Normal signs and common causes of faults in cold storage systems~~

                           Normal signs and common causes of faults in cold storage systems~~

 

一、 Normal operation sign of refrigeration system

 

1. After starting the compressor, it should run smoothly without any noise, and all protection and control components should be able to work normally.

2. The cooling water and refrigerant water should be sufficient, the water pressure should not be less than 0.12MPa, the water flow rate should meet the design requirements, and the cooling water temperature is generally around 32 ℃.

 

3. The outlet pressure of the oil pump shall be 1.5~3kg/C ㎡ higher than the suction pressure, the oil temperature shall not be lower than 70 ℃, and the oil shall not rise a lot of foam, and the oil level shall not be lower than 1/3 of the oil mirror.

4. The suction temperature is 5-15 ℃ higher than the evaporation temperature. During normal operation, the suction temperature should not exceed 15 ℃. For air conditioning systems, the evaporation temperature is about 5 ℃ lower than the temperature of the cooled medium. For refrigeration devices, the suction temperature is about 10-15 ℃ lower than the temperature of the cooled medium.

5. The exhaust temperature should not exceed 115 ℃. (R22). When the compressor is running normally, the condensing pressure does not exceed 1.4MPa (for water-cooled units), and for air-cooled condensers, the condensing pressure does not exceed 2Mpa.

 

 

6. For systems equipped with automatic oil return devices, the automatic oil return pipe should be cold and hot, and there should be no significant temperature difference before and after the liquid pipe filter. For systems equipped with reservoirs, the refrigerant level should not be lower than one-third of this level indicator.

7. There should be no local heating or frosting on the cylinder wall, and air conditioning products and suction pipes should not have frosting. For refrigerated products, frosting on the suction pipe is generally normal when it reaches the suction valve port.

8. When touching the horizontal condenser during operation, it should be hot on top and cool on the bottom. The interface between cold and hot is the refrigerant interface, while the upper and lower parts of the oil separator are not too hot. The interface between cold and hot is the oil interface.

 

 

 

9. The frost and condensation on the valve body of the expansion valve should be uniform (not in the air conditioning system), but there should be no thick frost at the outlet. When the liquid flows through the expansion valve, only a dull and small sound can be heard.

10. Under certain water pressure and quantity conditions, there should be a significant temperature difference between the inlet and outlet water, generally ranging from 3 to 5 ℃

11. There should be no leakage or oil leakage in the system, the pointers of each pressure gauge should be relatively stable, the compressor current should not exceed the rated current, and the insulation resistance should not be less than 5M Ω.

 

二、 Common faults in refrigeration systems

 

1. Exhaust pressure too high

Cause of malfunction:

There are non condensable gases such as air in the system;

Insufficient or too hot cooling water;

The water cooler is dirty and affects heat exchange;

There is too much refrigerant in the system;

The exhaust valve is not fully opened or the exhaust pipe is not unobstructed.

Solution:

Release non condensable gases such as air;

Adjust the cooling water volume and lower the water temperature;

Clean the water path of the condenser;

Recycling excess refrigerant;

Fully open the exhaust valve and unclog the exhaust pipe.

Non condensable gas hazards:

Causing an increase in condensation pressure;

Forming air resistance reduces the heat transfer efficiency of the condenser. Simultaneously corroding pipelines and equipment;

Causing a decrease in cooling capacity and an increase in power consumption;

If there is air present, accidents are prone to occur at high exhaust temperatures.

Method for judging non condensable gases:

The pointer of the exhaust pressure gauge of the refrigeration machine swings;

The exhaust pressure and exhaust temperature are both higher than normal pressure and temperature;

Air is lighter than fluorine gas, so it exists in the upper part of the horizontal condenser. When emptying, the air is not cool.

Reason for non condensable gas entering the system:

Incomplete vacuum pumping;

During maintenance, the air is not completely discharged, for example, during fluorine addition, the fluorine tube is not completely discharged;

The pressure in the low-pressure section of the refrigeration system remains under negative pressure for a long time;

The refrigerant itself is impure, containing air or impurities;

At high temperatures, oil decomposes into non condensable gases;

The hazards of excessive refrigerant:

Excessive refrigerant will occupy a portion of the condenser volume, reduce the heat transfer area, and lead to high condensation temperature and pressure;
The evaporation temperature of the refrigeration system increases, the evaporation pressure increases, and the refrigeration effect decreases;
Excessive suction pressure;

Excessive refrigerant, refrigerant liquid entering the compressor, causing wet compression, and even liquid shock;

The starting load increases, making it difficult to start the motor.

