Air compressor “jump” problem analysis and handling

     Usually caused by the external power supply "jump" fault, not the cause of the air compressor itself, do not need to deal with; other overload protector jump caused by "jump" fault must be treated seriously, if forced to run, may lead to the scrapping of the air compressor group.
    There are many reasons for jumping, the most common one is high temperature jumping, especially in the summer when the temperature is high, the phenomenon of air compressor jumping is still more common.
    The following are some of the other uncommon causes, which are usually difficult to maintain, and the unfamiliar after-sales service personnel will feel very "tricky" when they encounter these problems.
     1. Starting with pressure
    The so-called air compressor with pressure start refers to the air compressor start, the compressor back pressure is too high, caused by the jump machine. If the mechanical pressure gauge on the compressor oil and gas drum is checked on site, and if the gauge shows pressure, the initial judgment is that the system may not be fully relieved, resulting in the compressor starting with pressure. At this point, the air switch trips to protect the unit due to the high starting current.
  1. Excessive head resistance
    Excessive head resistance will lead to excessive compressor starting current, i.e. compressor overload, resulting in the air switch tripping. There are three main situations that can lead to increased head resistance: ① High viscosity of lubricating oil. Southern temperature changes with the season, the ambient temperature in summer can be as high as about 40 ℃, the minimum lubricant viscosity in winter and temperature is inversely proportional to the characteristics of the winter lubricant viscosity will be significantly higher than the summer lubricant viscosity; ② for single screw compressor, the head screw and star wheel easy to coke. The work of the single screw compressor is mainly through the engagement of the screw and the star wheel to complete the air compression process, the clearance between the screw and the star wheel determines the efficiency of the compressor; ③ too much lubricant in the head. Head export oil cut-off valve failure, the compressor shutdown oil cut-off valve if not closed in time, a large amount of lubricating oil will be pressed back into the head, resulting in the start-up process too much starting resistance, resulting in an increase in motor starting torque starting current, and lead to overload protection jump.
    3, electrical device failure
    Many users use 380V motor, using the star-delta conversion of the step-down starting method to start, earlier is to star mode of operation. When the starter starts, it turns to the triangular operation mode after 2 to 3s. If the star-delta changeover switch fails, the normal star-delta changeover is not possible. The star current is many times higher than the delta running current, usually around 5 to 7 times, and the compressor naturally jumps when the protector is delayed in arriving. In addition, the shortened start time set by the air switch due to vibration etc. may also cause the start to jump instantaneously. To determine whether it is an electrical fault or a mechanical fault, the most direct and effective method is to separate the motor from the head end, i.e. remove the coupling or belt at the head end of the connection, and manually disk the compressor host and motor respectively to eliminate mechanical problems.
  2. Unloading valve failure
    Unloading valve is an important part of the screw compressor, its main function is to control the loading and unloading of the unit, that is, to control the amount of air into the compressor. Unloading valve open in advance is a fault that is not easy to find. The unloading valve is closed before the compressor is started and opens slowly during the start-up process or fully after the start-up is complete. If the unloading valve is opened too early it means that the compressor starts with too much load, resulting in an increase in the compressor starting current and causing the compressor to jump.
  3. High motor temperature
    (1) When the instant voltage of the motor exceeds the rated voltage by more than 10% in summer or when the instant voltage of the motor is lower than the rated voltage by more than 5%, it will cause the motor to heat up and increase in temperature under the rated load, in which case the voltage should be checked and adjusted;
    (2) Too frequent starting of motor, too high temperature of using environment and poor ventilation will also lead to high temperature of motor. Reducing the number of starts, lowering the ambient temperature, ensuring smooth air ducts, eliminating dust and oil accumulation and keeping the fan running well can all help solve similar overheating problems;
    (3) Unbalance in the three-phase supply voltage of the motor will also cause the motor to heat up, because when the three-phase supply voltage is unbalanced by more than 5%, it will cause the three-phase current to be unbalanced, the solution is to check and adjust the voltage; (4) The contact problem of the motor’s power switch and the broken fuse of one phase will cause the motor to run out of phase, thus causing the motor’s temperature to rise. The solution is to repair or replace the damaged parts. Maintenance Case Share a maintenance case: Early in the morning of July 11, a customer called to say that the compressor would not start and there was a burnt smell inside the control box. The display showed that the inverter was faulty and we had to hurry up and deal with it because many equipment in the workshop needed gas to run and they were all pressing for when the compressor could be repaired. This company usually has minor problems with their compressors, which they can solve themselves, but only major problems and maintenance are entrusted to the manufacturer.
    We first rushed to the scene, check the inverter fault alarm e13 fault, query the relevant information to determine the display of overcurrent fault, and I personally feel that this is the phenomenon of lack of phase output. So with a universal pen to measure the motor resistance value is normal, AC contactor is normal, the main line is not found to be out of phase, power off and restart are not. So the telephone consultation inverter manufacturers, this 55kW screw compressor, there are two starting modes: an industrial frequency mode, a frequency mode; usually are frequency start, the purpose is to? electricity. Two days ago came a self-proclaimed manufacturer to do over maintenance, and this master just after maintenance, the air compressor on the ground after the oil leakage phenomenon, and finally found that it is the oil and gas separator tank a screw is not tightened. And by now in the morning it would not turn on properly. They also had a group of people come to repair the inverter before, which was not fixed. According to the operator it was the inverter that was broken and needed to be replaced with a motherboard, which of course didn’t cost much. In fact, I just checked the electric control box and there were signs of disassembly of the electric control box casing screws, but none of the components inside had been replaced, and I knew the reason at that time. Because this company has a certain strength in the local area, the workshop management ganged up and everyone wanted a piece of the pie. The family members of the maintenance plant also know this, so they focus on punishing the relevant personnel, repairing once directly to the bill to leave once, the next time a new problem can be repaired again. And for the inverter e13 fault, in the case of power failure, with a screwdriver to re-tighten the inverter out of the end of the screw again, power failure eliminated, before and after less than 5 minutes, power restart on the normal boot.
    For the daily electrical minor faults need to be carefully investigated, as long as the cause of the problem can be found, the solution is generally relatively simple.

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