[Mechanical Equipment Technology Edition] Daily Question 201801016: Common Faults in Refrigeration Systems (6.1)

The treatment of water entering the refrigeration system should involve identifying the source of this water ingress and eliminating it; issues such as cracked or corroded tubes in the condenser or evaporator must be addressed by plugging those tubes, and in severe cases, the tubes need to be replaced. Once the processing is complete, the system should be evacuated and dried, the filter element replaced, the desiccant changed, and refrigerant added as required. It can be used after completion. This is the only process that applies, provided there is no damage to the mechanical parts.

I. First, identify the source of the water or moisture; first find out where the water or moisture is coming from； ； 1. Leaking areas of the condenser: Add a small amount of fluorine, then apply pressure with nitrogen at 10 Kg. Use a leak-detection halogen lamp, or soapy water and dishwashing liquid, to check for possible leakage points. 2. Leakage location of the evaporator: Check whether there are oil stains in the chilled water; if so, there is a leak, otherwise there is no leak. 3. Water content in the added refrigerant: Release an appropriate amount of the refrigerant from the bottle into a clean, dry glass container, and after the refrigerant has evaporated, check whether water is present in the container. If water is present, it indicates that the refrigerant in that bottle contains a high level of water; identify the source of this issue. II. Procedure for dealing with excessive water inflow into the system (after identifying and fixing the leaks) ； Disassemble all the components that can be taken apart, such as the condenser, evaporator, compressor (with the oil filter removed), high-pressure dry filter, expansion valve, solenoid valve, globe valve, liquid storage tank, and connecting pipes (it is not necessary to move large components), to facilitate subsequent work. The decomposed components are pressurized with nitrogen and then the pressure is released instantly, in order to blow out as much water as possible from the components (the cleaner this is done, the easier the subsequent work will be). After restoring the entire unit, open all passages in the refrigeration system (the spools of the expansion valves, the high-pressure dry filter elements, and the spools of the solenoid valves are not to be installed at this stage; the oil filter inside the compressor as well as the refrigerant oil are not to be added yet). Perform vacuum pumping for a longer period than usual (it is advisable to be able to heat the components, and the compressor can be connected to an oil heater, with the aim of accelerating the evaporation of any remaining water in the system). After confirming that there is no moisture in the system, install a clean and dry oil filter and a high-pressure dry filter element, add refrigerant oil, etc., and proceed according to the normal assembly procedures for the unit. III. Steps for dealing with low water inflow into the system: Steps for dealing with low water inflow into the system (after identifying and fixing the leaks) (after identifying and fixing the leaks) ； At the location of the original high-pressure drying filter in the unit system, a larger drying filter should be installed in its place (the kind that manufacturers use during testing). If such a filter is not available on site, it is necessary to remove the original filter element from the high-pressure drying filter, create a pocket using clean and dry absorbent gauze, fill it with \"activated alumina particles\" (with a particle diameter greater than Φ6mm), add a small amount of color-changing silica gel to facilitate monitoring of moisture content, replace the refrigerant oil containing moisture in the compressor, and install a pressure gauge behind the compressor’s suction filter (the function of this gauge will be explained later). Start the machine manually, provided that everything in the unit system is normal except for the presence of moisture. Upon startup, it operates at 50% capacity first; pay close attention to the operating current, as well as the pressure difference between the high-pressure gauge, the low-pressure gauge, and the additional pressure gauge (this is very important!) Under normal conditions, the smaller the pressure difference, the better). During the initial operation, observe this difference; if the value rises to 3–4 Kg, replace the ‘alumina particles’ and colored silica gel in the high-pressure filter (pay attention to the color of the silica gel). When the pressure difference between the low and high pressure gauges at 50% operation level is already very small, it enters 75% operation mode. Repeat this sequence of operations until 100% operation is reached, until the system is dry. After confirming that there is no moisture in the system, replace the oil filter, high-pressure dry filter element, refrigeration oil, etc. with clean and dry ones, then proceed according to the normal assembly procedure for the unit.

