In the industrial power system, screw air compressors are crucial due to their high efficiency and stability, but overload faults occur frequently and have significant impacts, which will cause equipment shutdown or even damage, resulting in economic losses for enterprises. Mastering the causes and countermeasures is the key to ensuring stable operation. Overload is manifested as motor current exceeding the rated value, control panel alarm, and triggering emergency stop protection. The root causes of the fault are divided into electrical and mechanical system problems. In terms of electrical aspects, low power supply voltage, three-phase imbalance, aging of motor winding insulation, bearing wear, and failure of electrical control components will cause overload; In terms of mechanical aspects, the increased gap between the rotors of the screw main engine, bearing damage, blockage of the air intake system filter, failure of the regulating valve, and failure of the cooling system will cause excessive mechanical load and lead to overload. When handling, the principle of "mechanical first, then electrical" should be followed. For electrical problems, it is necessary to detect the voltage, maintain the motor, and calibrate the parameters; For mechanical faults, it is necessary to clean or replace the filter, overhaul the regulating valve, and maintain the screw main engine and cooling system. At the same time, a sound daily maintenance system should be established to prevent faults, including regular inspection, replacement of vulnerable parts, and reasonable planning of start and stop time. Handling the overload fault of screw air compressors tests the refinement of enterprise equipment management. It is necessary to identify the root cause, implement measures, and do a good job in maintenance to ensure its stable and efficient operation. Relevant information and precautions such as technical consultation are also provided at the end of the article.
Important Highlights
1. Serious Impacts of Overload Faults
Screw air compressors play a key role in the industrial production power system, and overload faults are very common and harmful. A slight overload will shut down the equipment, disrupt the production rhythm, and affect the product delivery time. In severe cases, the motor will be burned out. The cost of motor repair or replacement is high. Moreover, after the core components are damaged, not only the maintenance is difficult, but also the whole equipment may be unavailable for a long time, bringing huge economic losses to the enterprise. Therefore, solving the overload problem is extremely urgent.
2. Overload Caused by Electrical System
Problems in the electrical system are common causes of overload. In the power supply link, when the voltage is too low, such as during the peak power consumption period, the input voltage of the air compressor is lower than the normal range. In order to maintain power output, the motor current increases, which is prone to overload; Three-phase voltage imbalance, such as the three-phase voltage deviation exceeding the specified value due to line aging in a factory, resulting in uneven three-phase current of the motor, local overheating triggers overload protection. For motor faults, such as the aging of the winding insulation layer caused by long-term operation of the motor, resulting in inter-turn short circuit, or the eccentricity of the rotor caused by long-term bearing wear, resulting in increased operating resistance and increased load rate. In terms of electrical control components, the contactor contacts are ablated, such as overheating and deformation of the contacts caused by frequent start and stop, poor contact, and incorrect setting of the thermal relay setting parameters, which will indirectly cause overload.
3. Overload Caused by Mechanical System
Excessive load on the mechanical system will also cause overload. The male and female rotors of the screw main engine work for a long time, and the meshing gap becomes larger due to wear, resulting in increased gas leakage in the compression chamber. The main engine needs to continue to operate at high load to reach the set pressure. For example, a screw air compressor in a factory has not been overhauled for many years, and the rotor gap exceeds the standard range, resulting in frequent overload alarms of the equipment. Bearing damage makes the rotor rotate unsmoothly or even stuck, resulting in a significant increase in operating resistance, and the motor load increases sharply. In the air intake system, if the air filter is not cleaned or replaced for a long time and is blocked by dust, the air intake volume is insufficient, and the air intake efficiency of the main engine is reduced, just like a small horse pulling a cart and causing overload. If the intake regulating valve fails to open completely, it will also aggravate the overload. The failure of the cooling system, the high temperature of the lubricating oil and the decrease of viscosity, the increase of friction resistance of each component, and the high temperature reduce the compression efficiency and increase the motor load. For example, the failure of the cooling fan leads to high oil temperature and abnormal operation of the equipment.
4. Handling Principles and Methods of Overload Faults
To handle overload faults, the principle of "first check the mechanical system, then overhaul the electrical system" should be followed. For mechanical faults, the air filter should be cleaned or replaced regularly, such as inspection and maintenance after a certain period of operation; Overhaul the intake regulating valve to ensure that it opens and closes smoothly, which can be guaranteed through regular functional tests; Regularly detect the rotor gap and bearing status of the screw main engine, and repair or replace them in time if wear is found. Advanced testing equipment can be used for accurate detection; At the same time, ensure the good heat dissipation of the cooling system, replace the lubricating oil and filter element regularly, and maintain the appropriate oil viscosity. For electrical problems, timely detect the power supply voltage and three-phase balance, and adjust the transformer output or overhaul the line if abnormalities are found; Regularly check the insulation of the motor winding and detect the insulation resistance with professional instruments; Calibrate the setting parameters of the thermal relay to ensure its accurate action.
5. Preventive Measures for Overload Faults
To prevent overload faults of screw air compressors, a sound daily maintenance system should be established. Regularly inspect the equipment operation parameters, such as recording current, voltage, temperature and other data every day, and find abnormal trends in time through data analysis. For example, the gradual rise of current may indicate potential problems in the equipment. Replace vulnerable parts regularly according to the equipment manual, such as air filters and lubricating oil, to avoid parts running "with diseases" and prevent major faults caused by small parts damage. Reasonably plan the start and stop time of the air compressor to avoid the instantaneous high load impact caused by frequent start and stop. A scientific start and stop plan can be formulated according to production needs to reduce equipment loss.