Fault Analysis 0GD-25/I3B Air Compressor Starts Instant Jumping Accident Cause Analysis Wu Songlin, Yang Weiguo (Hengyang Hualing Steel Pipe Co., Ltd., Hengyang, Hunan 421001), the reason why the air compressor can not operate normally, summed up This type of air compressor starts several common causes of failure.
l bow 衡言衡阳åŽè±é’¢æœ‰é™å…¬å¸ (hereinafter referred to as Hualing Henggang has 2 OGD-25/13B air compressors, for Guangdong Zhengli Precision Machinery Co., Ltd. to produce fixed single screw air compressor, responsible for Valin The pressure supply of the coal injection system of Henggang Ironmaking Plant, the stability of the operation of the air compressor is directly related to the normal production of the coal injection system, and also directly affects the status of the ironmaking blast furnace.
Over the years, many times it has not been able to open normally. The phenomenon is that after pressing the start button of the air compressor, the motor is always in a high current state. After several 10s, it will automatically trip, and the trip point is the air switch on the wall.
2 OGD-25/13B air compressor structural characteristics and technical parameters 2.1 Air compressor structural characteristics 3 Single-screw rotor drives two symmetrically distributed star wheels for rotation, and the screw groove and the inner wall of the casing form a closed The elementary volume is such that the gas reaches the desired pressure. The structure is reasonable, not easy to wear, the foundation has no special requirements, the exhaust pulse is small, and the service life is long; the two star wheels in the Q main machine are symmetrically distributed, the screw is balanced, the operation is stable, the vibration is small, the running noise is low; the Q meshing pair can be very Work under small clearance to reduce leakage, thus high volumetric efficiency and energy saving; 0 oil and gas pipeline system is reasonable in design, high in automation, and multiple protection measures are set to ensure safe and reliable operation.
2.2 Air compressor technical parameters Model: OGD-25/13B single screw air compressor temperature. C. The viscosity and temperature characteristics of common lubricating oils are shown in the figure. * The screw and star wheel in the head are cokeed. The work of the screw air compressor mainly through the meshing of the screw and the star wheel to complete the gap between the screw and the star wheel determines the work efficiency of the air compressor. If the gap is too large, some of the gas leaks from the gap, and the air compressor has low work efficiency; if the gap is too small, the resistance between the star wheel and the screw is large, the load is large, and the energy consumption of the motor is large. The coke in the head can cause the gap between the star wheel and the screw to decrease, the frictional resistance in the meshing is large, and the current of the air compressor increases.
Screw and star wheel structure Figure 0 The amount of lubricant in the head is excessive. The oil outlet valve of the machine head has a fault. After the air compressor is stopped, the oil shut-off valve is not closed in time, and a large amount of lubricating oil is pressed into the machine head, causing the starting resistance to be large during the starting process, and the current is increased to cause the overload protection jump. machine.
Q artificial reel is the power component of the compressor, the transmission section is known as the valley flow: 25m3/min Nominal exhaust pressure: 1.3MPa Motor power: 185kW Rotation speed: 2980r/min 3 Failure analysis and judgment 3.1 Air compressor pressure start Start the instantaneous jump analysis and judge the on-site inspection of the mechanical pressure gauge on the air compressor barrel of the air compressor. If the pressure gauge shows pressure, it is preliminarily determined that there may be a system that does not completely depressurize, causing the air compressor to start with pressure, resulting in a starting current. The high induced air switch trips to protect the unit. Because in the screw air compressor, there is often a phenomenon that there is pressure in the system after the air compressor is stopped due to the failure of the minimum pressure valve or the clogging of the pressure relief system.
Pressure gauges show that there are two possibilities for pressure: one is that the system does have pressure; the other is that the pressure gauge is damaged and cannot be zeroed normally. The method of judging is to open the device or valve that can be relieved in the system. When the pressure relief valve is opened and it is found that the pressure gauge in the oil and gas barrel shows that there is still pressure, it is judged that the system has no pressure, and the pressure gauge cannot be returned to zero; , the system is under pressure.
