Worked for 10 years as a refrigeration master, personally taught valuable cold storage refrigeration maintenance experience, classic and practical
First of all, I thought about it and let me talk about the state of the normal operation of the cold storage (piston machine)
1 The oil level must be guaranteed to be 1/2 of the oil sight hole (to ensure its lubrication)
2 Exhaust temperature. This depends on the refrigerant (the commonly used R22 should not be higher than 145 °C, and the corresponding pressure is checked in the table)
3 The suction temperature must be 5-15°C higher than the evaporation temperature (the storage temperature minus 5-10°C is equal to the evaporation temperature). The difference between the suction temperature and the storage temperature is 0-5 °C is more appropriate. (corresponding to look-up table)
4 The oil separator can automatically return oil
5 The normal oil temperature should be 40-60℃, (some machines are equipped with crankcase heating)
6 The compressor oil pressure should be 0.15-0.3MP higher than the suction pressure
troubleshooting
1. The compressor suddenly stops working during operation
This is usually a protective shutdown
(1) When the oil level is low, the relay will act when it is lower than the protection value (check whether the system leaks oil and whether the oil is working normally)
(2) The exhaust pressure is too high, higher than the protection value, the relay will act (check the heat dissipation of the condenser)
(3) The lubricating oil pressure is too low, and the differential pressure protection relay operates (check the lubrication system)
(4) Motor overload, (measure the current, adjust the unit load to make it return to normal)
2. The exhaust pressure is too high when the compressor is running
(1) Insufficient condensing heat dissipation (check condensing equipment, water flow or air flow)
(2) Excessive oil accumulation in the condenser (draining oil accumulation)
(3) There is air in the system (the vacuum must be evacuated before debugging, it is better to delay some time, and the venting method should be tried at the highest end of the condenser)
(4) Too much refrigerant in the system (draining excess refrigerant)
3. Compressor wet stroke (compressor frost)
(1) The opening of the expansion valve is too large, and the return gas is filled with liquid (adjust the expansion valve)
(2) The solenoid valve fails, and the liquid supply continues after the shutdown. With fluid when power on again (replace or repair solenoid valve)
(3) Excessive refrigerant and poor evaporation (excessive refrigerant leaks out)
(4) The expansion valve temperature sensing package is not bundled well or wrongly (bundled according to the expansion valve manual)
4. The compressor cannot be started normally, and the general electrical fault is checked with a multimeter
(1) The protective shutdown of the compressor was not handled properly. The relay is not reset (reset or forcibly short-circuit to deal with the fault, and then recover)
(2) The power supply is cut off and the fuse is blown (check the power supply and the fuse)
(3) The starting relay or contactor is not in good contact (replace or repair)
(4) The thermostat or sensor is faulty (check it with a meter, and replace it if it is damaged)
(5) The pressure controller setting is unreasonable (adjust as needed)
(6) The compressor motor is damaged (check the resistance between the windings)
5. The expansion valve is faulty (when the expansion valve is replaced, it matches the working temperature, and the aperture matches the cooling capacity of the compressor)
(1) ice block,
Reason: High water content of refrigerant.
Phenomenon: Circulating frosting and defrosting during operation.
Solution: Use the method of heating and expansion to temporarily solve the problem, completely eradicate the recovery and replace the drier filter
(2) Dirty blockage
Reason: There are too many impurities in the system, and the installation is not careful. Welding oxide scale, etc.
Phenomenon: The evaporator does not frost and does not cool. But the operating pressure is indeed low or negative
Solution: remove the expansion valve and clean it with medium oil
(3) Expansion valve leaks
Reason: temperature sensor leaks, valve body leaks, valve body temperature sensing mechanism leaks
Phenomenon: no cooling, the effect is not good, the leakage in the valve body is similar to the dirty blockage
Solution: Replace or reassemble the valve body
(4) Improper adjustment
Reason: The opening is too small or too large
Phenomenon: The valve body is all frosted when the opening is too large, and when the opening is too large, there is frost at the outlet of the valve body without frost, and the compressor returns to the air with liquid.
Solution: adjust the expansion valve to the appropriate position
6. Filter failure
cause, blockage
Phenomenon: the surface is frosted, the liquid supply is insufficient, and the refrigeration cannot be performed normally
Solution: replace
Refrigeration failure analysis method
1. to see
(1) There is dew and no frost in the rear half of the evaporator. Insufficient or leaking refrigerant (if the expansion valve is properly adjusted without failure)
(2) The upper half is frost-free and the second half is frosted. Excessive charging of refrigerant (if the expansion valve is properly adjusted without failure)
(3) There is no dew or frost in the suction pipe, and the refrigerant is insufficient or leaked
(4) Pressure gauge, high and low pressure are lower than normal values, insufficient refrigerant or leakage
(5) Under normal working conditions of the expansion valve, there is slanted virtual frost, and there is no frost at the rear of the actual frost evaporator, and the refrigerant is insufficient.
2. Listen
(1) Expansion valve, the liquid flow can be heard normally. Sisi Sound The refrigerant is insufficient, if you can’t hear the sound, it is blocked.
3. touch
Compressor shell, cylinder, condensing pipeline, filter inlet and outlet, determine whether it is dirty and blocked
compressor failure
1. Cylinder
Oil problem, dirty or lack of oil. and lubricating oil temperature
2. Abnormal sound of cylinder
The valve plate is broken, the cylinder clearance is too small, and the pin clearance is too large
3. Crankcase oil has sound
The crankshaft collides with the oil, the screws are loose, and the joint clearance is too large
4. The compressor displacement becomes smaller
Excessive piston wear clearance
Post time: Nov-14-2022
