the loaded gas volume is greater than the unloading, so the pressure continues to increase.
If the air compressor cannot be unloaded, it is necessary to check whether the various valves are stuck or damaged. If necessary, they need to be repaired or replaced.