1 Inspect the entire refrigeration system to determine the cause of the freezing and locate the leak. 2 First, use an air compressor to blow out the moisture until no water mist is produced. Blow with high-pressure nitrogen, and the nitrogen can be heated while blowing. The refrigerant oil must be replaced after the compressor has been cleaned with water. 3 Restore the pipeline, purge it with nitrogen to ensure airtightness of the system, then connect a vacuum pump for vacuum drying. 4 Start up the system for testing after confirming that most of the moisture has been removed

Treatment for excessive water ingress in the refrigeration system: 1. Disassemble the components of the refrigeration system – the condenser, evaporator, compressor (remove the oil filter), high-pressure dry filter, expansion valve, solenoid valve, globe valve, liquid storage tank, and connecting pipes – as much as possible (it’s not necessary to move large components); this makes it easier to carry out the subsequent steps. 2. Segmented purging: Using nitrogen pressure followed by immediate release to blow out as much water as possible from the components. If the piping of the refrigerant system is complex, it is possible to use a welding torch to heat certain sections of the pipes and then blow out the moisture from those areas, depending on the specific circumstances. 3. Restore the refrigeration system: After restoring the entire unit, open all passages in the refrigeration system (do not install the valve elements of the expansion valves, high-pressure dry filters, or solenoid valves for now; also do not add oil filters or refrigerant oil to the compressor). Perform vacuum pumping for a longer period than usual (it is advisable to be able to heat the components, and the compressor can be connected to an oil heater, in order to accelerate the evaporation of any remaining moisture in the system). 4. Start up and operate: Ensure that most of the moisture in the system has been removed, then restore the refrigeration system by installing a clean oil filter and a high-pressure dry filter element, add refrigerant oil, and follow the standard assembly procedures for the unit.

　　I. Analyze the causes Check the entire refrigeration system to determine the reason for the freezing and identify the leakage points. 　　II. Segmented purging Water can first be blown away using an air compressor (to save nitrogen), until no water mist is produced. Blow again with high-pressure nitrogen; the nitrogen can be heated while blowing (heating of nitrogen cylinders is prohibited). 　　Due to the complexity of the refrigerant system’s pipelines, it is possible, depending on the specific circumstances, to use a welding torch to heat up certain sections of the pipes and blow out the moisture from them. Heating and drying: Small components such as capillaries, thermal expansion valves, and compressors can be placed in an oven to be dried by heating. The refrigerant oil must be replaced after the compressor has been cleaned with water. III. Vacuum Drying: Restore the piping, fill it with nitrogen to maintain pressure and ensure airtightness of the system, then connect a vacuum pump to carry out vacuum drying. (The dry filter tank must be placed at the front end of the vacuum pump to prevent excessive water vapor from entering the pump.) During vacuum drying, the parts of the pipeline where water tends to accumulate can be heated, with the duration depending on the specific conditions on site. 　　IV. Debugging and Operation Confirm that the moisture in the system has been basically removed. 　　Connect the external drying and filtering tank to the system, and replace the desiccant after 5 minutes of operation. At the same time, monitor the unit’s operating parameters and pay attention to the sound emitted by the compressor. If the dry filter is cold, the expansion valve is frosted, or there is a pressure difference of more than 0.5 kilograms before and after the return air filter, the unit should be stopped immediately. 　　Repeat the above process, continuously replacing the desiccant, with the interval between replacements gradually increasing as more repetitions are done. (Dry agents: Calcium chloride drying pellets have a high water absorption capacity and are used when there is an excess of moisture at the beginning; colored silica gel can accurately detect the moisture level and can be used for drying later on.) Finally, replace the desiccant with color-changing silica gel and run it for 24 hours to confirm that the color-changing silica gel retains its original color. 　　V. Repair completed: Remove the dry filter cartridge and restore the refrigerant lines. Check the amount of supplementary refrigerant. Power on the machine and check that its operating parameters are normal. 　　

