Operation and protection of common type compressors in winter

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　　Ordinary air compressors are vulnerable in summer, as the temperature inside the machine room is relatively high during this time, and compressors are most prone to high-temperature problems at such times. The air temperature is already high, and the heat generated by the compressor during operation contributes to even higher temperatures. This phenomenon can be alleviated as long as air circulation in the compressor room and cooling of the machine body are maintained. As the weather gets colder and winter arrives, compressors face additional problems as well. 　　The harsh winter arrives, posing a challenge for both living organisms and mechanical equipment. Animals such as frogs and snakes choose to hibernate in order to survive the harsh cold. For mechanical devices such as air compressors that must remain in operation throughout winter, as temperatures drop, improper use or lack of timely maintenance often lead to quality issues, resulting in significant economic losses and safety hazards. To ensure that the compressor can endure the cold winter in a stable and safe manner, users need to master certain techniques. Now, we will analyze the matters that need attention and the maintenance methods for compressors during winter operation, so that everyone can improve their maintenance plans and avoid unnecessary economic losses for the factory due to inadequate maintenance. 　　1. Before using the compressor, we need to open the side cover to check whether the oil has become thicker or frozen. If so, the fuel must first be heated, then all the exhaust valves on the compressor should be opened. After rotating the large flywheel 2-3 times, start the machine under no-load conditions. For units equipped with an oil pressure gauge, carefully check whether the pressure indicated on the gauge rises to the normal range (i.e., 0.3–0.4 MPa), and listen for any abnormal noises or gases being produced. Everything is normal. After operating under no-load conditions for 15 minutes, close the valve and check whether all control circuits are functioning properly, that is, whether the pressure regulating valve activates as specified, and whether the primary and secondary pressures are within normal ranges. Once everything is normal, the compressor enters its normal air supply mode. 　　2. Electric compressors experience relatively high oil viscosity in all their lubrication areas when started up in winter, and since the voltage in some mines is relatively low, this can make it difficult to start them at first. Generally, the unit is rotated 2-3 times first, and the electric compressor is started 3-4 times. The steel rod connecting the compressor to the air tank is removed or an exhaust valve is taken off. After the unit starts, it is allowed to run idle for 10 minutes before being shut down. Then, the removed parts are reinstalled and the unit is started again; this usually ensures that the unit operates properly. For electric compressors that are turned on daily, once they have been running properly, a multimeter can be used to measure the current level while they are in operation. Under normal circumstances, it should be within 5% of the motor’s rated current; if the current exceeds 10% of the normal level, it indicates that there is a problem with the unit or that the voltage is too low. The machine should be stopped for inspection, otherwise the motor is likely to overheat and get damaged. It is recommended that, if conditions permit, the compressor be placed in a suitable environment; indoor placement is ideal. If that’s not possible, a simple shelter can be built, which will help extend the service life of the air compressor. 　　3. As the seasons change, the special oil used in screw compressors also needs to be replaced, as the oil suitable for use in summer is different from that suitable for winter. Generally, piston compressors use 13# oil in winter (with the new standard being 100# compressor oil), while diesel-driven compressors are recommended to use 40CD oil in winter. In areas where temperatures are particularly low, it is necessary to use special oils with a freezing point lower than the local temperature. 　　4. For diesel mobile compressors, it is necessary to drain the water from the engine and the water tank after shutting down the machine. In particular, this applies to the drain valves located under the water tank, as well as those at the engine’s fuel inlet. There are also drain valves under the cylinders of water-cooled compressors, as well as at the inlet and outlet ports of the intercooler. Every winter, users experience cylinder cracking due to failure to drain water in a timely manner. Start using the diesel engine in the morning; it’s best to add hot water to the water tank, as this makes it easier to start the engine. 　　5. After shutting down in winter, be sure to drain the water, air, and oil from various pipes and air tanks. During operation in winter, the temperature of the units is relatively high; after shutdown, due to the lower external temperature, air cooling results in the formation of large amounts of condensate water, which accumulates in various control pipes, intercoolers, and air receivers. This can easily lead to blockages in the control pipelines and intercoolers, as well as cracks in the air receivers. In some places, the compressor stops working when it freezes. It is recommended that, if conditions permit, the compressor be placed indoors during winter or a temporary tent be built, as this can extend the service life of the unit. 　　6. The temperature difference between day and night is large in winter, which makes it very easy for components such as the screws and bearings of air compressors to become loose. Therefore, users must also systematically and step by step check for any looseness in the equipment. 　　