1. Thermostatic expansion valve adjustment skills and taboo To make the thermostatic expansion valve in one of the conditions to perform automatic adjustment function must be adjusted in the refrigeration system debugging, in order to ensure that the thermal expansion valve in the system operation can be correctly executed automatically adjust. The thermostatic expansion valve is adjusted by adjusting the lever to achieve. On the control rod screwed or screwed out, in essence, the spring is pressed or relaxed, that is, adjust the thermal expansion valve static load with superheat size to meet the needs of the cooling conditions. General Shun into the progress, anti-spin back. When you want to adjust the evaporation pressure, you can remove the cap, with a wrench clockwise adjustment rod, so that the compression of the spring increases, forcing the diaphragm up and off the valve, the evaporation pressure will gradually decline. Similarly, anti-spin adjustment lever will open a large valve to increase the evaporation pressure. When adjusting the thermal expansion valve, a low pressure gauge should be installed on the compressor suction stop valve to observe the change of the evaporation pressure. Normal evaporation pressure is hoarfrost or condensation knot to the suction pipe (medium and low temperature equipment, hoar frost; air conditioning dew condensation). If the hoarfrost or condensation knot to the suction stop valve, or even a half compressor, the valve is too large, it should be adjusted smaller, if the hoarfrost or condensation only to the evaporator outlet or can not reach the outlet, indicating the valve Too small, should be adjusted larger. Thermal expansion valve debugging, generally can be divided into two steps. The beginning is a rough adjustment, that is, each adjustment can be rotated around. When the equipment close to its operating conditions, to fine-tune, each rotation 1/4 ~ 1/2 laps. After each adjustment, make the system run for a few minutes or ten minutes, and observe the changes in low pressure gauge, and then decide the next adjustment. At the end of the expansion valve commissioning, the cap should be screwed and wrenched to prevent refrigerant leakage. Adjust the thermostatic expansion valve is a meticulous work, should not be urgent in the process of adjustment. The adjusted thermostatic expansion valve must not be adjusted for other reasons unless the refrigerator changes operating conditions. General machine factory, thermal expansion valve in the factory has been adjusted, the unit debugging in the field should not be adjusted. 2. Thermal expansion valve inspection and maintenance Thermal expansion valve common faults are blocked, the temperature package infusion of working fluid leakage and so on. (1) Valve hole blockage There are two cases of blockage of the valve hole and oil blockage. If the refrigeration system contains moisture, it will dissolve in the refrigerant, the amount of its dissolution and the temperature of the refrigerant, the temperature is high, the amount of its dissolution, the temperature is low, the amount of dissolved less. When the condensing temperature of about 30t refrigerant liquid flow into the expansion valve orifice throttling, immediately cooled to the evaporation pressure under the saturation temperature (evaporation temperature), part of the water is deposited, attached to the valve hole if the evaporation temperature is below 0 ℃ Will form ice, when the ice increases, the valve hole is blocked. Freezer oil and refrigerant will also dissolve each other, the amount of its dissolution is also related to temperature, high temperature, dissolved a large amount of low temperature, dissolved a small amount. When the liquid enters the expansion valve orifice and its temperature drops rapidly, part of the refrigeration oil is separated and stuck around the valve hole. When the evaporation temperature is lower than the freezing point of the freezing oil, the freezing oil condenses into a paste, As the oil increases, the valve orifice is blocked because the lower the evaporation temperature, the easier it is to separate the water and the oil, so ice plugging and oil blockage can easily occur in cryogenic refrigeration equipment where the evaporating temperature is lower. 1) Valve hole ice blockage or oil blockage judgment. When the refrigeration unit starts running normally after a period of operation, the suction pressure drops rapidly to negative pressure (vacuum), the library (room) temperature rise, the frost melts (first, the suction tube frost melts) The flow to the expansion valve sound. At this time can basically determine the valve hole ice blockage or oil blockage. To further confirm that the valve hole is obstructed, use an alcohol lamp to heat the expansion valve (without shut down). After a minute or two of heating, if you hear the sound of 嗟 ... and then you can hear the squeak, the suction pressure also rises The expansion valve outlet began to conclude that the valve hole is blocked by ice or oil. 2) troubleshooting methods. Replace desiccant in the dry filter. In more water, you can use reagent-grade anhydrous calcium chloride, to be prepared after a day or two cold pepper, and then replace the silica gel. If there is no drying filter in the system, you can temporarily connect a drying filter. (2) Expansion valve inlet filter clogged Expansion valve filter is over the possession of impurities in the dirt, not to plug the valve hole. When the impurities in the filter more, the mesh is not very smooth or even completely blocked. The phenomenon is suction vacuum pull on the month, the library (room) temperature does not drop, while the half or the entire expansion valve closed white listen to the expansion valve has a weak squeak, squeaky intermittent sound, which shows the filter is not smooth all blocked . When tap the inlet handle of the valve with the handle, if the sound is heard louder than the original sound, it is confirmed that most of the mesh is clogged. In severe cases, the sound of the refrigerant in the valve can not be heard and the valve Body also: generally use the wrench handle knocking the mouth connector is invalid. However, all filters are blocked to less. The obvious difference between the blockage of the filter and the blockage of the valve hole is that the blockage of the valve hole is normal during the start-up operation and the blockage of the filter block occurs at the beginning when the unit sucks up or pulls the vacuum. The phenomenon of refrigerant shortage and the phenomenon of clogging filter when the judgment of Chau should be distinguished. Refrigeration unit operation, if you hear the expansion valve hiss, louder, suction pressure is lower, suction pressure gauge fluctuations, the library (room) temperature is not low enough, part of the evaporation tube does not frost , Lack of refrigerant sake, do not mistakenly for expansion valve failure. Filter is blocked the exclusion method is to remove the filter with gasoline cleaning bake. (3) Leakage of working fluid in the induction mechanism When the leak in the induction mechanism leaks, the sensing pressure of the temperature sensing bulb disappears, so that the valve can not be closed. Tears refrigeration unit began to operate on the vacuum, the reservoir (room) temperature does not drop down a little, the expansion valve without a little air flow sound. Remove the expansion valve, remove the filter interface, the mouth with the mouth of the expansion valve outlet connector, such as suction barrier, and can live with his lips hanging, indicating that the valve hole does not pass. Indeed the valve is not closed, should be replaced by the same type of expansion valve.
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