3.2 The excessive resistance of the machine head triggers the analysis of the instantaneous jump machine and judges that the resistance of the head is too large, which causes the starting current of the air compressor to be too large, that is, the air compressor is overloaded, causing the air switch to trip. The role of lubricating oil in screw air compressors is very important. Its role is mainly in four aspects: cooling, lubrication, sealing, noise reduction, and the quality of oil, the amount of oil directly affects the air compressor The normal operation and the service life of the air compressor, especially the head part of the air compressor, are most obvious. According to the analysis of the model, there are mainly three cases that lead to an increase in head resistance: Q lubricant has a high viscosity. Hualing Henggang is located in the southern part of Hunan Province, China. The temperature varies greatly with the season. The summer ambient temperature can be as high as about 40 * C, and the lowest temperature in winter is below zero. According to the characteristics of the general lubricant, the viscosity is inversely proportional to the temperature. The viscosity of the oil is significantly increased compared to the past.
See the viscosity and temperature characteristics of several types of lubricating oils.
The most basic detection method for the connection of the fault analysis component and the linkage component and the free rotation. By checking the air compressor manually, the head and the motor can be freely rotated, and the resistance of the rotation is increased according to the previous cranking experience. When the ambient temperature is low, the temperature of the exhaust port displayed by the unit is used to determine the ambient temperature at that time. The large resistance may be caused by the decrease in temperature and the viscosity of the oil. As the viscosity of the lubricating oil in the head increases, the starting current of the motor becomes larger, and the starting time of the air compressor is prolonged. The time for starting the motor on the air switch can be extended slightly to ensure safety. If the motor is too long, it may cause a higher level of air switch to take off, thus affecting other electrical equipment to meet the increase in oil viscosity. The start time of the press is extended to ensure the normal start of the air compressor.
The oil coking in the head is a phenomenon often caused by the screw air compressor in the case of poor oil or high temperature. Due to the coking of the machine head, the gap between the screw and the star wheel becomes smaller, and the frictional resistance increases during the rotation. Large, the load of the unit increases and the current increases. In severe cases, the screw and the star wheel are glued together, and the unit cannot rotate freely.
The exhaust temperature of this type of air compressor is generally between 80100 ° C, and the temperature is high. When the oil is poor and the ambient temperature is low, the high temperature oil cooling speed is increased, and the possibility of coking of the unit is large. By opening the end cap of the machine head and inspecting the screw and the star wheel, it can be judged whether the coking is serious or not. If the coking is serious, the oil coke can be removed by washing with caustic soda or other special cleaning agent to restore the air compressor to normal.
The function of the oil shut-off valve on the 0-head filling pipe is to cut off the oil-filling pipe in time when the unit is shut down, to prevent a large amount of lubricating oil from being pressed into the machine head due to the residual pressure in the oil-gas tank, resulting in excessive lubricating oil in the machine head. Therefore, too much lubricating oil in the machine head after the shutdown is one of the reasons for the large starting current of the air compressor.
The most direct way to solve the problem of excessive oil in the machine head is to open the end cap of the machine head, release part of the lubricating oil inside the machine head, and repair or replace the oil shut-off valve.
3.3 Electrical equipment failure caused by the start of instantaneous jump analysis and judgment OGD-25/13B single screw air compressor power part is 380V low-voltage motor, using the star-delta conversion buck start mode to start, the early stage is run by star mode, when After starting the 10s air compressor, it will be turned into a triangular operation mode. If the star-delta switch is faulty, normal star-delta conversion cannot be performed, which will cause the air compressor to trip after 10s. In addition, the air switch is guided by vibration or the like during use, so that the set start time is shortened, which may cause the machine to jump immediately.
The most direct and effective way to determine whether it is an electrical fault or a mechanical fault is to open the motor and the nose, ie remove the coupling. The control system of this type of air compressor has a protection device. If the protection device is not opened, the air compressor is started, and the motor runs immediately. The motor current will be displayed on the control panel for about 40A, and the current is abnormal after 10s of operation. The motor automatically stops running because the protection unit will automatically stop when it detects that the current is greater than 10% of the maximum current or less than 90% of the minimum current. This will not judge the cause of the unit failure. When the protection is removed, the motor will run continuously for mechanical reasons; otherwise, the same trip will occur.
