Judgement of pipeline failure of unmanned vending machine

The unmanned vending machines in the supermarket are not refrigerated. We must first turn on the power to listen to the sound, make sure the compressor is running, and open the refrigerator door. The sound is crisp and squeaking, indicating that there may be no refrigerant in it, and it may be a high-pressure leak; what about the hissing sound? Touch the outlet of the capillary again. It is a bit cold, indicating that there is still a little refrigerant, which may be a low-pressure leak. The above is still the initial shutdown of the unmanned vending machine, which should be determined by combining the pressure and the filtering state. Stop the machine after listening to the sound, and open the process pipeline after 15-20 minutes. The ice will be blocked until the ice melts. When the tube is opened, the knife will cut it in half. Wrap the knife and process tube in a leak-proof plastic bag, and then fold it by hand. At this time, you can know the pressure inside the system: is it negative pressure? Zero pressure? A refrigerant with a small positive pressure or a refrigerant with a large positive pressure. If the unmanned vending machine sizzles and is a bit cold at first, it will still be refrigerated in a few days or even a month, but it will not be refrigerated in the end, but there will be a compressor running sound, which is very muffled and there is no other sound. The ice is blocked. In this case, it can be refrigerated after shutting down and melting the ice. If the unmanned vending machine determines that there is no leakage in the frozen open tube, it must be a refrigeration or variable temperature leak. An unmanned vending machine with a gurgling sound can check whether the door of the unmanned vending machine has any traces of water flowing through it and whether the cabinet in the middle is rusty. If there is a high pressure leak, it is found that the door tube can be thrown directly, but the outer condenser of the door tube cannot be found. The rust of the door frame is mostly caused by icing on the outlet pipe of the cold storage. If you have an open back, dispose of the outlet pipe, lift it to the backboard, dig out the foam in the water, and stick the leak. Just scrape the door frame and stick it on. Negative pressure, combined with the gurgling sound heard before, can be determined as a high-pressure leak. Positive pressure must be combined with filter conditions. Zero pressure is troublesome, and high and low pressure leakage may occur. It can only be determined based on the status of the filter. If there is a large amount of positive pressure, it is necessary to determine whether the compressor discharge is normal. Generally, the thumb cannot be used for support, and the compressor is okay. Regardless of whether the unmanned vending machine uses copper, iron, aluminum or composite pipes, it will not leak water in a dry and anhydrous environment. No matter how good the insulation material of the unmanned vending machine is, there will be more or less water in the refrigeration pipe after a few years of use. The water in the foam layer of the refrigerator compartment is between liquid and solid. The water in the foam layer of the unmanned vending machine used all the year round freezes. Iron pipes rust when exposed to water, and thin-walled copper pipes are the same. Too much water may rust. The aluminum tube itself is not easy to be hydrolyzed, but the current unmanned vending machines using aluminum tubes either have a capillary tube or a joint for the aluminum tube in the refrigerator. The capillary will be entangled for heat exchange, so the capillary will have heat, so even if it is hot The exchange part is in the freezing layer, and the water is still in a liquid state. The contact position of copper and aluminum will produce ionization reaction in the presence of liquid water, causing corrosion of the aluminum tube. Therefore, as long as there are leaks in the refrigeration or return air pipes, water must be involved. When the leak point is purple, water will be drawn into the system and stay in the filter. If there is water in the filter of the unmanned vending machine, you need to open the back to repair or replace the pipe. If there is no water in the filter due to zero pressure, the door pipe is generally eroded and perforated, and you only need to remove the door pipe or the external condenser.