1. Analyze the cause: Check the entire refrigeration system to determine the reason for the freezing and identify the leakage points. 　　2. Segmental purging: (1) The air compressor can be used first to blow away moisture (to save nitrogen), until no water mist is produced. Blow again with high-pressure nitrogen; the nitrogen can be heated while blowing (heating of nitrogen cylinders is prohibited). 　　(2) Due to the complexity of the refrigerant system’s pipelines, it is possible, depending on the specific circumstances, to use a welding torch to heat up certain sections of the pipes and blow out the moisture from them. 　　(3) Heat and dry: Small components such as capillaries, thermal expansion valves, and compressors can be placed in an oven to be baked and dried. The refrigerant oil must be replaced after the compressor has been cleaned with water. 　　3. Vacuum drying: (1) Restore the pipeline, purge it with nitrogen to ensure airtightness of the system, and then connect a vacuum pump for vacuum drying. (The dry filter tank must be placed at the front end of the vacuum pump to prevent excessive water vapor from entering the pump.) (2) During the vacuum drying process, the parts of the pipeline where water tends to accumulate can be heated; the duration of this heating depends on the specific conditions on site. 　　4. Debugging and operation: (1) Confirm that the moisture in the system has been basically removed. (2) Connect the external drying and filtering tank to the system, and replace the desiccant after 5 minutes of operation. At the same time, monitor the unit’s operating parameters and pay attention to the sound produced by the compressor. If the dry filter is cold, the expansion valve is frosted, or there is a pressure difference of more than 0.5 kilograms before and after the return air filter, the unit should be shut down immediately. (3) Repeat the above process, continuously replacing the desiccant; the interval between replacements can be increased gradually as the number of replacements increases. (Dryants: Calcium chloride drying pellets have a high water absorption capacity and are used when there is an excess of moisture at the beginning; colored silica gel can accurately detect the moisture level and can be used for drying later on.) (4) Finally, replace the desiccant with color-changing silica gel, and run it for 24 hours to confirm that the color-changing silica gel retains its original color. 5. Repair completed: (1) Remove the drying filter drum and restore the refrigerant pipeline. 　　(2) Check the amount of refrigerant to be added. Power on the machine and check that its operating parameters are normal.

Since chillers have a water system, there is a possibility that moisture from the water system may enter the refrigerant system if they are not operated properly. Therefore, process guidelines have been developed to address the issue of water ingress into the refrigeration system, to serve as a reference during maintenance. I. Analyze the causes: Inspect the entire refrigeration system to determine the reason for the freezing and identify the leakage points. II. Segmented purging: First, use an air compressor to blow out the moisture (to save nitrogen), until no water mist is produced. Blow again with high-pressure nitrogen; the nitrogen can be heated while blowing (heating of nitrogen cylinders is prohibited). Due to the complexity of the refrigerant system’s pipelines, it is possible, depending on the specific circumstances, to use a welding torch to heat up certain sections of the pipes and blow out the moisture from them. Heating and drying: Small components such as capillaries, thermal expansion valves, and compressors can be placed in an oven to be dried by heating. After the compressor has been cleaned with water, its refrigerant oil must be replaced. III. Vacuum Drying: Restore the piping, fill it with nitrogen to maintain pressure and ensure the system is airtight, then connect a vacuum pump to carry out vacuum drying. (The dry filter tank must be placed at the front end of the vacuum pump to prevent excessive water vapor from entering the pump.) During vacuum drying, the parts of the pipeline where water tends to accumulate can be heated, with the duration depending on the specific conditions on site. IV. Debugging and operation: Confirm that the moisture in the system has been essentially removed. Connect the external drying and filtering tank to the system, and replace the desiccant after 5 minutes of operation. At the same time, monitor the operating parameters of the unit and pay attention to the sound emitted by the compressor. If the dry filter is cold, the expansion valve is frosted, or there is a pressure difference of more than 0.5 kilograms before and after the return air filter, the unit should be stopped immediately. Repeat the above process to replace the desiccant continuously, with the interval between replacements gradually increasing as more replacements are done. (Dry agents: Calcium chloride drying pellets have a high water absorption capacity and are used when there is an excess of moisture at the beginning; colored silica gel can accurately detect the moisture level and can be used for drying later on.) Finally, replace the desiccant with color-changing silica gel and run it for 24 hours to ensure that the color-changing silica gel retains its original color. V. Repair completed: Remove the drying and filtering tank and restore the refrigerant piping. Check the amount of supplementary refrigerant. Power on the machine and check that its operating parameters are normal. Precautions: Dry filter drum: Since the gaskets used in external dry filter drums are usually asbestos gaskets, they do not provide a tight seal for the refrigerant. Therefore, it is not allowed to run connected to the system for long periods of time. It should be removed after maintenance is completed to prevent fluorine leakage. Ban on methanol: Adding methanol can raise the freezing point of water and thus prevent ice blockages, but it does not reduce the amount of water in the system. As time passes and this water circulates within the system, it can degrade the quality of the refrigeration oil, cause copper plating on the metal components of the system, and lead to corrosion of the compressor coils, resulting in electrical leaks that can cause serious injuries or deaths.

