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Adjustment of the thermal expansion valve is achieved by adjusting the rod. Rotation or twisting of the adjusting rod is essentially the compression or relaxation of the spring, that is, adjusting the size of the superheat of the static assembly of the thermal expansion valve to meet the needs of refrigeration conditions. General rotation into the forward, counter-rotation back. When you want to adjust the evaporation pressure, you can remove the cap and use a wrench to rotate the adjustment rod so that the compression of the spring increases, forcing the diaphragm to move upward and closing the small valve, and the evaporation pressure will gradually decrease. Similarly, the anti-rotation lever will open a large valve and increase the evaporation pressure.
When adjusting the thermal expansion valve, a low pressure meter should be installed on the compressor suction valve to observe the change of the evaporation pressure. The normal evaporating pressure is from the frost or condensation knot to the suction duct (white frost in medium and low temperature equipment; condensation in air conditioning equipment). If the frost or condensation is connected to the suction valve or even half of the compressor, the valve is too large and it should be turned down. If the frost or condensation is only connected to the evaporator outlet or the outlet is not, explain the valve. If you are too young, you should make some adjustments.
The adjustment of the thermal expansion valve can generally be carried out in two steps. The beginning is a coarse adjustment, that is, it can be rotated about once per adjustment. When the equipment is close to its operating conditions, fine-tune it by rotating 1/4 to 1/2 turn each time. After each adjustment, the system shall be operated for a few minutes or ten minutes, and the change of the low-pressure meter shall be observed, and the next adjustment shall be decided. At the end of the expansion valve commissioning, the cap should be screwed on and tightened with a spanner to prevent refrigerant leakage.
Adjusting the thermal expansion valve is a meticulous task. Avoid urgency during the adjustment process. The adjusted thermal expansion valve must not be adjusted for other reasons unless the chiller changes operating conditions. In general, the unit of the complete machine, thermal expansion valve has been adjusted before leaving the factory, the unit should not be adjusted in the field when debugging.
2. Inspection operation of the thermal expansion valve The common failure of the thermal expansion valve is clogging, leakage of the working fluid in the temperature sensing package, and the like.
(1) Valve hole plugging The valve hole is blocked by ice blocking and oil blocking. If the refrigeration system contains water, it will dissolve in the refrigerant, and the amount of dissolution is related to the temperature of the refrigerant. When the temperature is high, the amount of dissolution is large, and when the temperature is low, the amount of dissolution is small. When the refrigerant liquid with a condensing temperature of about 30t flows into the orifice of the expansion valve, it immediately cools down to the saturation temperature (evaporation temperature) under the evaporation pressure, and part of the water is precipitated. If the evaporation temperature is below 0°C attached to the valve hole portion, It forms ice, and when the ice builds up, the valve hole is blocked.
Refrigerator oil and refrigerant also dissolve each other, and the amount of dissolved oil is also related to the temperature. The high temperature has a large amount of dissolved, and the low temperature has a small amount of dissolved. When the liquid decompresses the orifice of the expansion valve and its temperature drops rapidly, part of the refrigerating machine oil is separated and sticks around the valve hole. When the evaporation temperature is lower than the freezing point of the refrigerating machine oil, the refrigerating machine oil will condense into a paste. As the oil gradually increases, the valve hole is blocked because the lower the evaporation temperature, the easier the water and oil are separated, so the ice blocking and the oil blocking can easily occur in the low-temperature refrigeration equipment with a low evaporation temperature.
1) The judgment of the valve hole ice blocking or oil blocking. When the refrigeration unit starts operating normally, after a period of time, the suction pressure rapidly drops to negative pressure (vacuum), the temperature of the warehouse (chamber) rises, and the frost layer melts (first the frost layer of the suction pipe melts), and the side ear cannot hear it. The sound of flow to the expansion valve. At this time, it can be basically judged that the valve hole is blocked by ice or oil. To further verify that the valve hole is blocked, an alcohol lamp can be used to heat the expansion valve body (without shutting down). After heating for a minute or two, if you hear the sound of hum... At the same time, the outlet of the expansion valve began to form a knot again. The valve hole was indeed blocked by ice or blocked by oil.
2) Troubleshooting. Replace the desiccant in the desiccant filter. When the moisture content is high, you can use reagent-grade anhydrous calcium chloride. After replacing the pepper for a couple of days, replace the silicone. If there is no dry filter in the system, a dry filter can be connected temporarily.
(2) Expansion filter inlet filter The filter mesh that blocks the expansion valve is overly contaminated with contaminants and does not cause the valve hole to become blocked. When there are many impurities in the filter, the mesh is not very open or even completely blocked. The phenomenon is also the vacuum suction month, the library (room) temperature does not fall, and half or the entire expansion valve end of the song listens to the expansion valve has a weak cymbal, cymbal intermittent sound, which shows that the filter is not smooth and all blocked . When tapping the valve's inlet joint with a spanner handle, if the sound is heard louder than the original sound, then it is confirmed that most of the filter mesh is plugged and blocked seriously. The sound of refrigerant in the valve cannot be heard. Body also: It is not valid to use a wrench handle to knock the mouthpiece joint. However, the filter was completely blocked.
The obvious difference between the plugging of the filter and the blockage of the valve hole is that the blockage of the valve hole occurs when the pump is operating normally within the time. If the unit starts to suck or pull the vacuum, the filter plugs. The phenomenon that occurs when the refrigerant is insufficient and the phenomenon when the filter is clogged should be distinguished in the judgment of the continent. When the cooling unit is running, if the expansion valve has a buzzing sound, the sound is louder, the suction pressure is also lower, the suction pressure fluctuation point, the library (room) temperature is not low enough, part of the evaporation tube is not frost Because of the shortage of refrigerant, do not mistaken for the failure of the expansion valve. The method of removing the plugged filter is to remove the filter and clean it with gasoline.
(3) Leakage of the working medium in the induction mechanism When the tear in the induction mechanism leaks, the induced pressure of the temperature sensing pack disappears, causing the valve to close. The tear chiller unit started to pull vacuum, and the temperature in the library did not fall. The expansion valve had no sound of airflow. Remove the expansion valve, remove the strainer interface, and use the mouth to inhale the outlet fitting of the expansion valve. If it fails to breathe, and can use the lips to hang it, it means that the valve hole does not pass through. It is true that the valve will not open and the same type of expansion valve should be replaced.
Thermal expansion valve adjustment tips and overhaul operations
1; thermostatic expansion valve adjustment techniques and contraindications to make the thermal expansion valve in its operating conditions to perform automatic adjustment function, must be adjusted in the cooling system debugging, so as to ensure that the thermal expansion valve in the system operation can be performed automatically adjust.