High-temperature failure analysis and treatment of oil-injected screw air compressor â–¡ Liu Linjiang Baogang Group Barrun Mining Co., Ltd. introduced 14 roller rigs, the main air compressor system of these 14 roller rigs used oil-injected screw Air compressor. The air compressor is the core component of the roller rig. In the actual operation, the high temperature alarm is the fault with the highest frequency of the air compressor. The ML-250 oil-injected screw compressor produced by Ingersoll Rand consists of a main engine and motor system, a lubrication and cooling system, a pneumatic system, an oil and gas separation system, a control system and a protection system. The unit of this type of compressor adopts IR's unique INTELLISYS control fel, which can accurately control the compressor's exhaust pressure, exhaust temperature, pre-separation pressure and overheating and overcurrent protection of the fan and main unit of the electric control system. The screw air compressor is designed with high temperature protection function. Once the exhaust temperature exceeds the set value (such as l9C>, the temperature switch is commanded by the temperature sensor to issue an alarm and automatically stop.
Air compressors are transmission machinery. High-speed running screws and compressed air generate a lot of heat. If they are not properly lubricated or cooled, high temperatures will occur. Excessive temperatures will change the performance of the rotor and bearing materials. In severe cases, the entire host will burn out. Although the manufacturer has installed a high-temperature protection device on the air compressor, the existence of the fault will cause the protection device to operate frequently and affect normal production.
Principle of operation of the oil-injected screw air compressor Principle When the air compressor is started, the air is filtered by the air filter to remove dust and impurities, and then enters the suction port of the compressor. When operating in the unloaded state, the intake valve is almost closed to keep the airflow through the device to a minimum, minimizing the starting torque of the compressor drive motor. The air entering the air compressor is mixed with the injected lubricating oil and compressed by the engagement of two screws (the female and male screws), and is discharged from the exhaust port through the check valve. At this time, the mixed gas of air and coolant is used. The mixed gas flows quickly to the separation gas storage tank and is separated by the oil/gas separation system. The minimum pressure valve ensures that one is maintained in the separator gas storage tank.
The minimum positive pressure of 17 MPa, which is sufficient to drive coolant from the separator to the air compressor mainframe. When the air compressor is loading and running, the deflation solenoid valve is closed, and the solenoid valve is loaded to make the pressure oil enter the control cylinder through the pipeline. The suction valve is fully opened under the action of the cylinder, and the air compressor enters the full load operation state. The air is separated from the coolant in the gas storage tank. The separated compressed air contains only a few PPM of oil, and flows out through the minimum pressure valve to the use system.
Cooling principle When the air compressor is in normal operation, the lubricating oil in the separation air tank relies on the exhaust pressure of the air compressor and the pressure difference at the fuel injection port to maintain circulation in the circuit. Under the action of this pressure difference, the lubricating oil is controlled by the thermostatic control valve to enter the oil cooler to be cooled and cooled, and then the oil filter is used to remove the impurity particles, which are sprayed into the compression chamber and the bearing of the air compressor.
The cooled lubricating oil forms an oil film between the rotors to seal the gap and lubricate the rotor, and mixes with the air to remove most of the heat generated by the compression to achieve a cooling effect.
Ingersoll Rand Air Compressor I Mining equipment in the field of commercial technology high-temperature failure analysis and handling of high-temperature faults, usually related to lubrication and cooling system anomalies, you can first analyze the oil supply from the system.
The oil supply temperature is high. One roller rig is installed and the air compressor high temperature alarm occurs during the test run. After the inspection, the installation error of the thermostatic control valve is found (3 port connection error>. In the lubrication and cooling system, the thermostatic control valve Installed in front of the oil cooler, its role is to maintain the head exhaust temperature above the pressure dew point, to avoid condensed water damage to the host. The thermostatic control valve has three interfaces: A oil filter inlet, B pressure storage tank, C is connected to the cooler outlet. The working process can be divided into three stages: when the oil temperature is low, the temperature control valve B is opened, the C port is closed, and the lubricating oil is directly injected into the machine head without cooling by the cooler; The temperature of the lubricating oil rises above 67C, the B port of the thermostatic control valve is gradually closed, the C port is gradually opened, and some of the lubricating oil is cooled by the cooler; the temperature of the lubricating oil rises above 70C, the B port is completely closed, and the C port is completely opened, cooling The maximum cooling of the lubricating oil can be seen from the above analysis. If the thermostatic control valve is installed incorrectly or fails, the lubricating oil that needs to be cooled may not pass through the cooler and cannot be effectively cooled.
In addition, poor ventilation and improper operation of the cooler can also result in high fuel supply temperatures, which can be easily detected and handled through frequent maintenance inspections.
The main engine oil supply is low. Winter is the high season of equipment failure. The Baiyun West Mine is located in the alpine region of the plateau. The winter is very cold and the temperature is -25C. The lowest temperature can reach -38 C. The design working temperature range of the standard air compressor For the first winter of the 1.7-wheel drilling rig operating in the Baiyun West Mine, high temperature failures were frequent. According to the analysis, in the low temperature (such as -20C> environment, the viscosity of the lubricating oil increases, the fluidity decreases, the lubricating oil in the oil cooler freezes, and the lubricating oil that needs to be cooled cannot enter the oil cooler at all (the thermostatic temperature control valve C port can not be opened), even if it enters the oil cooler, it will freeze due to the operation of the cooling fan. This will cause the lubricating oil to circulate poorly, resulting in the air compressor main unit being unable to effectively take away the heat generated by the compression process due to the small amount of oil supplied. Therefore, high-temperature alarm occurs. It has been proved that in this low-temperature environment, the injection screw air compressor cannot be started normally according to the manufacturer's instructions. The method adopted by Baiyun West Mine is to improve the starting mode of the air compressor.
The main difference between this starting method and the starting mode provided by the manufacturer is that the cooling fan switch is first disconnected to make the air compressor run at no load; when the temperature difference between the outlet and the inlet of the cooler rises to 90-95C, the temperature rises to 90-95C. Close the fan control switch. After adopting the new starting mode, White: Z5: The high temperature failure of the air compressor in the West Mine roller rig is greatly reduced in winter.
The reasons for the low oil supply are: the system has less oil storage, and the oil level should be kept in the middle of the oil sight glass when the oil filter is in the middle of the oil sight glass, the oil circulation is not smooth; the oil separator is blocked. These problems are easy to find and can be solved by routine maintenance.
Control and protection components In the winter of Baiyun West Mine, there was a high temperature alarm when the air compressor was started. Check the air intake device, the machine head, the cooler, the thermostatic control valve, the system oil quantity, the oil quality, the oil filter and the system parameter settings. Abnormally, it was found that there was ice on the periphery of the temperature sensor when checking the control and protection components. According to the analysis, in the low temperature environment, some components of the air compressor control system or the protection system fail, do not operate or malfunction, and in this case, a high temperature alarm may also occur. The high temperature failure of the air compressor was eliminated after heating to eliminate the icing on the periphery of the 7C piece.
There are many reasons for the high temperature of the air compressor. If you blindly search for the root cause of the fault, it is not only inefficient, but also a waste of manpower and material resources. This requires us to strengthen the maintenance of the æ›° according to the principle of the air-injection screw air compressor, and constantly summarize some effective methods of investigation. Through the analysis and treatment of the high temperature failure of the air compressor, the use of the air compressor is reliably guaranteed, and the maintenance cycle and service life of the air compressor are prolonged, and the effect is remarkable.
Ingersoll Rand M250 air compressor
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