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• Common oil shortages in Copeland scroll refrigeration compressors

Common oil shortages in Copeland scroll refrigeration compressors

Copeland vortex refrigeration compressors lack oil for a long time - the mechanism and each friction pair are overheated, causing the bearings to sinter and hold the shaft. Copeland vortex refrigeration compressor lacks oil for a short period of time - the mechanism and each friction pair are abnormally worn, resulting in high vibration and noise.

First, how to ensure the proper amount of oil

Copeland scroll refrigeration compressors also emit traces of refrigeration oil when the refrigerant is discharged. Even if there is only a 0.5% oiling rate, if the oil cannot be recycled through the system back to the Copeland scroll refrigeration compressor. If 5HP is used as an example, the circulation amount is about 330kg/h under ARI conditions, then the oil in the Copeland scroll refrigeration compressor can be taken out in 50 minutes, Copeland vortex cooling in about 2 to 5 hours. The compressor will burn out. Therefore, in order to ensure that the Copeland scroll refrigeration compressor does not lack oil, it should start from the following two aspects:

1. Ensure that the refrigerating machine oil from the Copeland scroll refrigeration compressor is returned to the Copeland scroll refrigeration compressor.

2. Reduce the oiling rate of the Copeland scroll refrigeration compressor. (The frequent start of the Copeland scroll refrigeration compressor is not conducive to oil return.)

Second, how to ensure that the discharged refrigeration oil returns to the Copeland scroll refrigeration compressor

        1. The flow rate of the suction pipe refrigerant should be ensured (about 6m/s) to return the oil to the Copeland scroll refrigeration compressor, but the maximum flow rate should be less than 15m/s to reduce the pressure drop and flow noise. It should also have a downward slope along the flow direction of the refrigerant, about 0.8 cm/m.

2. Prevent the freezing oil from staying in the evaporator.

3. Ensure that the oil return hole of the appropriate gas-liquid separator is too wet to compress. If it is too small, the oil will be insufficient, and the stagnant oil will be in the gas-liquid separator.

4. There should be no parts in the system where oil is retained.

5. Ensure that there is sufficient refrigeration oil in the Copeland scroll refrigeration compressor in the case of high piping height drop, usually confirmed by Copeland scroll refrigeration compressor with oil mirror.

3, how to reduce the oiling rate of Copeland scroll refrigeration compressor

1. When stopping, ensure that the refrigerant does not dissolve into the refrigerating machine oil (using a crankshaft heater).

2, should avoid excessive wet operation, because there will be too much oiling caused by foaming.

3. The oil separator device is installed inside.

4. Oil blistering inside the Copeland scroll refrigeration compressor allows the oil to be easily carried out of the Copeland scroll refrigeration compressor.

4, long piping high drop

When the length of the pipe is larger than the allowable value, the pressure loss in the pipe becomes large, so that the amount of the refrigerant in the evaporator is reduced, resulting in a decrease in capacity. At the same time, the oil retention in the piping caused the Copeland scroll refrigeration compressor to be deficient, resulting in the failure of the Copeland scroll refrigeration compressor. When the refrigerating machine oil in the Copeland scroll refrigeration compressor is insufficient, the same grade of refrigerating machine oil as the Copeland scroll refrigeration compressor should be added from the high pressure side.

5, the necessity of setting back to the oil bend

When the drop is more than 10m~15m, the oil return pipe should be installed on the air pipe side.

Necessity: When shutting down, avoid the return of the refrigerating machine oil attached to the piping to the Copeland scroll refrigeration compressor, causing liquid compression. On the other hand, in order to prevent the poor return of the trachea, the Copeland scroll refrigeration compressor is short of oil.

Return to the oil bend setting interval: Set a return oil bend every 10m drop.

6, How to ensure proper refrigeration oil viscosity

1. The refrigerating machine oil and the refrigerant are mutually soluble. When the machine is shut down, almost all of the refrigerant is dissolved in the refrigerating machine oil. Therefore, a crank heater is required to prevent dissolution.

2. The liquid-containing refrigerant should not be returned to the Copeland scroll refrigeration compressor during operation to ensure that the Copeland scroll refrigeration compressor has superheat.

