Compressor in the industrial chiller system produces wet stroke fault and troubleshooting

Compressor in the industrial chiller system produces wet stroke fault and troubleshooting

In the industrial chiller system, when the compressor sucks in wet steam, frost occurs on the cylinder wall, and the suction temperature and discharge temperature drop significantly. This is the wet stroke of the compressor, commonly known as frost. Slight wet stroke, generally no sound of liquid hammering. When the wet stroke is severe, more liquid is absorbed. When the compressor enters the compressor, frost appears on the crankcase and even on the exhaust port side, and the compressor makes an abnormal sound of liquid hammering. This is the phenomenon of the compressor’s liquid hammering cylinder.

　　 1. Causes of wet stroke failure

　　① When using manual control, the throttle valve is not adjusted properly, the opening is too large, or the float valve fails to close;

　　②The thermal expansion valve fails, or the temperature sensing bulb is installed incorrectly, and the contact is not real, resulting in excessive opening;

　　③The frosting of the evaporation coil is too thick and the load is too small;

　　④ Excessive oil accumulation in the system;

　　⑤The cooling capacity of the compressor is too large, or the thermal load of the warehouse is small;

　　⑥ Improper adjustment of valve operation;

　　⑦ The refrigerant in the refrigeration system is filled with too much refrigerant;

　　⑧The liquid supply solenoid valve is not closed tightly;

　　⑨ In the two-stage compression refrigeration cycle, when the low-pressure stage suction valve suddenly closes or opens (or the number of operating units suddenly decreases and increases), and in the intercooler. The serpentine coil suddenly enters liquid, which can easily cause the wet stroke of the high-pressure stage compressor.

　　 In short, there are many factors that cause the wet stroke of the compressor, and the reasons should be found out and eliminated according to the specific situation.

　　2. Instruments, tools and equipment used to detect the failure of the wet stroke of the refrigeration compressor

　　①Instrument: pressure gauge, multimeter, clamp meter, thermometer, double divergence meter.

　　②Tools: wrenches, pipe expansion tools, filling valves, pointed pliers, vise, flashlight, special tools.

　　③Equipment: working fluid bottle, nitrogen bottle, vacuum pump, complete set of gas welding.

　　3. General operation method for detecting wet stroke failure of refrigeration compressor

Since the refrigeration system of industrial chillers is a complex system composed of condensers, evaporators, expansion valves, and many equipment accessories that are interrelated and affect each other, once the refrigeration device fails, one should not only focus on certain On a local level, it is necessary to conduct a comprehensive inspection and comprehensive analysis of the entire system. In a nutshell, the general detection method is:

　　 "One listen, two touch, three look, four analysis" a set of basic methods.

　　 Have a look: look at the suction pressure and discharge pressure of the compressor; look at the cooling rate of the cooling chamber; look at the frosting state of the evaporator; look at the frosting situation of the thermal expansion valve.

　　 Second listening: Listening to the sound of the compressor running, there should be only the clear movement of the valve. When there is a "through-through" sound, it is the impact sound of liquid hammer; listen to the sound of refrigerant flowing in the expansion valve; listen to the sound of cooling fan operation; listen to the sound of solenoid valve working; listen to whether there is obvious vibration in the pipeline.

　　 Three touches: touch the temperature of the front and rear bearings of the compressor; touch the temperature of the compressor cylinder liner and cylinder head; touch the temperature of the suction and exhaust pipes. Four analysis: Use the relevant theory of the refrigeration device to analyze and judge the phenomenon, find the cause of the failure, and eliminate it in a targeted manner. The judgment of the liquid hammer failure is not only based on the frosting of the suction pipe, but mainly from the sharp drop in the exhaust temperature. At this time, the exhaust pressure will not change much, but the cylinder, crankcase, and exhaust chamber are all affected. Cold or frosty. In the case of hydraulic shock, it can destroy the lubrication system, worsen the work of the oil pump, sharply shrink the cylinder wall, and pierce the cylinder head in severe cases.

　　4. Troubleshooting of wet stroke faults of refrigeration compressors and methods for restoring normal operation

The handling of liquid shock accidents should be made promptly, and in severe cases, emergency vehicle handling should be carried out. When a single-stage compressor has a slight wet stroke, just turn off the compressor suction valve, close the liquid supply valve of the evaporation system, or try to reduce the liquid in the container. surface. And pay attention to the oil pressure and exhaust temperature. When the temperature rises to 50℃, try to open the suction valve. If the exhaust temperature continues to rise, you can continue to open it, and if the temperature drops, close it again.

　　 For the "wet stroke" of a two-stage compressor, the treatment method of the low-pressure stage wet stroke is the same as that of a single-stage compressor. However, when large z* ammonia liquid rushes into the cylinder, the high-pressure compressor can be used to depressurize and evacuate through the intercooler. Before evacuation, the liquid in the intercooler should be drained into the drain bucket, and then the pressure should be reduced to evacuate. Before depressurization, the cylinder cooling water jacket and oil should be cooled: drain the cooling water in the device or open the large water valve.

　　 When the liquid level of the intercooler is too high, the high-pressure compressor exhibits a "wet stroke". The treatment method should first turn off the low-pressure compressor suction valve, and then turn off the high-pressure compressor suction valve and the intercooler liquid supply valve. If necessary, discharge the ammonia in the intercooler into the drain bucket. If the high-pressure compressor is severely frosted, stop the low-pressure compressor. The subsequent treatment method is the same as that of single-stage.