2. Low exhaust pressure

Cause of malfunction:

The cooling water temperature is too low or the water volume is too large;

Damaged compressor exhaust valve plate or leakage in exhaust pipeline;

Insufficient refrigeration dose in the system;

Improper adjustment of energy regulation mechanism;

Premature opening of safety valve, high and low pressure bypass;

Exclusion method:

Adjust the water supply volume;

Check the exhaust valve and exhaust pipeline;

Replenish refrigerant;

Adjust the adjustable mechanism to make it normal;

Adjust the opening pressure of the safety valve;

3. Excessive suction pressure

Cause of malfunction:

Excessive opening of expansion valve;

There is a problem with the expansion valve or the position of the temperature sensing bulb is incorrect;

Excessive refrigerant volume in the system;

Excessive heat load;

High and low pressure gas leakage due to broken suction valve plate;

Premature opening of safety valve, high and low pressure bypass;

Exclusion method:

Correctly adjust the opening of the expansion valve;

Check the expansion valve and adjust the position of the temperature sensing bulb;

Recycling excess refrigerant;

Try to reduce the heat load;

Check the valve plate and the cause of gas leakage;

Adjust the opening pressure of the safety valve;

 

4. Low suction pressure

Cause of malfunction:

The expansion valve has a small opening or is damaged;

The suction pipeline or filter is blocked;

Leakage of temperature sensing package;

Insufficient cooling dose of the system;

Too much lubricating oil in the system;

The evaporator is dirty or the frost layer is too thick;

Exclusion method:

Open the expansion valve to the appropriate position or replace it;

Check the suction pipe and filter;

Replace the temperature sensing package;

Replenish refrigerant;

Repair the oil separator and recover excess oil;

Cleaning and defrosting;

5. Exhaust temperature too high

Cause of malfunction:

Excessive overheating of inhaled gas;

Low suction pressure and excessive compression ratio;

Leakage of exhaust valve plate or damaged spring;

Abnormal wear and tear of the compressor;

Oil temperature too high;

Premature opening of safety valve, high and low pressure bypass;

Exclusion method:

Adjust the expansion valve appropriately to reduce overheating;

Increase suction pressure and reduce compression ratio;

Check and replace the exhaust valve plate and spring;

Check the compressor;

Adjust the opening pressure of the safety valve;

Reduce oil temperature;

6. Oil temperature too high

Cause of malfunction:

The cooling effect of the oil cooler has decreased;

Insufficient oil cooling water supply;

Abnormal wear and tear of the compressor;

Exclusion method:

The oil cooler is dirty and needs to be cleaned;

Increase water supply;

Check the compressor;

7. Oil pressure too low

Cause of malfunction:

Damaged oil pressure gauge or blocked pipeline;

There is too little oil in the crankcase;

Improper adjustment of the oil pressure regulating valve;

Excessive refrigerant dissolved in the lubricating oil inside the crankcase;

The backlash or cross-sectional clearance of the oil pump gear is too large;

The oil suction pipe is not unobstructed or the filter is blocked;

There is Freon gas inside the oil pump;

Exclusion method:

Replace the oil pressure gauge or blow through the pipeline;

Add lubricating oil;

Correctly adjust the oil pressure regulating valve;

Reduce the opening of the expansion valve;

Replace or repair the gear clearance;

Blow through the oil suction pipe and clean the filter;

Fill the oil pump with oil and discharge the gas.

8. Oil pressure too high

Cause of malfunction:

The oil pressure gauge is damaged or the value is incorrect;

Improper adjustment of the oil pressure regulating valve;

Blocked oil discharge pipeline;

Exclusion method:

Replace the oil pressure gauge;

Correctly adjust the oil pressure regulating valve;

Blow through the oil discharge pipeline.

 

Address :	No. 328 on the 4th plant hengyong Road, Jiading District, Shanghai
Factory Address :	No. 328 on the 4th plant hengyong Road, Jiading District, Shanghai
Work Time :	8:30-17:30(Beijing time)
Phone :	86-021 -63184860-17(Work Time) 86--13916495206(Nonworking time)
Fax :	86-021-53750132
Email :	lucy@shkubao.com