3. When starting and defrosting, no liquid return should occur.

4. Avoid operating under excessive heat and avoid oil degradation.

5. The size of the oil return hole of the gas-liquid separator should be appropriate:

1Aperture too large, suction liquid refrigerant causes over-humidity operation

2 If the pore size is too small, the oil return will not be smooth, and the oil will remain in the gas-liquid separator.

7. The main cause of motor damage in Copeland scroll refrigeration compressors

1. Abnormal load and blockage.

2. Winding short circuit caused by metal chips.

3. Contactor problems.

4. The power supply phase loss and voltage are abnormal.

5. Insufficient cooling.

6. Vacuum with a Copeland scroll refrigeration compressor.

8, the main cause of abnormal load or blockage

If the pressure ratio is too large, or the pressure difference is too large, the compression process will be more difficult; the frictional resistance caused by the lubrication failure will increase, and the motor stall in extreme cases will greatly increase the motor load. If the load increases to the thermal protection action and the protection is automatically reset, it will enter the "blocking-heat protection-blocking" dead loop, frequent starting and abnormal load, so that the winding is subjected to high temperature test, which will reduce the enameled wire. Insulation performance. After the winding insulation performance is deteriorated, if there are other factors (such as metal scraps forming a conductive loop, acidic lubricating oil, etc.), it is easy to cause short circuit and damage.

1. Winding short circuit caused by metal chips

Sources of metal shavings include copper pipe scraps left during construction, welding slag, internal wear of Copeland scroll refrigeration compressors, and metal chips that fall off when parts are damaged. During operation, these metal chips or granules will fall on the windings under the action of the air flow. The normal vibration of the Copeland scroll refrigeration compressor and the twisting of the winding by the electromagnetic force each time it starts will promote the relative motion and friction between the metal chips and the winding enameled wire between the windings. Sharp edges and sharp metal chips can scratch the enameled wire insulation, causing a short circuit and causing the motor to burn out.

2, contactor problem

For safety and reliability, Copeland scroll compressor compressor contactors must simultaneously disconnect three-phase circuits. Contactors must be able to withstand harsh conditions such as fast cycling, continuous overload and low voltage. They must have a large enough area to dissipate the heat generated by the load current, and the choice of contact material must be prevented from soldering at high currents such as startup or stall. Otherwise, after the contactor contacts are welded, all controls (such as high and low pressure control, temperature control, defrost control, etc.) that rely on the contactor to disconnect the Copeland scroll refrigeration compressor power circuit will be completely disabled. The Copeland scroll refrigeration compressor is at rest. Unprotected state. Therefore, when the motor is burned, it is an indispensable process to check the contactor.

3, power supply phase loss and voltage abnormalities

The power supply voltage variation range cannot exceed ±10% of the rated voltage. The voltage imbalance between the three phases cannot exceed 3%. If a Copeland scroll refrigeration compressor is running when a phase loss occurs, it will continue to run but will have a large load current. The motor windings will overheat quickly and the Copeland scroll refrigeration compressor will be thermally protected under normal conditions. When the motor windings are cooled to the set temperature, the contactor will close, but the Copeland scroll refrigeration compressor will not start up, stall, and enter the "blocking-heat protection-blocking" endless cycle. If the phase loss occurs when the Copeland scroll refrigeration compressor is started, the Copeland scroll refrigeration compressor will not start up, stall, and enter the "blocking-heat protection-blocking" endless cycle. The calculation method of the voltage imbalance percentage is the ratio of the maximum deviation between the phase voltage and the average value of the three-phase voltage and the average value of the three-phase voltage. As a result of the voltage imbalance, the imbalance of the load current during normal operation is the voltage imbalance percentage. 4-10 times.

4, Copeland scroll refrigeration compressor motor cooling is insufficient

When the refrigerant leaks a lot or the evaporation pressure is low, the system mass flow is reduced, so that the motor cannot be cooled well, and frequent protection occurs when the motor overheats.

