Failure analysis and analysis of other common failures of screw refrigeration compressor

Failure analysis and analysis of other common failures of screw refrigeration compressor 1. Abnormal compression ratio: The compression ratio of the screw machine is too large: it proves that this system completely deviates from the design value. The main phenomena are that the temperature of the exhaust temperature is too high, the suction pressure is too low, and the temperature is too high. The compression ratio of the screw machine is too small: the main impact is the wet stroke (tide, frost), in fact, the screw machine is more afraid of the wet stroke, if a large amount of liquid returns to the compressor, it will cause the dilution of the lubricating oil, and the consequences are the same The gas temperature is too high. 2. Low condenser efficiency: The low efficiency of the condenser mainly affects the temperature of the liquid supply and whether liquid can be formed. If the condensation effect is too good, for example, the ring temperature is too low, the condensation effect is too good, which causes the liquid to enter the evaporator more efficiently, the suction superheat is very low, and the expansion valve sensitivity is low, which will cause startup liquid blow. 3. Low or high evaporator efficiency: The low efficiency of the evaporator mainly affects the cooling of the object to be cooled, and the wet stroke affects the compressor. The high efficiency will cause the suction superheat to be too large, which will affect the compressor discharge temperature. The wet stroke can be judged according to the pressure enthalpy diagram, or the value of the exhaust gas temperature minus the temperature after condensation. If this value is less than 30K, it can be judged as the wet stroke. 4. Oil circuit problem: The oil circuit is mainly reflected in the quality, cleanliness and oil return temperature of the oil. The main functions of the lubricating oil in the refrigeration system of the screw compressor are lubrication, cooling and sealing. The temperature of the oil return affects the service life of the screw compressor to a great extent. The recommended operating temperature is generally between 40 and 60 ℃, and some manufacturers have also marked 70 ℃ or 80 ℃. Excessively high oil temperature will cause coking of the oil and destroy the formation of oil film. The oil temperature also affects the exhaust gas temperature, which in turn affects the compression ratio. 5. Oil boiling during startup or operation: This fault belongs to compressor liquid intake, or there is too much refrigerant in the lubricating oil. Please adjust the throttle mechanism to check whether the refrigerant is overcharged. 6. The oil level is insufficient or too high: If it is insufficient, it should be considered whether it is an oil fault, insufficient fuel supply, and difficulty in returning oil to the evaporator. Pay attention to whether there is no liquid level in the reservoir during maintenance, and consider the failure of the throttle mechanism or the unreasonable installation. If it is too high, it should be considered that the oil filter is blocked, and the refrigerant is mixed into the oil. 7. The exhaust temperature is too high: There are many factors of high exhaust temperature, mainly considering too much or too little refrigerant, too high intake heat, unstable operating conditions, etc. 8. The suction pressure is low or fluctuating: The low suction pressure is mainly due to the lack of refrigerant, the adjustment of the throttle mechanism, the high condensation temperature, and the liquid blow. Screw compressor 1: internal structure

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