I. Analyze the causes Check the entire refrigeration system to determine the reason for the freezing and identify the leakage points. II. Segmented cleaning with air 　　First, use an air compressor to blow out the moisture until no water mist is produced. Blow again with high-pressure nitrogen; the nitrogen can be heated while blowing (heating of nitrogen cylinders is prohibited). 　　Due to the complexity of the refrigerant system’s pipelines, it is possible, depending on the specific circumstances, to use a welding torch to heat up certain sections of the pipes and blow out the moisture from them. Heating and drying: Small components such as capillaries, thermal expansion valves, and compressors can be placed in an oven to be dried by heating. The refrigerant oil must be replaced after the compressor has been dried with water ； III. Vacuum Drying Restore the pipeline, purge it with nitrogen to ensure airtightness of the system, and then connect a vacuum pump for vacuum drying. (The dry filter tank must be placed at the front end of the vacuum pump to prevent excessive water vapor from entering the pump.) During vacuum drying, the parts of the pipeline where water tends to accumulate can be heated, with the duration depending on the specific conditions on site. IV. Debugging and Operation Confirm that the moisture in the system has been basically removed. 　　Connect the external drying and filtering tank to the system, and replace the desiccant after 5 minutes of operation. At the same time, monitor the unit’s operating parameters and pay attention to the sound emitted by the compressor. If the dry filter is cold, the expansion valve is frosted, or there is a pressure difference of more than 0.5 kilograms before and after the return air filter, the unit should be stopped immediately. 　　Repeat the above process, continuously replacing the desiccant, with the interval between replacements gradually increasing as more repetitions are done. (Dry agents: Calcium chloride drying pellets have a high water absorption capacity and are used when there is an excess of moisture at the beginning; colored silica gel can accurately detect the moisture level and can be used for drying later on.) Finally, replace the desiccant with color-changing silica gel, and run it for 24 hours to confirm that the color-changing silica gel retains its original color ；

1) Analyze the reasons. Inspect the entire refrigeration system to determine the cause of the freezing and identify the leak. 2) Segmental fouling blowing. ①The moisture can first be blown away using an air compressor (to save nitrogen), until no water mist is produced. Blow with high-pressure nitrogen; the nitrogen can be heated while blowing (heating of nitrogen cylinders is prohibited). ② Due to the complexity of the refrigerant system’s pipelines, it is possible, depending on the specific circumstances, to use a welding torch to heat up certain sections of the pipes and blow out the moisture from them. ③Heating and drying: Small components such as capillaries, thermal expansion valves, and compressors can be placed in an oven to be dried by heating. The refrigerant oil must be replaced after the compressor has been cleaned with water. 3) Vacuum drying: ① Restore the piping, purge with nitrogen to ensure airtightness of the system, and then connect a vacuum pump for vacuum drying. (The dry filter tank must be placed at the front end of the vacuum pump to prevent excessive water vapor from entering the pump.) ② During the vacuum drying process, the parts of the pipeline where water tends to accumulate can be heated; the duration of this heating depends on the specific conditions on site. 4) Debugging and trial operation. ①Confirm that the moisture in the system has been essentially removed. ② Connect the external drying and filtering tank to the system, and replace the desiccant after running it for 5 minutes. At the same time, monitor the operating parameters of the unit and pay attention to the sound produced by the compressor. If the dry filter is cold, the expansion valve is frosted, or there is a pressure difference of more than 0.5 kilograms before and after the return air filter, the unit should be stopped immediately. ③ Repeat the above process, continuously replacing the desiccant; the interval between replacements can be gradually increased as the number of replacements increases. (Dry agents: Calcium chloride drying pellets have a high water absorption capacity and are used when there is an excess of moisture at the beginning; colored silica gel can accurately detect the moisture level and can be used for drying later on.) ④Finally, replace the desiccant with color-changing silica gel and run it for 24 hours to confirm that the color-changing silica gel retains its original color. 5) Repair completed: ① Remove the drying filter tank and restore the refrigerant pipeline. ②Check the amount of supplementary refrigerant. Power on the machine and check that its operating parameters are normal. Air compression compressor, drying and filtering tank, calcium chloride (granules), color-changing silica gel