1 Reason analysis There are two main reasons for the wet stroke of the refrigeration compressor: First, because the compressor cylinder sucks in a large amount of refrigerant wet steam (supersaturated vapor); Second, due to the influence of the piston ring of the compressor, a large amount of refrigeration oil Pick up into the cylinder of the compressor. 1. 1 compressor draws in a large amount of refrigerant (R12) wet steam In theory, the gas sucked by the compressor is optimal when it is saturated. In normal operation, because the return pipe is affected by the ambient temperature, the temperature of the R12 refrigerant gas sucked by the compressor is higher than that of evaporation. The temperature is slightly higher (about 5 ° C), and the refrigerant gas which is slightly above the evaporation temperature and is in the superheated state continues to evaporate in the return gas pipe, so that the wet stroke phenomenon does not occur in the compressor. Once the refrigerant does not evaporate well in the evaporator, a large amount of R12 wet vapor (supersaturated vapor) or liquid enters the compressor cylinder from the suction pipe. Thus, the piston compresses not the gas but the liquid, causing the compressor to stroke wet. (1) The opening degree of the externally balanced thermal expansion valve in the refrigeration system is too large or the valve is in the fully open position. It can be seen from the working diagram of the externally balanced thermal expansion valve in the refrigeration system that the working principle of the externally balanced thermal expansion valve is to change the opening degree of the expansion valve by using the change of the up and down pressure acting on the diaphragm of the expansion valve. . When increased, the valve moves down so that the opening of the expansion valve is large and there is more refrigerant entering the evaporator; vice versa. It can be seen that there are three main reasons for the excessive opening of the externally balanced thermal expansion valve: Improper opening adjustment; spring failure; there are particles in the thermal expansion valve. For the above reasons, a large amount of refrigerant liquid is sucked back by the compressor before the endurance gasification in the evaporator, and a wet stroke, that is, a hydraulic shock occurs. Working diagram of externally balanced thermal expansion valve (2) The temperature sensor package is loose or the installation position is incorrect. It can be seen that when the temperature sensitive package attached to the evaporator return pipe is loose or the position is wrong, the induced temperature will be higher than the actual temperature, the P value will increase, and P will also increase, resulting in The opening degree of the thermal expansion valve is too large, and the refrigerant liquid entering the evaporator is too much, causing the compressor to inhale excessively and cause a wet stroke phenomenon. (3) The refrigeration solenoid valve is not closed tightly. Because the spring in the cooling solenoid valve is broken by compression deformation, the valve core is rusted, or there are particles in the valve, the refrigeration solenoid valve is not closed tightly, so that a large amount of refrigerant liquid enters the evaporator after the refrigeration unit is shut down. In the next time the refrigeration unit is started, a large amount of supersaturated refrigerant wet steam is sucked by the compressor to cause a wet stroke. (4) The amount of refrigerant perfused in the refrigeration system is excessive. When the refrigerant is added during the operation, it is impossible to estimate how much refrigerant is added (the float of the liquid receiver in the refrigeration unit is easy to be broken), which may cause the refrigerant to be added to the refrigeration system too much, resulting in oversupply. The compressor has a wet stroke. (5) The heat exchange capacity of the evaporator is lowered. The reasons are as follows: the defrosting device of the refrigeration unit is faulty, so that the refrigeration unit is in a cooling condition for a long time and cannot be defrosted, resulting in excessive frosting of the evaporator, resulting in a decrease in the heat exchange area of ​​the evaporator; Not working or 2 are not working. 1. 2 a large amount of refrigeration oil enters the compressor cylinder Due to excessive wear of the piston ring or the elastic force of the piston ring itself, the backlash and backlash between the gas ring and the ring groove are increased, so that a large amount of refrigerating machine oil is charged therein, and the gas ring is in gas force, friction force and Under the combined action of the inertial forces, the relative movement is continuously carried out in the ring groove, which is equivalent to a squeeze type oil pump, thereby bringing the refrigerating machine oil to the top of the cylinder, causing a wet stroke. 2 solutions 2. 