3.4 Unloading valve failure triggering start-up trip analysis and judgment The unloading valve is an important part of the screw air compressor. Its main function is to control the loading and unloading of the unit, that is, to control the air intake of the air compressor. OGD-25/13B single screw air compressor unloading valve is composed of cylinder, piston rod, spring, piston, intake baffle, valve seat, seal and other components as shown. The working principle is to control the intake and exhaust of the cylinder through the solenoid valve on the tolerance valve to control the forward and backward movement of the intake piston, thereby controlling the opening and closing of the valve.
Unloading the valve is also a common symptom that affects the motor's starting current. It is mainly manifested in two cases: the Q unloading valve is not closed or not completely closed. The failure of the unloading valve to be closed or not fully closed is one of the common faults affecting the normal starting of the unit in the use of the screw machine. The current of the unit during the starting process is very large. When the unloading valve is not completely closed, it is equivalent to starting with load. The motor must provide both the power during the start-up process and the power supplied by the unit, which will inevitably lead to a large motor current and a long start-up time.
* The unloading valve opens early in the startup process. The loading of the air compressor is carried out after the startup is completed, that is, the opening of the unloading valve should be started after the air compressor is started. If the unloading valve is opened in advance when the air compressor is not completed, it will inevitably lead to air pressure. The structure of the 0GD-25/13B air compressor unloading valve is increased in the later stage of the start-up, and the starting time is extended, which causes the air switch to trip.
The most intuitive way to determine whether the unloading valve is closed or not is to remove the air filter and you can clearly see whether the air intake baffle of the unloading valve is closed or open. The failure of most unloading valves is that the intake baffle is stuck on the guide rod. At this time, the piston should be in the position to close the intake baffle, but the unloading valve cannot be closed because the intake baffle is stuck. In addition, there is a case where the unloading valve intake baffle is caught by foreign matter such as mechanical impurities, and the unloading valve is not completely closed. After removing the air filter, if the air intake baffle is stuck due to mechanical impurities, the unit can be smoothly opened after cleaning; if the air intake baffle is stuck on the guide rod, the guide rod is ground with sandpaper, and the guide rod is Apply a small amount of grease on it; if the unloading valve is seriously damaged, replace the unloading valve.
The unloading valve is opened in advance is a type of fault that is not easy to find, because the unloading valve is in the closed state when starting the unloading valve, and the unloading valve is slowly opened during the starting process, but the opening time is longer than the unit setting. The time is early, it may only be opened for a few seconds in advance, but it will cause the starting current of the air compressor to increase, causing the air compressor to jump. The reason why the unloading valve is opened early is that the spring elasticity of the piston rod and the guide rod for controlling the valve action is small, so that the control system does not send a load signal to the unloading valve, and the vacuum of the air intake flap at the head is negative. The pressure is sucked open, that is, the air compressor is loaded in advance, and the unit has not been fully started, so that the motor is always at a high current, and the star-delta conversion cannot be performed, causing the air switch to trip. To judge whether the unloading valve is opened in advance, it is necessary to accurately grasp the starting time of this type of air compressor, and at the same time, according to the time when the unloading valve is opened, compared with the starting time of the air compressor, if the former is larger than the latter, the unloading is proved. The valve is not opened in advance, otherwise the unloading valve is opened in advance. OGD-25/13B single screw air compressor start-up time is about 25s. If the unloading valve is opened less than 25s after starting, the air compressor will be loaded in advance. If the spring in the unloading valve is replaced, the air can be started smoothly. press.
4 Conclusions Screw air compressors, especially single-screw air compressors with 380V low-voltage motors, often encounter the problem of large current jumps during start-up. The main reasons are divided into three categories: 0 process system, Mechanical failure, electrical failure, in which the system has pressure start, excessive lubrication of the machine head, and high viscosity of the lubricating oil belong to the process system; * the coke resistance of the machine head increases, the unloading valve is not closed, and the unloading valve opens in advance is a mechanical failure. ; 0 air switch start setting value change, star-delta switch switch fault, etc. are electrical faults.
In short, the same fault, there are a variety of reasons that may lead to the fault, first of all to determine what kind of reasons, and then start from this type of fault, one by one, can be solved.
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