The common fault analysis of refrigeration compressors is here!
1. The suction temperature is too high Excessively high suction temperature is mainly caused by the increase of suction superheat. Note that high suction temperature does not mean high suction pressure, because suction is superheated steam. Under normal circumstances, the compressor cylinder head should be half cold and half hot. If the suction temperature is too high, all cylinder heads will heat up. If the suction temperature is higher than the normal value, the exhaust temperature will rise accordingly. The main reason for the excessively high temperature: 1. The refrigerant charge in the system is insufficient. Even if the expansion valve is opened to the maximum, there will be no change in the amount of liquid supplied, so that the refrigerant vapor is overheated in the evaporator and the suction temperature is increased. 2. The opening degree of the expansion valve is too small. As a result, the circulation amount of the refrigerant in the system is insufficient, the amount of refrigerant entering the evaporator is small, the degree of superheat is large, and the suction temperature is high. 3. The expansion valve port filter is blocked. The supply of liquid in the evaporator is insufficient, the amount of refrigerant liquid is reduced, and a part of the evaporator is occupied by superheated steam, so the suction temperature increases. 4. Other reasons cause the temperature to be too high. If the heat insulation of the return air pipeline is not good or the pipeline is too long, it can cause the suction temperature to be too high. 2. The temperature is too low The suction temperature is too low, which is mainly caused by the low suction superheat caused by the large liquid supply of the evaporator. 1. Too much refrigerant charge. Occupies part of the volume in the condenser to increase the condensing pressure, and the liquid entering the evaporator increases accordingly. The liquid in the evaporator cannot be completely vaporized, so that the gas sucked by the compressor contains liquid droplets. In this way, the temperature of the return air duct drops, but the evaporation temperature does not change because the pressure does not drop, and the degree of superheat decreases. Even if the expansion valve is closed, there is no significant improvement. 2. The opening of the expansion valve is too large. Because the temperature sensing element is too loosely bound, the contact area with the air return pipe is small, or the temperature sensing element is not wrapped with insulation material and the position of the wrapping is wrong, etc., the temperature measured by the temperature sensing element is inaccurate and close to the ambient temperature, causing the expansion valve to operate The opening degree increases, resulting in too much liquid supply. Reason: The refrigerant charge is insufficient, and it will flow from the evaporator to the compressor (note: need to be verified). In addition, due to external reasons, the refrigerant does not evaporate in the evaporator or even does not evaporate. At this time, it will form severe frost and even cause wet compression. (If the return air of the central air conditioner is insufficient or the filter of the air conditioning box is seriously blocked, the return pipe of the compressor of the chiller will be frosted, and the exhaust temperature will be very low) Three, the exhaust temperature is abnormal Factors affecting abnormal exhaust temperature: adiabatic index, compression ratio, suction temperature. Compressor exhaust temperature can be read from the thermometer on the exhaust line. It is related to the refrigerant's adiabatic index, compression ratio (condensing pressure/evaporating pressure) and suction temperature. The higher the suction temperature and the higher the compression ratio, the higher the exhaust temperature, and vice versa. When the suction pressure is constant, the exhaust temperature rises when the exhaust pressure rises; if the discharge pressure is constant, the exhaust temperature also rises when the suction pressure decreases, both of which are due to the increase in the compression ratio caused. Too high condensing temperature and exhaust temperature are detrimental to the operation of the compressor and should be prevented. Excessive exhaust temperature will make the lubricating oil thinner or even char and coking, which will deteriorate the lubrication conditions of the compressor. The discharge temperature is proportional to the compression ratio (condensing pressure/evaporating pressure) and the suction temperature. If the superheating temperature of the suction is high and the compression ratio is large, the exhaust temperature is also high. If the suction pressure and temperature do not change, when the exhaust pressure increases, the exhaust temperature also increases. Fourth, the main reasons for the increase in exhaust temperature are: 1. The suction temperature is higher. The refrigerant vapor is compressed and the discharge temperature is higher. 