1 external balance type thermal expansion valve opening too large or fully open adjustment (1) Re-adjust the opening degree of the externally balanced thermal expansion valve to achieve the specified degree of superheat (7 ° C ~ 9 ° C). First use a thermocouple to measure the outlet temperature of the evaporator at the temperature sensing package of the expansion valve, and then install a precision pressure gauge at the outer balance tube joint of the thermal expansion valve to measure the pressure, with the pressure of the refrigerant R12. The figure obtains the evaporation temperature of the refrigerant corresponding to each pressure, and the difference between the outlet temperature of the evaporator and the evaporation temperature of the refrigerant is the superheat of the thermal expansion valve. The adjustment process is as follows: Carefully remove the protective nut on the thermal expansion valve adjustment lever with a wrench; start the refrigeration unit, turn the adjustment lever clockwise with a suitable tool, measure the superheat of the expansion valve until the specified value is reached; screw the protection screw of the expansion valve cap. (2) Remove the four bolts and the outer balance tube of the thermal expansion valve, take out the upper part of the valve, and replace the spring. (3) Remove the particles in the thermal expansion valve and find out the source of the particles to eliminate them. If the valve is seriously damaged, replace the upper part of the valve or the entire expansion valve. Special attention should be paid here: when carrying out the operation, the refrigeration unit should be started first, the liquid outlet valve of the liquid storage device should be closed, the refrigeration unit should be evacuated, and the refrigerant in the system should be pumped back into the liquid storage device as much as possible. Once the reading of the low pressure gauge drops to 0.02 M Pa, stop the unit operation, close the liquid inlet valve of the liquid reservoir, and then repair or replace the thermal expansion valve. 2. 2 Check the condition and position of the thermal expansion valve temperature package The temperature sensing package of the thermal expansion valve should be wrapped around the evaporator return line at a position of about 30° from the horizontal line. At the same time, it is necessary to pay special attention to the fact that it cannot be installed on the return pipe with effluent, and the temperature sensitive bag is fixed firmly to make it sensitive to temperature. 2. 3 repair refrigeration solenoid valve Start the refrigeration unit, close the liquid outlet valve of the liquid storage device, and draw the refrigerant in the refrigeration unit back into the liquid storage device as much as possible. When the low pressure pressure gauge reads 0. 02 M Pa, turn off the refrigeration unit and The liquid inlet valve of the liquid reservoir, and then the refrigeration solenoid valve is repaired, the particles in the valve are removed, the source of the particles is found, and the damage is removed, and the damaged parts are replaced. Special attention should also be paid to the installation of the solenoid valve, the coil axis of the solenoid valve should be vertical upwards, the direction should be in the direction of the arrow on the valve body. 2. 4 methods for treating excessive refrigerant in the system (1) Prepare an empty fluorine bottle, connect the fluorine tube (can be replaced by a fluoride tube), one end is connected to the empty fluorine bottle, and the other end is connected to the fluorine-filled joint of the refrigeration unit to open the hand valve of the empty fluorine bottle. . (2) Start the refrigeration unit and simultaneously open the liquid outlet hand valve and the fluoride hand valve of the liquid reservoir. (3) Observing the amount of change of the refrigerant in the liquid reservoir, when the liquid level of the refrigerant reaches the specified value: static is between one-half of the apparent hole of the liquid reservoir and two-thirds of the upper visual hole, the dynamic When the reservoir is between one-half of the viewport and one third of the upper viewport, the gas fill valve is closed immediately. (4) All the refrigerant in the fluorine tube to be discharged into the fluorine bottle, close the fluorine bottle hand valve, remove the fluorine discharge tube, and put the fluorine bottle. 2. 5 treatment method for reducing the heat exchange capacity of the evaporator (1) Check the control circuit of the refrigeration unit and the defrost device, and find that the abnormal phenomenon should be processed: check whether the contact of the defrost temperature controller is rusted or whether the refilling agent in the temperature sensor is leaking. If there is a corresponding Handle or replace the defrost temperature controller; check if the spool of the defrost solenoid valve is stuck or blocked and the coil is good. If it is abnormal, replace the damaged part or even the whole solenoid valve. (2) Check the control circuit and motor of the evaporating fan and find that the damaged parts should be replaced. 2. 6 processing method of refrigerating machine oil entering the cylinder Replace the damaged air ring and oil ring. Special attention should be paid during installation. The slits of the piston rings should not be on the same line and should be at an angle of 120°. At the same time, it is recommended that in order to reduce the wear of the piston ring, the first gas ring should adopt a wear-resistant chrome ring, which effectively protects the other piston rings below, and the wear of the piston ring is greatly reduced.
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Air compressor wet processing presets and countermeasures