Empty and replace the expansion valve after servicing the refrigeration system

Empty and replace the expansion valve after servicing the refrigeration system Let's introduce the operation process when replacing the expansion valve in the refrigeration system. In the system, when the low pressure of the system is under pressure control, short-circuit the controller before venting the system to prevent the system from jumping during vacuum. After the entire emptying work of the system is completed, all control valves and controllers need to be restored according to the original operation. Let us first observe that there are several valves on the entire refrigerator that can lead to the external valves of the refrigerator system. The valves on the outside are often used for exhaust, and the lower one is used for drainage. When we observe whether there is air in the system, we must turn on the entire chiller water system, and then look at the pointer on the schedule table. If the pointer shakes back and forth, it means that there is air inside the body. At this time, all we have to do is to close all the valves, connect a tube to the valve at the highest position that leads to the body of the machine, both the leather tube and the water tube are possible, put the other end of the tube into the full Inside the water container, we can open the valve at this time. At this time, the water pipe will bubble in the water filled with the container, which means that the air in the refrigerant system is already shooting the air outside. When we see that the bubbles in the water are slowly disappearing, we will close the valve at this time, and the one-time emptying is over. The time for our one-time emptying is about 1 minute. According to this method of emptying, we perform several operations on the system to allow the air inside to be slowly removed, knowing that the pointer on the scheduling table gradually stabilizes, so that the refrigeration system can operate normally. . The performance of the expansion valve in the system in the working state can directly affect the normal operation. Expansion valves often have problems such as clogged filters and leakage of temperature sensitive agents. The adjustment response is not sensitive, the adjustment is out of control or cannot be adjusted. The inlet of the expansion valve is frosted or the valve cover is also frosted. The temperature of the inlet pipe is lower than normal temperature or even frosted; the expansion valve filter is clogged or there is a phenomenon of dirty or ice clogging. The following conditions will appear. The suction pressure of the compressor is lower than the corresponding pressure at the storage temperature, the machine operating temperature and the exhaust temperature are high, and the cooling temperature decreases slowly or not. We generally handle it like the following method, close the liquid supply main valve, open the compressor operation, when the suction pressure stabilizes below 0, close the compressor exhaust valve, and stop the compressor operation at the end of the closure (fluorine collection complete). Disassemble the inlet of the expansion valve, take out the filter and clean it, then put it back into the cold storage outlet, and replace the infusion dry filter or filter, check the performance of the infusion solenoid valve and restore it (check the cleaning is completed). Open the exhaust bypass port of the compressor (the other is still in the state of fluorine collection) and start the operation, so that the air from the liquid supply main valve to the compressor body is all drawn out from the exhaust port, when the suction pressure is stable below 0 vacuum (Pumping is completed) Close the exhaust port, open the compressor exhaust valve and liquid supply main valve, the system recovery operating pressure is generally greater than the suction pressure 0.01-0.02mpa, and at the same time look at the frost of the suction pipe to determine . If the evaporating pressure is too high and hoarfrost reaches the tail of the suction valve again, it means that the flow of expansion and expansion is too large, and it should be adjusted slightly lower. On the contrary, if the evaporating pressure is too low and hoarfrost does not reach the front end of the suction valve, it means that the flow path of the expansion valve is small. When judging the level of the evaporating pressure, do not be too irritable. Only when the equipment has been operating for a period of time (at least one hour or more), its evaporating pressure no longer changes greatly, and the heat load in the freezing and refrigerating room does not change Is the correct temperature and pressure. If the flow of the expansion valve is too small, you can manually increase it. If the pressure does not rise after the adjustment, it may indicate that the filter screen at the front of the expansion valve is blocked, and it can be eliminated after cleaning according to the regulations. The above is how to evacuate the system and how to replace the expansion valve. I hope it will be useful for you to operate the system.