2. Condensing temperature rises The condensing pressure is also high, causing the exhaust temperature to rise. 3. The exhaust valve plate is broken. The high-pressure steam is repeatedly compressed and the temperature rises. The cylinder and cylinder head are hot, and the indication value of the thermometer on the exhaust pipe also rises. The actual factors that affect the increase of exhaust temperature are: low intercooling efficiency, or excessive scale in the intercooler affects heat transfer, the suction temperature of the subsequent stage will inevitably be higher, and the exhaust temperature will also increase. The valve leaks and the piston ring leaks, which not only affects the increase in exhaust temperature, but also changes the pressure between stages. As long as the compression ratio is higher than the normal value, the exhaust temperature will rise. In addition, water-cooled machines lack of water or insufficient water will increase the exhaust temperature. The condensing pressure is abnormal and the exhaust pressure is reduced. 5. Higher exhaust pressure Exhaust pressure generally corresponds to the condensation temperature. Under normal circumstances, the discharge pressure of the compressor is very close to the condensing pressure. High exhaust pressure will increase the compression work and reduce the gas transmission coefficient, thereby reducing the cooling efficiency. When the condensing pressure increases, the compressor discharge temperature also increases. The compression ratio of the compressor increases and the air delivery coefficient decreases, thereby reducing the cooling capacity of the compressor. Increase in power consumption. If the exhaust temperature is too high, it will increase the consumption of compressor lubricating oil, make the oil thinner and affect the lubrication; when the exhaust temperature is close to the flash point of the compressor oil, it will also carbonize part of the lubricating oil and accumulate in the suction, The exhaust valve port affects the sealing performance of the valve. Reducing the temperature of the cooling medium can reduce the condensation temperature and the condensation pressure. However, this is limited by environmental conditions and is difficult to choose manually. Increasing the flow of the cooling medium can lower the condensation temperature a little (this method is often used). However, the flow of cooling water or air cannot be unilaterally increased, because this will increase the power of the cooling water pump or fan and motor, and should be comprehensively considered. Six, the main reason for this failure: 1. The flow of cooling water (or air) is small and the temperature is high; 2, there is air in the system, which increases the condensing pressure; 3. The refrigerant charge is too much, and the liquid occupies the effective condensation area; 4. The condenser is out of repair for a long time, and the heat transfer surface is seriously dirty, which can also cause the condensing pressure to rise. The presence of scale also has a greater impact on the condensation pressure. 5. The exhaust pressure is too low Exhaust pressure is too low It is mainly caused by low refrigerant flow in refrigeration system pipeline or even stop. The exhaust pressure is too low. Although the phenomenon is manifested at the high-pressure end, the cause is mostly at the low-pressure end. The reason may be that the expansion valve is blocked by ice or dirty, and the filter is blocked, which will inevitably reduce the suction and discharge pressure. Seven, insufficient exhaust Insufficient displacement is mainly compared with the compressor’s design gas volume. It is one of the most prone failures of the compressor. Its appearance is mainly caused by the following reasons: 1. The intake filter is clogged with fouling or the compressor suction pipe is too long and the pipe diameter is too small, which increases the suction resistance, affects the suction volume and reduces the discharge volume. 2. The reduction of compressor speed reduces the discharge volume. If the compressor is used in an improper environment, because the compressor's displacement is designed according to a certain altitude (this item is mainly an air compressor), suction temperature, humidity, and power supply, when it is used in excess of the above standards When the air compressor is used in the high environment, the suction pressure will be reduced, and the exhaust volume will also be affected. 3. Inadequate packing seal produces air leakage and reduces the exhaust volume. The reason is that the packing itself is unsatisfactory when it is manufactured; secondly, it may be caused by air leakage caused by wear and tear during installation; generally, lubricating oil is filled at the packing to lubricate, seal, and cool.
