1. Maintenance tools and equipment:
Pressure gauge, multimeter, megohmmeter, wrench, socket wrench, vacuum pump, nitrogen cylinder, connecting pipe,
Steel cylinder, welding tool, combination tool, common wrench, pipe expander, moisture absorbent, cutting knife, special square tenon wrench
2. Fault diagnosis and analysis of refrigeration system:
The refrigeration system operates under normal operating pressure and should be able to automatically shut down and operate automatically. Once a fault occurs, it cannot be cooled normally. The main faults include the following:
1) : Refrigerant leakage
2) : Blocked Ice Blocked Dirty Blocked 09G802
3) : Compressor fault
4) : Compressor does not operate
We have a basic understanding of the fault through: seeing, listening, and touching
Look: Determine whether there is any oil stain on each connection part of the refrigeration system, components, temperature changes, and whether the pressure gauge has a pressure value
Listen: When the compressor is running, listen for abnormal sounds from moving parts
Touch: When the compressor is running, listen for abnormal sounds from moving parts? Check whether the compressor temperature, solenoid valve, throttling device, filter, condenser, evaporator, and other components are abnormal
3. Fault phenomenon and analysis:
A. Refrigerant leakage:
Is there a pressure value for the pointer indicator of the pressure gauge? Is there any oil stain at the connection of the refrigeration system?
The method of inspection is:
After starting the machine and observing for more than ten minutes, the pointer of the high pressure gauge does not rise, the low pressure gauge shows a strong vacuum state, the condenser is not hot, the evaporator does not frost, and the throttle valve does not change in temperature, indicating a refrigerant leak
Troubleshooting:
Nitrogen leak detection method:
Totally enclosed system:
For refrigeration systems with suction and exhaust shut-off valves, a pressure gauge can be connected to the bypass hole of the suction and exhaust shut-off valves. The pressure gauge is connected to the pressure reducing gauge of the nitrogen cylinder through a conduit, and a pressure of 0.4-0.8Mpa is charged to the refrigeration system. Close the nitrogen cylinder and shut-off valve. Then, apply soapy water or detergent to each connection of the refrigeration system to detect leaks. Repair the leak
For refrigeration systems without shut-off valves:
A short pipe is welded out of the process pipe of the compressor, which is connected to a three-way pressure gauge. The pressure gauge is connected to a nitrogen cylinder through a conduit. Open the three-way valve and the nitrogen cylinder, and then fill the refrigeration system with 0.4-0.8Mpa of nitrogen. Then, apply soapy water or detergent to each connection of the refrigeration system to identify any leaks. Repair the leak
The three methods of air tightness test are:
Pressure test, vacuum test, working medium test (refrigerant, refrigerant)
Why should we vacuum the refrigeration system? "Because refrigerants can only fully boil and absorb heat at an absolute atmospheric pressure, we should remember the boiling temperatures of several commonly used refrigerants, such as R12: - 29.8 ℃, R22: - 40.5 ℃, and so on."
New refrigerant (environmentally friendly):
123:27.81℃ (R11) 134a:-26.5℃ (R12) 502:-45.44℃.(R22)
If the refrigeration system does not perform vacuum pumping, the following adverse factors may occur:
Poor cooling effect. Slow cooling speed, frost formation, and uneven condensation
The condensation pressure is on the high side, the temperature is on the high side, and the pointer of the pressure gauge shakes
Therefore, we must vacuum the refrigeration system. The vacuum degree is - 0.1 Mpa
B. Blocking Ice Blocking Dirty Blocking
Ice blockage:
The refrigeration system contains water and circulates with the refrigerant in the system. When under a certain pressure and temperature, ice forms at the outlet of the throttle valve, causing blockage in the refrigeration system and abnormal circulation of the refrigerant. Heat exchange between steam absorption and exhaust cannot be achieved
The phenomenon of forming (periodic) cooling is called ice blockage
Do not charge methanol into the refrigeration system when troubleshooting ice blockage
The correct removal method is: nitrogen cleaning method
The nitrogen cleaning operation steps are as follows:
1) Install a pressure gauge at the bypass hole of the suction and exhaust stop valves, and connect the pressure gauge to the nitrogen cylinder through a connecting pipe
2) In a fully enclosed refrigeration system, a short pipe is welded to the process pipe and a pressure gauge is installed to connect with the nitrogen cylinder through a conduit
3) Disconnect the low pressure pipeline and open the solenoid valve. Charge the refrigeration system with 0.3-0.4Mpa of nitrogen, which flows out of the low pressure pipeline (dirt, debris, oil, water)
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