How to install and debug the expansion valve

three-point quality, seven-point installation", reasonable installation and commissioning of thermal expansion valve, is conducive to improve the utilization rate of evaporatorand and the adaptability of the system when changing operating conditions, to ensure the safe and reliable operation of refrigeration equipment, improve operating efficiency, energy conservation, reduce operating costs are of great significance, internal balance and outer balancedifferent according to the balance, thermal expansion valve is divided into internal equilibrium (Figure 1) and outer balance (Figure 2)1) The internal equilibrium pressure is taken at the evaporator entrance, for the system where the pressure loss of the refrigerant in the evaporator is small, and the balance pressure of the outer equilibrium2) is taken at the outlet of the evaporator, and the pressure loss of the refrigerant in the evaporator is greaterii, the valve body installation1) thermal expansion valve body as far as possible close to the evaporator entrance of the horizontal liquid pipe, in order to reduce the pressure and temperature loss after the throttle of the expansion valve2) the valve body should be installed vertically and should not be tilted or reversed3) the valve body is generally installed at the outlet of the drying filter, in order to prevent the valve core from appearing "dirty block" or "ice block"Sometimes, the valve body before and after the installation of the cut-off valve, convenient for the maintenance of the thermal expansion valve and replacement4) valve body installation should be solid, to ensure that there is no obvious vibration during operation, and to allow sufficient space for commissioning and maintenancethree, the installation of temperature pack1) temperature pack is generally installed on the top of the suction tube, at the same time need to ensure that the temperature package close to the suction pipe, improve the temperature package and the heat transfer effect of refrigerant in the suction pipe, reduce the time lag2) temperature pack as far as possible installed near the evaporator outlet of the horizontal suction pipe, should be away from the suction port of the compressor, and should not be installed verticallyIf the temperature-sensitive package must be installed on a vertical suction pipe, then the temperature-sensitive bag capillary should enter from the upper end of the temperature pack, the temperature pack head down:3) in order to protect the temperature package from cooling air or liquid, should be wrapped in a layer of insulation materialSpecial insulation forms can be provided, or plastic insulation belts can be used to ensure that the temperature pack accurately detects the suction pipe temperature4) The temperature pack needs to be secured to the suction pipe with copper flakes, rust-free mechanism screws and nutsTemperature pack to maintain good thermal contact with the suction pipe, the joint should be both clean and strong, before installation must be with a wire cotton brush suction pipe contact and temperature pack, the surface of the oxidation skin removed, revealing the metal color, to avoid poor contact and reduce the sensitivity of the sensing5) the liquid work in the thermal head is always kept in the temperature pack, so the temperature package is fixed as far as possible below the top of the valve on the suction pipe of the corrugated diaphragm cavity, if the temperature package installation position must be higher than the corrugated membrane cavity on the top of the valve body, the capillary at the temperature pack connection should be bent into the upside "U" type;6) the temperature pack can not be installed in the suction pipe has accumulated liquid, oil, fittings, valves or other large metal components place, so as not to cause the temperature package reaction lag, affecting the thermal expansion valve stable work7) According to the different diameter of the straw pipe, the installation angle of the temperature pack on the horizontal suction pipe is different:A) For 12 to 16mm tube diameter, the temperature package should be installed in the "1 o'clock" position of the suction pipeB) for 18 to 22mm tube diameter, temperature package should be installed in the "2 o'clock" position of the suction pipeC) for the 25 to 28mm tube diameter, temperature package should be installed in the "3 o'clock" position of the suction pipeD) for 32 to 35mm pipe diameter, temperature package should be installed in the "4.30" position of the suction pipe
the reasons are as follows:the suction pipe is mainly evaporated refrigerant, but there is also a small amount of refrigerant liquid and oilthe following image shows refrigerant vapor and some fluid beads flowing through the larger tube diameter suction pipeDue to the large diameter of the tube, the flow rate of refrigerant vapor is often very low, and the refrigerant beads and oil are deposited at the bottom of the pipelinefour, the installation of the outer balance expansion valve balance tube1) the external balance tube pressure position is always between the temperature pack and the compressor suction port, as close as possible to the temperature pack position, but not before the temperature pack, otherwise the valve body leakage of a small amount of refrigerant liquid through the outer balance tube into the heating bag before the suction pipe, will form the illusion of evaporator oversupply 2) When the suction pipe is equipped with a regulator valve, the outer balance pipe should be installed between the evaporator and the regulator valve, not after the adjustment valve, otherwise the adjustment valve regulation pressure, the pressure introduced by the outer balance pipe distortion, 3) for a multi-temperature refrigeration system, the outer balance pipe should be installed in their respective evaporator outlets, must not be installed on the total suction pipe five, the thermal expansion valve zuijia fixation if the accuracy of thermal expansion valve regulation can not be guaranteed, in the intermittent start-stop compressor system or the operation of the operating conditions change dramatically in the process will be accompanied by a lot of pressure fluctuations, temperature fluctuations and energy consumption fluctuations if the thermal expansion valve is not selected properly or improperly adjusted, it will cause the compressor suction pipe periodic strap liquid, making the refrigeration system oscillation phenomenon; the current international widespread use of the exporter export temperature fluctuation analysis of the zuijia calibration method, the specific debugging steps are as follows: the first step of the : start refrigeration system, let the compressor run for more than 20 minutes, to ensure that the system is in a stable state, the use of temperature sensor to measure the evaporator outlet temperature second step: 1) If the evaporator outlet temperature has a fixed amplitude of self-exciting oscillation, first the thermal expansion valve under the valve cap unscrewed, clockwise rotation valve stem half a turn or a turn (i.e., increase the spring force, increase the static overheating setting ); Rotating valve stem until the evaporator outlet temperature again oscillating phenomenon, then then a clockwise rotation of the valve stem a turn, in this position to ensure that the thermal expansion valve supply stability, but also to ensure that the evaporator heat transfer area of the full use of 4) if the evaporator outlet temperature does not oscillate, but the outlet temperature is too high, the counterclockwise rotating valve half a turn or a ring (i.e., reduce the spring force, reduce static overheating setting ); Gradualadjustment, until the evaporator outlet temperature oscillating phenomenon, and then turn the valve stem a lap, 6) if the clockwise rotation of the valve stem to the top of zui, the evaporator outlet temperature is still self-exciting oscillation, it indicates that the thermal expansion valve selection is too large, should be re-selected the smaller model of thermal expansion ;