Basic skills for screw compressor overhaul

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This post was last edited by YORK Industrial Refrigeration on 2017-4-29 17:35 Screw refrigeration compressors occupy a dominant position in refrigeration devices in today's refrigeration industry due to their low basic cost, low operating costs, large cooling capacity, and resistance to liquid shock. The maintenance of screw refrigeration has naturally become a highlight. However, due to improper maintenance of some units, it failed to show its unique advantages. The screw compressor operates at high speed for a long time, and the most vulnerable thing to damage is the bearing. Its damage will lead to high oil temperature, severe machine vibration and other accidents. The key to its maintenance and replacement should be to focus on the following three links. 1 The selection process of screw refrigeration bearings takes the LG25IIA450 screw refrigeration compressor as an example. It consists of 6 sets of bearings, and the models are as follows: Single row cylindrical roller bearings: Nu2317Ec/P6SKF1 set ； Nu2318Ec/P6SKF2 sets ； Nu2319Ec/P6SKF1 set ； Four point contact ball bearings: QJ318N2／P6／C2SKF1 set ； QJ319N2/P6/C2SKF1 set. Among them, two sets of four-point contact ball bearings are respectively located at the exhaust ends of the yin and yang rotors to balance the thrust. Whether the bearing is durable or not, the material of the cage is very critical. As we all know, most refrigerants in the chemical industry are ammonia (NH), so the cage should not only have high strength, but also have good ammonia resistance. The random bearings of screw compressors are all imported bearings, and their cages are made of ammonia-resistant high-strength resin. However, some domestic bearing cages are made of copper or steel, so it is understandable that the service life is short. Therefore, the selection of bearings should be based on the principles of applicability and durability. 2. Rotor exhaust end clearance adjustment. Place the fuselage on the self-made platform with the output end upward. Place the dryness meter on the output end cover with its contacts in proper contact with the rotor. Use the lifting nose to slowly lift the rotor and read the number on the dial indicator. If the read data is smaller than the standard clearance, the outer adjustment ring needs to be ground; otherwise, the inner adjustment ring needs to be ground. In this way, after repeated inspections, until the gap reaches the required value of the equipment (many methods, for reference only) 3. High cleanliness in the screw refrigerator assembly process. Due to the high speed and efficiency of the bearings, high cleanliness in the body is bound to be required. Otherwise, the bearing will suffer pitting damage early and cause other accidents. Therefore, when assembling parts, you should do: (1) Parts that have passed the inspection must be derusted first. Parts that need to be dried, such as the suction end seat, body, slide valve, etc., should be dried. (2) Parts should be cleaned and stain-free before each assembly process, and there should be no bumps or scratches on the processed surface. (3) Parts should be placed on cork or rubber in order. (4) The tools and places used for assembly should be clean, and the wire ropes used for lifting should be free of sand and other dirt. (5) The hands of the assembly personnel must be clean, and water and other dirt are not allowed to be carried out. (6) During the assembly process, a little clean lubricating oil should be applied to the mating surface, and a clean white silk cloth should be used to wipe the inner cavity. 4. Making more suitable tooling. Since the disassembly and assembly of the screw refrigeration compressor requires good centering and irregular shape, it is necessary to make one gantry and one small support platform, and two sets of guide chains (3t). The guide chains on both sides are used when the fuselage is turned over, and the guide chain and small support platform in the middle are used for adjusting the gap and installing the rotor exhaust end cover. Appropriate tooling ensures the efficiency of assembly. I believe that if you grasp the above four links, you will get twice the result with half the effort.