Basic Equipment Operation Skills of Refrigeration Workers!
1. Nitrogen filling welding
If nitrogen protection is not carried out during brazing or sufficient nitrogen is not filled, oxides will be produced on the inner surface of the copper pipe, which will cause: Blockage of the refrigerant system, such as the blockage of the electronic expansion valve, oil return capillary, etc.; causing the compressor to burn out , poor air conditioning and other faults. Therefore, generally major manufacturers will require nitrogen protection.
Nitrogen filling welding points: Air pressure 0.2~0.5kgf/cm2;
The place where the nitrogen-filled hose is inserted into the port of the copper pipe must be wrapped well to avoid air leakage;
When brazing, pass nitrogen gas to the refrigerant pipe for more than 10s, and ensure that it is until the end of welding.
2. Nitrogen purge
Nitrogen purging can remove oxide powder or partial oxide skin in the copper tube. When the tube is not sealed tightly, it can remove the dirt and moisture in the tube. The purging is carried out before the copper tube is connected to the internal machine. The nitrogen filling pressure can be set to 0.4~0.6MPa.
Operation method:
a. Install the pressure gauge on the nitrogen cylinder.
b. The high pressure end of the pressure gauge is connected to the fluorine injection nozzle of the small pipe (liquid pipe).
c. Use blind plugs to plug all the copper pipe joints except the A side of the indoor unit.
d. Open the nitrogen cylinder valve and maintain the pressure at 40kgf/cm2.
e. Check whether nitrogen flows through the indoor unit A liquid pipe.
g. Close the nitrogen main valve.
h. Repeat the above operation for indoor unit B.
Press the insulating material in your hand against the nozzle, and when the pressure cannot be resisted, quickly release the insulating material. Then use the insulating material to press the nozzle, repeat this several times, and then use a wooden board with white paper to check the distance between 300 and 500mm from the sewage outlet.
3. Air tightness test
The airtightness test is what we often call pressure retention. Key points of the air tightness experiment: Each refrigerant system must be pressurized from both sides of the gas pipe and the liquid pipe at the same time; therefore, the pressure on both sides of the gas and liquid can protect the electronic expansion valve on the indoor unit side of the multi-line system from damage; The air tightness test must use dry nitrogen as the medium. In addition, the vacuuming can only be carried out after the leak detection is qualified by filling with nitrogen.
4. Pressure test
The pressure test of the R410A refrigerant copper tube should be divided into three stages, as follows:
The first stage: pressurize at 3.0 kgf/cm2 for more than three minutes, and a large leak can be found;
The second stage: pressurize at 15.0 kgf/cm2 for more than three minutes, and a large leak can be found;
The third stage: pressurized at 40.0 kgf/cm2 for more than 24 hours, and tiny leaks can be found.
special reminder:
For every ±1°C temperature difference in ambient temperature, there will be a pressure difference of ±0.1 kgf/cm2; Correction formula: actual value = pressure during pressurization - (temperature during pressurization - temperature during observation) × 0.1 kgf/cm2, 24 hours Internal pressure drop within 0.2 kgf/cm2 is acceptable. In addition, we need to write down the time, temperature and pressure of nitrogen charging (the method of sticking white tape in the picture above can be used for comparison), so that we can make corrections after 24 hours.
5. Leak detection
Leak detection of soap bubbles: evenly wipe the area around the inspected area, and carefully observe whether there are bubbles. If soap bubbles appear, it means that there is a leak there. Sometimes, it is necessary to charge the system with 0.8-1.0Mpa (8-10kgf/cm2) nitrogen gas first.
Charge pressure leak detection: After the refrigeration system has been repaired and welded, before charging the refrigerant, it is best to charge 1.5Mpa nitrogen at the end of get off work, and close the three-way inspection valve (the valve itself cannot leak), if the gauge pressure does not drop. , indicating that the repaired refrigeration system does not leak, if the gauge pressure drops, it means that there is a leak, and then the soap bubble leak detection method is used to detect the leak.
Electronic leak detector leak detection: use the electronic leak detector probe to move to the place where there may be leakage, if there is a leak, the leak detector will issue an alarm. This device is quick and easy to detect leaks. Focus on checking the welding parts of the suction and exhaust pipes of the compressor; the small elbows of the evaporator and the condenser, the inlet and outlet pipes and the welding parts of the branch pipes: such as filter driers, stop valves, solenoid valves, thermal expansion valves, distribution connections to the device, storage tank, etc.
6. Vacuum
Vacuuming is an essential and important process before charging refrigerant in the production or maintenance process of refrigeration equipment. That is, the vacuum pump is connected to the pipeline of the refrigeration system. That is, the process of connecting the high and low pressure sides at the same time to remove the non-condensable gas and moisture in the system pipeline. The normal system vacuum degree should be below -756mmHg. The vacuuming time should be determined according to the size of the refrigeration system of the model and the size of the vacuum pump.
Seven, add refrigerant
Calculate the additional amount of refrigerant according to the pipe diameter and length of the piping connected to the liquid side of the outdoor unit and the indoor unit, add refrigerant, and record the additional refrigerant amount on the refrigerant addition instruction plate of the outdoor unit. Before adding refrigerant, it is necessary to confirm whether the vacuum drying has been completed. Qualified to complete.
The amount of refrigerant to be additionally filled in the multi-line must be calculated according to the formula in the relevant technical data of the outdoor unit before filling. It is absolutely impossible to fill with the operating current, pressure, temperature, etc., because the current, pressure, etc. will change depending on the temperature and the length of the piping.
