- Contact：Mr. Song
- Phone：0086-13705113637
- Tell：0086-0515-88809180
- Fax：0086-0515-88809181
- E-mail：jsjckt@126.com
- Address：No. 18, Rongguang Road, National High-tech Park, Yancheng City, Jiangsu Province
[Jiangsu Jincheng Air Conditioning Engineering Co., Ltd.] In order to ensure the service life of the refrigeration unit, it is necessary to carry out the necessary maintenance and maintenance of the refrigeration unit, especially before the refrigeration unit is turned on again after one quarter of operation, the refrigeration unit should be Carry out detailed inspection and maintenance.
First, the main work content of the regular inspection of the freezer
1. Perform an interpretation analysis of the operational records, indicate abnormal data, and make recommendations for improvement.
2. Check the refrigerant and frozen oil for signs of leakage.
3. Check the refrigerant system for obvious abnormal temperature and pressure.
4. Check if the capacity control is normal and the electronic expansion valve works well. Whether the freezer unit is running and the current is normal.
5. Whether the control system functions are normal, it is necessary to carry out simulation actions.
6. Is the power and control wiring clean?
7. The freezer unit has no abnormal noise and vibration.
8. Whether the water temperature and water pressure are normal when the freezer unit is running.
9. Submit an inspection report or recommend to the owner for acceptance.
Second, the maintenance of the refrigeration unit
The main contents are: cold water flow low alarm, refrigerant charge inspection, adding refrigerant, pumping refrigerant, oil level switch disconnection, running oil, oil discharge and oil inspection, oil filter replacement.
1. Low cold water flow alarm:
The freezer pump is not turned on.
The cold water pipe shutoff valve is not open.
The cold water target flow switch is not closed: check the flow switch palladium and adjust the flow switch.
2, refrigerant charge inspection
The freezer unit can only use HFC134a refrigerant.
Do not overfill the refrigerant. Otherwise, the exhaust pressure will be too high, it will consume more cooling water and electricity, and it may damage the compressor.
3. How to judge the shortage of charge
The sight glass on the liquid tube shows that there are insufficient bubbles to judge the shortage of refrigerant. The electronic expansion valve works well in this case.
A low saturated suction temperature is also insufficient to judge the refrigerant deficiency, especially when the oil forms a foam in the evaporator.
Verify that the freezer unit is operating at 100% load.
Verify that the evaporator cold water effluent temperature is between 4.5 and 7.5 °C.
Verify that the evaporator cold water inlet and outlet water temperature difference is between 5 and 6 °C.
Verify that the heat transfer temperature difference in the evaporator is between 0.5 and 2 °C.
If the above conditions are satisfied, and the electronic expansion valve opening degree is greater than 60%, and the mirror shows air bubbles, it can be judged that the refrigerant unit lacks refrigerant.
Verify that the freezer unit is operating at 100% load.
Add 2.5 kg of liquid with the top of the evaporator or the bottom angle valve.
Observe the opening of the electronic expansion valve after the refrigeration unit is running stably.
If the electronic expansion valve is more than 60% open and there are air bubbles in the mirror, add 2.5 kg of liquid refrigerant.
In order to confirm that enough refrigerant is added, it is necessary to continuously operate the freezer unit under full load conditions, so that the outlet water temperature of the evaporator is 6±1.5°C, and the temperature difference between the inlet and outlet water is between 5 and 6°C.
The expansion valve opening is between 40~60%.
The evaporator heat transfer temperature difference is between 0.5 and 2 °C.
4, pumping refrigerant
Do not use a bulk compressor to draw refrigerant from the evaporator. Because the compressor may be damaged when the suction pressure is less than 1 kg. The refrigerant pumping device should be used to pump the refrigerant.
5, the oil level switch is disconnected
If the refrigeration unit is repeatedly turned off because of the oil level switch, it means that the oil in the oil is insufficient and a large amount of oil is in the evaporator.
If the oil level switch is always off, use the oil pump to add two liters of oil to the oil. Do not refuel at any other location. Confirm that the oil level switch is closed, restart the freezer unit, and operate at 100% load for at least 1 hour under normal conditions.
If the newly added oil exceeds two liters, the oil needs to be re-extracted. If the oil is less than two liters, the oil can flow in the freezer unit, but it should be noted on the freezer unit.
6, running oil
When excess oil enters the evaporator and the refrigerant mixes, a large amount of foam is produced and the control system will be able to detect this and make the correct response. When oil foam is produced, the heat transfer temperature difference in the evaporator will increase, and the expansion valve will open, allowing more refrigerant to enter the evaporator, increasing the refrigerant level, causing the oil to be sucked away by the compressor and returned to the oil.
The reason for running oil
Low exhaust superheat results in poor oil performance.
The saturated exhaust gas temperature of the freezer unit is too low (the cooling water temperature is low), resulting in low oil pressure difference, which makes the oil supply cycle difficult.
How to prevent running oil
The condensate inlet water temperature is required to be >20 °C. If the condensate inlet water temperature is < 20 °C, a three-way valve should be installed on the condenser water pipe. The PID parameters of the three-way valve controller should be properly adjusted to prevent oscillation of the control.
7, draining & refueling
Close the service angle valve.
The refrigerant is withdrawn from the condenser.
The nitrogen is pressurized to the condenser and the viscosity of the oil will be very high.
The weight of the frozen oil was measured.
Vacuum the freezer unit.
Add new oil (equivalent to the extracted oil).
Avoid oil exposure to the atmosphere when refueling.
At this point, the freezer should check the oil once a year.
Oil samples were collected and sent to the laboratory for analysis.
If the analysis proves that the oil has deteriorated or is contaminated, it must be replaced.
8, replace the built-in oil filter
The compressor's oil filter should be checked when the freezer unit is in operation for 1000 hours.
After every 4000 hours of operation, the internal oil filter should be replaced immediately when the pressure difference between the oil filter and the front is found to exceed 2.1 bar.
The oil filter pressure drop should be checked when the following two conditions occur:
The compressor stops due to the "maximum oil pressure difference of the oil supply circuit" alarm
The compressor stops due to the "oil level switch open" alarm
To determine the pressure drop of the built-in oil filter, the pressure of the oil filter service angle valve and the oil filter service hole can be measured.
These two pressure differences are the pressure drop across the built-in oil filter, check valve and fuel supply solenoid valve.
The pressure drop across the check valve and the fuel supply solenoid valve is approximately 0.4 bar, and subtracting 0.4 bar from the measured differential pressure is the pressure drop of the built-in oil filter.
9, oil filter replacement process
Shut down and pull the compressor air switch off.
As a simulation, the oil supply solenoid valve is repeatedly operated several times to ensure that the solenoid valve is closed.
Close the oil filter to service the angle valve.
Connect the hose with the oil filter to remove the pressure and oil from the oil filter.
Open the oil filter plug and pull out the old oil filter.
Wet the “O” ring with oil, install a new oil filter, and replace with a new one. The pressure in the freezer unit is less than the absolute pressure of 100Pa.
Add the previously extracted refrigerant.
Jiangsu Jincheng Air Conditioning Engineering Co., Ltd. focuses on:
Industrial air conditioners, chemical fiber industrial air conditioners, chemical fiber industry refrigeration, textile industry air conditioners, clean room refrigeration, ventilation ducts, cooling towers, refrigeration machines and other air conditioning units and accessories.