7. Cold weather can affect the service life of lubricants; therefore, it is recommended that users shorten the replacement interval accordingly. It should be noted that the same grade of lubricant cannot be used in winter and summer. This is because ordinary lubricants generally have one characteristic: their viscosity decreases at high temperatures and increases at low temperatures. Therefore, the compressor requires appropriate lubricating oil to be selected based on different seasons (mainly summer and winter), that is, according to different temperatures. In our country, the higher the grade of lubricating oil, the greater its viscosity. Therefore, where conditions permit, the lubricating oils used in winter and summer should be different. In conventional piston compressors, the cylinder-sealant area uses compressor oil grade 19 in summer and grade 18 in winter. The crankshaft-conrod assembly can use 50-grade machine oil in summer. In winter, machine oil grades 30 and 40 can be used, which provides better lubrication for the compressor. Generally, single-acting small compressors use compressor oil grade 13 in winter and grade 19 in summer. 　　In northern regions, the ambient temperature in winter is far below the designed operating temperature range for compressors, which results in a higher failure rate of these compressors during winter. High exhaust temperature, high compressor temperature, and low exhaust pressure are the most common compressor failures in winter, and lubricant has an impact on the occurrence of all three of these failures. 　　Due to a lack of experience, many users often resort to replacing the lubricant after a failure occurs. After the compressor ran normally for a week or two with the new lubricant, the fault reappeared. This results in frequent replacement of the compressor lubricant, imposing a significant burden on production costs. 　　The most prominent feature of winter is the cold weather. When replacing the lubricant, it is necessary to start the compressor and run it for an hour in order to ensure optimal results. This is done so that the lubricant can return to its normal temperature, and to carry out a simple yet thorough cleaning of the entire compressor system, especially the lubrication system. By adding new lubricant afterward, its service life can be significantly extended, and the performance of the entire system can also be greatly improved. 　　8. Make sure to keep the environment clean and tidy; in particular, pay attention to ensuring that there is no water accumulation on the ground around the air compressor, to prevent freezing and slipping that could cause operators to fall. 　　In the cold winter, not only are higher technical requirements placed on compressor end-users, but more safeguards are also required of various compressor distributors and suppliers. It is very important for customers to conduct inspections of compressors in snowy weather; knowing about faults early helps to reduce machine failures. Early detection and prompt treatment prevent significant losses to customers’ production due to prolonged interruptions in gas supply. 　　In fact, in addition to the widely used industrial compressors, there are a large number of engineering compressors (mobile compressors) in use across various industries such as mining, infrastructure construction, and firefighting. Therefore, the maintenance and operation of these engineering compressors when used outdoors during winter cannot be ignored. 　　In the winter in the northern or western plateau regions of our country, the compressor has difficulty starting due to the low ambient temperatures. The main reason is that at the end of compression in the diesel engine compressor cylinder, the air temperature does not reach the level required for starting, and the pressure of the compressed air inside the cylinder is also significantly lower than the pressure required for starting ； The optimal operating temperature for batteries is 20–40°C; as the ambient temperature drops, their output capacity decreases accordingly, which leads to a reduction in the power of the diesel engine compressor starting system ； At lower ambient temperatures, the viscosity of the engine oil increases, which raises the resistance between various friction pairs and results in a lower starting speed for the diesel engine compressor. Meanwhile, the viscosity of the diesel increases as well, leading to poorer fuel atomization and an extended ignition delay period ； Air density and the oxygen content in the air decrease as altitude increases; the higher the altitude, the more difficult it is to start a diesel engine compressor. 　　Under low-temperature conditions, to ensure that various types of machinery can be used safely in cold environments, regular maintenance should be carried out, and it is advisable to install a low-temperature auxiliary starting system. Several common methods for low-temperature starting: (1) Use diesel engine compressor oil with good low-temperature performance; such oil has a low viscosity at low temperatures, ensuring good lubrication between all friction surfaces and reducing starting resistance, thereby facilitating starting. For multi-grade oils in use today, such as those with ratings like 15W/40W, the smaller the number, the better the oil’s flowability at low temperatures. Therefore, 10W or 5W engine oil is recommended at low temperatures ； 　　(2) Use batteries with good low-temperature performance; if necessary, insulate the batteries to ensure that they can be charged properly under low-temperature conditions and provide sufficient output current, thereby enhancing the power of the starting system ； 　　(3) Flame preheating start ； 　　(4) Fill with cold start fluid ； 　　(5) Circulating water heating system (also known as fuel heater heating system) ； 　　(6) Other preheating methods. 　　In addition to the aforementioned preheating methods, low-temperature startup can also be achieved using various other methods such as hot water preheating, steam preheating, and electric preheating. 　　Summary: Although cold weather increases the risk of failures in compressor equipment, proper precautions by users can still ensure that these systems provide a continuous supply of compressed air to businesses and users in an efficient and stable manner.