1. Abnormal compression ratio:
Compression ratios are not new to anyone who knows compressor performance. The difference between a screw machine and a piston machine is that the piston machine will only undercompress, while the screw machine will overcompress.
The compression ratio of the screw machine is too large: the system may deviate from the design value. The main phenomena are that the discharge temperature and pressure temperature are too high, the suction pressure is low, and the temperature is high.
The compression ratio of the screw machine is too small: the main effect is the wet stroke. 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 dilution of the lubricating oil, and the consequence is equivalent to high exhaust temperature.
2. The efficiency of the condenser is low:
Low efficiency of the condenser: mainly affects the temperature of the liquid supply and whether it can form a liquid. If the condensation effect is too good, it will not work. For example, if the ambient temperature is low, the condensation effect is too good, resulting in higher efficiency of liquid entering the evaporator, low suction superheat, and low sensitivity of the expansion valve, which will cause liquid shock when starting up.
3. Evaporator efficiency is low or high:
Low efficiency of the evaporator: the main effect is the cooling of the object to be cooled, while the wet stroke affects the compressor. The high efficiency will cause the suction superheat to be too high, 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.
4. Oil circuit problem:
Oil circuit: mainly reflected in oil quality, cleanliness, oil return temperature, etc. The main functions of lubricating oil in the refrigeration system of screw compressors are lubrication, cooling and sealing. The temperature of the oil return greatly affects the service life of the screw compressor. Generally, the recommended operating temperature is between 40 and 60°C, and some manufacturers also mark 70°C or 80°C. Excessive oil temperature will cause oil coking and damage the formation of oil film. Oil temperature also affects the exhaust temperature, which in turn affects the compression ratio.
5. Oil boiling during startup or operation:
Engine or oil boiling during operation: This fault is caused by liquid entering the compressor, or there is too much refrigerant in the lubricating oil. Please adjust the throttling mechanism to check whether the refrigerant is overcharged.
6. The oil level is insufficient or too high:
Insufficient oil level: It should be considered whether it is an oil fault, the amount of refueling is insufficient, and it is difficult to return oil to the evaporator. When maintaining, pay attention to whether there is no liquid level in the liquid reservoir. It should be considered that the throttling mechanism is faulty or caused by 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:
High exhaust temperature: There are many factors, mainly due to too much or too little refrigerant, too high suction superheat, and unstable working conditions.
8. Low or fluctuating suction pressure:
Low suction pressure: The main reason is the lack of refrigerant, the imbalance of the throttling mechanism, the high condensation temperature, and liquid shock.
