With the arrival of cold waves, what precautions should be taken for air compressor systems?

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In the cold winter, if proper maintenance is not carried out, it can lead to failures in the air compressor. Today, we will share some preventive measures for shutting down and starting various types of air compressors in winter. Friendly reminder: As different brands and models exist, the information in this article is for reference only. Precautions for starting and stopping oil-injected screw air compressors: 1. Before starting the air compressor, ensure that the oil temperature is at least +2°C; if the temperature is too low, use a heating device to warm the oil tank and the main unit. In the case of a water-cooled unit, it is necessary to check whether the water cooler and water circuits are frozen; if there is freezing, heating treatment is also required. 2. Check that the oil level is at the proper level, and ensure that all condensate drainage outlets are closed; they should be opened if the machine is to remain shut down for an extended period of time. The water-cooled unit should also be checked to ensure that the cooling water discharge valve is closed; this valve should be opened when the unit is shut down for an extended period of time. 3. After powering off the equipment, manually rotate the main unit coupling; it should turn smoothly. For machines that are difficult to rotate, do not start them blindly; check whether there are any faults with the machine or motor, and whether the lubricant has become thickened and ineffective. Only after the faults have been resolved can the machine be started. 4. For machines that have been shut down for an extended period of time or whose oil filters have been in use for a long time, it is recommended to replace the oil filter before restarting them. This prevents insufficient oil supply to the engine due to the reduced ability of the oil filter to filter the oil when it is thick, which can cause the engine to overheat momentarily upon startup and lead to engine failure. 5. After performing the above checks, the machine should be started for a test run for the first time, in order to check its operating conditions and whether the sounds produced during startup are normal. In the event of a sudden temperature change, stop the machine immediately for inspection; do not start it frequently, and add an appropriate amount of coolant to the machine if necessary. The method for intermittent preheating is as follows: Press the start button, wait for the air compressor to run for 3–5 seconds, then press the emergency stop button. After the air compressor stops, wait 2–3 minutes before repeating the above process. If the ambient temperature is 0°C, repeat this process 2–3 times; if the ambient temperature is below -10°C, repeat it 3–5 times. 6. If a heat recovery system is installed, close the oil circuit valve of that system, and once the unit is operating properly, slowly open the control valve for the oil circuit of the heat recovery system. 7. For two-stage compression machines, especially those of high power, when restarting after a period of shutdown, an appropriate amount of lubricating oil should be added at the air inlet and the machine should be started up in 2-3 pulses. The oil supply control valve that connects the oil tank to the machine body should be fully opened at the time of startup. If the exhaust temperature is too low once the machine is running stably, the water flow rate through the customer’s cooling water valve can be adjusted to control the temperature; if necessary, the oil supply volume can also be adjusted via the oil supply valve to achieve an appropriate exhaust temperature, depending on the actual temperature conditions. Precautions for shutting down and starting up dry oil-free screw air compressors: 1. During periods of inactivity, if possible, heat should be supplied to the air compressor as much as possible ； If this is not possible, the compressor should be covered as much as possible with plastic sheeting or other shielding materials to block the wind and snow. 2. The temperature of the air compressor unit is relatively high during operation ； After shutdown, due to the low external temperature, a large amount of condensate is generated and remains in the pipes. If not discharged in time, the cold weather in winter can cause blockages, freezing, and cracking of equipment such as the air compressor’s exhaust pipe. Therefore, after the air compressor is shut down for cooling in winter, it is essential to drain all gas, oil, and liquid water from the compressor and pipelines. 3. After shutting down the machine during the holiday, the operator should turn off the power supply, open all the drainage and waste discharge valves, and then manually rotate the coupling quickly in the direction indicated by the arrows, so as to make the machine rotate rapidly and drain as much water as possible from it. 4. Before turning the machine on for the first time after the break, please check all the valves that were opened before the break. Before starting the machine for the first time (with power off), manually rotate the coupling to ensure it operates properly; only after confirming there are no abnormalities can the machine be started. 5. Care should be taken when starting the machine suddenly, as low ambient temperatures can reduce the fluidity of the lubricant and cause damage to the machine; if possible, raise the ambient temperature before starting it. Pay close attention to the oiling pressure at the moment of startup; some machines have gears that rotate at very high speeds, and if oiling is not carried out in a timely manner, the gears can be damaged. 6. It is not recommended to use the automatic operation function of air compressors in extremely cold environments. Precautions for starting and stopping water-lubricated screw air compressors. Initial startup: 1) Place the unit on a flat surface and connect it to the equipment that requires air supply at the rear end. 2) Check the water level of the lubrication water in the water-gas separator; the normal water level should be between the upper and lower scale lines on the water level gauge. 3) Close all air supply valves of the compressor unit. 4) Connect the power supply and check whether the readings of all instruments are normal. 5) Press the start button on the controller to start the unit. 6) After the unit is started and preheated at the lowest frequency, it automatically switches to the loading mode; at this point, the motor operates at its rated speed, and the exhaust pressure on the controller panel rises gradually. 7) Close all maintenance doors to control the noise of the unit and ensure proper flow of cooling air. 8) Check whether the readings on the instruments on each dashboard are normal. 9) After the first operation, shut down the system following the shutdown procedure, and check whether the water-gas separation tank requires lubricating water to be added; also check whether there is any looseness at the various connections and if there is any leakage. Normal start-up: 1) Place the unit on flat ground and connect the gas-consuming equipment at the rear. 2) Check the water level of the lubrication water in the water-vapor separation tank ； The normal water level should be between the upper and lower scale lines on the water level gauge. 3) Check and drain the condensate at the bottom of the water-gas separation tank and the gas storage tank. 4) Follow steps 3)–8) of the initial startup procedure to shut down the unit. 1) Close all air supply valves, press the shutdown button on the controller screen; the unit will shut down automatically after a delay. 2) In the event of an emergency that requires immediate shutdown, the emergency stop button can be pressed quickly, and the unit will shut down promptly. It should be noted that when the unit stops suddenly, its cooling and lubrication system for the compressor ceases to function immediately; at the same time, the unit is still at a high operating temperature, and there is still high pressure in the water circuit, which can cause significant damage to the intake valves and mechanical seals. Therefore, frequent use of the emergency stop function can cause serious damage to the unit, so it should not be used for shutting down the unit unless an emergency occurs. Note: Be sure to drain all the condensate from the gas storage tank and pipelines after work to prevent the pipelines from freezing and cracking.