9, the main cause of liquid damage of Copeland scroll refrigeration compressor - liquid return

When it is returned to the liquid, it is easy to cause a liquid impact accident. Even if no liquid impact is caused, the liquid return of the high pressure chamber structure will dilute or wash away the lubricating oil on the sliding surface, which will aggravate the wear. The return of the low pressure chamber structure will dilute the oil in the oil pool. Lubricating oils containing a large amount of liquid refrigerant have low viscosity and cannot form a sufficient oil film on the friction surface, resulting in rapid wear of the moving parts. In addition, the refrigerant in the lubricating oil will boil when it is heated during the conveying process, which affects the normal transportation of the lubricating oil. The farther away from the oil pump, the more obvious the problem becomes. If the bearing at the motor end is severely worn, the crankshaft may settle to one side, which may easily cause the stator broom and the motor to burn out.

For refrigeration systems that are difficult to avoid with liquid return, installing a gas-liquid separator and using an evacuation shutdown control can effectively prevent or reduce the hazard of liquid return.

X. The main cause of liquid damage in Copeland scroll refrigeration compressors

On the oil sight glass, it is possible to clearly observe the blistering phenomenon when the liquid is started. The root cause of liquid start-up is that a large amount of refrigerant dissolved in the lubricating oil and sinking under the lubricating oil suddenly boils when the pressure suddenly drops, and causes foaming of the lubricating oil. The refrigerant with liquid start-up enters the crankcase in a "refrigerant migration" manner. Since the partial pressure of the refrigerant vapor in the lubricating oil is low, the refrigerant vapor on the oil surface is absorbed, causing the air pressure in the oil pool to be lower than the air pressure of the evaporator. The lower the oil temperature, the lower the vapor pressure and the greater the absorption of refrigerant vapor. The steam in the system slowly "migrates" to the Copeland scroll refrigeration compressor. The longer the downtime, the more refrigerant will migrate into the lubricant. Refrigerant migration will dilute the lubricant. It is also easy to cause liquid shock to the low pressure chamber. Liquid refrigerants or mixtures of oil and refrigerant are not good lubricants, causing wear and even seizure. At this point, the overload protector on the motor will not operate because the motor is immersed in the liquid. Installation of crankcase heaters, gas-liquid separators, and evacuation shutdown control can effectively prevent or reduce refrigerant migration.

XI, the main reason for the liquid damage of Copeland scroll refrigeration compressor - too much lubricant

For low-pressure chamber Copeland scroll refrigeration compressors, high-speed rotating components such as rotors will frequently hit the oil surface. If the oil level is too high, it will cause a lot of splashing of lubricating oil. Once the splashed lubricant enters the intake port and is brought into the cylinder, it may cause a liquid impact.

12. The main cause of high temperature damage in Copeland scroll refrigeration compressors

Overheating of the motor due to problems such as over-range use, abnormal power supply, motor overload, refrigerant leakage, and high condensing pressure, such as high temperature of the motor, excessive exhaust temperature, and burnt grease. The surface temperature of the Copeland scroll refrigeration compressor is one of the important indicators for determining whether the Copeland scroll refrigeration compressor is overheated. If the surface temperature exceeds 135 ° C, the Copeland scroll refrigeration compressor is considered to be in a severely overheated state; and if the surface temperature is below 120 ° C, the Copeland scroll refrigeration compressor is normal. The motor generates a large amount of heat. If the power supply is abnormal, the heat generated by the motor will increase. For example, if the voltage is unstable, the voltage is too low or too high, the voltage is unbalanced, and the voltage is not equal, the power supply is abnormal.

Copeland vortex refrigeration compressors frequently start, link axles, piston squeezing cylinders, insufficient lubrication or lack of oil will greatly increase the heat. Excessive use of Copeland scroll refrigeration compressors can easily cause overheating and damage to the motor and insufficient motor cooling. The evaporation temperature is low and the refrigerant mass flow rate is small, resulting in insufficient motor cooling. When the refrigerant leakage is relatively large, the refrigerant mass flow rate is small, resulting in insufficient motor cooling.

Thirteen, the main reason for excessive exhaust temperature

The main reasons for the overheating of the exhaust gas are as follows: high return air temperature, large motor heating, high compression ratio, high condensing pressure, and improper refrigerant selection.

The above content was provided by A&S Aerodynamic Co., Ltd.